Patent Publication Number: US-2020282589-A1

Title: Method and system for forming grooves in a board element and an associated panel

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of Swedish Application No. 1950281-4, filed on Mar. 5, 2019, and the benefit of Swedish Application No. 1950280-6 filed on Mar. 5, 2019. The entire contents of each of Swedish Application No. 1950281-4 and Swedish Application No. 1950280-6 are hereby incorporated herein by reference in their entirety. 
     TECHNICAL FIELD 
     The disclosure generally relates to a method and a system for reducing weight in a board element. More specifically, the disclosure relates to a method and a system for forming at least one groove in a board element. The disclosure also relates to a corresponding board element comprising at least one groove. The board element may be a panel per se. Alternatively, the board element may be dividable or may be divided into at least two panels. The panel per se or any panel of said at least two panels may be a building panel, floor panel, wall panel, ceiling panel or furniture panel. Optionally, the panel per se or any panel of said at least two panels may comprise a locking system on at least one edge portion of the panel, preferably on two opposite edge portions of the panel. 
     BACKGROUND 
     Thermoplastic flooring currently attracts an increased interest in the market. Thermoplastic floor components may be flexible, such as Luxury Vinyl Tiles (LVT), or rigid, such as so called Stone Plastic (Polymer) Composite (SPC) flooring. LVT tiles and SPC panels typically comprise PVC, a filler, such as chalk or stone powder, and additives. LVT tiles preferably comprise plasticizers. 
     A problem with these types of panels is that they may become heavy which may negatively impact their performance as well as their production and transportation costs. Moreover, the transportation and the handling of the panels may become cumbersome. Thereby, there is a need to reduce the weight of the panels. As a consequence of a weight reduction of the panels, less material may be needed for manufacturing the panels and, additionally, cost savings may be made. 
     WO 2013/032391 discloses LVT panels comprising flexing grooves for increasing the flexibility of the panels as well as for decreasing their weight. There is also disclosed methods for forming such grooves. The grooves may be formed with rotating jumping tools or with knives, or they may be formed when the panel is pressed. 
     WO 2014/007738 discloses building panels comprising thermosetting resins or a thermoplastic material, preferably comprising a filler, and being provided with core grooves. There is also disclosed methods for producing such panels as well as recycling material that has been removed when forming the core grooves. The core grooves may be formed with rotating saw blades, milling or carving. 
     However, there is need for improved methods and systems of providing such grooves in panels. There is also need for improved panels. 
     SUMMARY 
     It is therefore an object of at least embodiments of the present inventive concept to provide an improved method for forming grooves in a board element. 
     More specifically, it is an object of at least embodiments of the present inventive concept to provide a method that makes the forming of the grooves more controllable. 
     It is also an object of at least embodiments of the present inventive concept to provide a corresponding system. 
     Additionally, it is an object of at least embodiments of the present inventive concept to provide a corresponding panel comprising at least one groove. 
     It is also an object of at least embodiments of the present inventive concept to provide a panel comprising at least one groove that has improved balancing properties and/or that has improved strength properties, such as locking strength properties, for example while saving more material. 
     At least some of these and other objects and advantages that will be apparent from the description have been achieved by the various aspects described below. 
     In accordance with a first aspect of the inventive concept, there is provided a method for forming grooves in a board element. The method comprises arranging the board element in contact with a support member, such as on the support member, and forming at least one groove in a rear side of the board element by removing material, such as chips, from the board element by a processing tool. 
     As described further below, the board element may be a panel per se or it may be dividable into at least two panels. 
     The board element or panel may comprise a front side and a rear side. The front side may adapted to be visible and, at least in some embodiments, the rear side may be adapted to be concealed in an installed state of the board element or panel, which may be a building panel, floor panel, wall panel, ceiling panel or furniture panel. In non-limiting examples, the floor panel may be an LVT tile, an SPC panel, an EPC panel (Expanded Polymer Core), or an WPC (Wood Plastic Composite) panel. Moreover, the board element or panel may comprise a pair of opposite edge portions. The board element or panel may comprise a first pair and a second pair of opposite edge portions. The first pair and the second pair may comprise long edge portions and short edge portions of the board element/panel, respectively. 
     In the following, it is understood that every embodiment and example discussed in relation to a board element in the first, second, third, and fourth aspects, are equally applicable to a panel. 
     The at least one groove may have a longitudinal extension and a transverse extension. The longitudinal extension may be larger than the transverse extension. In a first example, the longitudinal extension and the transverse extension may be parallel to a long edge portion and a short edge portion, respectively. In a second example, the longitudinal extension and the transverse extension may be parallel to a short edge portion and a long edge portion, respectively. In a third example, the longitudinal extension may be non-linear. 
     The board element may be fed towards the support member and/or processing tool in a feeding direction F. Preferably, for a board element comprising short edge portions and long edge portions, the feeding direction is parallel with the long edge portions. Thereby, the at least one groove may be formed in parallel with the long edge portions. However, it is equally feasible that the feeding direction is parallel with the short edge portions. Thereby, the at least one groove may be formed in parallel with the short edge portions. In either of the above cases, depending on how the board element is divided into at least two panels, if at all divided, the at least one groove in a panel may be parallel with long edge portions or short edge portions of the panel. 
     In operation of the method or a system configured to implement the method, the board element, such as the front side and/or the rear side, may be essentially parallel with a horizontal plane HP. The horizontal plane may extend in a direction parallel to the feeding direction F and in a lateral direction L. 
     During operation, the feeding direction F and/or the lateral direction L may be parallel with a first x and/or second y horizontal direction of the board element. The first and second horizontal directions may be perpendicular to each other. In a first example, the first and second horizontal directions extend in parallel with long edge portions and short edge portions of the board element, respectively. In a second example, the first and second horizontal directions extend in parallel with short edge portions and long edge portions of the board element, respectively. A vertical direction z of the board element may be perpendicular to the first and second horizontal directions. 
     The support member and/or the processing tool may be connected to a frame member. For example, the horizontal plane HP may be parallel to a supporting structure, such as a support floor, preferably being planar, on which the frame member is arranged during operation. The frame member may extend in a longitudinal direction X, a transverse direction Y, and a vertical direction Z. During operation, the feeding direction F of the board element may be parallel to the longitudinal direction X. Moreover, the lateral direction L may be parallel to the transverse direction Y during operation. For example, the longitudinal X and/or the transverse Y direction may be parallel to the supporting structure. An upward direction may be a direction parallel to the vertical direction Z of the frame member, such as directed away from the supporting structure. A downward direction may be a direction opposite to the upward direction. 
     It is emphasized that throughout this disclosure, any embodiment involving a board element may also be an embodiment involving a panel per se. It is noted, however, that the panel preferably comprises, or may be intended to comprise, a locking system. 
     The method may further comprise displacing the board element in a feeding direction, such as during the forming of the at least one groove. The board element may be displaced by a transportation device, such as a conveyor belt, at least one roller, etc., and/or by the support member. 
     The method may comprise arranging a receiving surface of the board element in contact with the support member, such as on the support member. 
     The receiving surface may be a front side of the board element, preferably facing downwards during the forming of the at least one groove. Thereby, the rear side may face upwards. Alternatively, the rear side may face downwards during the forming, the receiving surface preferably facing downwards. 
     The method may further comprise displacing the processing tool with respect to the support member during forming of the at least one groove, such as at least in a direction perpendicular to a feeding direction of the board element, the support member preferably being fixedly mounted in a frame member, and the direction preferably being parallel to a vertical direction of the frame member. The processing tool may be displaceably mounted in the frame member. Thereby, the processing tool may be displaced with respect to the board element. The processing tool may be displaced towards the support member in a first stage and away from the support member in a second, subsequent, stage. 
     By being fixedly mounted in the frame member, the support member may be fixed, such as in a direction perpendicular to a feeding direction, in particular during the forming of grooves. 
     The method may further comprise displacing the support member with respect to the processing tool during forming of the at least one groove, such as at least in a direction perpendicular to a feeding direction of the board element, the processing tool preferably being fixedly mounted in a frame member, and the direction preferably being parallel to a vertical direction of the frame member. The support member may be displaceably mounted in the frame member, such as being displaceable between a first position and a second position. 
     By being fixedly mounted in the frame member, the processing tool may be fixed, such as in a direction perpendicular to a feeding direction, in particular during the forming of grooves. It is clear, however, that the processing tool per se may comprise components that are displaceable; for example, it may comprise a rotating cutting device which may rotate during the forming of the grooves. 
     In some embodiments, the method comprises displacing the processing tool as well as the support member during forming of the at least one groove. 
     The processing tool may comprise or may be a rotating cutting device comprising a plurality of tooth elements configured to rotate around a rotational axis. 
     The rotating cutting device may comprise at least two cutting elements, preferably a plurality of cutting elements. A plurality of tooth elements may be arranged on each cutting element, preferably symmetrically. The cutting elements may be arranged on at least one shaft during the forming of the grooves. The rotational axis may coincide with one shaft axis. Each or any cutting element may be a cutting blade, preferably being circular. For example, adjacent cutting elements configured to form grooves in an individual floor panel, or a portion of a board element corresponding to an individual floor panel, may be separated by a distance of 0.5-20 mm, such as 3-9 mm, along the rotational axis. Moreover, a width of the cutting elements may be 2-5 mm, such as 3-4 mm. 
     The plurality of tooth elements may be provided in at least one set, such as a plurality of sets, around the rotational axis, each set comprising a plurality of tooth elements. The plurality of tooth elements of each set may be disposed along a joining curve, such as a straight line or, more generally, a non-linear curve. For example, the joining curve may follow a centre portion or outermost portion of the tooth elements. Preferably, such as when diameters d0 of the cutting elements are the same, the joining curve is provided in a surface of a right circular cylinder having the rotational axis as a centre axis. Moreover, when diameters d1, d2, . . . of the cutting elements are different, the joining curve is preferably provided in a surface of a cylinder having a varying radius and having the rotational axis as a centre axis. When projected from the surface of the cylinder, e.g. the right circular cylinder, onto a plane, the projected joining curve may be a monomial curve or a polynomial curve of order S, for example, P S (x)=a 0 +a 1  x+a 2  x 2 +a 3  x 3 + . . . +a S  x S , where a 0 , a 1 , a 2 , a 3 , . . . , as are constants any of which may be zero or non-zero. S may be any natural number S=0, 1, 2, 3, 4, 5, 6, . . . For example, the monomials P 1 (x)=a 1  x or P 2 (x)=a 2  x 2  may be used. Other joining curves are equally conceivable. For example, when projected from the surface of the cylinder onto a plane, the joining curve may be a stepwise constant curve, such as a sawtooth wave or a triangle wave or a square wave, or a Taylor series, such as a trigonometric function, e.g. sine or cosine. 
     Each set around the rotational axis may have the same type of joining curve. 
     In some embodiments, the tooth elements in a set of tooth elements may be angularly aligned along the rotational axis, thereby corresponding to a set of tooth elements disposed along a straight line. 
     A first tooth element may be angularly offset with respect to a second tooth element, such as along the rotation axis. 
     The first tooth element may be provided on a first cutting element and the second tooth element may be provided on a second cutting element. The first and second cutting elements may be provided along the rotational axis and preferably are spaced from each other. 
     The first and second tooth elements may be configured to rotate around the same rotational axis. The first tooth element may be angularly offset around the rotational axis with respect to the second tooth element. 
     Preferably, the first and second tooth elements are provided in the same set. 
     More generally, a plurality of tooth elements may be angularly offset around the rotational axis. The tooth elements may be provided in the same set. Moreover, each of the tooth elements may be provided on a respective cutting element. 
     In some embodiments, each of the tooth elements of a set may be angularly offset with respect to an adjacent tooth element in the set, such as two adjacent tooth elements. 
     The method may further comprise driving the board element in a lateral direction during forming of the at least one groove. The lateral direction may be parallel to a rotational axis of a rotating cutting device. 
     The board element may be driven towards an aligning element. The aligning element may be fixedly mounted in the frame member and/or the support member. The aligning element may be displaceably mounted in the frame member, such as when the support member is displaceably mounted in the frame member. Optionally, the aligning element may comprise a chamfer, preferably at a longitudinal end portion thereof, for laterally aligning the board element. 
     The board element may be provided between the aligning element and a blocking element. Thereby, a twisting of the board element may be counteracted. Optionally, the blocking element may comprise a chamfer, preferably at a longitudinal end portion thereof, for laterally aligning and/or guiding the board element. 
     The method may further comprise controlling a position, preferably a position in a lateral direction, of an aligning element and/or a blocking element. 
     In some embodiments, the aligning element may comprise roller members or wheels. Thereby, a friction between the aligning element and the board element may be reduced. 
     A cutting surface of at least one tooth element may be inclined. Thereby, the rotating cutting device may drive the board element in a lateral direction, such as towards an aligning element. Also, the removed material may be directed at least partly in a lateral direction. Preferably, at least a portion of the cutting surface is planar. Preferably, the cutting surface of each tooth element of a cutting element is inclined. 
     For example, the cutting surface may be inclined by having an inclined axial angle and/or an inclined top bevel angle. The axial angle may be inclined by 1°-70°, preferably 1°-25°, more preferably 1°-10°. The top bevel angle may comprise an inclined planar portion. Additionally, or alternatively, the cutting surface may be inclined by having an inclined rake angle, such as between −30° and +30°, preferably −20° and +20°, and more preferably −10° and +10°. 
     A shape and/or an inclination of a cutting surface of a first tooth element and a cutting surface of a second tooth element may be different. Preferably, the first and second tooth elements are provided on the same cutting element. 
     Any or each cutting surface of the first and second tooth elements or, more generally, of a plurality of tooth elements, may be configured to remove a different material shape and/or a different amount of material from the board element, for example by having a different width W and/or a different radial depth D. For example, the cutting surface may comprise a recess on at least one of its sides. Moreover, top surfaces of the cutting surfaces, such as top bevel angles, may be different. An advantage of these embodiments, is that a power consumption of the processing may be reduced and/or wear of the cutting elements may be reduced. In addition, a shape and/or size of the removed material, such as the shape and/or size of the chips, may be adjusted and, preferably, optimized. 
     The rotating cutting device may be configured to operate in an up-cut direction or a down-cut direction. The up cut may improve the control the board element during operation of the rotating cutting device. The down cut may provide a smoother cutting surface. Also, a power consumption of the rotating cutting device may be reduced. 
     The rotating cutting device may be a first rotating cutting device and the processing tool may further comprise a second rotating cutting device comprising a plurality of tooth elements configured to rotate around a rotational axis, the second rotating cutting device preferably being located downstream of the first rotating cutting device in a feeding direction. 
     Preferably, the rotational axes of the first and second rotating cutting devices are parallel. In some embodiments, the processing device comprises a plurality of rotating cutting devices, the rotational axes of the each preferably being parallel. It is emphasized that embodiments of the second rotating cutting device or of any individual rotating cutting device of the plurality of rotating cutting devices may be the same as any of the embodiments for the first rotating cutting device described above. 
     The first and second rotating cutting devices may both be configured to operate in the same direction, such as in an up-cut direction or in an down-cut direction. 
     The first and second rotating cutting devices may be configured to operate, such as rotate, in opposite directions. Thereby, cutting forces and/or feeding forces may be decreased. In a first embodiment, the first rotating cutting device may be configured to operate in a down-cut direction and the second rotating cutting device may be configured to operate in an up-cut direction. By means of the up cut, the board element may be better controlled during forming of the grooves. In a second embodiment, the first rotating cutting device may be configured to operate in an up-cut direction and the second rotating cutting device may be configured to operate in a down-cut direction. 
