Abstract:
Workpiece rests are disclosed for holding workpieces in machining systems which machine the workpieces using a cutting beam, e.g., a laser beam. A workpiece rest includes a frame, a plurality of rest elements that are arranged adjacent to one another in the frame so as to support the workpiece, and a supporting element attached to at least one of the rest elements.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional application of U.S. Ser. No. 12/276,557, filed on Nov. 24, 2008, and is a continuation and claims priority under 35 U.S.C. §120 to PCT Application No. PCT/EP2006/004985, filed on May 24, 2006. The contents of these priority applications are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a workpiece rest for holding a workpiece, e.g., a plate-like workpiece, in a machining system which machines the workpiece using a cutting beam, e.g., a laser beam. 
       BACKGROUND 
       [0003]    To machine workpieces, for instance plate-like workpieces such as sheet metal, in laser machining systems, a workpiece rest is generally provided. The workpiece rest may, for example, include a frame with a plurality of rest elements which are arranged generally parallel to one another and on which the workpiece to be machined rests. The rest elements usually have supporting point peaks at regular intervals and form a rest field for the workpiece(s). 
         [0004]    Laser machining systems of this type comprise a laser cutting head which is movable relative to the workpiece rest in order to machine a substantially stationary workpiece, which rests on the supporting point peaks of the rest elements, by means of a laser beam. During the machining, problems occur as the laser beam passes over the supporting point peaks, such as for example damage to the supporting point peaks as a result of welding deposits, damage to the supporting point peaks as a result of their being melted away, and/or a non-uniform cut between the product part and the residual part, since the cutting conditions at the supporting point peaks are different from those at the adjacent supporting point peaks. 
         [0005]    In order to reduce the above-stated problems in the machining of the workpieces, DE 38 03 918 A1 describes a workpiece rest in which the rest elements can be lowered as a function of the position of the laser beam during the machining process. A mechanism which is coupled to the cutting head serves to lower in each case that rest element which is situated in the impingement region of the laser beam during the machining process. 
         [0006]    A similar design is likewise known from JP 59127988 A. The rest strips are activated by means of a cam guide, with a lowering movement and a displacement movement in the longitudinal direction of the rest element being provided simultaneously. 
         [0007]    In both of the above-described workpiece rests, a lowering of the supporting point peaks is effected over the entire length of the rest elements, reducing weld deposits on the supporting point peaks as they are traversed during the cutting process. However, non-uniform cuts may still occur, in particular when a workpiece is almost completely cut out from the workpiece table and rests with one end on the lowered supporting point peaks. 
         [0008]    JP 2001-259878 A2 describes a laser machining system for producing electronic printed circuit boards, in which uniform bore diameters and bore shapes are required. A printed circuit board of this type rests, for machining, on a workpiece rest. In order that machining can take place in a manner not influenced by the workpiece rest, the workpiece rest has a series of parallel depressions which are arranged adjacent to one another and in which rest peaks are provided so as to be longitudinally movable. Said rest peaks are moved as a function of the machine data for producing the printed circuit boards, thereby making uninfluenced machining possible. However, during the machining process, burned-off portions, slag and dust which are deposited, and the chips which are generated during the production of bores, may contaminate or block the guides of the rest peaks, and can therefore result in the workpiece rest becoming non-operational. Handling tends to be impaired on account of the high cleaning expenditure. Furthermore, during the machining of printed circuit boards, there is not the problem that, after the machining process, a separate product part and residual part is present, with it being necessary for the product part and also the residual part to be reliably held by the rest elements until the complete unloading of the workpiece rest. 
       SUMMARY 
       [0009]    Workpiece rests are disclosed herein in which the rest elements have a long service life and the separate product parts and residual parts are reliably held. 
         [0010]    In one aspect, the invention features a workpiece rest for supporting a workpiece in a machining system which machines the workpiece using a cutting beam. The workpiece rest comprises a frame, a plurality of rest elements which are arranged adjacent to one another in the frame so as to support the workpiece, and a supporting element attached to at least one of the rest elements. 
         [0011]    In some implementations, the workpiece rest comprises a plurality of supporting elements, each of which is attached to one of the rest elements. 
         [0012]    Before it is loaded with one or more workpieces, the workpiece rest is prepared for the impending machining process by attaching one or more supporting elements to one or more of the rest elements. The supporting elements may be positioned so as to provide adequate support as a function of the overlapping of the product parts in a workpiece. 
