Method for cutting sheet material

Abstract: A method of cutting sheet material comprising: preparing a generally rectangular layup of sheet material having a length between opposite ends of the layup and a width between opposite sides of the layup; positioning the layup on the support surface of a cutting table (11) of a cutting machine having a cutting tool (28) movable relative to the support surface and the layup; characterized by determining the centerline (110), extending between the opposite sides of the layup (114) and the location of said centerline on the cutting table; establishing a generally rectangular marker (120) of pattern pieces to be cut from the generally rectangular layup, the marker having a length between opposite ends of the rectangle, a width between opposite sides of the rectangular and an origin point (118) located at a known position with respect to the sides and ends of the rectangle, the location of the pattern pieces in the marker being referenced to the origin point; registering the origin point (118) of the marker relative to the cutting table (11) and the centerline (110) of the layup so that one half of the marker is disposed on one side of the centerline; and the other half is disposed on one side of the centerline; and then cutting the layup of sheet material in accordance with the marker as registered.

Description: BACKGROUND OF THE INVENTION The present invention relates to a method for cutting sheet material, particularly limp sheet material such as cloth, paper, plastic and the like which is held in a spread condition while it is worked on by a tool such as a cutting blade, drill or other tool. In the prior art, it is well known to spread cloth and other limp sheet materials on a support surface for cutting, drilling and other operations. In the garment industry it is known to spread cloth in single or multiple plies on a cutting table having an air-permeable bed, and to then cut pattern pieces from the material. The pattern pieces are then assembled in garments or other finished articles by cutting blades, lasers, water jets and other types of tools. A conveyorized vacuum table formed with bristle beds for loading layups of one or more plies of sheet material onto the bed holds the layups in a compressed and stationary position under vacuum during cutting. The cut material is unloaded after the cutting operation is completed on one or more segments or "bites" of the sheet material. When the layup is held in place by vacuum, a plastic or other air-impermeable overlay is frequently placed on the layup to develop compression forces for compacting the material in addition to holding the layup in position. Related pattern pieces are grouped into arrays called markers. A marker is usually a rectangular array and allows the related pattern pieces to be cut sequentially from a generally rectangular layup in a single cutting operation. A marker has an origin point, usually at a corner of the marker, from which the positioning of each pattern piece in the marker is referenced. Locating the origin of a marker on a layup therefore determines the location on the layup where the pattern pieces will be cut, as documented in US-A-3 805 650. Some markers, such as those needed in producing T-shirts, also require symmetric features to be cut from a layup of tubular material. Accordingly, the marker must be precisely centered with respect to the layup. Otherwise, the cut pattern pieces will not be aligned with the axis of the tubular material and the resulting garment will be flawed. Precise centering of a marker is also required when the material to be cut is ornamented, such as striped material. Markers that are not precisely centered with respect to the ornamentation will result in cut pattern pieces with misaligned patterns. It would be advantageous to locate the origin point of the marker such that the centerline of the marker corresponds to the centerline of the layup. It is an object of the present invention to provide a method for cutting layups of sheet material where the origin points of the markers are registered relative to the center of the fabric. This object is solved by a method as defined in claim 1. An aspect of the present invention is to provide a method and apparatus for determining the centerline of the layup and registering the origin point of the marker relative to the centerline so that one half of the marker is disposed on one side of the centerline and the other half is disposed on the other. FIG. 1 is a perspective view of a cutting machine with multiple layups of sheet material positioned in a side-by-side relationship for cutting in accordance with the present invention. FIG. 2 is a top plan view of a marker having an origin which is established relative to the center of the layup, the center being manually identified. FIG. 3 is a flow chart showing the steps involved in registering the marker origin relative to the center of the layup, the center being manually identified. FIG. 4 is a top plan view of a marker having an origin which is established relative to the center of the layup, the center being calculated by two edge points. FIG. 5 is a flow chart showing the steps involved in registering the marker origin relative to the center of the layup, the center being calculated by registering two end points. FIG. 1 illustrates a numerically controlled cutting machine, generally designated 10, for cutting pattern pieces from a length of sheet material S that is spread over a cutting table 11. As illustrated, the cutting machine cuts a plurality of closely nested pattern pieces P in an array referred to in the garment industry as a marker. However, the invention described hereinafter is not limited to the garment industry and may be used in a wide range of