Patent Publication Number: US-2003230178-A1

Title: Continuous system and method for cutting sheet material

Description:
BACKGROUND OF THE INVENTION  
       [0001] This invention relates to the art of performing operations such as cutting on sheet material such as cloth, and more particularly to a new and improved continuous system and method for cutting sheet material such as cloth.  
       [0002] One area of use of the present invention is in performing cutting, punching, marking and other operations on cloth, but the principles of the present invention can be variously applied to other types of sheet material such as leather hides, cloth laminates and the like. In cutting and otherwise operating on such sheet material at least two important objectives are reducing waste of the material and increasing throughput of the system and method. It would, therefore, be highly desirable to provide, in accordance with the present invention, a continuous system and method to increase throughput and having the capability of adjusting the pattern of operations to minimize waste of the material.  
       SUMMARY OF THE INVENTION  
       [0003] It is therefore, a primary object of this invention to provide a new and improved system and method for performing operations such as cutting on sheet material such as cloth.  
       [0004] It is a more particular object of this invention to provide such a system and method which yields increased throughput.  
       [0005] It is a more particular object of this invention to provide such a system and method which minimizes waste of the sheet material.  
       [0006] It is a further object of this invention to provide such a system and method wherein the operation is adjusted to compensate for flaws in the sheet material.  
       [0007] It is a further object of this invention to provide a new and improved conveyor for use in such a system and method.  
       [0008] It is a further object of this invention to provide a new and improved tool assembly for use in such a system and method.  
       [0009] The present invention provides a system and method for performing operations such as cutting on sheet material such as cloth wherein the sheet material is scanned at an inspection station to determine the existence and location of flaws in the material, the material is transferred to a conveyor where operations such as cutting are performed on the sheet material as it is moved by the conveyor, and the speed of the conveyor and the speed, direction and mode of the operations are controlled all according to a predetermined pattern of operation for the sheet material and the pattern is re-nested or adjusted in accordance with the existence and location of flaws in the material as determined by the scanning. The “on-the-fly” cutting of the material greatly increases system throughput, and the re-nesting of the pattern greatly reduces waste of material. The operations are performed by computer-controlled gantry-style cutters, and preferably two such cutters are employed wherein the portions of the cutting operation to be performed by the respective cutters are computer-controlled. The conveyor table provides vacuum or suction hold-down of the material, includes an outer belt of perforated flexible material and an inner belt of rigid link structure wherein the inner belt is moved by the conveyor drive means and the outer belt is moved by engagement with the inner belt. A controlled tool assembly on the head of each gantry-style cutter moves a tool, such as a cutting blade, into and out of engagement with and in different orientations with respect to the sheet material.  
       [0010] The foregoing and additional advantages and characterizing features of the present invention will become clearly apparent upon a reading of the ensuing detailed description together with the included drawing wherein: 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
     [0011]FIG. 1 is a diagrammatic top plan view of a system according to the present invention for “on-the-fly” scanning, digitizing, nesting and cutting sheet material such as cloth;  
     [0012]FIG. 2 is a diagrammatic side elevational view of the system of FIG. 1;  
     [0013]FIG. 3 is an enlarged diagrammatic top plan view with parts removed illustrating operation of the system of FIGS. 1 and 2;  
     [0014]FIG. 4 is a block diagram of the control for the system of FIGS.  1 - 3 ;  
     [0015]FIG. 5 is a diagrammatic view illustrating the flaw scanning aspect of the operation of the system of FIGS.  1 - 4 ;  
     [0016]FIGS. 6A and 6B are diagrammatic views illustrating one aspect of the nesting operation in the system and method of FIGS.  1 - 4 ;  
     [0017] FIGS.  7 A- 7 D diagrammatic views illustrating another aspect of the nesting operation in the system and method of FIGS.  1 - 4 ;  
     [0018]FIG. 8 is a diagrammatic view illustrating another aspect of the operation of the system of FIGS.  1 - 4 ;  
     [0019]FIGS. 9 and 10 are diagrammatic views further illustrating operation of the system of FIGS.  1 - 4 ;  
     [0020]FIG. 11 is a top plan view of the conveyor for use in the system of FIGS.  1 - 3 ;  
     [0021]FIG. 12 is a side elevational view of the conveyor of FIG. 11;  
     [0022]FIG. 13 is an end elevational view of the conveyor of FIG. 11;  
     [0023]FIG. 14 is a perspective view of a controlled tool assembly for use in the system of FIGS.  1 - 3 ;  
     [0024]FIG. 15 is a longitudinal sectional view of a portion of the assembly of FIG. 14; and  
     [0025]FIG. 16 is a longitudinal sectional view of an alternative form of the tool assembly of FIGS. 14 and 15. 