         [0013]    Some implementations include one or more of the following features. Each supporting element has at least one rest surface on which the product part and/or the residual part rests. The supporting elements are attached to the rest element(s) in such a way that the cutting contours run adjacent to the rest surface of the supporting element for the product part. At the same time, the supporting elements are positioned with respect to one another on the rest element of the workpiece rest in such a way as to enable the product part(s) to be securely held after the cutting process. By means of the attachment of the supporting elements as a function of the overlapping cutting process of the plate-like workpiece to be machined, a durable workpiece rest is created since a direct traversing of the rest elements by the cutting beam is prevented and the rest elements are protected by the at least one supporting element. Furthermore, it is generally possible for damage to the workpiece to be machined as a result of welding deposits or reflections during the cutting process to be prevented. 
         [0014]    In one advantageous refinement of the workpiece rest, the supporting elements are pluggable onto the rest element and are in particular provided so as to be movable along the rest element. As a result of said pluggable arrangement of the supporting elements, simple attachment is made possible, which is carried out within a short time without additional auxiliary means for the fastening thereof. As a result of the movability of the supporting element(s) along the rest element, precise positioning is made possible with regard to the overlapping of the subsequent machining program. 
         [0015]    According to one preferred embodiment of the workpiece rest, the rest element is provided with a corrugated or sawtooth-shaped structure to which the supporting element is attachable, so as to be prevented from moving. It is therefore possible to ensure, after setting the position of the supporting element, that an inadvertent displacement or movement of the supporting element as a result of the loading and unloading of the workpiece rest is prevented. Such a sawtooth-shaped, tooth-shaped or corrugated structure may also permit sufficiently fine adjustment of the position. 
         [0016]    It may alternatively be provided that the rest element comprises a rectilinear, preferably horizontal section or a plurality of rectilinear sections which are separated from one another, for example by means of a small depression. In particular, a continuous, horizontally aligned section permits a simple geometry of the rest elements, which permits stepless or gridless positioning of the rest elements. 
         [0017]    According to a first preferred embodiment, one supporting element comprises at least one rest peak or rest surface for a product part and is a product-part supporting element, and a further supporting element has at least one rest peak or rest surface for a residual part and is a residual-part supporting element. Preferably, the rest surface or peak of the product part is arranged at a higher level than that of the residual part. In this way, it is made possible that, after the machining process is complete, the product parts are held at a higher level than the residual part(s). This permits simplified removal of the product parts and subsequently of the residual parts. A quick visual check of the machining status is also made possible. 
         [0018]    According to an alternative embodiment, the supporting element has a rest peak or rest surface for a product part and, at least adjacent thereto, a rest peak or rest surface for a residual part, with the rest surface of the product part being provided at a higher level than that of the residual part. Said arrangement makes it possible for both the cut edge region of the residual part and also that of the product part to assume a defined rest position. 
         [0019]    It is preferably provided that a height difference between the rest surface of the product part and the rest surface of the residual part is greater than a thickness of the plate-shaped material. In this way, after the cutting process, a precise separation between the product part and residual part can take place and a seizing of the parts with respect to one another can be prevented. 
         [0020]    In a further advantageous embodiment, the rest surface of the product part or that of the residual part is of electrically insulating design. In this way, it is possible to detect, by measuring an electric potential difference, whether the product parts have been completely cut away from the residual part(s). 
         [0021]    In some implementations, the supporting element is formed in one piece as a cut and bent part or as a punched and bent part. This permits simplified production, such that new supporting elements can in some cases be produced by means of the machining system itself. 
         [0022]    The supporting elements are preferably placed onto the rest elements by means of a handling device, with the positioning of the supporting elements being selected taking into consideration the overlapping of the subsequent machining process. Here, the cutting contour of the overlapping is taken into consideration, in order that the rest surfaces of the supporting elements for the product part and residual part do not lie in the traversed region, but rather the product part and residual part lie at an elevated level with respect to the rest elements in order to prevent damage to the rest elements as the cutting beam passes over, or to protect the rest elements by the supporting element in the region traversed by the cutting beam. Furthermore, as a function of the geometry of the product parts, at least three-point support is defined in order to provide a secure hold. 
         [0023]    According to a first embodiment of the invention, the supporting elements comprise a U-shaped cross section, which is open in the downward direction, with at least one supporting point peak which is provided on the rest element being covered by the supporting element. The supporting element preferably rests simultaneously on the at least one supporting point peak. In this way, the supporting element can provide protection of the underlying supporting point peak. Furthermore, the U-shaped cross section has the advantage that simple application to, removal from, and displacement along the rest element is made possible. 