work operations on sheet material which is drilled or cut by many different types of tools including reciprocating cutting blades, ultrasonic knives, rotatable knives, laser beams or water jets. The cutting table 11 of the cutting machine 10 is a conveyor table. The sheet material S is loaded onto the cutting table 11 from a spreading and loading conveyor 12 and cut by the cutting machine 10 on the cutting table 11. The cut pattern pieces together with the surrounding material are unloaded from the cutting table by means of an unloading conveyor 14. Eventually the cut pattern pieces P are removed from the unloading conveyor and are transported to a sewing room for assembly into a garment. The length of the marker or array of pattern pieces that is cut from the sheet material S may be substantially larger than the cutting machine itself. Under such circumstances the material is fed in segments or "bites" onto the cutting table 11 for cutting all of those pattern pieces P in the one segment of the marker while the material is stationary on the cutting table 11. Thereafter, the next segment is fed onto the cutting table, and the previously-cut pieces are drawn onto the unloading conveyor 14. The sequence of alternately feeding and cutting the material is controlled by a computer 16 to which signals indicative of the marker data from memory 18 are supplied and continues until the entire marker has been cut. The cutting machine 10 includes an X-drive carriage 22 which is moveable back and forth relative to the base 20 in the illustrated X-coordinate direction, and a Y-carriage 24 which is mounted on the X-carriage 22 for movement therewith and is moveable relative to the X-carriage back and forth relative to the base in the illustrated Y-coordinate direction. A cutting tool in the form of a reciprocating cutting blade 28 is suspended from the Y-carriage 24 and can be moved up or down relative to the carriage to be brought into and out of cutting engagement with the sheet material S. The cutting blade is also rotatable about the -axis in order to be oriented generally tangentially of cutting paths defined by the peripheries of the pattern pieces P. The X-carriage 22 rides on stationary roundways 30 and 32 at opposite sides of the cutting table and is driven back and forth in the illustrated X-coordinate direction by means of an X-drive motor 34 and a pair of drive belts 36, 38 coupled to the carriage 22 at each side of the table. The Y-carriage 24 is moved back and forth on the X-carriage relative to the sheet material in the illustrated Y-coordinate direction by means of a servomotor 40 and a drive belt 42 trained over pulleys at opposite ends of the X-carriage. The rotation of the cutting blade 28 about the -axis is accomplished by the -servomotor 44 mounted on the Y-carriage 24. In addition, the cutting blade is lifted from or plunged into cutting relationship with the sheet material by means of a servomotor not shown. Collectively the X-servomotor 34, the Y-servomotor 40 and the -servomotor 44 cooperate to move the cutting blade 28 in cutting engagement with the sheet material at the periphery of the pattern pieces in response to commands transmitted to the motors from the control computer 16 in response to the signals indicative of the marker data in the computer memory 18. Additionally, the computer 16 controls the bite feeding of the sheet material onto and off of the cutting table 11 as well as the operation of the loading and unloading conveyors 12 and 14. As indicated above, the cutting table 11 is a conveyor table on which the sheet material S is loaded from the loading conveyor 12, then cut by the cutting blade 28 and then discharged onto the unloading conveyor 14. While the material is being cut, the cutting table 11 and the segment of material S on the table remains stationary with respect to the base 20. Thus, the cutting blade 28 performs all of the cutting motions. To accommodate the cutting blade, the cutting table 11 is formed by a penetrable bed 52 of bristle blocks whose bristles project upwardly into a plane defining the support surface of the table. The bristle blocks are arranged in rows extending in the Y-coordinate direction forming a conveyor that can be driven in the illustrated X-coordinate direction by the drive motor 46 and drive sprockets 48 in Fig. 1. The bristle blocks have perforate bases or are spaced slightly from one another for air permeability and are coupled to a vacuum pump 50 that evacuates the region of the bristles and the associated support surface of the table 11 at least in the vicinity of the cutting blade 28, if the table is provided with vacuum zoning. By drawing a vacuum at the support surface through the air permeable bristle bed and with a plastic overlay 55 covering the sheet material S, the sheet material is drawn toward the support surface of the bristles and held firmly in position during cutting. For further details concerning the construction and operation of such a table, reference may be had to U.S. Patents 4,646,911 or 5,189,936. The cutting machine 10 makes possible the simultaneous cutting of multiple layups 56 and 58 arranged in side-by-side relationship on the cutting table 11. Multiple markers, one for each of the layups, are used, some or all of which may require bite feeding. In conventional fashion all the pattern pieces that fall within one bite between the lines b-b in Fig. 1 are cut, then the table is advanced before the pattern pieces that are in the next bite are cut. Registering the origins of the markers relative to the center of each layup 56 or 58 is advantageous in that it allows the marker to be precisely centered upon the layup. This allows symmetric features to be cut from tubular material without misaligning the cuts of the pattern