CA2500087A1

CA2500087A1 - Device and method for cutting textiles

Info

Publication number: CA2500087A1
Application number: CA002500087A
Authority: CA
Inventors: Juergen Held; Siegfried Held; Markus Boehn
Original assignee: Schuler Held Lasertechnik GmbH and Co KG
Current assignee: Individual
Priority date: 2002-10-01
Filing date: 2003-09-30
Publication date: 2004-04-15
Also published as: WO2004030876A1; DE10245730A1; PL374170A1

Abstract

The invention relates to a cutting installation (1) that is designed to stac k patterned pieces of fabric, taking into account particular distortions of individual pieces of fabric, in such a way that the patterns of the individu al pieces of fabric and in particular the positions of predefined marker points on the pieces of fabric are precisely aligned above one another. This is achieved by the individual recording of the particular distortions of the pieces of fabric and the stacking of said pieces, taking into account said distortions. The pieces of fabric that have been stacked on top of one anoth er in the correct position can be cut as a group. The average distortion presen t in the stack is first determined and the cutting contour is adapted to said distortion. If the distortion of an individual cut piece is of such quality or proportion to prevent it from being positioned on the existing stack, the stacking process is stopped and the relevant cut piece is used as the first layer of a new stack. Said installation and method permits patterned fabrics to be cut with a high production efficiency.

Description

Device and Method for Cutting Textiles The present invention relates to a device and a method for cutting textiles, in particular those that are woven or knitted. The device and the method are particularly suitable for cutting out patterned textiles.
As a rule, patterned textiles are cut out from a single layer of material in order that each single piece that is cut out can be matched to the pattern. In contrast to this, as a rule, unpatterned woven textiles are laid up in several layers at a time and thus cut out as a stack by a cutter such a laser cutout machine. This results in a high level of efficiency.
In contrast to this, when patterned textiles are cut out one layer at a time, only a low level of efficiency can be achieved.
Proceeding from the foregoing, it is the objective of the present invention to describe a device and a method with which it is possible to enhance productivity when cutting out fabric or other textiles, in particular if these bear a pattern that must be taken into account when pieces are cut out.
This objective is achieved by the cutout machine according to the present invention, as set out in Claim 1, as well as by the method as set out in the claims relating to method.
The cutout machine incorporates a carrier that is designed to accommodate a stack of pieces of fabric that are to be cut out. In addition, it incorporates a sensing device that records the positions of marker points either before or after individual pieces of fabric have been cut off from a web of material. A separator serves to divide the pieces of fabric into individual pieces, so that these can be stacked after the separation process.
The controller is designed to control the carrier and/or the conveyor in such a way that the marker points of the individual pieces of fabric are so positioned as to lie one above the other as exactly as possible. When this is done, distortion, stretching, shrinkage (including non-isotropic shrinkage) can be taken into account as a function of textile tension, humidity, and the like which, under normal circumstances, change the position of patterns or markings on the fabric relative to one another. Using the present invention, as an alternative or selectively, it is also possible to implement two measures cumulatively;
namely, steps can be taken to ensure that the patterns of individual pieces of fabric lie above one another in a stack, within the required tolerances and/or the outlines of the cut are matched to the distortions, shrinkages, rotation, and the like of the pattern that have been identified. These distortions or other dimensional changes that the actual pieces of fabric have in relation to an idealized pattern can be identified by sensing the markings, and can then corrected by matching the cut outline. The simultaneous cutting of a plurality of patterned pieces of fabric in a stack results in a considerable enhancement of production efficiency.
The marker positions can be sensed prior the separation of a piece of fabric from the web of material. Given known material parameters such as elasticity, resilience, etc., the positions of the marker positions sensed in this way can be converted with sufficient accuracy into the positions of the marker points that are to be anticipated in the relaxed 1 S state. This is effected in a coordinate system that is fixed in the textile. This entails the advantage that a change in the position of the marker points in a series of stretches and shrinkages can be taken into consideration when the piece of fabric is being separated from the web of material. In this way, incorrect separation of pieces of fabric from the web of material can be largely precluded. Correction values can be calculated from the deviations of the marker-point positions from their desired positions.
Correction values are associated with each marker point, and these identify the magnitude and direction of the deviation of the marker-point position from its desired position. All of the correction values taken together form a data set that identifies the distortions of a piece of fabric like an "eyeglass." At this time, local distortions can also be taken into account.
This data set can be in the form of tables, matrices or interpolation functions. It can be used to distort the cut outlines in the same way, in order to establish the relative position of the cut lines to the available marker points, which can thus be used as anchor points as precisely as would be the case with an undistorted piece of fabric and an undistorted cut line.
It is preferred that work be done with a coordinate system that is fixed in the textile. This can be "locked" onto selected marker points. For example, three marker points are sufficient to set up an X-Y coordinate system, with one forming the point of origin. The two others can determine the compression or the extension of the X or Y
coordinates.
Additional marker points in the field of sight or field of measurement can then establish an additional distortion matrix.
Individual aspects of the advantageous embodiments of the present invention are set out in the brief description of possible embodiments of the present invention that follows:
As an example, when being pulled off a roll, the webs of material are measured optically along previously set measurement tracks. Previously determined marker points, so-called anchor points, are stored in memory. These anchor points can be characteristic features of a pattern.
The webs that are drawn off the bale are cut off along predetermined shape lines and positioned one above one another on the carrier, for example, a cutting grid, as pieces of fabric. Subsequently, this cutting grid moves the stack of pieces of fabric that is positioned on it into the actual cutting device. Once the piece of fabric has been measured and positioned on the cutting grid, a check is made to ensure that all the marker points on the web that is to be put into position lie within predetermined tolerances. If this is the case, then the current piece of fabric is laid on the stack that is already on the cutting grid.. If, on the other hand, this is not the case, then the cutting grid is replaced and the piece of fabric that was to be laid on it then forms the first layer of the stack that is to be built up on the next cutting grid. This means that the size of the stack that is to be cut is determined dynamically during the stacking process, which is to say that the buildup of the stack is terminated as soon the size of an incoming piece of fabric does not match the already stacked pieces of fabric within predetermined limits.
Using this procedure, it is possible, in particular, to take into consideration long-wave variations of the elongation within a bale of fabric. These can occur in a sequence of variations of fabric variations in a bale of fabric. For example, the inner layers of a bale of fabric may be more or less elongated than the outer layers.