     A cutting element of the second rotating cutting device may be laterally offset, such as completely laterally offset, with respect to a cutting element of the first rotating cutting device. Thereby, the first and second rotating cutting devices may cut at least partly consecutively, whereby cutting forces may be more controlled. A cutting element of the first rotating cutting device at a lateral position corresponding to a lateral position of the cutting element of the second rotating cutting device may thereby be absent. 
     A cutting part of the second rotating cutting device may be aligned with a cutting part of the first rotating cutting device. Thereby, the grooves may be formed sequentially. Also, wear of the tooth elements may be decreased. At least one cutting element of the second rotating cutting device may be laterally aligned with respect to a corresponding number of cutting elements of the first rotating cutting device. 
     The first and second rotating cutting devices may comprise the same number of cutting elements and, optionally, all of them may be aligned. 
     The forming of at least one groove may comprise forming a first groove arrangement and forming a second groove arrangement. Each of the first and second groove arrangements may comprise at least one groove, preferably a plurality of grooves. 
     A groove of the first groove arrangement may be adjacent to at least one groove, preferably two grooves, of the first groove arrangement, such as in the first x and/or second y horizontal direction(s). A groove of the second groove arrangement may be adjacent to at least one groove, preferably two grooves, of the second groove arrangement, such as in the first and/or second horizontal direction(s). In other words, the grooves of each groove arrangement may be arranged together. 
     Grooves of the first and/or second groove arrangement(s), such as a longitudinal extension of the grooves, may be parallel to each other. 
     Generally, grooves of the respective first and second groove arrangement may have the same characteristics, such as cross sections, for example groove depths. The groove depths of the first and second groove arrangements may be different from each other. 
     Alternatively, or additionally, grooves of the first groove arrangement may have the same groove widths and/or grooves of the second groove arrangement may have the same groove widths. The groove widths of the first and second groove arrangements may be different from each other. 
     For example, the groove depths and/or groove widths of the first groove arrangement may be larger than the groove depths and/or groove widths of the second groove arrangement. 
     Generally herein, the groove depth of a groove may be a maximal groove depth, such as from a horizontal plane provided along the rear side to an innermost portion of the respective groove. Moreover, the groove width of a groove may be a maximal groove width. 
     More generally, the forming at least one groove may comprise forming a plurality of groove arrangements. Grooves of the each groove arrangement may have the same characteristics, such as cross sections, for example groove depths and/or groove widths. In some embodiments, the characteristics of at least two groove arrangements, such as all of them, may be different from each other. 
     The first groove arrangement may be spaced from the second groove arrangement in a first horizontal direction x and/or in a second horizontal direction y of the board element. 
     In one embodiment, the first and second groove arrangements each have groove depths and/or groove widths that are different from a groove depth and/or a groove width of a third groove arrangement. In a first example, the groove depths and/or the groove widths of the first and second groove arrangements are the same. In a second example, the groove depths and/or the groove widths of the first and second groove arrangements are different. The third groove arrangement may be disposed between the first and second groove arrangements, wherein the grooves of each of the first, second and third groove arrangements preferably extend in parallel with an edge portion of the board element or panel, preferably being a long edge portion, but may also be a short edge portion. 
     In examples, the groove depths of each of the first and second groove arrangements may be smaller than groove depths of the third groove arrangement, wherein the first and/or the second groove arrangement preferably is disposed adjacent to a respective edge portion, such as a long edge portion or a short edge portion, each optionally comprising a locking system. 
     The first and second groove arrangements may be at least partially, such as completely, formed by the same component of the processing tool, such as a single rotating cutting device. In a first example, the rotating cutting device may comprise cutting elements having the same diameter. In a second example, the rotating cutting device may comprise cutting elements having at least two different diameters. 
     In some embodiments, the groove depths of a plurality of grooves vary along the first x or the second y horizontal direction of the board element, such as along its long edge portions. Thereby, the indentation value and/or the balancing properties of the board element may be improved. A linking portion provided between or joining the grooves may be spaced from the rear side in a vertical direction z towards the front side. In a first example, the groove depths vary continuously such that substantially no portion of the grooves has a constant groove depth. In a second example, the groove depths of at least the end portions of the grooves vary continuously. Optionally, a centre portion of at least some of the grooves provided between the end portions may have a constant groove depth. 
     The processing tool may comprise a first and a second group of cutting elements, the first group and second group comprising cutting elements each having a first diameter and a second diameter, respectively, wherein the second diameter is different from the first diameter. The first and second diameters may be outer diameters of the respective cutting element. 
     The first groove arrangement may be at least partially, such as completely, formed by the first group of cutting elements and the second groove arrangement may be at least partially, such as completely, formed by the second group of cutting elements. Optionally, a third groove arrangement may be formed by a third group of cutting elements configured to rotate around the first or the second rotational axis. 
     The first and second groups of cutting elements may be configured to rotate around the same rotational axis. 
     The first and second groups of cutting elements may be configured to rotate around two different rotational axes, such as a first and a second rotational axis. 
     In a first example, the cutting elements of the first and/or the second group may be provided adjacent to each other, such as during forming of grooves. In a second example, at least some of the cutting elements of a group, such as the first or the second group, may be provided spaced from each other by at least one cutting element from a different group, such as the second or first group, respectively. 
     More generally, the rotating cutting device may comprise at least three groups of cutting elements, each group comprising cutting elements having the same diameter, and wherein the diameters of each of the different groups are different from each other. 
     The first groove arrangement may be formed at least partially, such as completely, by a first rotating cutting device and the second groove arrangement may be formed at least partially, such as completely, by a second rotating cutting device. 
     The first rotating cutting device may comprise cutting elements each having the same diameter, such as an outer diameter. 
     The second rotating cutting device may comprise cutting elements each having the same diameter, such as an outer diameter. 
     The first and/or the second rotating cutting device(s) may comprise cutting elements having at least two different diameters. 
     More generally, each or some of a plurality of groove arrangements may be spaced from each other in the first and/or second horizontal direction(s). Thereby, the balancing properties of the board element may be better controlled. 
     The method may further comprise counteracting, such as preventing, a displacement of the board element away from the support member during forming of the at least one groove. 
     For example, an undesired displacement of the board element may be counteracted. 
     The board element may be prevented to be displaced beyond a critical position, preferably along a direction being parallel with the vertical direction of the frame member. The critical position may be a position beyond which the board element is prevented to be displaced. 
     The counteracting, such as preventing, may comprise arranging at least a portion of the board element between an obstruction element and the support member. The critical position may be determined by a surface of the obstruction element, the surface preferably being configured to face the board element in operation. 
     The obstruction element may be mounted in the frame member and/or to the support member. 
     In operation, the obstruction element may be provided above or below the support member. 
     The obstruction element may have a constant profile, for example a constant thickness, such as along a longitudinal direction X. 
     The obstruction element may have a varying profile, such as a varying thickness, along a longitudinal direction X, preferably being parallel to a feeding direction F of the board element, and optionally comprising a chamfer on at least one side of the obstruction element along the longitudinal direction. Preferably, at least one chamfer is configured to face an incoming board element. Thereby, the board element may be guided and/or aligned between the obstruction element and the support member in an improved manner. Also, a friction between the obstruction element and the board element may be reduced, e.g. since a contact surface between them may be reduced. 
     The varying profile of the obstruction element may be configured to face the board element in operation. 
     The counteracting, such as preventing, may comprise adjusting a distance, such a vertical distance Z 1 , between the obstruction element and the support member. Hence, a pressure exerted by the obstruction element and/or the support member on the board element may be adjusted. 
     The portion of the board element may engage with the obstruction element and the support member during forming of the at least one groove, preferably by a pressured engagement, such as a pretensioned engagement. The system may comprise a pressure member, such as a resilient member, for providing the pressured engagement, such as the pretensioned engagement. 
     The forming of the at least one groove may comprise arranging a portion of the processing tool through at least one slot in the obstruction element. Thereby, the board element may be processed while counteracting the displacement of the board element. The number of slots may be correspond at least to the number of grooves to be formed and/or to the number of cutting elements of a rotating cutting device. 
     The at least one slot may be closed or open, such as open towards one lateral side of the obstruction element. 
     The method may further comprise forming the at least one slot by the processing tool. 
     Thereby, the slots and the grooves may be formed by the same processing tool, for example during a single operation thereof. Thereafter, the obstruction element with the formed slot(s) may be reused. 
     It is clear that in embodiments where cutting elements are configured to rotate around two or more different rotational axes, there may be one respective obstruction element for each rotational axis. In some embodiments, however, there is no counteracting of a displacement of the board element. For example, the obstruction element may be missing. 
     An extension of any, some, or each of the formed at least one groove may be larger along the first horizontal direction x than along the second horizontal direction y of the board element, the first horizontal direction preferably being parallel to a feeding direction of the board element during operation. 
     A depth of any, some, or each of the at least one groove may be at least 0.2, such as at least 0.3, preferably at least 0.4, times a thickness of the board element. 
     After forming the grooves, an area of a rear side of the board element may be less than 90%, such as less than 80%, preferably less than 70%, of an area of a front side of the board element. 
     The forming of any, some or each of the at least one groove may comprise forming a first groove profile and, thereafter, a second groove profile, the second groove profile having a larger cross-sectional area than the first groove profile. The first and/or the second groove profile(s) may extend at least along a longitudinal portion of the groove which is to be formed. In a first example, the first and second groove profiles are formed by the same component of the processing device, such as a rotating cutting device. In a second example, the first and second groove profiles are formed by different components of the processing device, such as a first and a second rotating cutting device, respectively. 
     The first groove profile of a groove may correspond to a portion of a final groove profile. In a first example, the second groove profile of a groove may correspond to a final groove profile of the groove. In a second example, the second groove profile of a groove may correspond to a portion of the final groove profile. The method may comprise forming a third groove profile after forming the second groove profile, the third groove profile having a larger cross-sectional area than the second groove profile. The third groove profile may correspond to a final groove profile of the groove or, alternatively, the third groove profile may correspond to a portion of the final groove profile and the method may comprise forming of at least one additional groove profile; the last one of these groove profiles may correspond to a final groove profile of the groove. 
     The first and second groove profiles may have different shapes. For example, the width and/or the depth of the groove profiles may be different. 
     The first and/or second groove profile(s) may comprise one bevel or two bevels, each preferably being disposed between a respective groove wall and the rear side. 
     A shape of each of the first and second groove profiles may correspond to a shape of a corresponding tooth element. Thereby, a tooth element may comprise one tooth bevel or two tooth bevels. 
     Any, some or each of the at least one groove, such as a plurality of grooves, may be formed in an interior of the rear side being spaced from a pair of opposite edge portions, such as opposite short edge portions, of the board element, preferably being spaced from all edge portions of the board element. Here, any of the edge portions may be an outermost edge portion of the board element. Alternatively, or additionally, the at least one groove may be spaced from a locking system at a pair of opposite edge portions, such as opposite short edge portions, of the board element, preferably being spaced from locking system at all edge portions. 
     In some embodiments, the at least one groove, preferably a plurality of grooves, may extend to at least one edge portion of a pair of opposite edge portions, such as opposite short edge portions, of the board element. 
     The forming of the at least one groove may comprise forming at least two grooves having different lengths along a feeding direction F of the board element. Thereby, grooves having different lengths along the first and/or the second horizontal direction(s) of the board element (or panel) may be formed. Preferably, the grooves at least partially overlap along the first and/or the second horizontal direction(s) of the board element. 
     End portions of the grooves, preferably longitudinal end portions of the grooves, may be disposed along a joining curve, such as a straight curve or a non-linear curve. For example, the joining curve may follow an outermost portion of the grooves. In a first example, the joining curve may be a monomial curve or a polynomial curve of order N, for example, Q N (x)=b 0 +b 1  x+b 2  x 2 +b 3  x 3 + . . . +b N  x N , where b 0 , b 1 , b 2 , b 3 , . . . , b 1  are constants any of which may be zero or non-zero. N may be any natural number N=0, 1, 2, 3, 4, 5, 6, . . . . For example, the monomials Q 1 (x)=b 1  x or Q 2 (x)=b 2  x 2  may be used. In a second example, the joining curve may be a stepwise constant curve, such as a sawtooth wave or a triangle wave or a square wave. In a third example, the joining curve may correspond to a Taylor series, such as a trigonometric function, e.g. sine or cosine. 
     The method may further comprise collecting the removed material, such as at least from the board element and/or the support member, preferably by suction and/or blowing, and preferably during a displacement of the board element. 
     The method may further comprise feeding the removed material created from the forming at least one groove into a container element, such as a cyclone. Thereby, at least parts of the removed material may be collected and, optionally, recycled. 
     The method may further comprise separating the removed material into a first and a second group of material elements, a characteristic of material elements of the first group being different from a corresponding characteristic of material elements of the second group, the characteristic preferably being at least one selected from the group of a material composition of the material elements, a size of the material elements, a weight of the material, a shape of the material, and a density of the material. 
     The separation may be implemented by a material separating device. The separating may be a cyclonic separation. For example, a cyclone may be utilized. 
     The characteristic of the material elements may be determined based on an ensemble of material elements or based on individual material elements. 
     The material elements may comprise, or may be, chips, particles, dust particles, etc. from the removed material. A dust particle may have a maximal extension of 0.1 mm. For example, chips and particles may be separated from the dust particles. In a first example, any, some or each of the size, the weight or the density of the material elements may be an average size, average weight, or an average density of the material elements. The shape may be an approximate shape. In a second example, any, some or each of the size, the weight or the density of the material elements may be a maximal size, a maximal weight, or a maximal density of the material elements. 
     The processing tool may be at least partially enclosed by an enclosure element. 
     The enclosure element may comprise at least one orifice. The orifices may be air inlets and/or air outlets. For example, enclosure element may comprise a housing and the obstruction element, wherein the orifice(s) may correspond to the slot(s) of the obstruction element. The material separation device may be connected to the enclosure element. 
     The board element may be a panel. It is again emphasized that any of the embodiments of the board element described herein thereby is equally valid for the panel, such as layer structure and material compositions. For instance, the grooves of a panel may correspond to grooves of a portion of the board element. It is noted, however, that the panel preferably comprises, or is intended to comprise, a locking system. 
     The panel may be part of a board element that has been divided into at least two panels. 
     Moreover, the panel may be adapted to be installed on a substructure, such as in the case of a floor, ceiling or wall panel, or it may be a furniture panel or building panel. The panel may be a panel with or without a locking system, such as a mechanical locking system. For example, the locking system may be formed or provided in the panel before, during or after forming the grooves therein. 
     The method may further comprise dividing the board element into at least two panels, such as by sawing, cutting or breaking. The board element may be a dividable slab. In a first example, the dividing is performed after forming the at least one groove. In a second example, the dividing is performed before forming the at least one groove. In a third example, the at least one groove is formed at least partially at the same time as the dividing. 