pieces with the axis of the tubular material. It also allows pattern pieces that are cut from ornamented material to have a desired ornamentation at a precise position on the cut pattern pieces. Markers that are not precisely centered with respect to the ornamentation will result in cut pattern pieces with misaligned ornamentation. Two methods for registering the origins of the markers relative to the center of the layup are disclosed. It is useful to note that registering the origins of the markers relative to the center of each layup may be performed upon a plurality of layups positioned in a side-by-side relationship, or upon a single layup. Turning to FIGS. 2 and 3, the first method for registering the origin of the marker relative to the center of the layup consists of centering the marker 120 on the centerline 110 of the layup 114. The centerline may be established by hand measurement or visual inspection, as shown by S13. For example, the centerline may be indicated by a centered ornamentation on the layup 114 such as a stripe. With such a centered ornamentation, determining the centerline 110 of the layup 114 is accomplished by visual inspection. The centerline 110 of the layup 114 can also be determined by measuring the width of the layup between the sides. The location of the centerline 110 is then determined as halfway between this width. Once the centerline 110 has been determined, any point on this line is registered, as shown in S14, so that the computer 16 can store the Y coordinate Y 3 of the location of the centerline 110 in memory 18 for use in registering the origin point of the marker. A preferred method of registering the location of a center point 116 on the centerline 110 of the layup 114 is by positioning the light pointer 54 (Fig. 1) such that it illuminates a desired center point 116 location and pressing an origin switch on the computer 16. After the location of the center point 116 is registered, the marker 120 is established, as shown in S15, by user selection through the computer 16 and the marker width w m is determined, as shown in S16. The marker width w m is divided by two and the resulting half-width w m /2 is subtracted from the Y coordinate Y 3 of the selected center point 116 to calculate the Y coordinate of the origin 118 of the marker 120, as shown in S17. The following equation describes the calculation of the Y coordinate of the origin 118 of the marker 120: Y 3 - W m 2 The cutting tool can then cut the layup 114 in accordance with the marker as registered. A second method for registering the origins of the markers relative to the center of the layup, depicted in FIGS.4 and 5, allows the centering of a marker 120 on a layup 114 without having to manually measure or calculate the centerline. The user locates the top and bottom edges of the layup 114 preferably by positioning a light pointer such that the light pointer illuminates the desired corner points 122 and 124 of the layup 114, as shown in S18 and S19. The marker 120 is then established or identified in memory, as shown in S20, and the marker width w m is determined, as shown in S21. The Y coordinate Y 3 of the center point 126 of the layup 114 is calculated as the average of the Y coordinates Y 2 and Y 1 of the two selected points 122 and 124, in accordance with the following equation: Y 3 = Y 1 + Y 2 2 The marker width w m is divided by two and the resulting half-width w m /2 is subtracted from the Y coordinate of the center point 126 to calculate the Y coordinate of the origin 118 of the marker 120, as shown in S22, in accordance with the following equation: Y 1 + Y 2 2 - W m 2 The cutting tool can then cut the layup 114 in accordance with the marker as registered.

Claims: A method of cutting sheet material comprising: preparing a generally rectangular layup of sheet material having a length between opposite ends of the layup and a width between opposite sides of the layup; positioning the layup on the support surface of a cutting table (11) of a cutting machine having a cutting tool (28) movable relative to the support surface and the layup; characterized by determining the centerline (110) extending between the opposite sides of the layup (114) and the location of said centerline on the cutting table; establishing a generally rectangular marker (120) of pattern pieces to be cut from the generally rectangular layup, the marker having a length between opposite ends of the rectangle, a width between opposite sides of the rectangle and an origin point (118) located at a known position with respect to the sides and ends of the rectangle, the location of the pattern pieces in the marker being referenced to the origin point; registering the origin point (118) of the already establisshed marker relative to the cutting table (11) and the centerline (110) of the layup so that one half of the marker is disposed on one side of the centerline and the other half is disposed on the other side of the centerline; and then cutting the layup of sheet material in accordance with the marker as registered. A method of cutting sheet material as defined in claim 1, characterized in that the step of registering the origin point (118) of the marker includes: establishing the distance of the origin point (118) of the generally rectangular marker from the centerline (110) extending between the ends of the rectangular marker; and locating the origin point offset from the centerline of the layup by the same distance that the origin point is offset from the centerline of the marker.

Inventors: MARKOWITZ IVAN, POMERLEAU ROBERT J, VIVIRITO JOSEPH R, MARKOWITZ, IVAN, POMERLEAU, ROBERT J., VIVIRITO, JOSEPH R.
Applicants: GERBER TECHNOLOGY INC, GERBER TECHNOLOGY, INC.
Application year: 1996
Main classification: B26F1
IPC codes: B26F1, B26D5