Provision can also be made such that the lines of separation of the individual pieces of fabric are not rectilinear or perpendicular to the direction in which the fabric is drawn off, but can be programmed freely within specific limits as predetermined by the parameters of the machine. A gripper carriage, in which a plurality of grippers can be adjusted individually to the shape of the line of separation, can be used for relocation. This can be done by means of servomotors, for example, in that the individual grippers move in the direction of the edge of the fabric until one of the sensors installed on this responds and thereby stops the movement of the gripper. All the grippers are adjusted at the touch of a button.
It is also possible to match the predetermined cut line to a more or less pronounced distortion of the web of fabric with the help of the marker-point positions picked up when the web of fabric is drawn off. This can be effected, for example, in that the deviations of the marker points adjacent to the intended cut line from their desired values are recorded and used to correct the position of the cut line.
The marker points can serve to position the cut line, in that anchor points of the cut outline are superimposed on the marker points or positioned in predetermined relative positions to these. They can also serve to influence the cut outline itself. A
fabric coordinate system that is somewhat distorted can be set up by at least two of the actual marker points that have been detected. If the cut outline that is given in a predetermined coordinate system is converted, the cut can be guided and matched to the distortions in the fabric.
In a simple case, it is sufficient to perform a single-axis elongation. It is, however, also possible to take into account elongations in both directions, at least about an axis that is perpendicular to the plane of the fabric. If necessary, distortions can be taken into account. In the simplest case, conversion is carried out on the basis of a single coordinate-transformation matrix that applies to the whole piece of fabric.
If, however, only local distortions are to be taken into account and compensated for, a coordination transformation matrix can be associated with each marker point. This then applies locally for the marker points and their surroundings. Both isotropic and almost any anisotropic elongations of the textile structure can be sensed and compensated for by using this method. Conversion of the nominal cut outline into the actual cut track that is to be followed can be performed in a processor. For example, the ideal cut outline (nominal cut outline) can be preset from a programming station and converted into the actual adapted outlines.
When the pieces of fabric are laid above one another in several layers, starting with the first layer that is laid down, a check is carried out to ensure that the next layers after this are within the preset tolerances. For example, the positions of the marker points of the first piece of fabric can predetermine the middle of the current tolerance fields.
In a refined method, the tolerance field of each marker point is predetermined dynamically. This can be effected in that in the case of each piece of fabric that is to be added a check is made to ascertain whether or not it is possible to find the desired marker-point positions for the marker points of the pieces of fabric that have already been stacked as well as for the marker points of the pieces of fabric that are still to be added, the tolerance field of said desired marker-point positions including all marker points (those that already exist and those that are to be added). Using this method, it is possible to avoid premature termination of the stacking process that is unnecessary in and of itself.
Then, depending on the position of the markers of the piece of fabric of the subsequent layers, the marker points of the piece of fabric of the first layer can also take in the boundary layers of the tolerance band. In this case, the complementary fabric distortions of the cut outline that are required to correct existing distortions of the fabric are so calculated that they are optimal for the whole stack of fabric pieces.
It is possible to establish individual tolerance fields for every marker point. In particular, it is possible to establish such marker points within very narrow tolerance limits that lie in critical points relative to the cut outline. Marker points that are spaced at a relatively great distance away from the cut outline are not as critical as marker points that are within the immediate vicinity of the cut outline. In addition, marker points that form anchor points for a cut outline, i.e., on which a cut outline is established, can be of different significance, depending on the function of the piece that is cut out for a subsequent garment or another article. To this extent, sections with different quality requirements can be defined on the cut outline, which then, as a consequence, have different tolerance limits for the marker points in question.
The cut outlines can contain geometric elements (lines, circles, arcs, etc.).
These can be defined on individual marker points (or anchor points). When this is done, different parts of the cut outline can be subjected to different distortion processes. This permits correction of even complex distortions.
It is advantageous to subject the fabric web to constant tension when it is being drawn off. This creates defined conditions. The piece of fabric that is then laid out freely relaxes again. The position that it then takes up can then be calculated using known fabric parameters.
In one configuration of the present invention, the carrier can perform a solid-body movement for the whole piece of fabric and all the cut-outline sections that are located on this and which incorporate a shift in the X or Y direction andlor rotation about the vertical axis. The solid-body movement can be determined on the basis of the measured marker points so as to position the piece of fabric that is to be picked up within the tolerance fields. Alternatively, a conveyor, with which the piece of fabric is positioned on the carrier, can be controlled in such a way as to lay the piece of fabric down in the correction position, in which its marker points hit the tolerance fields. The position of the markers follows from the position of the carrier carriage and the deviations of the markings that have been detected from the preprogrammed point of the camera's field of mew.
Additional details of the present invention are set out in the description, secondary claims, and drawings that follow. These drawings show the following:
1. A diagrammatic view of a cutting installation;
2. A diagrammatic view of a piece of fabric with distortions;