     The board element may be divided along the first and/or second horizontal direction(s) of the board element. In a first example, the dividing is performed in parallel with a longitudinal extension of the at least one groove. In a second example, the dividing is performed transversely to the longitudinal extension of the at least one groove. In a third example, the dividing is performed in parallel with and transversely to the longitudinal extension of the at least one groove. 
     The dividing of the board element may comprise forming at least one notch in the board element. Thereby, the dividing may be simplified. The at least one notch may be formed in a front side of the board element, but may alternatively be formed in the rear side. The at least one notch may be formed along the feeding direction of the board element. For example, the notch may be formed after extrusion or calendaring of the board element, preferably while the board element has a temperature exceeding a critical temperature. 
     The method may further comprise forming at least one functional groove in the board element, preferably in the rear side. The functional groove may be configured to perform a function. For example, the at least one functional groove may be at least one guiding groove. Generally, it may assist in controlling the board element during various processing or treatment acts of the board element. For example, it may assist in guiding the dividing of the board element, guiding the board element when providing a layer on the board element, such as a backing layer, or guiding the board element when providing a locking system therein. 
     The functional groove may be positioned at a predetermined distance from an edge portion, such as an outermost edge portion. By way of example, the position of the functional groove may be more exact than positions of the grooves. Thereby, the associated function may be implemented in a more secure manner. 
     The method may further comprise controlling a processing or treatment of the board element, such as the dividing, by providing a guiding element in the at least one functional groove of the board element. Thereby, the dividing process may be better controlled. At the same time, due to the functional groove, material may be saved. 
     The at least one functional groove may extend to at least one edge of the board element, preferably to each of a pair of opposite edges. In some embodiments, however, the at least one functional groove may be provided in an interior of the rear side, thereby being spaced from each of a pair of opposite edge portions, preferably all edge portions of the board element. 
     The guiding element may be resilient, such as in a vertical direction Z. 
     The at least one functional groove may be formed in the board element before, during, or after forming the grooves. For example, at least one functional groove may be formed in the board element after an extrusion or calendering of, at least portions of, the board element. 
     The at least one functional groove may be a calibrating groove. A calibrating groove may facilitate locking of the panels, such as when the panels have diverging thicknesses or when no underlay element, such as a foam, is used. The calibration groove may be embodied as described in WO 2014/182215, page 2, lines 13-22, the disclosure of which is hereby expressly incorporated by reference in its entirety. 
     The method may further comprise forming a locking system on at least one edge portion of the panel or the at least two panels, preferably on two opposite edge portions thereof. The method may further comprise forming a locking system on a first pair and a second pair of opposite edge portions of the panel or the at least two panels, the first pair preferably comprising long edge portions of the panel or the at least two panels and the second pair preferably comprising short edge portions thereof. The locking system may comprise a horizontal locking system and/or a vertical locking system, the horizontal locking system preferably being integrally formed with each panel. 
     In some embodiments, such as when the panel is a floor panel, the panel may be configured to be installed in a floating floor system. In some embodiments, no horizontal or vertical mechanical locking system may be formed in the panel. For example, the panels may be configured to be nailed or glued to a subfloor. In another example, the panels may be configured to be installed loosely on a subfloor without any mechanical locking system, optionally being interconnectable by separate connecting elements, such as adhesive strips. 
     In some embodiments, the wall panels may comprise a locking system comprising a tongue and groove configuration and/or separate clips, optionally being connectable to a wall substructure, such as a rail. 
     The vertical locking system may be integrally formed with the panel. Alternatively, the locking system may be configured to comprise a separate locking tongue for vertical locking. Optionally, the method may further comprise: forming a displacement groove in an edge of the panel or the at least two panels, and providing the separate locking tongue in the displacement groove. 
     The forming of the at least one groove may comprise carving or scraping the board element. The processing tool may comprise a carving tool or a scraping tool. 
     The forming of the at least one groove may comprise drilling or milling the board element. 
     The processing tool may comprise a drilling tool or a milling tool. 
     The board element may comprise at least one layer, wherein any layer, some layers, or each layer preferably comprises a thermoplastic material and, optionally, a filler. The filler may be a functional filler and/or an extender. One layer of the at least one layer may be a core layer. 
     The method may comprise forming the at least one groove in any layer or some layers, or in each layer of the at least one layers. 
     The filler of any layer may be a mineral material, such as calcium carbonate (CaCO 3 ) or stone material, such as stone powder, or similarly. Alternatively, or additionally, an organic material, such as organic fibers, e.g. wood flour or rice husks, or a clay material, such as kaolin, are feasible. It is noted that calcium carbonate may be provided in the form of chalk, limestone or marble. For example, the amount of filler in the board element, such as in any layer (such as a layer the grooves are being formed in), may be 20-85 wt %, such as 40-80 wt %. 
     The thermoplastic material of any layer, some layers, or all layers may be or may comprise polyvinyl chloride (PVC). Alternatively, or additionally, the thermoplastic material of any layer, some layers, or all layers may be or may comprise PE, PP, PET or ABS. Optionally, each layer, some layers, or any layer may comprise a plasticizer and/or additives and/or pigments. For example, the amount of thermoplastic in the board element, such as in any layer (such as a layer the grooves are being formed in), may be 20-85 wt %, such as 40-80 wt %. 
     The board element may comprise at least two layers. The at least two layers may be laminated together or bonded together by an adhesive. One layer may be a core layer and other layer(s) may be a decorative layer and/or a wear layer. Optionally, the board element may further comprise a backing layer and/or a cover layer. The backing layer may be a balancing layer. Moreover, the cover layer may cover the grooves. The cover layer may be an insulation layer, and may impact the thermal and/or sound properties of the board element. Alternatively, or additionally, the cover layer may be configured to compensate for uneven surface portions of a substructure, such as a subfloor, on which the panel or board element is to be installed. For example, the cover layer may be a flexible layer, such as a foam layer. In non-restrictive examples, the cover layer may comprise an irradiated cross-linked polyethylene (IXPE) foam, Ethylene Vinyl Acetate (EVA) foam, foam rubber, cork, a natural material, or Polyurethane (PU) foam. 
     More generally, the board element may comprise at least three layers. The at least three layers may be laminated together or bonded together by an adhesive. One layer may be a core layer, one layer may be a decorative layer, and one layer may be a wear layer. 
     Optionally, the board element may further comprise a backing layer and/or a cover layer. 
     Optionally, a finish layer may be provided on the at least one the layer. For example, the finish layer comprise a lacquer, which may be curable by ultra-violet radiation (UV) or by an electron beam (EB). The finish layer may be a water based lacquer. Optionally, the finish layer may comprise PU. 
     The forming at least one groove may comprise forming a first portion of the at least one groove in a first layer and, thereafter, forming a second portion of the at least one groove in the first layer and/or in a second layer. 
     The first portion may be formed in the first layer only, and the second portion may be formed in the second layer only. Thereby, the removed material of first and the second layer may be easily separated. This may be advantageous when the materials of the first and second layers are different and e.g. need to be recycled separately. For example, the first and second layers may comprise different material compositions, such as different amounts of thermoplastic material, fillers, plasticizers, additives, pigments, etc. 
     More generally, the method may comprise consecutively forming a portion of the at least one groove in a plurality of layers in analogy with the discussion above, i.e. first forming in a first layer, then forming in a second layer, then forming in a third layer, etc. 
     The board element may comprise at least one reinforcement layer, such as at least one glass fibre layer. The forming the at least one groove may comprise removing at least a portion of the at least one reinforcement layer. The removed portions may correspond to at least one opening of the at least one reinforcement layer, preferably fully penetrating the reinforcement layer. 
     The method may further comprise controlling a penetration depth of the processing tool such that the at least one reinforcement layer is left unprocessed. Thereby, wear of the processing tool may be reduced. Moreover, a function of the at least one reinforcement layer may remain intact. 
     The method may further comprise extruding and/or calendering at least one layer, each preferably comprising thermoplastic material, for forming the board element. The method may comprise coextruding at least two layers, each preferably comprising thermoplastic material, for forming the board element. 
     It is noted that the steps of the method in accordance with any of the embodiments and examples above do not have to be performed in the exact order disclosed above. 
     According to a second aspect of the inventive concept, there is provided a panel obtainable by a method according to the first aspect. For example, the board element in the method according to the first aspect may be a panel. 
     Embodiments and examples of the panel in accordance with the second aspect are largely analogous to those of the first, third and fourth aspects, wherein reference is made thereto. 
     Further embodiments are provided in an embodiment section below. 
     According to a third aspect of the inventive concept, there is provided a system for forming grooves in a board element. The system comprises a frame member, a support member for supporting the board element during the forming, and a processing tool. 
     Embodiments and examples of the system in accordance with the third aspect are largely analogous to those of the first, second, and fourth aspects, wherein reference is made thereto. In fact, some embodiments of the system in accordance with the third aspect have been described in under the first aspect. Further embodiments are provided in an embodiment section below. In addition, the following embodiments are conceivable. 
     The system may further comprise a transportation device adapted to displace the board element in a feeding direction F. Optionally, the transportation device may comprise the support member. 
     The support member may be displaceably mounted in the frame member, such as being displaceable at least in a direction perpendicular to a feeding direction of the board element. Alternatively, or additionally, the support member may be fixedly mounted in the frame member. 
     The processing tool may be displaceably mounted in the frame member, such as being displaceable at least in a direction perpendicular to a feeding direction of the board element. Alternatively, or additionally, the processing tool may be fixedly mounted in the frame member. 
     The processing tool may comprise or may be a rotating cutting device comprising a plurality of tooth elements configured to rotate around a rotational axis. 
     The rotating cutting device may comprise at least two cutting elements, preferably a plurality of cutting elements. 
     A first tooth element may be angularly offset around the rotational axis with respect to a second tooth element. 
     A cutting surface of at least one tooth element may be inclined, such as 1°-70°, preferably 10°-55°, more preferably 15°-25°. 
     A shape and/or an inclination of a cutting surface of a first tooth element and a cutting surface of a second tooth element may be different. 
     The rotating cutting device may be configured to operate in an up-cut direction or a down-cut direction. 
     The rotating cutting device may be a first rotating cutting device and the processing tool may further comprise a second rotating cutting device comprising a plurality of tooth elements configured to rotate around a rotational axis, the second rotating cutting device preferably being located downstream of the first rotating cutting device in a feeding direction F. 
     The first rotating cutting device may be configured to operate in a down-cut direction and the second rotating cutting device may be configured to operate in an up-cut direction. 
     Clearly, the other combinations described above are equally conceivable. 
     A cutting element of the second rotating cutting device may be laterally offset with respect to a cutting element of the first rotating cutting device. 
     At least one cutting element of the second rotating cutting device may be laterally aligned with respect to a corresponding number of cutting elements of the first rotating cutting device. 
     The first rotating cutting device may comprise cutting elements each having the same diameter and/or the second rotating cutting device may comprise cutting elements each having the same diameter. 
     At least one of the first and second rotating cutting devices may comprise cutting elements having at least two different diameters. 
     The system may further comprise an aligning element, optionally comprising a chamfer, for example at a longitudinal end portion thereof. Moreover, the system may further comprise a blocking element, wherein the board element is configured to be provided between the aligning element and the blocking element, the blocking element optionally comprising a chamfer, for example at a longitudinal end portion thereof. 
     The system may further comprise an obstruction element configured to counteract, such as prevent, a displacement of the board element away from the support member. 
     The obstruction element may have a varying profile, such as a varying thickness, along a longitudinal direction X, preferably being parallel to a feeding direction F of the board element, optionally comprising a chamfer on at least one side of the obstruction element along the longitudinal direction. 
     A portion of the processing tool may be configured to be arranged through at least one slot in the obstruction element. The at least one slot may be closed or open, such as open towards one lateral side of the obstruction element. 
     The system may further comprise a pressure member, optionally being a resilient member, configured to exert pressure on, such as providing a pretensioned engagement against, the board element. The pressure member may be connected to the frame member. 
     The pressure member may comprise the obstruction element and/or the support member. 
     Thereby, the obstruction element and/or the support member may exert pressure on the board element. The pressure member may comprise at least one actuator element configured to displace the obstruction element and/or the support member in at least in a direction perpendicular to a feeding direction of the board element, wherein the direction preferably is parallel to a vertical direction of a frame member. 
     When the pressure member is embodied as a resilient member, it may comprise at least one resilient element, such as a spring element. The resilient member may comprise the obstruction element and/or the support member. Thereby, the obstruction element and/or the support member may be pretensioned against the board element. The resilient member may comprise a resilient covering. For example, the resilient covering may be provided on the support member and/or on the obstruction element. 
     The system may further comprise a material collecting device, such as a suction device and/or a blowing device, for collecting the removed material. The system may further comprise a material separating device and/or an enclosure element. 
     The system may further comprise a board dividing device configured to divide a board element into at least two panels. The board dividing device, or a separate notching apparatus, may be configured to provide notches in the board element as described above. 
     The system may further comprise a guiding element for controlling the dividing of the board element. 
     The system may further comprise a locking system unit configured to form a locking system on at least one edge portion of a panel or at least two panels, preferably on two opposite edge portions thereof. 
     The processing tool may comprise a carving tool or a scraping tool. The carving tool or scraping tool may comprise at least one tooth element, preferably being provided in a tooth holder. In a first example, the tooth holder is fixedly mounted in the frame member. In a second example, the tooth holder comprises at least two tooth units and is configured to rotate intermittently between the tooth units. In a third example, which optionally may be combined with the second example, the tooth holder is displaceably mounted in the frame member. 
     The processing tool may comprise a drilling tool or a milling tool. 
     According to a fourth aspect of the inventive concept, there is provided a panel comprising at least one layer. The panel comprises at least one groove in a rear side of the panel, preferably a plurality of grooves. 
     Embodiments and examples of the panel in accordance with the fourth aspect are largely analogous to those of the first, second, and third aspects, wherein reference is made to the above. Further embodiments are provided in an embodiment section below. In addition, the following embodiments are conceivable. 
     The at least one groove may comprise one bevel or two bevels, each preferably being disposed between a respective groove wall and the rear side. Any or both bevels may be at least partly planar or rounded. Each groove of the at least one groove may comprise such a bevel or bevels. 
     A groove profile, preferably a cross-sectional groove profile, of a groove may comprise the bevel or bevels. 
     The at least one groove may comprise a first groove arrangement and a second groove arrangement, each of the first and second groove arrangements comprising at least one groove, preferably a plurality of grooves. Generally, grooves of the first and/or second groove arrangement(s) may have the same characteristics, such as cross sections. More details of embodiments have been described in relation to the first aspect. 
     Generally herein, the cross sections may include groove depths and/or groove widths. 
     Grooves of the first groove arrangement may have the same groove depths and grooves of the second groove arrangement may have the same groove depths, wherein groove depths of the first and second groove arrangements are different from each other. 
     The first groove arrangement may be spaced from the second groove arrangement in a first horizontal direction x and/or in a second horizontal direction y of the panel. 
     The at least one groove may comprise a third groove arrangement comprising at least one groove, preferably a plurality of grooves, the first and second groove arrangements each having characteristics, such as groove depths and/or groove widths, that are different from characteristics, such as groove depths and/or groove widths, of the third groove arrangement, the third groove arrangement preferably being disposed between the first and second groove arrangements, and wherein the grooves of each of the first, second and third groove arrangements preferably extend in parallel with an edge portion of the panel, preferably being a long edge portion. 