         [0024]    The limbs of the supporting element are preferably positioned with respect to one another so as to bear with at least a slight preload against the side surfaces of the rest element. At least a slight clamping action is obtained in order to permit secure positioning, with a low-vibration or vibration-free arrangement of the supporting elements on the rest elements being provided. 
         [0025]    According to a further advantageous refinement of the first embodiment of the supporting elements, a protective section is provided adjacent to the rest surface of the product part or between a rest surface of the product part and a rest surface of the residual part, which protective section covers at least one supporting point peak. Said protective section lies below the cutting gap in the cutting contour. In this way, the rest element and the at least one underlying supporting point peak are protected. Furthermore, it is preferably provided that said protective section is at least slightly inclined with respect to a rest surface of the workpiece. In this way, back-spatter or reflections during the cutting machining process can be reduced, such that the underside of the product part also has a high-quality surface. 
         [0026]    In an alternative embodiment, the supporting element engages with a first and a second fastening section on a rest element which comprises a protective strip which is inclined with respect to the rest plane of the workpiece, which protective strip at least partially covers a retaining strip as the cutting beam passes over. In this way, it is made possible for the retaining strip to be free from slag and other influences as a result of melting or material spatter or the like, such that a system, or engagement surface for the supporting element, which is insusceptible to contamination is provided for secure positioning. 
         [0027]    The retaining strip is preferably arranged in a V-shape with respect to the protective strip, with the protective strip being provided between the workpiece and the retaining strip. The retaining strip subsequently merges into a vertically aligned rest strip which is preferably fastened to the frame of a workpiece rest and which is in particular supported by support struts which are arranged at right angles with respect to said frame. 
         [0028]    In the above-described embodiment, the supporting element can have a first fastening section, for example legs, which are supported at least on the retaining strip and which in particular partially engage behind said retaining strip, and a further fastening section, for example arms, which engage on a side, which faces away from the workpiece, of the protective strip. In this way, it is made possible that the arms and legs of the supporting element engage in each case on rest surfaces which are insusceptible to dirt. In this way, it is possible to ensure that the rest surfaces of the supporting elements which are positioned on the rest element lie in a uniform contact plane, such that uniform operating conditions and a precise alignment of the workpiece on the workpiece rest are made possible. 
         [0029]    The rest elements for holding the supporting elements preferably have, between the protective strip and the retaining strip, cutouts into which the legs at least partially engage. As a result of said arrangement of the covering protective strip, the legs engage in a protected manner on the retaining strip, such that, during the cutting process, a fusion of the legs to the rest element, or baking of the legs onto the rest element, by the cutting beam which acts from above, or by the slag, sparks and other spatter, is prevented. The same applies to the arms which bear in a supporting manner against the underside of the protective strip. 
         [0030]    For the fixing, and vibration-free holding, of the alternative embodiment of the supporting elements, a spring element can be provided on an underside of the protective strip, which spring element secures the supporting element in a retaining position after the positioning with respect to the rest element, in particular with respect to the retaining strip. This can also provide increased process reliability during the loading and unloading of the workpiece or of the product parts and residual parts. 
         [0031]    To increase the machining quality of a surface of the workpiece which is aligned toward the rest element, on the supporting element, all the free end surfaces which point in the direction of the workpiece can be inclined with respect to a rest plane of the workpiece. In this way, adverse effects as a result of reflections can be considerably reduced. 
         [0032]    The alternative embodiment of the supporting element preferably has a V-shaped design, or a design similar to this, as viewed in plan view. In this way, simple assembly and disassembly can be provided by means of the design of the arms and legs. Furthermore, it is possible to use a relatively thin bent sheet-metal part which can absorb high loads. 
         [0033]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0034]      FIG. 1  is a perspective illustration of a machining system. 
           [0035]      FIG. 2  shows a schematic side view of a rest element with supporting elements arranged thereon. 
           [0036]      FIG. 3  shows a rear view of the supporting elements as per  FIG. 2 . 
           [0037]      FIGS. 4   a  to  4   c  show schematic side views of the supporting element as per  FIG. 3 . 
           [0038]      FIG. 5  is a perspective illustration of a cutout from a machined workpiece which is resting on the workpiece rest. 
           [0039]      FIG. 6  is a perspective illustration of an alternative embodiment of the supporting element. 