3. A diagrammatic view of a piece of fabric with a plurality of blanks.

The cutting installation shown in Figure 1 is used to produce fabric blanks 2 from a stack 3 of pieces of patterned fabric 4. The pieces of fabric 4 are first drawn off a bale 5 in the form of a web 6 and then cut off.
As can be seen in Figure 1, a holder to hold a bale 7 and support it in bearings is part of the cutting installation. A table 8 is adjacent to the holder 7, and the web 6 can be laid out across this table 8. Between the table 8 and the holder 7 there is a cutter 9 for separating a piece of fabric 4 from the web 6. The cutter 9 can, for example, be a laser head 11 or another device for separating the fabric. The laser head 11 is mounted in bearings so as to move transversely to the web 6 on a crossbeam 12. If the cut is not to be made transversely, but obliquely, in an S-shape, or along an undulating path instead of in a straight line, the laser head 11 can be fitted with a dewing device.
Alternatively, the crossbeam 12 can be supported in bearings on rails 13, 14, on slides, so as to be able to move in the X and Y directions.
A gripper device 15 can be used to draw the web 6 from the bale 5, and this gripper device 15 has a number of gripper heads 17 that are mounted on X-linear adjustment devices 16. All of the X-linear adjustment devices 16 can also be mounted on a crossbeam 18 that can, if necessary, be mounted in bearings so as to be able to move in the X direction, as is shown diagrammatically in Figure 1. In this way, the forward edge of the web 6 can be gripped and sensed individually, and the web of fabric can be drawn off the bale 5 by movement of the crossbeam 18 in the X direction.
The table 8 is bridged across by a carrier 19 on which is/are mounted a camera 21, or several cameras or inspection devices. The carrier 19 can be disposed close to the holder 7 so as to sense the web 6 as it is drawn off the bale 5. However, it is also possible to mount the camera 21 above the table 8 (as is shown) so as to examine the web that has been drawn off as a whole.
The camera 21 constitutes a sensing device 22 for the marker points on the web 6. The corresponding camera images or measurement data are passed to a controller 23 that controls the cutting installation 1.