     The groove depths of each of the first and second groove arrangements may be smaller than groove depths of the third groove arrangement, wherein the first and/or the second groove arrangement(s) preferably is disposed adjacent to a respective edge portion, such as a long edge portion or a short edge portion, each optionally comprising a locking system. 
     The panel may comprise at least two grooves, wherein at least one pair of grooves are provided in an offset relation in a first x and/or a second y horizontal direction of the panel. 
     The at least one groove may be provided in an interior of the rear side being spaced from a pair of opposite edge portions, such as opposite short edge portions, of the panel, preferably being spaced from all edge portions of the panel. 
     The at least one groove may extend to at least one edge portion of a pair of opposite edge portions, such as opposite short edge portions, of the panel. 
     The at least one groove may comprise at least two grooves having different lengths along the first x and/or second y horizontal direction(s) of the panel. Preferably, the longitudinal lengths of the at least one groove are different. 
     End portions of the grooves, preferably longitudinal end portions of the grooves, may be disposed along a joining curve, such as a straight curve or a non-linear curve. The joining curve may be a monomial curve or a polynomial curve of order N, where N is any natural number N=0, 1, 2, 3, 4, 5, 6, . . . , wherein the joining curve is a stepwise constant curve, such as a sawtooth wave or a triangle wave or a square wave, or wherein the joining curve corresponds to a Taylor series, such as a trigonometric function, e.g. sine or cosine. 
     The panel may comprise at least a first layer and a second layer, such as a plurality of layers, for example comprising a core layer, a decorative layer and/or a wear layer. 
     The panel may further comprise a backing layer and/or a cover layer. 
     At least two layers may be laminated together or bonded together by an adhesive. 
     The at least one groove may be provided in the first layer only. More specifically, any, some or each groove may be provided in the first layer only. For example, the grooves may completely penetrate the first layer. 
     The at least one groove may be provided in the first and second layers only. More specifically, any, some or each groove may be provided in the first and second layers only. 
     For example, the grooves may completely penetrate the first and second layers. 
     The panel may comprise at least one reinforcement layer. The at least one reinforcement layer may comprises at least one opening. 
     Any layer, some layers, or each layer may comprise a thermoplastic material, such as PVC, PE, PP, PET or ABS and, optionally, a filler, such as a mineral material, such as calcium carbonate or stone material, such as stone powder. Each layer, some layers, or any layer of the at least one layer may comprise a plasticizer and/or additives and/or pigments. Other conceivable alternatives and combinations of the layer compositions are described under the first aspect. 
     Any layer, some layers or each layer may be calendered or extruded, such as coextruded, each of the calendered or extruded layer preferably comprising a thermoplastic material, such as PVC, and optionally a filler. 
     The panel may further comprise a locking system on a first pair and a second pair of opposite edge portions of the panel, the first pair preferably comprising long edge portions of the panel and the second pair preferably comprising short edge portions thereof. 
     Preferably, the at least one groove is provided inwardly of the locking system on the first and/or second pair. 
     The at least one groove may have a substantially vertical groove wall. For example, such grooves may be formed by drilling or milling. 
     Further aspects of the inventive concept and embodiments and examples of each of the first, second, third and fourth aspects are provided in an embodiment section below. It is emphasized that the embodiments and examples of any aspect may be combined with embodiments and examples of any other aspect. 
     Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to “a/an/the [element, device, component, means, step, etc]” are to be interpreted openly as referring to at least one instance of said element, device, component, means, step, etc., unless explicitly stated otherwise. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will in the following be described in connection to exemplary embodiments and in greater detail with reference to the appended exemplary drawings, wherein: 
         FIG. 1  illustrates in a perspective view an embodiment of a system for forming grooves in a board element. 
         FIGS. 2 a -2 g    illustrate in a perspective view, top views, a side view, and a cross-sectional top view embodiments of a system for forming grooves in a board element and embodiments of cutting elements. 
         FIGS. 3 a -3 h    illustrate in perspective views and a side view embodiments of a system for forming grooves in a board element and embodiments of cutting elements. 
         FIGS. 4 a -4 e    illustrate in a perspective view and a front view embodiments of a cutting element and in perspective views and a side view embodiments of a system for forming grooves in a board element. 
         FIGS. 5 a -5 g    illustrate in perspective views, top views and a side view embodiments of a system for forming grooves in a board element. 
         FIGS. 6 a -6 g    illustrate in perspective views, top views and a side view embodiments of a system for forming grooves in a board element. 
         FIGS. 7 a -7 h    illustrate in perspective views, a zoomed-in perspective view, a cross-sectional side view, front views and side views embodiments of a system for forming grooves in a board element, embodiments of forming such grooves, and embodiments of tooth elements. 
         FIGS. 8 a -8 f    illustrate side views of embodiments of a system for forming grooves in a board element. 
         FIGS. 9 a -9 h    illustrate side views of embodiments of an obstruction element. 
         FIGS. 10 a -10 e    illustrate in a perspective view and side views embodiments of a system for forming grooves in a board element comprising a pressure member, such as a resilient member, and in a front view and a cross-sectional perspective view embodiments of a material collecting device. 
         FIG. 11  is a flow chart illustrating a method for forming grooves in a board element according to an embodiment. 
         FIGS. 12 a -12 k    illustrate perspective views and side views of embodiments of dividing of the board element into panels and in side views embodiments of a functional groove. 
         FIGS. 13 a -13 d    illustrate in cross-sectional side views embodiments of a board element and a panel. 
         FIGS. 14 a -14 g    illustrate a side view, bottom views and cross-sectional side views of embodiments of a panel. 
         FIGS. 15 a -15 k    illustrate bottom views of embodiments of a panel. 
         FIGS. 16 a -16 d    illustrate in a perspective view, a top view, a zoomed-in perspective view embodiments of a system for forming grooves in a board element and in a perspective view an embodiment of an obstruction element. 
         FIG. 16 e    illustrates a cross-sectional side view of an embodiment of a panel. 
         FIGS. 16 f -16 g    illustrate embodiments of an obstruction element in side views. 
         FIGS. 17 a -17 c    illustrate in a side view, a perspective view and a top view embodiments of a system and components thereof for forming grooves in a board element. 
         FIGS. 17 d -17 e    illustrate embodiments of a panel in bottom views. 
         FIGS. 18 a -18 b    illustrate in a perspective view and a side view an embodiment of a processing tool comprising a carving or scraping tool. 
         FIGS. 18 c -18 e    illustrate an embodiment of a panel in a side view, a bottom view and a zoomed-in side view an embodiment of a panel. 
         FIGS. 18 f -18 g    illustrate an embodiment of an asymmetric cutting element and an embodiment of a dividing of a board element into panels in a bottom view. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1, 2   a - 2   g ,  3   a - 3   h ,  4   a - 4   e ,  5   a - 5   g ,  6   a - 6   g ,  7   a - 7   h ,  8   a - 8   f ,  9   a - 9   h ,  10   a - 10   e ,  16   a - 16   d ,  16   f - 16   g ,  17   a - 17   c ,  18   a - 18   c  and  18   f  illustrate embodiments of a system  100  for forming grooves  10  in a board element  200 . The system is capable of implementing a method for forming grooves in the board element. 
     The system  100  comprises a frame member  110 , a support member  120  for supporting the board element  200  during the forming, and a processing tool  130 . The system preferably further comprises a transportation device  140  adapted to displace the board element in a feeding direction F towards the support member and/or processing tool. For example, a feeding speed may be 0.5-350 m/min, such as 20-130 m/min. 
     In the perspective view in  FIG. 1  the frame member  110  is shown only schematically by a broken line, but it is understood that the support member and/or the processing tool may be connected thereto. The frame member extends in a longitudinal direction X, a transverse direction Y, and a vertical direction Z. 
     The support member  120  may comprise at least one roller  122 . Each roller is configured to rotate and may thereby displace the board element during the forming of grooves. It is understood that other support members are equally conceivable, such as a conveyor belt, a plate, etc. Preferably, the support member is fixedly mounted in the frame member and may be fixed at least in the vertical direction Z of the frame member. 
     Grooves  10  may be formed in a board element  200  arranged in contact with the support member  120  by the processing tool  130 , e.g. by displacing a rotating cutting device  131  with respect to the support member. The displacement may be controlled by a control unit  186 . 
     The transportation device  140  may comprise a first  142  and/or a second  144  roller arrangement, and optionally parts of the support member, such as the at least one roller  122 . Preferably, and as shown in e.g.  FIG. 1 , the first  142  and second  144  roller arrangements are provided upstream and downstream of the support member, respectively, along the feeding direction F. Each of the first  142  and second  144  roller arrangements may comprise at least one roller  141 ,  143 , configured to be provided above and/or below the board element  200  during operation. At least one roller  122 ,  141 ,  143  may be driving. For example, a shaft  121 ,  145  of a driving roller may be driven by means of a motor, e.g. via a gearwheel configuration  146  of the driving roller (cf.  FIG. 4 c   ). It is understood that other embodiments of the transportation device are equally conceivable, such as at least one conveyor belt and/or any combination with the support member or roller arrangements. 
     Components of the transportation device  140 , such as the first  142  and/or a second  144  roller arrangement(s), may be configured to position the board element  200 , such as in the vertical direction Z. 
     The support member  120  and the processing device  130  may overlap along the longitudinal direction X, as shown in e.g.  FIG. 1 . In some embodiments (not shown), however, the support member and the processing device may be spaced along the longitudinal direction X. For example, the support member may comprise components of the transportation device  140 , such as the first  142  and/or a second  144  roller arrangement(s). 
     The processing tool  130  is configured to remove material  80 , such as chips. In  FIGS. 1 and 2   a - g  the processing tool comprises a rotating cutting device  131  comprising at least two cutting elements  132 , preferably a plurality of cutting elements, arranged on a shaft  150  configured to rotate around a rotational axis A 1 . The rotational axis A 1  and the transverse direction Y may be essentially parallel. The shaft  150  may be driven by any method known in the art, such as by a motor. The cutting elements may be circular cutting blades or saw blades, such as diamond cutting blades or hardened saw blades, preferably comprising tooth elements comprising hardened tooth elements. For example, the hardened saw blades may be carbide saw blades comprising tooth elements comprising cemented carbide. A plurality of tooth elements  133  are arranged on each cutting element  132 , see e.g.  FIG. 2 e   . The rotating cutting device  131  is displaceably mounted in the frame member  110 , since it is displaceable at least in the vertical direction Z, such as downwards and/or upwards, with respect to the frame member  110  and/or the support member  120  between a first and a second position (see arrow B 1 ). The rotating cutting device  131  may be a jumping tool. 
     A diameter d0 of each cutting element may be 50-400 mm, such as 100-200 mm. Moreover, a rotation speed may be 1000-12000 rpm, such as 2000-6000 rpm, preferably 3000-4500 rpm. For example, a cutting element having a diameter of 100-200 mm, such as 150 mm, may be rotated at a rotation speed of 2000-6000 rpm, such as 3000-4500 rpm. 
     Generally, the rotating cutting device may operate in an up-cut direction R 1  or a down-cut direction R 2 , but  FIGS. 1 and 2   a - 2   g  illustrate the former operation.  FIGS. 2 e -2 f    illustrate a cutting direction CD which is parallel to the feeding direction F during operation of the system  100 . Generally, in the up cut, the cutting direction CD and the feeding direction F of the board element may be opposite. Moreover, in the down cut, the cutting direction CD of the rotating cutting device and the feeding direction F of the board element may be the same. 
     The system  100  may further comprise an aligning element  160 , preferably fixedly mounted in the frame member  110 . Optionally, the aligning element may comprise a chamfer  161 , preferably at a longitudinal end portion  164  thereof, for laterally aligning the board element  200 , cf.  FIGS. 2 b   - 2   c.    
     The system  100  may further comprise a blocking element  162 , preferably fixedly mounted in the frame member  110 . In operation, the board element may be provided between the aligning element  160  and the blocking element  162 , such as during forming of the grooves  10 . Optionally, the blocking element may comprise a chamfer  163 , preferably at a longitudinal end portion  165  thereof, for laterally aligning and/or guiding the board element  200 , cf.  FIGS. 2 b   - c.    
     In some embodiments, a position, preferably a position in a lateral direction L, of the aligning element  160  and/or the blocking element  162  may be controlled, such as by the control unit  186 . 
     The system  100  may further comprise an obstruction element  170 , preferably fixedly mounted in the frame member  110 . The obstruction element is configured to counteract, such as prevent, a displacement of the board element  200  away from the support member  120 , such as in the vertical direction Z. At least a portion of the board element may be arranged between the obstruction element  170  and the support member  120 , such as in the vertical direction Z, and preferably during forming of the grooves  10 . A portion of the rotating cutting device  131  may be configured to be arranged through at least one slot  171  in the obstruction element  170 , preferably during forming of the grooves  10 . 
       FIGS. 2 a -2 c    show in a perspective view and in top views an embodiment comprising an alignment element  160  and a blocking element  162 , but without an obstruction element. 
     The longitudinal end portion  164  of the aligning element preferably is provided upstream of the rotating cutting device  131  along the feeding direction F. The longitudinal end portion  165  of the blocking element  162  may be provided upstream or downstream of the rotating cutting device  131  as shown in  FIGS. 2 b  and 2 c   , respectively. 
     As shown in a perspective view and a side view in  FIGS. 2 d - e   , each tooth element  133  comprises a cutting surface  134 .  FIG. 2 f    illustrates a cross-sectional top view along the line A-A in  FIG. 2 d   . As shown, a cutting surface  134 , preferably all of them, may be inclined. 
     Thereby, the board element may be driven in a lateral direction L, for example towards the aligning element  160 , see  FIGS. 2 a   - 2   c.    
       FIG. 2 g    illustrates a top view or a cross-sectional top view along the line B-B of a tooth element  133 , wherein the cutting surface  134  is inclined by an axial angle α. The axial angle may be an angle between the cutting surface  134  and an axis AR which is parallel to a rotational axis AC of the cutting element  132 . The axial angle may be 1°-70°, preferably 1°-25°, more preferably 1°-10°. 
     Alternatively, or additionally, the cutting surface  134  may be inclined by a rake angle β, see  FIG. 2 e   . The rake angle may be an angle between the cutting surface and a radial direction of the cutting element. 
     It is clear that in some embodiments, the cutting surface  134  of the tooth elements  133  is not inclined. For example, the axial angle and/or the rake angle may be zero. 
       FIGS. 3 a -3 c    illustrate in perspective views and a side view an embodiment similar to the embodiments in  FIGS. 1 and 2   a - 2   g . However, tooth elements of each pair of adjacent cutting elements are angularly offset with respect to each other around the rotational axis A 1 . More specifically, a plurality of tooth elements are provided in a plurality of sets  20  around the rotational axis A 1 , each set comprising a plurality of tooth elements. As shown in  FIG. 3 d   , the plurality of tooth elements of each set  20  may be disposed along a joining curve  21 . Preferably, the joining curve  21  is provided in a surface  31  of a cylinder  30  having the rotational axis A 1  as a centre axis and, preferably, a radius given by a distance from the rotational axis A 1  to an outer portion of the cutting elements, such as an outermost portion. 
     When projected P from the cylindrical surface  31  onto a flat plane  32 , the projected joining curve  22  may in this embodiment be a stepwise constant curve, such as a sawtooth wave or a triangle wave. For example, a portion of the cylindrical surface  31  may be cut along a direction which is parallel to the rotational axis A 1 , as indicated by the marked bold lines, and thereafter being straightened into a flat surface in the flat plane  32 . 
     In some embodiments, and as shown in  FIGS. 1 and 2   a - 2   g , the tooth elements  133  may be angularly aligned along the rotational axis A 1 , thereby corresponding to a set  20  of tooth elements disposed along a straight joining line  21  as well as a straight projected joining line  22 . 
       FIGS. 3 e -3 f    and  FIGS. 3 g -3 h    illustrate perspective views of embodiments wherein the projected joining curve  22  is a stepwise constant curve comprising two straight lines and an inclined line, respectively. 
     A shape and/or an inclination of the cutting surfaces  134  of a cutting element  132  or several cutting elements may be the same. In some embodiments, however, the shape and/or an inclination of the cutting surfaces may be different.  FIGS. 4 a -4 b    illustrate in a perspective view and a front view cutting surfaces having different shapes and inclinations. Any or each cutting surface may be configured to remove a different material shape and/or a different amount of material, for example by having a different width W and/or a different radial depth D. The width may be a length along the rotational axis AC and the radial depth may be a length along a radial direction RD of the cutting element  132 . In the present embodiment, a first cutting surface  134  (right subfigure in  FIG. 4 b   ) has a first radial depth D 1  and a first width W 1 , a second cutting surface  134  (middle subfigure) has a second radial depth D 2  and a second width W 2 , and a third cutting surface  134  (left subfigure) has a third radial depth D 3  and a third width W 3 . W 3  may correspond to a final width of a groove and D 3  may provide a final depth of the groove. The first and second widths may be smaller than the third width. Moreover, first and second radial depths may be smaller than the third radial depth. The first and second cutting surfaces may comprise a recess  136  on a respective one of their sides. 
     As shown in  FIGS. 4 a -4 b   , at least some of the top surfaces  135  of the cutting surfaces, such as the top bevel angles, may be different. For example, the top surfaces  135  of the first and second cutting surfaces may be oppositely inclined. 