           [0040]      FIG. 7  shows a schematic side view of the supporting element as per  FIG. 6 . 
       
    
    
       [0041]    Like reference symbols in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0042]      FIG. 1  shows a perspective partial view of a machining system  11 , in particular a laser machining system. A workpiece rest  14  which is arranged in a loading and unloading region  12  is provided for traveling into a machining machine, in particular laser machining machine  16 , of which a housing  17  is partially illustrated. In said laser machine, a cutting head is moved, by means of a linear system (not illustrated in any more detail), above a workpiece  19 , which rests on the workpiece rest  14 , in order to form a cutting contour. 
         [0043]    The workpiece rest  14  is composed of a frame  21  which holds a plurality of rest elements  22  which are arranged adjacent to one another. In a first exemplary embodiment, the rest elements  22  comprise a rest strip  24  and, arranged above the latter, supporting point peaks  26  which comprise a rest peak which tapers to a point. 
         [0044]      FIG. 2  shows a schematic side view of a first embodiment of a rest element  22  with supporting elements  31  which are arranged thereon and which hold the workpiece  19 . After the machining process, on account of the cutting process, the workpiece  19  is divided into a product part  32  and a residual part  33 . 
         [0045]    The supporting element  31  comprises a U-shaped body  34  ( FIG. 4   a ) which is open in cross section in the downward direction and is plugged onto the rest element  22  and which, in the exemplary embodiment, engages over three supporting point peaks  26  and covers two supporting point peaks  26 . For this purpose, protective sections  37  are provided which simultaneously serve as a stop or rest surface of the supporting element  31  on the supporting point peaks  26 . Provided adjacent to the protective section  37  is a rest surface  38  for the product part  32 , which is arranged at an elevated level with respect to a rest surface  39  of the residual part  33 . After the cutting of the workpiece  19 , the residual part  33  falls in relation to the product part  32 , thereby making visual monitoring possible since the product parts  32  are situated at a high level and the residual parts  33  are situated at a low level, and are simultaneously separated in this way. 
         [0046]    The supporting elements  31  are positioned by being simply plugged onto the rest element  22 . The supporting element  31  engages with its limbs  41  on side surfaces  42  of the rest element  22  and is thereby fixed. This permits a low-vibration or vibration-free arrangement. The supporting elements  31  may also, on account of this design, be provided so as to be movable in the longitudinal direction along the rest elements  22 . For positive fixing in terms of position, it may be provided that the supporting elements  31 , in particular the protective sections  37 , have a contour, which contours engage on the supporting point peaks  26  and can be moved, at predefined spacings, into adjacent positions. 
         [0047]    The section lines I and II illustrated in  FIG. 3  are shown in the illustrations of  FIG. 4   b  and  FIG. 4   c , and  FIG. 4   a  shows a side view of  FIG. 3 . Said illustrations clearly show the design of the supporting element  31  as a punched and bent part or as a cut and bent part, which is preferably produced from one piece. The two limbs  41 , which run parallel to one another, of the supporting element  31  are connected to one another by means of a connecting web or hoop  43 . The free distance between the limbs  41  can, by means of the degree of bending, be provided so as to be smaller than the width of the rest element  22 , such that, after the supporting element  31  is placed onto the rest element  22 , the limbs  41  bear in a clamped fashion with an at least slight force loading. The protective section  37  is provided by means of an angled portion on one of the limbs  41  at 90° with respect to the limb  41  or preferably at less than 90°. The rest surfaces  38  and  39  are formed as an elongation of one limb  41 . Said exemplary arrangement of a supporting element  31  as per  FIGS. 2 ,  3  and  4   a  to c permits a cost-effective design. 
         [0048]      FIG. 5  is a perspective illustration of a workpiece  19  after the cutting process, with the product part not being illustrated for the purpose of clarity, said product part otherwise resting, at a higher level than the residual part  33 , on the rest surfaces  38  of the supporting elements  31 . The supporting elements  31  are positioned, as a function of the provided overlapping for the cutting process, in such a way as to provide for example three-point support for the product part, as can be seen from  FIG. 5 . This provides secure support for the product part. At the same time, the supporting element  31  may be positioned in such a way with respect to the cutting contour that the protective section  37  lies in the region traversed by the cutting beam. It is thereby possible firstly for the at least one underlying supporting point peak  26  to be protected, and secondly for both the product part and also the residual part  33  to be held in the edge region or close to the cutting contour, thereby assisting tilt-free mounting of the two parts. The positioning of the individual supporting elements  31  in the present geometry of the product part is merely exemplary. 