A carrier 24 is adjacent to the table 8, and this is used to accommodate the stack 3. The carrier 24 is formed, for example, by a cutting grid 25 that accommodates the stack 4 in such a way that it can be cut by a laser beam, perpendicular to the horizontal plane.
A conveyor 26 moves the individual piece of fabric 4 onto the stack3; in the present embodiment, this conveyor 26 can be formed by the gripper device 15.
Corresponding rails 27, 28 that extend in the X direction guide the crossbeam 18 so that it can slide in the X direction, and extend from the table 8 to the cutting grid 25.
The cutting grid is, in its turn, supported in bearings on sections of rails that can be adjusted linearly in the X direction and the Y direction by a positioning device 29; if necessary, these can be pivoted about a vertical axis Z. Rails 31, 32 are connected to these sections of rail that lead into and through a laser cutter 33.
The cutting installation 1 described so far operates as follows:
The controller 23 has a data set that describes one or a plurality of cut outlines S of a fabric blank 2, as shown in Figure 2. In addition, the controller 23 has a plurality of marker points P(i, j). The cut outline S is set in relation to the marker points P(i, j). The marker points P(i, j) thus serve as anchor points. They can lie on the cut outline S or alternatively can be set in a regular or irregular grid.
First, the grippers 17 draw a web of fabric 6 off the bale 5. The camera 21 senses the web of fabric that enters the field of view and searches for the marker points P(i, j) in the pattern. Not all the marker points are, as a rule, where they should be. Thus, there is a deviation V(i, j) between the actual marker point P;St(i, j) and the desired marker point Pso,i(i, j). The deviations V(i, j) thus form a vector field (as shown in Figure 2) for the distortion of the web of material or of the piece of fabric 4.
Initially, the line of separation T on which the piece of fabric 4 is to be cut from the web of fabric 6 has to be identified. To this end, it is assumed that the desired line of separation T, which is shown as a vertical, broken line in Figure 2, passes through the marker points P(n, k) and P(n, 0). Here, the distortion vectors V(n, k) and V(n, 0) are to be marked. Now, the actual line of separation T is displaced towards the line of separation T that was originally set and that is indicated by the broken line.
This is done in that the vectors V(n, j) (j goes from 0 to k) are added to the corresponding control data.
The fabric blank indicated in Figure 2 by the bold line is obtained. The same procedure is followed if the line of separation T is not a straight line. Two marker points or two distortion vectors are sufficient to establish the line of separation T if it is a straight line.
Once the piece of material 4 has been separated from the web 6, it must be transferred to the cutting grid 25. To this end, the grippers 17 (Figure 1 ) grip the edge of the fabric and move the piece of fabric 4 onto the carrier grid 25, where the piece of fabric 4 is laid down and the next piece of material is separated from the web 6, as has been described heretofore.
The next problem to be dealt with is to place the second piece of fabric that is now on the table 8 onto the existing piece of fabric 4 of the carrier grid 5 in such a way that the marker points P(i, j) are positioned one above the other as exactly as possible. If the vector field V(i, j) that describes the distortions of the actual blank 4, which is on the table 8, deviate by only an insignificant amount from the distortion vector field V(i, j) of the blank 4 that is on the carrier grid, the new blank 4 can simply be laid on the previous blank, when the marker points P(i, j) will be one above the other. In many instances, the distortion in different pieces of fabric 4 are not identical, but different.
The controller 23 now computes the position in which the new piece of fabric 4 is to be laid onto the previous piece of fabric 4 so that the marker points P(i, j) are above one another as exactly as possible. In detail, this can be done in that an average distortion for the piece of fabric 4 is computed as to amount and direction and then the difference between this distortion and the corresponding distortion of the previous piece of fabric is computed.
This difference is taken into account complementarily when this piece of fabric is laid onto the previous piece of fabric and compensated for thereby. A stack made up of many pieces of fabric can gradually be built up in this manner, and all the individual marker points will be above one another fairly exactly. The average of all the marker points P(i, j) of the pieces of fabric that are above one another now forms a stack marker point.
Taken as a whole, all the stack marker points characterize the average distortion of the pieces of fabric 4 that form the stack.