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT  
     [0026] Referring to FIGS. 1 and 2 there is shown a system  10  according to the present invention for continuous or “on-the-fly” scanning, nesting and cutting sheet material such as cloth. The system  10  of FIGS. 1 and 2 is a fully integrated conveyor cutter that automatically scans the material to determine flaws, reorganizes the pattern or “nest” to be cut based on the flaw locations, and cuts the parts around the flaws. The system is continuous in that all of the foregoing can be done while the material is moving.  
     [0027] Sheet material  12  at a storage location  14  is fed by means of roll  16  to an inspection station  18  where it is inspected to determine the existence and location of flaws in the sheet material. Inspection station  18  includes a table or platform  20  providing a substantially planar surface for supporting a section of the sheet material to be inspected. In the system shown, inspection is performed by a video camera  22  which scans the section of sheet material on platform  20  to obtain a video image transmitted via line  24  for use by the system control for reorganizing the pattern or “nest” to be cut based on flaw locations. In other words, the section of sheet material  12  in the scanning area of camera  22  is video analyzed to determine the location of unusable sections of the material, i.e. flaws, whereupon the pattern to be cut is then reorganized or re-nested based upon the information provided by the video image. This allows for the maximum material utilization to be achieved in the cutting process.  
     [0028] In particular, tape or other suitable type marks  26   a - 26   d  are applied to the table surface to define a 1 meter in the x axis by 1.5 meters in the y axis rectangle. The x axis is along the table  20  and the y axis is across the table. The camera  22  is adjusted by tilting it and moving it up or down so that these tape marks are aligned with a rectangle which is superimposed over the camera image as displayed on the computer monitor. The distance in the x axis from the tape mark closest to the conveyor to the laser pointer or other reference on the gantry (downstream of table  20  and which will be described) when the gantry is at table home, i.e. a reference position, is entered into a configuration file on the computer as the camera x offset. The distance in the y axis from the lower most tape mark to the laser pointer is entered as the y camera offset. In this way the size and relative position of the camera image is known in relation to the gantry.  
     [0029] The operator inputs flaws using camera  22  in the following manner. The camera image of the fabric moving onto the conveyor is displayed to the operator and updated on a regular basis (approx. 1/sec.) using a library of software functions provided by the frame grabber manufacturer. The frame grabber is an interface between video camera  22  and the software. When the operator sees a flaw on the computer screen, a mouse is used to click on a button which first stops the conveyor and then freezes the camera display. While the conveyor is stopped the gantries can continue to cut if there are parts in the cut zone. As shown in FIG. 5, the operator uses the mouse to draw a rectangle  27  around the flaw  28  by clicking on two opposite corners of the rectangle. Once the rectangle is drawn, the operator clicks another button which enters the flaw into the system. The operator at that time may enter another flaw or click on a button to restart the conveyor and camera. Once the flaw is input into the system and is in the nesting area, the software does trial tests of several methods and selects the one which results in the best material utilization, all of which will be described in detail presently.  
     [0030] Thus, using any of various inspection arrangements, including also a digitizing table well-known to those skilled in the art, the system inspects successive sections of the sheet material  12  as they pass through inspection station  18  prior to cutting or other operations being performed on the sheet material. The inspecting of the sheet material and renesting of the cutting patterns based on the flaw locations can be done at the same time while cutting operations are being performed.  