         [0049]    After a machining program has been run through in its entirety, the supporting elements  31  can be raised or removed from the rest elements  22 . The loading and unloading of such supporting elements  31  may preferably take place by means of handling devices  35 , such as for example by means of single-axis or multi-axis linear axis systems or robots, which are used for example for the loading and unloading of the workpiece rest  14 , or by means of a linear axis system in the machining machine  16 . Similarly, manual loading may also take place. The positioning of the supporting elements  31  may be assisted by means of an external display unit  36 , for example a data projector. Said display unit  36  is provided for example on the housing  17  of the machining system  11  and projects the individual loading positions of the supporting elements  31  onto the rest element(s)  22  of the workpiece rest  14 . 
         [0050]    An alternative embodiment, which is not illustrated in any more detail, of the supporting elements  31  as per  FIGS. 1 to 4   c  provides that only rest surfaces  38 ,  39  for product parts  32  or for residual parts  33  are provided. Furthermore, it may alternatively be provided that a rest surface  38  for the product part  32  and at least one rest surface  39  for the residual part  33  are provided on a supporting element at the same height. It is likewise possible for embodiments to be provided in which the product part  32 , after having been cut out from the workpiece  19 , is situated at a lower level than the residual part  33 . The statements made above apply analogously here. 
         [0051]      FIGS. 6 and 7  illustrate an alternative embodiment of a supporting element  31  and of a rest element  22 . The rest element  22  comprises a protective strip which is provided above a retaining strip  52  which is arranged for example in a V-shape with respect to the protective strip  51 . The retaining strip  52  merges into a preferably vertically aligned rest strip  24  which is fastened to the frame  21  of the workpiece rest  14 . Cutouts  54  are provided between the retaining strip  52  and the protective strip  51 . Legs  56  of the supporting element  31  engage on and into said cutouts  54 . Furthermore, the supporting element  31  is fixed by means of arms  58  which engage on or bear against an underside of the protective strip  51 . By means of said design of the rest element and arrangement of the supporting element  31 , it is ensured that the rest surfaces or contact surfaces for the legs  56  and arms  58  are protected from contamination, since said rest surfaces or contact surfaces are situated below the protective strip  51 . This permits a precise arrangement and alignment of the supporting elements  31  even after multiple uses of said rest elements  22 . The inclination of the protective strip  51  also has the advantage that beam reflections and material spatter are deflected away from the cutting gap, such that an underside of the product part has a high level of quality. 
         [0052]    The legs  56  and arms  58  are connected to one another by means of a support section  59 , with a rest surface  38  for the product part  32  being provided on a head part  60  of the support section  59 . In the exemplary embodiment illustrated in  FIG. 6 , a rest surface  39  for the residual part  33  is provided adjacent to the rest surface  38 . An alternative embodiment provides that the supporting element  31  is designed as a product-part supporting element only having one or more rest surfaces  38 , and as a residual-part supporting element only having one or more rest surfaces  39 . 
         [0053]    The supporting element  31  is formed as a sheet-metal part. Firstly, the contour is punched or cut and a V-shaped arrangement of the supporting element  31  is subsequently formed in a bending process. A stiffening of the support section  59 , which has at least the rest surface  38 , is obtained in this way. 
         [0054]    In  FIG. 7 , a spring element  61  is provided on an underside of the protective strip  51 , which spring element fixes the supporting element  31  in its retaining position on the rest element  22 , and in particular fixes the legs  56  on the retaining strip  52  so as to at least partially engage behind the latter. 
         [0055]    The spring element  61  as per  FIG. 7  may be designed as a spring element which is continuous along the protective strip  51 . Alternatively, further designs may be obtained in order to obtain a clamping action, such as for example by means of a type of eccentric shaft or a clamping plate or a form-fitting connection which, after the complete positioning of the supporting element  31 , effects a clamping action. 
         [0056]    The rest surface  38  of the supporting element  31  is provided outside or eccentrically with respect to the engagement points of the arms  58  and legs  56 . In this way, the position of the supporting element  31  is stabilized, and tilting is prevented, when a product part and residual part  32 ,  33  are resting thereon. 
         [0057]    The supporting elements  31  according to the above embodiments can be formed from different materials, thereby permitting an adaptation to the material of the workpiece to be machined. 
         [0058]    All of the features described above may be combined with one another in any desired manner. 
       Other Embodiments 
       [0059]    A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.