     It is clear that the above embodiment is only exemplifying and that any other combination of at least one selected from the group of shapes, widths, radial depths, top surfaces and inclinations are equally conceivable. 
       FIGS. 4 c -4 e    illustrate in perspective views and a side view an embodiment in which the rotating cutting device  131  is fixedly mounted in the frame member  110 . Thereby, the rotating cutting device may be fixed at least in the vertical direction Z. The support member  120  is displaceably mounted in the frame member, by being displaceable at least in the vertical direction Z with respect to the frame member  110  and/or the processing tool  130  between a first and a second position (see arrow B 2 ). The support member may be a jumping support member. In non-limiting examples, the support member may be displaced by means of a device comprising a, preferably linear, actuator. For example, the actuator may comprise a ball screw, a ball bushing, a linear guiding system or a cam curve, any e.g. being pneumatically controlled or servo controlled. 
     Embodiments of the support member  120  may be similar to any embodiment described elsewhere in this disclosure, for example comprising at least one roller  122 . Moreover, the support member may comprise a displaceable portion  123 , such as in the form of a displaceable roller  124 . 
     Hence, grooves  10  may be formed in a board element  200  arranged in contact with the support member  120  by displacing the support member with respect to the processing tool  130 , e.g. a rotating cutting device  131 . The displacement may be controlled by a control unit  186 . 
     Other features and functionalities of the embodiment in  FIGS. 4 c -4 e    may be similar to the embodiments described elsewhere in this disclosure, e.g. in relation to  FIGS. 1, 2   a - 2   g  and  3   a - 3   h , whereby reference is made thereto. 
       FIGS. 5 a -5 g , 6 a -6 g  and 7 a -7 h    illustrate embodiments of a system  100  comprising a processing device  130  comprising first rotating cutting device  131   a  and a second rotating cutting device  131   b  located downstream of the first rotating cutting device in the feeding direction F. Thereby, the second rotating cutting device may operate after the first rotating cutting device. 
     It is emphasized that embodiments of any or each of the frame member  110 , support member  120 , components of the processing tool  130 , transportation device  140 , aligning element  160 , blocking element  162  and obstruction element  170  may be the same as the embodiments described elsewhere in this disclosure, e.g. in relation to  FIGS. 1, 2   a - 2   g ,  3   a - 3   h ,  4   a - 4   e ,  8   a - 8   f ,  9   a - 9   h ,  10   a - 10   e ,  16   a - 16   d  and  16   f - 16   g . For example, the first and/or second rotating cutting device(s) may be the same as any rotating cutting device in these embodiments. 
     The first and second rotating cutting devices  131   a ,  131   b  may comprise the same number of cutting elements  132   a ,  132   b.    
     In the embodiments in  FIGS. 5 a -5 g   , the cutting elements of the first and second rotating cutting devices preferably are aligned. Thus, for each cutting element of the first rotating cutting device there may be a corresponding cutting element of the second rotating cutting device, whereby both cutting elements may contribute to forming the same groove  10 . 
     In the embodiments in  FIGS. 6 a -6 g  and 7 a -7 b   , the cutting elements of the first and second rotating cutting devices preferably are laterally offset with respect to each other. In  FIGS. 7 a -7 b    the cutting elements of the first rotating cutting device preferably are completely laterally offset with respect to the cutting elements of the second rotating cutting device. 
       FIGS. 5 a -5 b , 6 a -6 c  and 7 a -7 b    show in perspective views and a top view a first and a second rotating cutting device  131   a ,  131   b , each comprising sets  20  of tooth elements  133  that each are disposed along a straight joining line  21  and/or a straight projected joining line  22  as described in relation to e.g.  FIGS. 1, 2   a - 2   g  and  3   g - 3   h . A portion of such a joining curve  21  is shown in  FIG. 6 c    for each of the first and second rotating cutting devices. For example, at least some, preferably all, the tooth elements may be angularly aligned along the respective rotational axis A 1 , A 2 . 
       FIGS. 5 c -5 g  and 6 d -6 g    show in perspective views, top views and side views a first and a second rotating cutting device  131   a ,  131   b , wherein tooth elements of each pair of adjacent cutting elements  132   a ,  132   b  in each rotating cutting device are angularly offset with respect to each other around the respective rotational axis A 1 , A 2 . The tooth elements are provided in a plurality of sets  20  around the respective rotational axis A 1 , A 2 . A projected joining curve  22  of each set may be a stepwise constant curve, such as a sawtooth wave or a triangle wave as described in relation to e.g.  FIGS. 3 a -3 f   . A portion of a corresponding joining curve  21  is shown in  FIG. 5 f    and  FIG. 6 f    for each of the first and second rotating cutting devices. 
     In any of the embodiments herein, the first and second rotating cutting devices  131   a ,  131   b  may both be configured to operate in the same direction, such as in an up-cut direction R 1  as shown in e.g.  FIGS. 5 g  and 6 g    or in an down-cut direction R 2  as shown in the embodiment in  FIG. 7   f.    
     Furthermore, in any of the embodiments herein, the first and second rotating cutting devices  131   a ,  131   b  may be configured to operate in opposite directions. As shown in the embodiment in  FIG. 7 g   , the first rotating cutting device  131   a  may be configured to operate in an up-cut direction R 1  and the second rotating cutting device  131   b  may be configured to operate in a down-cut direction. Moreover, as shown in the embodiment in  FIG. 7 h   , the first rotating cutting device  131   a  may be configured to operate in a down-cut direction R 2  and the second rotating cutting device  131   b  may be configured to operate in an up-cut direction R 1 . 
       FIGS. 7 c -7 e    illustrate in embodiments a zoomed-in perspective view of the system  100  in operation and a board element  200 , a cross-sectional side view of the board element, and front views of tooth elements  133 . The forming of the grooves  10  may be implemented e.g. by the system  100  in  FIGS. 5 a -5 g    and may correspond to the steps S 13  and S 15  in the method S 10  described below, cf.  FIG. 11 . 
     A first cutting element  132   a  of a first rotating cutting device  131   a  may form a first groove profile  11 , and, thereafter, a second cutting element  132   b  of a second rotating cutting device  131   b  may form a second groove profile  12 . The second groove profile  12  has a larger cross-sectional area C 2  than a cross-sectional area C 1  of the first groove profile  11 . 
     The cross-sectional area may be an area defined by the rear side  220  of the board element and the respective groove profile  11 ,  12 , such as at a specific longitudinal position of the groove which is to be formed. The first  11  and second  12  groove profiles extend along a longitudinal portion of the groove to be formed, which here is parallel to the first horizontal direction x. 
     The first  11  and second  12  groove profiles may have different shapes. For example, the width and/or the depth of the groove profiles  11 ,  12  may be different. As illustrated in the cross-sectional side view in  FIG. 7 d   , the first and/or second groove profile(s) may comprise one bevel or two bevels  14 ,  15 , each preferably being disposed between a respective groove wall  18  and the rear side  220 . Each or any bevel  14 ,  15  may correspond to a bevel of a final groove profile  13  of a groove  10 . 
     The second groove profile  12  may correspond to a final groove profile  13  of a groove  10 . 
     Alternatively, however, there may be additional removal of material before forming the final groove profile  13 . 
     As shown in  FIG. 7 e   , a shape of each of the first  11  and second  12  groove profiles may correspond to a shape  137 ,  138  of a corresponding tooth element  133 . For example, a cutting surface  134  of a tooth element may comprise one tooth bevel  139  or two tooth bevels. 
     In some embodiments (not shown), the processing device  130  may comprise a plurality of rotating cutting devices  131 . Each rotating cutting device, such as a third and, optionally a fourth, rotating cutting device consecutively arranged along the feeding direction F may be laterally aligned or offset with respect to the first and/or the second rotating cutting device(s). 
       FIGS. 8 a -8 f    illustrate side views of embodiments of a system  100  in operation. In  FIGS. 8 a -8 b  and 8 e   , a front side  210  and a rear side  220  of the board element  200  are configured to face downwards and upwards, respectively, during forming of the at least one groove  10 . 
     Moreover, the rotating cutting device(s)  131  and the support member  120  are configured to be provided at least partially above and below the board element, respectively, in operation. In  FIGS. 8 c -8 d  and 8 f   , a front side  210  and a rear side  220  of the board element  200  are configured to face upwards and downwards, respectively, during forming of the at least one groove  10 . Moreover, the rotating cutting device(s)  131  and the support member  120  are configured to be provided at least partially below and above the board element, respectively, in operation. An advantage of having such a system is that the removed material may be driven downwards by gravity G. Reference is made to other parts of this disclosure, such as in relation to  FIGS. 1 and 2   a - 2   g , regarding embodiments of any, some or all of the transportation device  140 , the alignment element  160 , and the blocking element  162 . For example, the transportation device may comprise a first  142  and/or a second  144  roller arrangement, and optionally parts of the support member, such as the at least one roller  122 . 
     Embodiments of any or each rotating cutting device  131 ,  131   a ,  131   b , support member  120 , and obstruction element  170  in  FIGS. 8 a , 8 c , 8 e  and 8 f    may be similar to any of the embodiments in  FIGS. 1, 2   a - 2   g ,  3   a - 3   h ,  5   a - 5   g ,  6   a - 6   g ,  9   a - 9   h ,  10   a - 10   e ,  16   a - 16   d ,  16   f - 16   g  and  18   f , whereby reference is made to those parts of the disclosure. Moreover, embodiments of the rotating cutting device  131 , support member  120 , and obstruction element  170  in  FIGS. 8 b  and 8 d    may be similar to the embodiment in  FIGS. 4 c -4 e   , whereby reference is thereto. It is noted that the displacements of the rotating cutting device(s)  131  and/or the support member  120  in  FIGS. 8 c , 8 d  and 8 f    may be reversed, since their positioning with respect to the board element is reversed as described above. 
     In  FIGS. 8 a , 8 c  and 8 e -8 f   , the support member  120  and the rotating cutting device(s)  131  may be fixedly mounted and displaceably mounted in the frame member  110 , respectively. 
     Moreover, in  FIGS. 8 b  and 8 d   , the support member  120  and the rotating cutting device  131  may be displaceably mounted and fixedly mounted in the frame member  110 , respectively. 
     In some embodiments, however, any, some or each of the rotating cutting device(s)  131  and the associated support member  120  in  FIGS. 8 a -8 f    may be displaceably mounted, each thereby preferably being displaceable at least in the vertical direction Z, such as downwards and/or upwards, with respect to the frame member  110 . Clearly, any of the embodiments in  FIGS. 8 a -8 f    are conceivable for at least two support members and at least two rotating cutting devices. 
     As shown in the side view in the embodiment in  FIG. 9 a   , the obstruction element  170  may have a constant profile, such as a constant thickness T, preferably along the longitudinal direction X. The thickness T may be a thickness along the vertical direction Z. However, as shown in side views in the embodiments in  FIGS. 9 b -9 h   , the obstruction element  170  in any of the embodiments of the present disclosure may have a varying profile, such as a varying thickness T, along the longitudinal direction X. At least a portion of a surface  179  of the obstruction element configured to face the board element  200  in operation may have a varying profile. The obstruction element may comprise a first segment  172  and a second segment  173  extending along the longitudinal direction X. 
     The obstruction element  170  comprises a slot portion  17  comprising at least one slot  171 , cf.  FIG. 1 , showing closed slots. In any of the embodiments in  FIGS. 9 a -9 g   , at least a portion of the slot portion  17  may have a constant profile, such as a constant thickness, along the longitudinal direction X. 
       FIGS. 9 b -9 d    show how a board element  200  may be fed into the system  100  in the feeding direction F and may be guided and/or aligned between the obstruction element  170  and the support member  120 . Generally, and as shown in  FIG. 9 b   , the rotating cutting device  131  may be a first  131   a  or a second  131   b  rotating cutting device. In  FIGS. 9 b -9 d   , the second segment  173  is provided downstream of the first segment  172  in operation. The first segment has a varying profile, such as a varying thickness T 1 , and the second segment has a constant profile, such as a constant thickness T 2 . The first segment comprises a first chamfer  175  and, optionally, a second chamfer  176  along the longitudinal direction X. 
     The first segment  172  of the embodiments in  FIGS. 9 e -9 f    may be similar to the first segment  172  in  FIGS. 9 b -9 d   , whereby reference is made to the above. In  FIG. 9 e   , the second segment  173  has a varying profile, such as a varying thickness T 2 . The profile may descend or the thickness T 2  may decrease, preferably continuously decrease, in a direction towards a longitudinal end of the obstruction member  170 , such as in the feeding direction F. In  FIG. 9 f   , the second segment  173  is provided between the first segment  172  and a third segment  174  provided downstream of the second segment in operation. The second segment  173  has a constant profile, such as a constant thickness T 2 , and the third segment  174  has a varying profile, such as a varying thickness T 3 . The third segment may comprise a first chamfer  177  and, optionally, a second chamfer  178  along the longitudinal direction. 
     In  FIG. 9 g   , the first  172  and third  174  segments have varying profiles, such as a varying thickness T 1  and T 3 , respectively. The second segment  173  may have a constant profile, such as a constant thickness T 2 . Any or each of the profiles may descend or the thickness T 1  and/or T 3  may decrease, preferably continuously, in a direction towards each longitudinal end of the obstruction member  170 . In  FIG. 9 h   , the profile or thickness T may vary continuously. The profile may descend or the thickness T may decrease, preferably continuously, in a direction towards each longitudinal end of the obstruction member  170 . 
     At least a portion of any, some or each of the chamfers  175 ,  176 ,  177  or  178  may be planar. 
     The obstruction element  170  may comprise a slot portion  17  comprising at least one open slot  171 . The perspective view in  FIG. 16 d    illustrates in an embodiment such an obstruction element comprising one open slot  171  which is open towards one lateral side of the obstruction element, here being parallel with the Y direction. Other features and characteristics of the obstruction element comprising open slots may be similar to those of the obstruction element comprising closed slots, whereby reference is made to the discussion above. For example, the obstruction element may comprise a first chamfer  175  and/or a second chamfer  178  on at least one side. 
     In some embodiments, and as shown e.g. in  FIGS. 9 a -9 b   , a distance Z 1 , such as a minimum distance, between the support member  120  and the obstruction element  170  may correspond or substantially correspond to a thickness Tz, such as a maximal thickness, of the board element  200  along the vertical direction z. 
       FIG. 10 c    schematically illustrates in a side view an embodiment wherein the support member  120  is a displaceable conveyor belt or a stationary plate. The conveyor belt and/or the transportation device  140  may displace the board element  200  in the feeding direction F, preferably being parallel to the longitudinal direction X. The obstruction element and the support member may be connected to the frame  110  and may be displaceable independently of each other. 
     In any of the embodiments of this disclosure, at least a portion of the surface  179  of the obstruction element  170  and/or a surface of the support member  120  configured to face the board element  200  may comprise a friction-reducing material or mechanism, such as a coating, for example comprising a lubricant or a physical vapour deposition (PVD) coating. 
     Moreover, a friction-reducing mechanism may comprise the provision of an air cushion, such as between the support member  120  and the board element. This may be useful when the support member is a displaceable conveyor belt or a stationary plate. In some embodiments, the friction-reducing mechanism may comprise wheels, rollers or balls, which may be provided on the obstruction element and/or the support member. 
     Generally herein, the obstruction element may comprise a pressure member  180  configured to exert pressure on the board element  200 . Thereby, a distance, such a vertical distance Z 1 , between the obstruction element  170  and the support member  120  may be adjusted. The pressure member may comprise at least portions of the obstruction element  170  and/or at least portions of the support member  120 . 
     The pressure member  180  may be controlled by a control unit  186 . In a first example, a pressure exerted by the pressure member may be dependent on a thickness Tz along the vertical direction z, such as a maximal thickness, of a portion of the board element  200 . In a second example, the exerted pressure may be determined by a predetermined pressure cycle, such as a constant predetermined pressure. In a third example, the exerted pressure may be determined by a predetermined force cycle, such as a constant predetermined force. In operation, said portion of the board element may be a portion along the longitudinal direction X and/or the feeding direction F. 
     For example, during operation of the pressure member, the distance Z 1 , such as the minimum distance, between the support member  120  and the obstruction element  170  may be smaller than the thickness Tz along the vertical direction z, such as the maximal thickness, of a portion of the board element  200 . 
       FIG. 10 c    illustrates an embodiment wherein the pressure member  180  comprises actuator elements  181 ,  182  configured to displace the obstruction element  170  and/or the support member  120 , such as in the vertical direction Z, as indicated by the arrows K 1 , K 2 . 
     Thereby, the distance Z 1  may be adjusted. In non-limiting examples, the actuator elements  181 ,  182  may be pneumatically controlled or servo controlled. 
     As shown in the embodiments in  FIGS. 4 c -4 e    and in an embodiment shown in a perspective view and a side view in  FIGS. 10 a -10 b   , the pressure member  180  may comprise a resilient member  183  configured to provide a pretensioned engagement against the board element. 
     The resilient member may comprise the obstruction element and/or the support member. In non-limiting examples, the resilient member  183  may comprise at least one spring element  184 , such as comprising a mechanical spring, a pneumatic element, an elastic material or a magnet. 
     In  FIGS. 4 c -4 e   , the resilient member  183  may be configured to pretension the obstruction element  170  towards the board element  200 . As shown, the resilient member may be connected to the support member  120 , e.g. by at least one linking arm  125 . Thereby, the obstruction element may be displaced with respect to the support member. In some embodiments, the obstruction element may be connected to other parts of the system  100 , such as the frame  110 , optionally while being unconnected to the support member and being independently displaceable with respect thereto. 
     Alternatively, or additionally, the resilient member  183  may be configured to pretension the support member  120  towards the board element  200 . 