     [0031] The sheet material  12  is transferred from inspection station  18  to a conveyor  30  where operations such as cutting are performed on the sheet material as it is moved along conveyor  30  in a manner which will be described. Optionally an accumulator  32  comprising rollers  34 ,  36  and  38  can feed the sheet material from inspection station  18  to conveyor  30  to provide a time delay or interval of sufficient magnitude to provide enough time between the inspection, i.e. video scanning, and the cutting operations performed on conveyor  30  to enable the system computer control to automatically re-nest the cutting patterns in the event flaws are detected in the sheet material.  
     [0032] Conveyor  30  includes a moving belt  40  which supports and conveys the sheet material  12  along the path indicated by arrow  42  in FIG. 1 from an input end  44  to an output end  46 . Conveyor  30  will be shown and described in further detail presently. While sheet material  12  is moved by conveyor  30  along path  42  operations such as cutting are performed on the sheet material by at least one operation means movable in directions substantially parallel to and substantially perpendicular to path  42 . In the system shown, two such operation means generally designated  50  and  52  are provided, and each operation means comprises a gantry means movable longitudinally along conveyor  30 , a head means movable along the gantry means laterally of conveyor  30  and an assembly on the head means for moving a tool such as a cutting blade into and out of engagement with and in different orientations with respect to the sheet material  12 . In particular, the first operation means  50  comprises a gantry  54  movable along rails or similar supports (not shown in FIGS. 1 and 2) extending longitudinally of the conveyor frame and driven by suitable motor means (not shown). A head  56  is movably carried by gantry  54  and driven back and forth along gantry  54  by suitable motor means (not shown). The aforementioned tool assembly, which will be shown and described in detail presently, is carried below head  56 . Similarly, the second operation means  52  comprises a gantry  60  movable along the aforementioned rails or similar supports on the conveyor frame and driven back and forth thereof by suitable motor means. A tool assembly is carried below head  62 . Gantry  54  is the one closest to table  20  and is used as the reference in calibrating camera  22  as previously described.  
     [0033] Gantries  54  and  60  are movable longitudinally of conveyor  30  toward and away from each other under system control as will be described. Both gantry style cutters  50  and  52  are operable for cutting “on-the-fly”. In other words, either or both cutters  50  and  52  move relative to conveyor  30  and to each other to operate on the sheet material  12  simultaneously with movement of the sheet material along conveyor  30  in the direction of arrow  42  in FIG. 1.  
     [0034] Conveyor  30  is a vacuum or suction hold down conveyor table wherein suction is provided along a portion of the path for sheet material  12  travelling along conveyor  30 . The hold-down or suction portion is delineated by the broken line area designated  70  in FIG. 1. The material of conveyor belt  40  is air permeable as will be described presently to facilitate the hold-down of material  12 . The portion of the conveyor path between output  46  and the edge of hold-down region is a non-suction area designated  76  which serves as a pick-up area for finished product.  
     [0035] During the foregoing operation, the speed of conveyor belt  40  and the speed, direction and mode of operation of either or both gantries  54  and  60 , heads  56  and  62  and tool assemblies are controlled all according to a predetermined pattern of operation for the end product to be obtained from the sheet material. This can include, in accordance with the present invention, adjusting the pattern as determined by the existence and location of flaws in the sheet material as a result of the scanning or similar operations performed at inspection station  18 .  
     [0036] When a roll of sheet material  12  is finished, a butt seamer  80  is employed to join the end of the first roll to the beginning of a subsequent roll  82  in a known manner. The resulting seam will appear as a flaw, and the system will re-nest the pattern to be cut around the butt joint.  
     [0037] The operation of the system of FIGS. 1 and 2 is illustrated further in FIG. 3. As previously described, conveyor belt  40  moves sheet material  12  to be cut over the conveyor table. The two gantry style cutters  50  and  52  cut the fabric synchronously with the movement or conveyance of the fabric to be cut. This results in double “cutting on the fly”.  
     [0038] Cutter  50  has the ability to cut in the area designated  90  in FIG. 3, cutter  52  has the ability to cut in the area designated  92  and both cutters  50  and  52  have the ability to cut in the overlap area designated  94 . Encoders (not shown) operatively associated with cutters  50  and  52  and the tracks on which they move provide information on the instantaneous locations of cutters  50 ,  52  which is monitored by the system software. Thus the software knows when either cutter  50 ,  52  enters the common area  94 . This, in turn, provides a signal to the system control to prevent the other gantry from entering area  94  at that time. Cutters  50  and  52  also are provided with proximity sensors  100  and  102  operatively coupled to the system control for providing “crash” protection to stop and shut off both cutters  50 , 52  if they come too close to each other during the foregoing operation.  
     [0039] A control system for the arrangement of FIGS.  1 - 3  is shown in FIG. 4 and includes motion control hardware components  110 ,  112  and  114  for conveyor  30 , gantry  50  and gantry  52 , respectively. In accordance with a preferred mode of the present invention, gantry  52  is slaved to gantry  50 , i.e. gantry  50  gives gantry  52  “permission” to move during operation. The primary and secondary motion control software is represented at  116  and  118 , respectively. Control over the cut files is provided by software component  120  which in turn receives data and commands from the flaw monitoring software  122  illustrated in connection with FIG. 5 in association with the camera operation  126  previously described and nesting operation  126  which will be described in detail presently.  
     [0040] Cutting on the fly is accomplished by using the functionality provided by the motion control hardware to link axis. The X axis of the gantries  50 ,  52  are linked to the conveyor axis so that motion commanded on the X axis is done relative to motion commanded on the conveyor axis. The gantry x axes are parallel to the longitudinal axis of conveyor  30 . To keep the system modular and expandable, three motion control boards are used, one for the conveyor and one for each of the two gantries. These are indicated at  110 ,  112  and  114  in FIG. 4. While only the one conveyor motion control board actually controls the conveyor motor, the two gantry control boards are configured to have phantom axes which are programmed to have a motion profile which mimics the actual conveyor axis. The X axis on each gantry is linked to the phantom axis on the same motion control board. In particular, the primary control  116  always has information on movement of conveyor  30  along the X axis, i.e. movement of conveyor  30  along its longitudinal axis, and primary control  116  sends a software message to each gantry hardware control component  112  and  114  so that each gantry control has that conveyor movement information. By virtue of the foregoing this information can be provided advantageously without hardwire connection between the conveyor and gantry controls. Alternatively, the system can obtain the necessary information via an encoder associated with conveyor  30  and hardwire connections to controls  112  and  114 .  
     [0041] The actual conveyor axis is synchronized with the phantom conveyor axis described above in the following manner. The motion control components  110 ,  112  and  114  are connected with a synchronization wire so that the motion commanded on each board begins at the same time. While the voltage level on the synchronization line is set to the ready state, each board is programmed to make identical motions (in the phantom axes), but the motions do not begin until the synchronization line changes to the go state. In order words, the actual velocity and acceleration of conveyor  30  is identical in each of the phantom axes for the gantry controls  112  and  114 . Once all the boards have been programmed, the synchronization line is changed to the go state and all boards begin the motion at the same time. In this way any number of motion control components can be synchronized, therefore any number of gantries or other devices could be added to the system.  
     [0042] Crash avoidance in the common overlapping addressable area  94  shown in FIG. 3 is accomplished in the following manner. Since each gantry  50 ,  52  is capable of addressing the center area  94  of the conveyor  30 , a method of preventing both gantries from entering this area at the same time and thus crashing is provided by way of software communication between the primary gantry and secondary gantry under control of software components  116  and  118 . The secondary gantry communicates to the primary gantry the amount of conveyor space it needs to cut the parts it has been programmed to process. The primary gantry releases conveyor space to the secondary gantry after it completely cuts all of its parts in that area. Since the released area is relative to the conveyor belt, as the conveyor moves the released area decreases and the secondary gantry may need to move in order to stay in the released area.  