     The resilient member  183  may comprise at least one resilient covering  185 , for example comprising a rubber material, as illustrated in  FIG. 10 b   , but is equally conceivable in  FIGS. 4 c -4 e   . In embodiments wherein the support member  120  comprises at least one roller  122 , and optionally when the transportation device  140  comprises a first  142  and/or a second  144  roller arrangement, any, some or each of these rollers  122 ,  141 ,  143  may comprise the resilient covering  185 , for example comprising a rubber wheel covering. 
       FIGS. 16 f -16 g    illustrate embodiments wherein the obstruction element  170  comprises a first unit  170 ′ and a second unit  170 ″ situated before and after the processing tool  130  along the feeding direction F, respectively. The slot portion  17  may thereby comprise a single slot  171  formed by the space between the units  170 ′,  170 ″. Other characteristics of the obstruction element may be the same as those described elsewhere herein. For example, the obstruction element may comprise a pressure member  180 , a constant or varying profile, or it may comprise at least one chamfer  175 ,  176 ,  177 ,  178 . Moreover, the first and second unit(s) may be separately displaceable w.r.t. the support member  120 . 
     The system  100  may further comprise a material collecting device  190 , such as a suction device and/or a blowing device, for collecting the removed material.  FIGS. 10 d -10 e    illustrate a front view and a cross-sectional perspective view of an embodiment in which the material collecting device  190  comprises an enclosure element  191  at least partially enclosing the rotating cutting device  131 . The system further comprises a material separating device  192  connected to the enclosure element  191  by a communication member  193 , such as at least one pipe. The material separating device  192  may comprise a cyclone. Moreover, the material separating device may comprise at least one material outlet O 1 , O 2  for the separated material. 
     Preferably, the enclosure element  191  comprises at least one orifice  195 . The orifices may be air inlets and/or air outlets. In this embodiment, the enclosure element comprises a housing  194  and the obstruction element  170 , and the orifices  195  correspond to the slots  171  of the obstruction element. It is clear, however, that other types of enclosure elements are equally conceivable. 
     Next, an embodiment of a method for forming grooves in a board element  200  (Box S 10 ) will be described with reference to the flow chart in  FIG. 11 . The method may be implemented in the system  100 , such as in any of the embodiments in  FIGS. 5 a -5 g , 6 a -6 g , 7 a -7 h  and 8 e   - 8   f.    
     As illustrated in a cross-sectional side view in an embodiment in  FIG. 13 a   , the board element comprises a layer structure  240  comprising at least one layer  241 ,  242 ,  243 ,  244 , each layer preferably comprising a thermoplastic material and, optionally, a filler. One layer may be a core layer  243  and other layers may be a decorative layer  242  and/or a wear layer  241 . Optionally, the board element may further comprise a backing layer  244  and/or a cover layer  245  covering the grooves  10 . Preferably, the backing layer comprises a thermoplastic material and, optionally, a filler. Moreover, the cover layer may be a flexible layer, such as foam layer. The layer structure  240  may be calendered or extruded, such as coextruded. Moreover, the layer structure may be laminated together or bonded together by an adhesive. 
     In some embodiments of the board element or panel, at least the lowermost layers, such as a first  243 ′ and/or a second  243 ″ core layer, and optionally the backing layer  244 , comprise a thermoplastic material and, optionally, a filler. 
     Optionally, the board element may further comprise at least one reinforcement layer  250 , such as at least one glass fibre layer. 
     First, a receiving surface  201  of the board element is arranged in contact with or on the transportation device  140  (Box S 11 ). The receiving surface may be a front side  210  or rear side  220  of the board element, preferably facing downwards as shown in e.g.  FIGS. 8 e  and 8 f   , respectively. 
     Thereafter, as shown e.g. in  FIGS. 9 b -9 d   , the board element is transported in the feeding direction F to the first rotating cutting device  131   a  (Box S 12 ), which then is displaced with respect to support member  120  for removing material from the board element (Box S 13 ). 
     For example, a first groove profile  11  may be formed, see  FIGS. 7 c -7 e    and the discussion above related thereto. Optionally, a position, preferably a position in a lateral direction L, of the aligning element  160  and/or the blocking element  162  may be controlled. 
     The board element is then, again as shown e.g. in  FIGS. 9 b -9 d   , transported to the second rotating cutting device  131   b  (Box S 14 ), which subsequently is displaced with respect to support member  120  for removing material from the board element (Box S 15 ). For example, a second groove profile  12  may be formed. The second groove profile may have a larger cross-sectional area C 2  than the first groove profile C 1 , see  FIGS. 7 c -7 e    and the discussion above related thereto. 
     A first groove arrangement  41  and a second groove arrangement  42  spaced from the first groove arrangement  41  in a first x and/or a second y horizontal direction of the board element may thereby be formed, e.g. as shown in embodiment of a panel in  FIGS. 13 b -13 d  and 14 a -14 g    and described further below. For example, the first  41  and/or the second  42  groove arrangement(s) may be formed by the first and second rotating cutting devices  131   a ,  131   b.    
     Any or both of the steps S 13  and S 15  may comprise the act of counteracting, such as preventing, a displacement of the board element  200  away from the support member  120  during displacement of the respective rotating cutting device  131   a ,  131   b  as described elsewhere in this disclosure. 
     In a non-limiting example, the at least one slot  171  may be formed by the rotating cutting device, such as during a first repetition of the method S 10 . During subsequent repetitions of the method S 10 , the at least one slot may thereby already be formed. In these examples, the obstruction element  170  may comprise a processable material, such as rubber, polymer-based material, solid wood or wood fibres. 
     The grooves are preferably formed in an interior of the rear side  220  and are preferably spaced from a first pair of opposite edge portions  231 , more preferably spaced from all edge portions  230  of the board element. Moreover, at least two grooves may have different lengths LE along the first x and/or second y horizontal direction(s) of the board element  200 , cf.  FIGS. 15 a -15 k    described below. 
     During or after each step S 13  and S 15 , the removed material may be collected from the board element and/or the support member and separated into a respective first  81  and a second  82  group of material elements (Box S 18  and S 19 ). For example, the material collecting device  190  and material separating device  192  in  FIGS. 10 d -10 e    may be utilized. 
     A characteristic of material elements of the first group may be different from a corresponding characteristic of material elements of the second group. The characteristic may be at least one selected from the group of a material composition of the material elements, a size of the material elements, a weight of the material, a shape of the material, and a density of the material. 
     In some embodiments, and as illustrated in a cross-sectional side view in an embodiment in  FIG. 13 b   , the first rotating cutting device  131   a  only removes material  80 , such as chips, from a first layer of the board element and, thereafter, the second rotating cutting device  131   b  only removes material  80 , such as chips, from a second layer of the board element. When the first and second layers comprise different material compositions, the material elements may thereby be grouped into a first  91  and second group  92 , preferably based on different material compositions. 
     In some embodiments, the first and/or the second rotating cutting device(s)  131   a ,  131   b  may remove material  80 , such as chips, from a first and a second layer of the board element. 
     When the first and second layers comprise different material compositions, the material elements may thereby be separated, e.g. as described in relation to  FIGS. 10 d - e   , and grouped into a first  91  and second group  92 , preferably based on different material compositions. 
     In a first example, and as shown in  FIG. 13 b   , the first layer may be a backing layer  244  of the board element and the second layer may be a core layer  243  of the board element. In a second example, the first and second layers may be a first  243 ′ and a second  243 ″ core layer of the board element, respectively. 
     In some embodiments, the board element may comprise at least one reinforcement layer  250 . In a first example, the step(s) S 13  and/or S 15  may then comprise the act of removing at least a portion of the at least one reinforcement layer  250  by penetrating it with the first and/or second rotating cutting device  131   a ,  131   b . In a second example, the step(s) S 13  and/or S 15  may then comprise the act of controlling a penetration depth of first and/or second rotating cutting device such that the at least one reinforcement layer  250  is left unprocessed. The controlling may be implemented by the control unit  186 . 
     Lastly, the board element  200  may be further processed, in this case post-processed, or treated. In a first example, a format of the board panel may correspond to a desired format of a panel  300 . In a second example, it may be desired to change a format of the board element by dividing it into at least two panels  300  (Box S 21 ). In either scenario, a locking system  360  may be formed on at least one edge portion  330  of the panel or at least two panels (Boxes S 22  and S 23 ), preferably on a first pair  331  and a second pair  332  of opposite edge portions. Preferably, the locking system  360  is formed after the dividing of the board element, but it is equally conceivable to form at least a part of the locking system before the dividing. For example, the locking system on one pair  331 ,  332  of opposite edge portions may be formed before dividing and the locking system on the other pair  332 ,  331  of opposite edge portions may be formed after dividing. In some embodiments, at least a part of the locking system is formed at least partially simultaneously with the dividing. 
     It is clear that in some embodiments, the board element  200  is a panel  300  per se and therefore do not need to be divided. Nevertheless, a locking system may be formed in analogy with the discussion above. 
     Embodiments of the dividing of the board element  200  into panels  300  are shown in perspective views in  FIGS. 12 a -12 e  and 12 i    and in a bottom view in  FIG. 18 g   . In  FIGS. 12 a  and 12 d   , at least two panel substrates  202  are formed by dividing the board element  200  along at least one first dividing line  71 . Each first dividing line in  FIGS. 12 a  and 12 d    may be parallel with the second y and first x horizontal directions of the board element, respectively. In  FIG. 18 g   , at least two panels  300  are formed by dividing the board element  200  along at least one first dividing line  71 . In operation, the first dividing line(s)  71  may be parallel with the lateral direction L. The longitudinal extension of the grooves  10  may extend in parallel with the feeding direction F as shown in e.g.  FIG. 18 g   . Thereby, grooves  10  having a longitudinal extension being parallel to a long edge portion (e.g.  FIGS. 12 a -12 e   ) or a short edge portion (e.g.  FIG. 18 g   ) of the panel  300  may be formed. 
     In some embodiments, the panel substrates  202  formed in  FIGS. 12 a  and 12 d    correspond to panels  300 , which may be provided with locking systems. In some embodiments, the panel substrates  202  formed in  FIGS. 12 a  and 12 d    may be further divided. As shown in  FIGS. 12 b  and 12 e   , at least two panels  300  may be formed by further dividing the panel substrate  202  in  FIGS. 12 a  and 12 d   , respectively, along at least one second dividing line  72 . Each second dividing line in  FIG. 12 b    may be parallel with the first horizontal direction x. Moreover, each second dividing line in  FIG. 12 e    may be parallel with the second horizontal direction y. Any of these divisions may form the panels  300  shown in  FIG. 12   c.    
     In  FIGS. 12 a -12 e , 12 i  and 18 g    the dividing may be any dividing process known to a person skilled in the art, such as sawing, cutting or breaking, and may be implemented by a board dividing device  400 . However, other dividing processes are conceivable. The embodiment in  FIGS. 12 f -12 h    shows a dividing of the board element  200  or of the panel substrate  202  by forming at least one notch  203  in a side, such as a front side  210 , thereof. For example, the notch(es)  203  may be formed along the feeding direction F of the board element. 
     In some embodiments, the notches  203  may be formed after forming the grooves  10 . 
     Preferably, however, and as shown in  FIGS. 12 f -12 g   , the notches  203  may be formed before forming the grooves  10 . For example, the notches  203  may be formed after or in relation to extrusion or calendering of the board element, preferably while the board element has a temperature exceeding a critical temperature, such as exceeding 60° C., preferably exceeding 70° C. or even exceeding 100° C. In a first example, a notch may be formed by removing material, for example by cutting the board element, such as with a knife or by carving. In a second example, a notch may be formed by providing a dent in the material, preferably without removing material. 
     The board element  200  or panel substrate  202  may then be divided into panel substrates  202  or panels  300 , respectively, as shown in  FIG. 12 h   . The dividing may be performed along the first  71  or the second  72  dividing line. Preferably, the dividing is performed by processing, such as cutting, sawing or breaking, the board element  200  or panel substrate  202  on the side in which the notches  203  are provided. Hence, in the present embodiment the front side  210  is processed. However, it is also possible to process the opposite side in which the notches  203  are provided, such as the rear side  220 . 
     The board element  200  may comprise at least one functional groove  70  in the rear side  220 . In the embodiment shown in  FIG. 12 i   , the at least one functional groove  70  is formed before dividing the board element. The functional groove(s) may extend to at least one edge of the board element, preferably to each of a pair of opposite edge portions, such as the first pair  231  or a second pair  232 . 
     The functional groove(s)  70  may be positioned at a predetermined distance PD from an edge portion  230 , which is shown as an edge portion of the first pair  231  in  FIG. 12 i   . Preferably, the at least one functional groove extends in parallel with the edge portion  230 . 
     The functional groove(s)  70  may be a guiding groove. As illustrated in  FIGS. 12 j - k   , a guiding element  73  may be provided in the guiding groove when dividing the board element for controlling the dividing process. In the present non-limiting embodiment, the guiding element  73  is displaceable in the vertical direction Z. The guiding element may be resilient, such as in the vertical direction Z. 
     In some embodiments (not shown), the functional groove(s)  70  may be provided in an interior of the rear side  220 , thereby being spaced from each edge portions of a pair of opposite edge portions, such as the first pair  231 , preferably all edge portions  230  of the board element. 
     In some embodiments, the functional groove(s)  70  may be formed in the board element  200  before or after the forming of the grooves  10  therein. In some embodiments, the functional groove(s)  70  may be formed in the board element  200  during the forming of the grooves  10  therein. The functional groove(s) may be formed by a rotating cutting unit. In a first example, the rotating cutting unit is a rotating cutting device  131  of any of the embodiments described herein. In a second example, the rotating cutting unit is separately formed from the rotating cutting device. 
     The board element  200  in  FIGS. 13 a -13 b    may correspond to a panel  300 . If so, elements of the board element, such as  10 ,  40 ,  210 ,  220 ,  230 ,  231 ,  232 ,  240 ,  241 - 244 ,  250 , etc., may correspond to elements of the panel, such as  10 ,  40 ,  70 ,  310 ,  320 ,  330 ,  331 ,  332 ,  340 ,  341 - 344 ,  350 , etc., respectively. In a first example, the panel may be provided with a locking system  360 , such as a mechanical locking system. In a second example, the panel does not comprise any mechanical locking system; when the panel is a floor panel, it may be nailed or glued to a subfloor, or may even be installed loosely thereon. 
     The method described may produce a panel  300  comprising at least one groove  10  in a rear side  320  of the panel as illustrated in any of the embodiments in  FIGS. 13 c -13 d  and 14 a - g   . The panel may be a building panel, floor panel, wall panel, ceiling panel or furniture panel. 
     The panel  300  may comprise a first pair of opposite edge portions  331 , which may be long edge portions, and a second pair of opposite edge portions  332 , which may be short edge portions. Preferably, the grooves  10  are formed in an interior of the rear side  320  and are spaced from the first  331  and/or second  332  pair(s) of opposite edge portions, preferably both of them. The shape of end portions  16  may be curved along the longitudinal extension of the groove, e.g. obtained when the grooves are formed by a rotating cutting device  131 . 
     In some embodiments, however, and as shown in the side view in  FIG. 14 a   , the grooves  10  may extend to at least one edge portion  330  of a pair of opposite edge portions, such as opposite short edge portions, of the panel. The shape of end portion(s)  16  may be straight along the longitudinal extension of the groove. When the grooves  10  extend to a locking groove  363  or  368 , they are preferably provided below an underside  381  or  382 , respectively, of the corresponding edge portion  330 . The underside  381 ,  382  may be a lowermost portion of the edge portion  330 . 
       FIGS. 13 c -13 d  and 14 a -14 g    show in embodiments a panel comprising a layer structure  340  comprising at least one layer, any, some or each layer preferably comprising a thermoplastic material and, optionally, a filler. One of the layers may comprise a front side  310  of the panel. Alternatively, there may be another layer provided on the layer structure and thereby comprising the front side  310 , such as a finish layer. For example, the finish layer may be a UV or EB cured layer, preferably comprising a water based lacquer. As shown in  FIG. 13 d   , one layer may be a core layer  343  and other layers may be a decorative layer  342  and/or a wear layer  341 . Optionally, the board element may further comprise a backing layer  344  and/or a cover layer covering the grooves  10 , cf. the cover layer  245  in  FIG. 13 a   . The layers in the layer structure  340  may be calendered and/or extruded, such as coextruded. Moreover, the layer structure may be laminated together or bonded together by an adhesive. 
     Generally, a bottom of the at least one groove  10  may be rounded, as e.g. in  FIGS. 13 c    and  FIGS. 14 f -14 g   , or may comprise sharp edges, as e.g. in  FIGS. 13 a -13 b    and  13   d.    
     As shown in  FIGS. 13 c -13 d   , the panel, such as a floor panel, may comprise a locking system  360  on the first pair  331  of opposite edge portions. The locking system may comprise a tongue  361  and a tongue groove  362  on the respective edge portion for vertical locking, optionally being integrally formed with the panel. The locking system may further comprise a locking groove  363  and a locking element  364  on the respective edge portion for horizontal locking. The locking element is preferably provided on a strip  365  extending horizontally beyond an upper portion of the panel  300 . 
     Moreover, the panel, such as a floor panel, may comprise a locking system  360  on the second pair  332  of opposite edge portions. The locking system may comprise a tongue  366  and a tongue groove  367  on the respective edge portion for vertical locking. For example, and as shown in  FIG. 14 a   , the tongue  366  may be a separate locking tongue  60  provided in a displacement groove  61 . The locking system may further comprise a locking groove  368  and a locking element  369  on the respective edge portion for horizontal locking. The locking element is preferably provided on a strip  370  extending horizontally beyond an upper portion of the panel  300 . 