     [0043] By way of example, in an illustrative system, each motion control component  110 ,  112  and  114  is a DSP Series Motion Controller commercially available from Motion Engineering Inc. under the designation Model LC/DSP.  
     [0044] The software component  120  in the system of FIG. 4 provides the basic interface to the operator of the machine in allocating operations of the cutters  50  and  52  for splitting a particular job. Component  120  imports a cut file which typically would be used by a single headed machine and therefore must split the file so that each gantry  50 ,  52  processes part of the whole job. Such a cut file is illustrated in FIG. 8. The method used to split the job will depend on the specific requirements of the complete machine. In particular, splitting the job can be along the entire length of the job so that parts on the top and bottom half are cut by separate gantries. Optimizing the splitting of the job can be done so that the time required by each gantry to process each half is nearly the same so as to prevent one gantry from unnecessarily waiting for the other gantry to process its parts. Splitting the job can be done by function. Each gantry may have different tools mounted to it so that one gantry may be cutting and the other labeling or one cutting and the other punching, etc.  
     [0045] In the illustrative cut file of FIG. 8, pen speed is the gantry speed when penning which is similar to labelling, move speed is the gantry speed when not penning or cutting, the acceleration and overall speed are that of the gantry, and the cut speed, pressure and overcut data are for the situation where a particular type of tool (here designated R 1 ) is carried by the gantry. The foregoing illustrative data shown is for one gantry and similar data would be shown for the other gantry.  
     [0046]FIGS. 8 and 9 further illustrate the manner in which the system of FIG. 4 controls conveyor  30  and using the software  120  splits the marker into table bites of equal cut times designated  134  and  136 , and shown at two different times during movement of the conveyor belt to the left as viewed in FIGS. 8 and 9. Controls  116  and  118  send these two distinct cut files to the motion controllers  112  and  114 . Each gantry cutter  50  and  52  is working on non-overlapping table or cut bites, i.e. those designated  134  and  136  in FIGS. 8 and 9, but since the table bites are being conveyed continuously along conveyor table  30  the regions addressed by each gantry cutter  50  and  52  are overlapping.  
     [0047]FIGS. 6 and 7 illustrate pattern re-nesting according to the present invention based on flaw information. The system of FIG. 4 recognizes a flaw in sheet material  12  upon scanning by video camera  22  and operator interaction with the “mouse” device and computer screen as described in connection with FIG. 5. Once a flaw has been located, software component  126  of the system of FIG. 4 then re-nests the pattern based on this new flaw information in the following manner. Once the flaw is input into the system and is in the nesting area, the software  126  does trial tests of several methods and selects the one which results in the best material utilization. One method, breaking open pre-nest, is illustrated in FIGS. 6A and 6B where the various rectangles represent patterns of parts to be cut from the sheet of material  136 . In the case of a butt-flaw  138 , which is a flaw that goes completely across the width of the fabric, the pre-nest of FIG. 6A is opened up so that the parts which would be cut in the flawed material are moved down the material to a good area of material. This is illustrated in FIG. 6B. If the flaw occurs at a location in the pre-nest where there is little overlapping of parts so that only a few parts are affected evenly, the technique of opening up of the pre-nest can result in efficient use of the material.  
     [0048] Another method is removing individual parts affected by a spot flaw which does not extend completely across the fabric. In the case of a spot flaw, the individual parts affected are removed from the nest. It may be possible to insert smaller parts in place of those parts removed.  
     [0049] Another method is optimizing the pre-nest and is illustrated in FIGS.  7 A- 7 D. The pre-nest of FIG. 7A is similar to the pre-nest of FIG. 6A. The pre-nest is opened as shown in FIG. 7B. After opening the pre-nest or removing parts at flaws, it is often possible to improve the yield by removing the left most parts of the pre-nest and shifting the pre-nest to the left. Part  140  shown in FIG. 7B is removed from the pre-nest designated  142 , whereupon the pre-nest is shifted to the left to provide the optimized pre-nest shown in FIG. 7C. Thus if there is a section of the pre-nest which more closely matches the shape of the flaw, less material will be wasted without disturbing the efficiency of the original nest.  
     [0050] In accordance with another aspect of the nesting process of the present invention there is provided filling in parts using a reservoir. In particular, in certain situations, the nesting results can be improved by adding additional parts to the nest. Since it is not desirable to remove parts from the pre-nest for this purpose, because removing parts from the pre-nest will reduce the efficiency of the pre-nest, a reservoir of parts is provided according to the present invention for this purpose. Parts are added to the reservoir by the following methods. One is parts that are at a flaw and removed by the optimization process. An example is part  140  removed from pre-nest  142  in FIG. 7B. Another is extra parts needed in the manufacturing process, i.e. to compensate for damaged parts. Still another is that the pre-nest can be made intentionally leaving out a few parts and then these parts are added to the reservoir. For example, this can be seen in FIGS. 7B and 7C where the open region between parts  144  and  146  could be the result of intentionally leaving out a small part for this purpose.  
     [0051] Information describing the boundary of the area where parts can be nested into, as well as any flaws in that area and data describing the perimeter of the parts and the maximum number of each part which can be used, is provided to a nesting routine which is standard in the industry. An example of one such routine is found in U.S. Pat. No. 5,146,821 issued Sep. 15, 1992 and entitled “Method of Cutting Blanks From Webs of Material”, the disclosure of which is hereby incorporated by reference. An example of the boundary where parts can be nested into is indicated at  150  in FIG. 7D.  
     [0052] Another aspect of the nesting process of the present invention is removing additional parts from pre-nest to provide larger boundary area for nesting. The nesting routine  126  is called several times with different boundary conditions which result from removing additional parts from the pre-nest to provide the nesting routine a larger nesting area and therefore more options for improving the nest results. The nest with the best efficiency is selected from the various techniques.  
     [0053] Once the optimum nest of parts is achieved, it would resemble, for example, the file of parts shown in FIG. 8 whereupon software  120  is called to allocate the tasks between cutters  50  and  52 .  
     [0054] The conveyor  30  of FIGS.  1 - 3  is shown in further detail in FIGS.  11 - 13 . In the arrangement illustrated, a single operation means  170  is shown comprising a gantry  172  and head  174 , it being understood that conveyor  30  is useable with either one or two operation means such as the gantry-style cutters. Conveyor  30  comprises a frame  180  supported by legs  182  on a surface  184  such as the floor of a cutting room. A first conveyor belt  190  in the form of air permeable sheet material extends along a first continuous loop-like path including an upper portion which defines a surface  192  upon which the sheet material  12  (not shown in FIGS.  11 - 13 ) lays and is supported while operations such as cutting are performed on the material. By way of example, in an illustrative conveyor, belt  190  comprises 1 mm thick urethane or PCV bonded to a woven polyester belt. The belt  190  is provided with holes therethrough so as to be air permeable for a purpose which will be described. A plurality of rollers  196 , in particular rubber coated rollers, are rotatably mounted in frame  180  for supporting and guiding movement of conveyor belt  190  along the aforementioned first continuous loop-like path. In addition, a belt tension pulley take-up  198  is mounted in frame  180  and contacts belt  190 .  
     [0055] Conveyor  30  further comprises a second conveyor belt  200  in the form of a rigid plastic chain style link belt extending along a second continuous loop-like path wherein at best a portion of the second conveyor belt  200  is in contact or frictional engagement with the first conveyor belt  190 . That portion coincides with the upper portion  192  of belt  190  as seen in FIG. 12. A pair of rollers  204  are rotatably mounted in frame  180  for guiding movement of conveyor belt  200  along the aforementioned second continuous loop-like path.  