     As shown in  FIG. 13 d   , the panel  300  may comprise at least one functional groove  70  in the rear side  320 , which may extend to at least one edge of the board element, preferably to each of a pair of opposite edge portions, such as the first pair  331  or a second pair  332 . 
     The features and characteristics of the at least one functional groove may be similar to those of the board element  200 , whereby reference is made to the discussion above. For example, the at least one functional groove may be positioned at a predetermined distance PD from an edge portion  330 , such as an edge portion of the first  331  or second  332  pair. 
     In some embodiments, the at least one functional groove  70  may be a calibration groove  70 ′ preferably being provided at an edge portion  330  of the panel. The calibration groove  70 ′, illustrated by a broken line in  FIG. 13 c   , may be provided adjacent, such as directly adjacent, to the locking groove  363  or  368 . 
     The panel  300  may comprise at least two groove arrangements  40 , such as a plurality of them. A longitudinal extension of the grooves  10  in each groove arrangement may be parallel to each other. Preferably, a longitudinal extension of each groove arrangement, such as along the first horizontal direction x, may be parallel to each other and preferably extends in parallel with an edge portion of the panel, preferably a long edge portion, which may be an edge portion of the first pair  331 . Grooves of the each groove arrangement may have the same characteristics, such as groove depths and/or groove widths. The groove depths GD and/or groove widths of at least two of the groove arrangements may be different from each other. In non-limiting examples, any groove depth GD may be at least 0.2, such as at least 0.3, preferably at least 0.4, times a thickness of the board element. For example, when the thickness is 2-40 mm, a groove depth of any of the grooves may be at least 0.5-10 mm. For example, a floor panel having a thickness of 2-10 mm may have groove depth which is at least 0.5-5 mm. 
     As noted under steps S 13  and S 15  above, the panel  300  in  FIG. 13 b -13 d    comprises a first groove arrangement  41  and a second groove arrangement  42 . 
       FIGS. 14 b  and 14 c    illustrate in bottom views groove arrangements  41 ,  42 ,  43  that are spaced in the first x and second y horizontal direction, respectively. A first  41  and a second  42  groove arrangement of the panel each have groove depths GD that are different from groove depths of a third groove arrangement  43  disposed between the first  41  and second  42  groove arrangements. As shown in a bottom view in  FIG. 14 b    and in  FIG. 14 f   , which is a cross-sectional side view of the embodiment in  FIG. 14 c   , the groove depths GD of each of the first  41  and second  42  groove arrangements may be smaller than groove depths of the third groove arrangement  43 . In any of these cases, the groove depths of the first and second groove arrangements may be the same. 
     More generally, as shown in a bottom view in  FIG. 14 d   , each pair of the groove arrangements  41 - 49  may be spaced in the first x and/or second y horizontal direction(s). 
     For example, the pair  41  and  44  are spaced in the first horizontal direction x, the pair  41  and  42  are spaced in the second horizontal direction y, and the pair  41  and  45  are spaced in the first x and second y horizontal directions. 
     By means of any of the embodiments in  FIGS. 13 b -13 d  and 14 a -14 g   , more material may be saved while maintaining the balancing properties of the panel and/or strength of the panel, such as a locking strength. In a first example, by having first  41  and second  42  groove arrangements arranged adjacent to short edge portions of the panel as in  FIG. 14 b   , each having groove depths GD which are smaller than the groove depths of the third groove arrangement  43 , more material may be saved in the centre of the panel while maintaining the strength, such as the locking strength, along the short edge portions of the panel and/or the balancing properties of the panel. In a second example, by having first  41  and second  42  groove arrangements arranged adjacent to long edge portions of the panel as shown in  FIGS. 14 c  and 14 f   , each having groove depths GD which are smaller than the groove depths of the third groove arrangement  43 , more material may be saved in the centre of the panel while maintaining the strength, such as the locking strength, along the long edge portions of the panel and/or the balancing properties of the panel. 
     In the cross-sectional side view in  FIG. 14 g    there is illustrated a plurality of groove arrangements  40 , wherein bottom portions, such as bottommost portions, of the grooves  10  are disposed along an envelope curve  52 , which preferably is a continuous curve. 
     Generically, the envelope curve may be a monomial curve or a polynomial curve of order M, where M is any natural number M=0, 1, 2, 3, 4, 5, 6, . . . , a stepwise constant curve, such as a sawtooth wave or a triangle wave or a square wave, or it may correspond to a Taylor series, such as a trigonometric function, e.g. sine or cosine. The envelope curve  52  may be provided in a cross-sectional plane HPC of the panel  300 , which may be perpendicular to a plane provided along the front  310  and/or rear  320  side(s) of the panel and may be parallel with a vertical plane VP extending along an edge portion  330  of the panel, such as an edge portion of the second pair  332 . Each groove arrangement  40  may comprise at least one groove, preferably provided in parallel with the first pair  331  of edge portions. In some embodiments (not shown), a groove arrangement  40 , preferably provided in a centre portion of the panel between the edge portions  330 , may comprise at least two grooves  10 , such as a plurality of grooves, i.e. thereby having a constant characteristic, such as a constant groove depth. 
       FIG. 14 e    shows that in any embodiment of this disclosure, at least one pair of grooves  10  may be provided in an offset relation in the first x and/or second y horizontal direction(s). 
     A groove arrangement may be at least partly, such as completely, spaced in the first x and/or second y horizontal direction(s) from another groove arrangement. As shown in  FIG. 14 e   , the groove arrangement  44  is at least partly spaced in the second horizontal direction y, and completely spaced in the horizontal direction x, from the groove arrangement  41 . 
     Any groove  10 , or preferably all of them, may comprise one bevel  14  or two bevels  14 ,  15 . 
     As shown in the embodiments cross-sectional side views in  FIGS. 16 e  and 7 d   , each bevel may be disposed between a respective groove wall  18  the rear side  320 . Any or both bevels  14 ,  15  may be at least partly planar or rounded. 
     The groove arrangements  40  in any of the embodiments in  FIGS. 13 b -13 d  and 14 a -14 f    may be formed in various ways using embodiments of the system  100  disclosed herein. 
     In some embodiments, at least the first  41  and second  42  groove arrangements may be formed by the same component of the processing tool  130 , such as a single rotating cutting device  131 , as shown e.g. in  FIGS. 1, 2   a - 2   g ,  3   a - 3   h ,  4   a - 4   e ,  8   a - 8   d ,  10   a - 10   c  and  16   a - 16   b.    
     A penetration depth of the rotating cutting device  31  may be controlled for intermittently forming different groove depths of the first  41  and second  42  groove arrangements, which preferably are formed consecutively along the feeding direction F during operation, see e.g. 
       FIG. 14 b   . Preferably, the rotating cutting device comprises cutting elements  132  having the same diameter. 
     Alternatively, however, and as shown in in the embodiment in  FIGS. 16 a -16 c   , the rotating cutting device  131  may comprise cutting elements  132  having at least two different diameters d1, d2. Thereby, at least one groove arrangement  41 ,  42 ,  43 , and optionally  44 ,  45 ,  46  and/or  47 ,  48 ,  49 , which are offset along the lateral direction L during operation, may be formed. At least two groove arrangements, such as the first  41  and second  42  groove arrangements, may be formed at least partially simultaneously. 
     Generally, the processing tool  130  may comprise a first  93  and a second  94  group of cutting elements  132 ,  132   a ,  132   b  comprising cutting elements each having a first diameter d1 and a second, different, diameter d2, respectively. The first  93  and second  94  groups of cutting elements may be configured to rotate around the same rotational axis A 1 , as shown e.g. in  FIGS. 16 a -16 c   , or around two different rotational axes A 1 , A 2 , as shown e.g. in  FIGS. 7 b    and  8   e.    
     In some embodiments, the first  41  and second  42  groove arrangements may be formed by different components of the processing tool  130 , such as a first and a second rotating cutting device  131   a ,  131   b , as shown e.g. in  FIGS. 5 a -5 g , 6 a -6 g , 7 a -7 h  and 8 e   - 8   f.    
     A penetration depth of the first and second rotating cutting devices may be controlled for forming different groove depths of the groove arrangements  40 , at least some of which preferably are formed consecutively along the feeding direction F during operation, see  FIGS. 14 b  and 14 d -14 e   . For example, the first rotating cutting device may form the first groove arrangement  41  and the second rotating cutting device may form the second groove arrangement  42 . Preferably, each of the first and second rotating cutting devices comprises cutting elements  132   a ,  132   b  having the same diameter.  FIG. 8 e   , however, illustrates that the cutting elements of the second rotating cutting device may have a different, preferably larger, diameter that cutting elements of the first rotating cutting device. 
     As noted above, at least one rotating cutting device  131  may comprise cutting elements  132  having at least two diameters, cf.  FIGS. 16 a -16 c   . Thereby, in analogy with the discussion above relating to a single rotating cutting device, at least two groove arrangements  40 , which are offset along the lateral direction L during operation, may be formed by each rotating cutting device having different diameters. 
     Generally herein, the first and second rotating cutting devices may operate consecutively, but an at least partially simultaneous operation by them is equally conceivable. 
     It is clear that in any of the embodiments above regarding the forming of the groove arrangements, the penetration depth may be controlled by displacing the processing device  130  and/or the support member  120 . Moreover, the components of the system, such as the processing device and/or the support member, may be controlled by the control unit  186 .  FIGS. 15 a -15 k    illustrate in bottom views embodiments wherein at least two grooves  10  have different lengths LE along the first x and/or second y horizontal direction(s) of the panel  300 . Preferably, the longitudinal lengths of the at least one groove are different. The discussion below is limited to one edge portion  330 , which may be provided in the second pair  332 , but is equally valid on one or on both edge portions of a pair of opposite side edge portions, such as the second pair  332 . 
     End portions  16  of the grooves, preferably longitudinal end portions of the grooves, may be disposed along a joining curve  51 , which generally may be a non-linear curve. A portion of such joining curves  51  are shown in  FIGS. 15 a -15 b  and 15 e   - 15   j.    
       FIG. 15 a    shows end portions  16  disposed along a straight curve, which may be inclined with respect the edge portion  330 , and  FIGS. 15 b -15 h    show end portions disposed along a stepwise constant curve, such as a sawtooth wave or a triangle wave or a square wave. 
       FIGS. 15 i -15 j    show end portions disposed along joining curve  51  having a continuous wave form, such as a trigonometric function. 
     In some embodiments, and as shown in  FIGS. 15 b -15 c  and 15 h -15 j   , the end portions  16  may be disposed symmetrically around a centre line CL of the edge portion  330 , preferably extending in perpendicularly to the edge portion. In some embodiments, and as shown in  FIGS. 15 a  and 15 d -15 g   , the end portions may be disposed asymmetrically around the centre line CL. 
     The grooves  10  in  FIGS. 15 a -15 j    may be formed by a single rotating cutting device  131 , such as any of those in  FIGS. 1, 2   a - 2   g ,  3   a - 3   h ,  4   a - 4   e ,  8   a - 8   d ,  10   a - 10   c  or  16   a - 16   b . Alternatively, the grooves  10  in  FIGS. 15 a -15 j    may be formed by at least two rotating cutting devices  131   a ,  131   b , such as any of those in  FIGS. 5 a -5 g , 6 a -6 g , 7 a -7 h    or  8   e - 8   f.    
     In some embodiments, and as schematically shown in  FIGS. 17 a -17 c   , the forming of the at least one groove  10  may comprise drilling or milling the board element  200  or panel  300 . The processing tool  130  may comprise a drilling tool  151  or a milling tool  152 , such as an end milling tool, each of which may be a rotational cutting device  131 . The drilling tool  151  or milling tool  152  may comprise a plurality of cutting elements  132  configured to rotate around a rotational axis A 3  provided essentially in parallel with a normal N 1  of the board element or panel in operation. In a first example, all the cutting elements  132  rotate in the same direction R 3 . In a second example, some of the cutting elements  132 , such as about half of them, rotate in opposite directions R 3 . In the second example, the twisting of the board element or panel may be reduced. Each cutting element  132  may comprise a cutting surface  134 . A diameter of the cutting elements may be 1-15 mm, such as 1-6 mm or 2-4 mm. 
     Other features of the processing tool  130  may be the same as described elsewhere herein, whereby reference is made thereto. For example, the processing tool may be displaceably mounted in a frame member  110 , such as being displaceable at least in a direction B 1  perpendicular to a feeding direction F and preferably being parallel with the vertical direction z in operation. The milling tool  152 , such as the cutting elements  132 , may also be displaceable along and/or perpendicularly to the feeding direction F, preferably being parallel with the first x and/or the second y horizontal direction(s) in operation. The support member  120  (not shown) may be fixedly mounted in the frame member. Clearly, the roles may be reversed as detailed elsewhere herein, so that the processing tool and the support member may be fixedly and displaceably mounted in the frame member, respectively. 
     The processing tool  130  comprising a drilling  151  or milling  152  tool may be configured to form grooves intermittently. The transportation of the board element  200  may be interrupted when the grooves are formed so that the board element is temporarily stationary with respect to the processing tool. Optionally, the processing tool  130  comprising a milling tool  152  may be configured to form grooves during feeding of the board element, such as when the milling tool is displaced horizontally, at least in the lateral direction L. 
     The processing tool comprising a drilling  151  or a milling  152  tool may form grooves  10  having substantially vertical groove walls  18 . For example, the grooves, preferably their cross-sections, may have substantially circular shapes or non-linear shapes as illustrated in the embodiments in  FIG. 17 d    and  FIGS. 15 k , 17 e   , respectively. In a non-limiting example, the non-linear shapes may be formed by end milling, such as by a single row  155  of cutting elements  132  in  FIG. 17 c   , whereby the end milling tool is displaceable as described above. 
     Optionally, as shown in  FIG. 17 a   , the system  100  may further comprise an obstruction element  170 , preferably fixedly mounted in the frame member  110 . A portion of the rotating cutting device  131  may be configured to be arranged through at least one slot  171  in the obstruction element  170 , preferably during forming of the grooves  10 . The lower subfigure in  FIG. 17 b    shows a portion of such an obstruction element in a perspective view. 
     In some embodiments, and as schematically shown in  FIGS. 18 a -18 b   , the forming of the at least one groove  10  may comprise carving or scraping the board element  200  or panel  300 . 
     The processing tool  130  may comprise a carving or scraping tool  153 , which may comprise at least one tooth element  133 , preferably a plurality of tooth elements  133 , configured to be fixedly mounted in a tooth holder  154 . In a first example, the tooth holder  154  is fixedly mounted in the frame member  110 . In a second example, the tooth holder  154  is displaceably mounted in the frame member  110  and is displaceable in a direction B 2  perpendicular to a feeding direction F and preferably being parallel with the vertical direction z in operation. The tooth elements  132  may be arranged along each other along the feeding direction F in operation, preferably being vertically displaced with respect to each other as shown in  FIG. 18 b   . Thereby, the tooth elements may gradually remove material from the board element. Each tooth element  133  may comprise a cutting surface  134 . Optionally, the tooth holder  154  is horizontally displaceable with respect to the board element in operation. 
     In some embodiments, the tooth holder  154  comprises at least two tooth units  156 , out of which one is shown in  FIG. 18 b   . The tooth holder  154  may be configured to rotate intermittently between the tooth units  156  along a tool path TP. Optionally, the tooth units  156  may be displaceable in a direction B 2  as disclosed above. 
     As shown in the embodiments in  FIGS. 18 c -18 e   , grooves  10  may be formed such that their groove depths GD vary along the first x or the second y horizontal direction of the board element or panel, such as along its long edge portions. For example, such grooves may be formed by an asymmetric cutting element  132  shown in the embodiment in  FIG. 18 f   . A rotation speed of the asymmetric cutting element  132 , the number of tooth elements  133 , the diameter d0, the feeding speed, etc. may be adapted so that a desired shape of the grooves is obtained. 
     As shown in the embodiment in  FIGS. 18 c -18 d   , a linking portion  19  joining the grooves  10 , such as along the long edge portions, may be spaced from the rear side  320  by a distance Gz&gt;0. The groove depths GD of at least the end portions  16  of the grooves may vary continuously and, optionally, a centre portion  19 ′ of the grooves between the end portions may have a constant groove depth. 
     The embodiment in  FIG. 18 e   , illustrating a portion of a panel  300 , shows that the groove depths GD may vary continuously such that substantially no portion of the grooves  10  has a constant groove depth. Optionally, a linking portion  19  provided between the grooves  10  may be provided along the rear side  320 , such that the distance Gz=0. 
     Aspects of the inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of aspects of the inventive concept, as defined by the appended patent claims and items in an embodiment section below. For instance, the embodiments disclosed in relation to a single rotating cutting device are equally applicable to embodiments wherein at least two rotating cutting device are utilized. For example, the embodiments in  FIGS. 4 c -4 e  and 8 a -8 f    may be used for at least two rotating cutting devices, including embodiments of at least two obstruction elements and/or at least two pressure devices associated thereto. Moreover, embodiments of rotating cutting devices, such as embodiments of the cutting elements, e.g. inclined cutting surfaces, may be similar. 
     EMBODIMENTS 
     Further aspects of the inventive concept are provided below. Embodiments, examples etc. of these aspects are largely analogous to the embodiments, examples, etc. as described above, whereby reference is made to the above for a detailed description. 
     1. A method for forming grooves ( 10 ) in a board element ( 200 ;  300 ), comprising:
         arranging the board element in contact with a support member ( 120 ), and   forming at least one groove in a rear side ( 220 ;  320 ) of the board element by removing material ( 80 ), such as chips, from the board element by a processing tool ( 130 ).
 