     [0056] There is provided controlled drive means in frame  180  and in operative engagement with the second conveyor belt  200  for moving belt  200  along the second continuous loop-like path at a controlled speed. The drive means comprises a plurality of toothed pulley wheels  210  fixed on a shaft  212  rotatably mounted in frame  180  at one end thereof and drivenly coupled by a belt or chain type coupling  214  to the output drive shaft  216  of a drive motor-reducer gear combination  218 . The speed control for motor  218  is connected to control  110  as previously described. The teeth of pulley wheels  210  drivingly engage the open mesh structure provided by the rigid plastic chain style link belt  200  causing movement of the same. Another plurality of identical pulley wheels  222  are fixed to a shaft  224  rotatably mounted in frame  180  at the opposite end. The idler pulley wheels  222  similarly engage the openings in belt  200  and serve to support and guide the same.  
     [0057] A suction or vacuum chamber  230  is defined by an enclosure within frame  180  in a known manner and is in fluid communication with at least a portion of the path along which sheet material moves between the input and output ends of conveyor  30 . A duct  232  converts chamber  230  to a vacuum blower (not shown) or other source of suction in a known manner. Preferably chamber  230  terminates at a location inwardly of the output end  44  of conveyor  30  to define a non-vacuum pick-up area  236  to facilitate removal of finished pieces or product from conveyor  30 .  
     [0058] A plurality of plastic runner strips  240  shown in FIG. 11 are mounted in frame  180  for the purpose of providing additional support for the moving belts  190  and  200 . A cable carrier  244  for the gantry style plotter cutter  172 ,  174  is mounted along one side of frame  180  and is operatively contacted by one end of gantry  172  as it moves along conveyor  30 .  
     [0059] In operation, the apparatus of FIGS.  11 - 13  comprises a continuous cutting machine that utilizes a gantry style cutter. The vacuum conveyor table  30  draws air through the two belts  190  and  200  that are supported by the runners  240 . The sheet material to be cut is loaded from the left side of the table and held in place by the air vacuum pressure created by suction chamber  230 . A cutting knife (not shown) is mounted to head  174  and cuts against belt  190  which is supported by belt  200  which in turn is supported by the runners  240 .  
     [0060] The two belts  190  and  200  on conveyor  30  allow a full, pliable cutting surface (provided by belt  190 ) but maintain rigidity and low friction (belt  200 ) which conveying under vacuum or suction. The rigid plastic, for example acetal, link belt  200  spans the gap between the plastic runner strips  240 , giving a rigid platform with a minimum amount of friction. Also, the link belt  200  tracks or travels straight along the conveyor table better than a non-rigid belt. The operative or driving contact between the two belts  190  and  200  is provided and enhanced by the vacuum or suction.  
     [0061] By way of example, in an illustrative continuous cutting apparatus as shown in FIGS.  11 - 13 , the gantry style cutter  172 ,  174  was an M 9000  high speed platter/cutter commercially available from Eastman Technology Systems Ltd. of Buffalo, N.Y., suction was provided by a  25  hp vacuum motor, and the material cut was 10 mm trilaminate with circular knit scrim. A rapid advance of 30 cm/sec. was used in loading material into position for cutting. During cutting, the move speed of the conveyor belt  190  was 2.350 cm/sec. the system settings were gantry move speed 130 cm/sec., cutter head move speed 130 cm/sec. and acceleration 1.0 g. The “on-the-fly” continuous cutting greatly increased throughout. Cutting to the edge of the material and minimal part buffers resulting in reduced waste.  
     [0062]FIGS. 14 and 15 illustrate a controlled tool assembly  250  for use in the system shown in FIGS.  1 - 3 . A tool assembly  250  is carried on each head  56  and  62 , in particular being located below each head, and each tool assembly  250  moved a tool such as a cutting blade into and out of engagement with and in different orientations with respect to the sheet material  12 . Referring first to FIG. 14, the tool assembly  250  is mounted in the lower region of the corresponding head by means of a bracket including a main body  252  fixed to the head and leg numbers  254 ,  256  and  258  extending therefrom. A pneumatic cylinder  260  has the housing  262  thereof fixed to bracket leg  254  and is characterized by the piston rod thereof comprising a spine shaft  264  having a longitudinal axis and extending out from housing  262  and terminating in a lower end as viewed in FIG. 14. Cylinder  260  is operated by a controlled source of pressure carried by the gantry-style cutter on which tool assembly  250  is mounted, the operation being controlled by the gantry control board, i.e. one of the controls  112  and  114  shown in FIG. 4. A tool means generally designated  268  in FIG. 14 is mounted on the lower end of spline shaft  264 . In the tool assembly shown, tool means  268  comprises a blade in the form of a round knife. Alternatively, tool means  268  can comprise a drag knife, a high pressure water jet cutter, a laser cutter, an ultrasonic cutter, or a round punch or similar marking implements.  
     [0063] Tool assembly  250  further comprises motor means  274  in the form of a theta axis servo rotational motor, the housing  276  of which is fixed to bracket by 256. A coupling member in the form of a theta axis pulley  280  is fixed to spline shaft  264  by means of a spline shaft nut  282 . A coupling means in the form of a belt  286  operatively engages pulley  280  and the output shaft  290  of motor  274  for causing rotation of spline shaft  264  in response to rotation of motor output shaft  290 . The rotational movement of servo motor  274  is controlled by the gantry control board, i.e. one of the controls  112  and  114  shown in FIG. 4.  
     [0064] Thus, operation of pneumatic cylinder  260  moves spline shaft  264  to force the tool  268  into sheet material  12 , and operation of motor  274  changes the orientation of tool  268  relative to the longitudinal axis of spline shaft  264 . Tool assembly  250  features spline shaft  264  integrated into the structure of pneumatic cylinder  260  to act as the rod thereof. This allows rotational orientation of the cylinder rod to be controlled by means of servo motor  274 .  
     [0065]FIG. 15 shows in further detail how spline shaft  264  is incorporated to become the rod of pneumatic cylinder  260 . This allows low friction rotational movement of the piston/rod assembly as cylinder  260  is actuated. Torque is transmitted via belt  286  from servo motor  274  to pulley  280 . Since pulley  280  is rigidly connected to nut  282  of spline shaft  264 , the rotational load is ultimately transferred to the tool  268  at the lower end  294  of spline shaft  264 . The recirculating ball bearings in spline shaft nut  282  allow very low friction movement of shaft  264  even under torque loads. The ball bearings in spline shaft nut  282  increase wear life, and nut  282  provides an improved holding of the tool in contrast to a mere bushing which would have play. It is important to hold the tool as precisely as possible to achieve a sharp, accurate cut in the material. This is enhanced by the accuracy and tolerance provided by the ball bearings in nut  282 . The piston  296  of pneumatic cylinder  260  is attached to spline shaft  264  in a manner allowing the shaft to rotate independently of piston  296 . The lateral loads are isolated from the endcaps of pneumatic cylinder  260  by the bearing  298  which is mounted in bracket leg  258 . To prevent the pneumatic cylinder  260  from experiencing excess friction while either fully extended or fully retracted, thrust bearings  300  are located within housing  262  at opposite ends thereof. By way of example, spline shaft nut  282  is a standard ball spline type LT model 200LE commercially available from THK.  
     [0066]FIG. 16 shows an alternative arrangement wherein spline shaft  264 ′ and cylinder shaft  304  are separate and joined by a coupling  306 . The portion of thee shaft in cylinder  262 ′ is subject to wear and can be replace separately by virtue of coupling  306  without having to replace the entire spline shaft.  
     [0067] It is therefore apparent that the present invention accomplishes its intended objects. While embodiments of the present invention have been described in detail, that is done for the purpose of illustration, not limitation.