2. The method according to item 1, further comprising displacing the board element in a feeding direction (F), such as during said forming.
 
3. The method according to item 1 or 2, comprising arranging a receiving surface ( 201 ) of the board element in contact with the support member.
 
4. The method according to any of the preceding items, wherein said receiving surface is a front side ( 210 ;  310 ) of the board element, preferably facing downwards during said forming of the at least one groove.
 
5. The method according to any of the preceding items, further comprising displacing the processing tool with respect to the support member during forming of said at least one groove, such as at least in a direction perpendicular to a feeding direction (F) of the board element, said support member preferably being fixedly mounted in a frame member ( 110 ), and said direction preferably being parallel to a vertical direction of the frame member.
 
6. The method according to any of the preceding items, further comprising displacing the support member with respect to the processing tool during forming of said at least one groove, such as at least in a direction perpendicular to a feeding direction (F) of the board element, said processing tool preferably being fixedly mounted in a frame member ( 110 ), and said direction preferably being parallel to a vertical direction of the frame member.
 
7. The method according to any of the preceding items, wherein the processing tool comprises or is a rotating cutting device ( 131 ) comprising a plurality of tooth elements ( 133 ) configured to rotate around a rotational axis (A 1 ).
 
8. The method according to item 7, wherein the rotating cutting device comprises at least two cutting elements ( 132 ), preferably a plurality of cutting elements.
 
9. The method according to item 7 or 8, wherein a first tooth element is angularly offset with respect to a second tooth element, such as along the rotation axis (A 1 ).
 
10. The method according to any of the preceding items 7-9, wherein a cutting surface ( 134 ) of at least one tooth element is inclined.
 
11. The method according to any of the preceding items 7-10, wherein a shape and/or an inclination of a cutting surface ( 134 ) of a first tooth element and a cutting surface ( 134 ) of a second tooth element are different.
 
12. The method according to any of the preceding items 7-11, wherein the rotating cutting device is configured to operate in an up-cut direction or a down-cut direction.
 
13. The method according to any of the preceding items 7-12, wherein said rotating cutting device is a first rotating cutting device ( 131   a ) and wherein processing tool further comprises a second rotating cutting device ( 131   b ) comprising a plurality of tooth elements ( 133 ) configured to rotate around a rotational axis (A 2 ), the second rotating cutting device preferably being located downstream of the first rotating cutting device in a feeding direction (F).
 
14. The method according to item 13, wherein the first and second rotating cutting devices are configured to operate in opposite directions, said first rotating cutting device preferably being configured to operate in a down-cut direction and said second rotating cutting device preferably being configured to operate in an up-cut direction.
 
15. The method according to item 13 or 14, wherein a cutting element of the second rotating cutting device is laterally offset with respect to a cutting element of the first rotating cutting device.
 
16. The method according to any of the preceding items 13-15, wherein at least one cutting element of the second rotating cutting device is laterally aligned with respect to a corresponding number of cutting elements of the first rotating cutting device.
 
17. The method according to any of the preceding items, wherein said forming of at least one groove comprises forming a first groove arrangement ( 41 ) and forming a second groove arrangement ( 42 ), wherein grooves of the first groove arrangement preferably have the same characteristics, such as cross sections, and grooves of the second groove arrangement preferably have the same characteristics, such as cross sections.
 
18. The method according to item 17, wherein said first and second groove arrangements are at least partially, such as completely, formed by the same processing tool, such as a single rotating cutting device.
 
19. The method according to item 17 or 18, wherein said first groove arrangement is at least partially, such as completely, formed by a first rotating cutting device ( 131   a ) and said second groove arrangement is at least partially, such as completely, formed by a second rotating cutting device ( 131   b ).
 
20. The method according to any of the preceding items, wherein the processing tool comprises a first ( 93 ) and a second ( 94 ) group of cutting elements, said first group and second group comprising cutting elements each having a first diameter (d1) and a second diameter (d2), respectively, wherein the second diameter is different from the first diameter.
 
21. The method according to item 20, wherein the first rotating cutting device comprises cutting elements each having the same diameter (d0), such as an outer diameter and/or wherein the second rotating cutting device comprises cutting elements each having the same diameter (d0), such as an outer diameter.
 
22. The method according to any of the preceding items, further comprising controlling a position, preferably a position in a lateral direction, of an aligning element ( 160 ) and/or a blocking element ( 162 ).
 
23. The method according to any of the preceding items, further comprising counteracting, such as preventing, a displacement of the board element away from the support member during forming of said at least one groove.
 
24. The method according to item 23, wherein said counteracting, such as preventing, comprises arranging at least a portion of the board element between an obstruction element ( 170 ) and the support member ( 120 ).
 
25. The method according to item 23 or 24, wherein said obstruction element has a varying profile, such as a varying thickness (T), along a longitudinal direction (X), preferably being parallel to a feeding direction (F) of the board element, and optionally comprising a chamfer ( 175 ,  176 ,  177 ,  178 ) on at least one side of the obstruction element along the longitudinal direction (X).
 
26. The method according to any of the preceding items 23-25, wherein said counteracting, such as preventing, comprises adjusting a distance, such a vertical distance (Z 1 ), between the obstruction element and the support member.
 
27. The method according to any of the preceding items 24-26, wherein said portion of the board element engages with the obstruction element and the support member during forming of the at least one groove, preferably by a pressured engagement, such as a pretensioned engagement.
 
28. The method according to any of the preceding items 23-27, wherein said forming at least one groove comprises arranging a portion of the processing tool through at least one slot ( 171 ) in the obstruction element.
 
29. The method according to any of the preceding items, wherein the forming of any, some or each of said at least one groove comprises forming a first groove profile ( 11 ) and, thereafter, a second groove profile ( 12 ), said second groove profile having a larger cross-sectional area than said first groove profile.
 
30. The method according to any of the preceding items, wherein the forming of the at least one groove comprises forming at least two grooves having different lengths (LE) along a feeding direction (F) of the board element.
 
31. The method according to any of the preceding items, further comprising collecting the removed material ( 80 ), such as at least from the board element and/or the support member, preferably by suction and/or blowing, and preferably during a displacement of the board element.
 
32. The method according to any of the preceding items, wherein said board element ( 200 ) is a panel ( 300 ).
 
33. The method according to any of the preceding items 1-31, further comprising dividing said board element ( 200 ) into at least two panels ( 300 ).
 
34. The method according to item 33, wherein said dividing of the board element comprises forming at least one notch ( 203 ) in the board element.
 
35. The method according to any of the preceding items, further comprising forming at least one functional groove ( 70 ) in the board element, preferably in said rear side.
 
36. The method according to item 35, when depending on item 33 or 34, further comprising controlling said dividing by providing a guiding element ( 73 ) in the at least one functional groove of the board element.
 
37. The method according to any of the preceding items, wherein said forming of the at least one groove comprises carving or scraping the board element, or drilling or milling the board element.
 
38. The method according to any of the preceding items, wherein the board element comprises at least one layer ( 340 ), wherein any layer, some layers, or each layer preferably comprises a thermoplastic material and, optionally, a filler.
 
39. The method according to any of the preceding items, wherein the board element comprises at least two layers ( 341 ,  342 ,  343 ,  344 ).
 
40. The method according to item 38 or 39, wherein said forming at least one groove comprises forming a first portion of the at least one groove in a first layer and, thereafter, forming a second portion of the at least one groove in the first layer and/or in a second layer.
 
41. The method according to any of the preceding items, wherein the board element comprises at least one reinforcement layer ( 250 ;  350 ) and wherein the method further comprises controlling a penetration depth of said processing tool such that said at least one reinforcement layer is left unprocessed.
 
42. The method according to any of the preceding items, further comprising extruding and/or calendering at least one layer for forming said board element.
 
43. A panel ( 300 ) obtainable by the method according to any of the preceding items 1-42.
 
44. A system ( 100 ) for forming grooves ( 10 ) in a board element ( 200 ;  300 ), comprising:
   a frame member ( 110 ),   a support member ( 120 ) for supporting the board element during said forming, and   a processing tool ( 130 ).
 
45. The system according to item 44, wherein the processing tool comprises or is a rotating cutting device ( 131 ) comprising a plurality of tooth elements ( 133 ) configured to rotate around a rotational axis.
 
46. The system according to item 45, wherein the rotating cutting device comprises at least two cutting elements ( 132 ), preferably a plurality of cutting elements.
 
47. The system according to item 45 or 46, wherein a first tooth element is angularly offset around said rotational axis with respect to a second tooth element.
 
48. The system according to any of the preceding items 45-47, wherein a cutting surface ( 134 ) of at least one tooth element is inclined.
 
49. The system according to any of the preceding items 45-48, wherein a shape and/or an inclination of a cutting surface of a first tooth element and a cutting surface of a second tooth element are different.
 
50. The system according to any of the preceding items 45-49, wherein said rotating cutting device is a first rotating cutting device ( 131   a ) and wherein processing tool further comprises a second rotating cutting device ( 131   b ) comprising a plurality of tooth elements ( 133 ) configured to rotate around a rotational axis (A 2 ), the second rotating cutting device preferably being located downstream of the first rotating cutting device in a feeding direction (F).
 
51. The system according to item 50, wherein said first rotating cutting device is configured to operate in a down-cut direction and wherein said second rotating cutting device is configured to operate in an up-cut direction
 
52. The system according to item 50 or 51, wherein a cutting element of the second rotating cutting device is laterally offset with respect to a cutting element of the first rotating cutting device.
 
53. The system according to any of the preceding items 50-52, wherein at least one cutting element of the second rotating cutting device is laterally aligned with respect to a corresponding number of cutting elements of the first rotating cutting device.
 
54. The system according to any of the preceding items 50-53, wherein the first rotating cutting device comprises cutting elements each having the same diameter (d0) and/or wherein the second rotating cutting device comprises cutting elements each having the same diameter (d0).
 
55. The system according to any of the preceding items 50-54, wherein at least one of the first and second rotating cutting devices comprises cutting elements having at least two different diameters (d1, d2).
 
56. The system according to any of the preceding items 44-55, further comprising an aligning element ( 160 ), optionally comprising a chamfer ( 161 ), for example at a longitudinal end portion ( 164 ) thereof.
 
57. The system according to item 56, further comprising a blocking element ( 162 ), wherein the board element is configured to be provided between the aligning element and the blocking element, the blocking element optionally comprising a chamfer ( 163 ), for example at a longitudinal end portion ( 165 ) thereof.
 
58. The system according to any of the preceding items 44-57, further comprising an obstruction element ( 170 ) configured to counteract, such as prevent, a displacement of the board element away from the support member.
 
59. The system according to item 58, wherein said obstruction element has a varying profile, such as a varying thickness (T), along a longitudinal direction (X), preferably being parallel to a feeding direction (F) of the board element, optionally comprising a chamfer ( 175 ,  176 ,  177 ,  178 ) on at least one side of the obstruction element along the longitudinal direction (X).
 
60. The system according to item 58 or 59, wherein a portion of the processing tool is configured to be arranged through at least one slot ( 171 ) in the obstruction element.
 
61. The system according to any of the preceding items 44-60, further comprising a pressure member ( 180 ), optionally being a resilient member ( 183 ), configured to exert pressure on, such as providing a pretensioned engagement against, the board element.
 
61. The system according to any of the preceding items 44-61 further comprising a material collecting device ( 190 ), such as a suction device and/or a blowing device, for collecting the removed material ( 80 ).
 
62. The system according to item 61, further comprising a material separating device ( 192 ) and/or an enclosure element ( 191 ).
 
63. The system according to any of the preceding items 44-62, further comprising a board dividing device ( 400 ) configured to divide a board element into at least two panels ( 300 ).
 
64. The system according to item 63, further comprising a guiding element ( 73 ) for controlling the dividing of the board element.
 
65. The system according to any of the preceding items 44-64, wherein the processing tool comprises a carving tool or scraping tool or a drilling tool ( 151 ) or a milling tool ( 152 ).
 
66. A panel ( 300 ) comprising at least one layer ( 340 ), wherein the panel comprises at least one groove ( 10 ) in a rear side ( 320 ) of the panel, preferably a plurality of grooves.
 
67. The panel according to item 66, wherein the at least one groove comprises one bevel ( 14 ) or two bevels ( 14 ,  15 ), each preferably being disposed between a respective groove wall ( 18 ) and said rear side.
 
68. The panel according to item 66 or 67, wherein the at least one groove comprises a first groove arrangement ( 41 ) and a second groove arrangement ( 42 ), each of the first and second groove arrangements comprising at least one groove, preferably a plurality of grooves.
 
69. The panel according to item 68, wherein grooves of the first and/or second groove arrangement(s) have the same characteristics, the characteristics of the first and second groove arrangements being different from each other.
 
70. The panel according to any of the preceding items 66-69, wherein said at least one groove is provided in an interior of the rear side being spaced from a pair of opposite edge portions ( 330 ), such as opposite short edge portions, of the panel, preferably being spaced from all edge portions of the panel.
 
71. The panel according to any of the preceding items 66-70, wherein the at least one groove comprises at least two grooves having different lengths along the first (x) and/or second (y) horizontal direction(s) of the panel.
 
72. The panel according to any of the preceding items 66-71, wherein end portions ( 16 ) of the grooves, preferably longitudinal end portions of the grooves, are disposed along a joining curve ( 51 ), such as a straight curve or a non-linear curve.
 
73. The panel according to any of the preceding items 66-72, comprising at least a first layer and a second layer, such as a plurality of layers ( 341 ,  342 ,  343 ,  344 ), for example comprising a core layer ( 343 ), a decorative layer ( 342 ) and/or a wear layer ( 341 ).
 
74. The panel according to item 74, further comprising a backing layer ( 344 ) and/or a cover layer.
 
75. The panel according to item 73 or 74, wherein the at least one groove is provided in the first layer only.
 
76. The panel according to items 73 or 74, wherein the at least one groove is provided in the first and second layers only.
 
77. The panel according to any of the preceding items 66-76, wherein the panel comprises at least one reinforcement layer ( 350 ), the at least one reinforcement layer optionally comprises at least one opening.
 
78. The panel according to any of the preceding items 73-77, wherein any layer, some layers, or each layer comprises a thermoplastic material, such as PVC, and, optionally, a filler, such as a mineral material.
 
79. The panel according to any of the preceding items 73-78, wherein any layer, some layers or each layer is calendered or extruded, such as coextruded, each of the calendered or extruded layer preferably comprising a thermoplastic material, such as PVC, and optionally a filler.
 
80. The panel according to any of the preceding items 66-79, wherein the at least one groove has a substantially vertical groove wall ( 18 ).