Using the stack marker points, the controller 23 can now correct the cut outline S (see Figure 2). If the points P(i, j) now represent stack marker points, the cut outline S will be similarly distorted according to the average distortion of the pieces of fabric 4. The distorted and thereby corrected cut outline S' is shown by a broken line in Figure 2. In summary, an example for a procedure for the collective cutting out of patterned fabric will be described below:
1. Grip edge of fabric and draw off web of fabric / lay out fabric 2. Inspect fabric, identify marker points P(i, j), determine xstoet~, ystoet~
coordinates in a measurement coordinate system 3. Determine the field of the coordinate vectors V(i, j) from the differences of the actual positions xsto~ yscofr and the desired positions xsoii, ysoii of the marker points P(i, j) 4. Convert the coordinates of the desired line of separation according to the distortion vectors V(i, j) that are adjacent to the cut outline into corrected cut coordinates in order to determine the corrected line of separation T.
S. Cut off the section of fabric 6. Define the transformation matrix for each marker point P(i, j) in order to convert the actual coordinates x;, y~ of the marker point into the desired coordinates of the particular marker point P(i, j) 7. Define an averaged transformation matrix from the transformation matrices of (all) the marker points, e.g., by the least error squared method 8. Transfer the piece of fabric onto the cutting grid 9 Perform Steps 1 to 7 on the next piece of fabric 10 Determine the deviation of the marker points from their desired positions, a) if the deviations are small - continuation with Point 8 b) if the deviations are too large - determine a coordinate matrix from the difference of the two transformation matrices and move the cutting grid into a corrected position, as well as position the piece of fabric onto the cutting grid in its corrected position. Then continue as in Point 9 c) if the deviations are so large or such that no corrected position is possible -transfer the cutting grid into the cutter and lay the piece of fabric on an empty cutting grid. Continue as in Point 9 11. Match the predetermined cut outline for the piece of fabric in the cutter to the average distortions in the stack of pieces of fabric on the basis of the transformation matrices that have been defined, in that these are averaged to form an overall distortion matrix.
The cutting installation 1 according to the present invention is equipped to stack pieces of patterned fabric-taking into account the distortions in individual pieces of fabric-in such a way that the pattern of the individual pieces of fabric and in particular the positions of predetermined marker points on the pieces of fabric are to a large extent exactly above one another. This is made possible by individual determination of the selected distortions of the pieces of fabric and stacking, taking these distortions into account. The pieces of fabric that have been positioned precisely above one another can be cut out as a group. To this end, the average distortion in the stack is first determined.
The outline of the blank is matched to this distortion. If the distortion of a selected blank is of a quality or size that is so large that the particular blank cannot be placed in any position on the existing stack, the stacking process is terminated and the particular blank is used as the first layer in a new stack that is to be built up.
Using this installation and this method it is possible to cut out patterned fabrics at a very high level of productivity.
In its simplest configuration, the cutting installation according to the present invention observes the pieces of fabric and identifies distortion on the basis of existing marker points. If the distortions are in the identical area as the distortions in the pieces that have already been laid on a stack, the current piece can be laid on this same stack. However, if the deviations are too large, the stack that is formed is moved into the cutter and the current piece forms the first layer of a new stack.
Figure 3 shows another embodiment of the method according to the present invention in diagrammatic form. A plurality of fabric blanks 2-1, 2-2, and 2-3 are to be cut from a piece of fabric 4. The outlines in question form a first set of geometric elements. A hole A-1, A-2, A-3 is to be cut in each piece of fabric 2-1, 2-2, 2-3. The holes A-1, A-2, A-3 constitute a second set of geometric elements. Marker points 1.1 to 1.3 are distributed over the surface of the piece of fabric 4. The points 1.1 to 1.4 can form a first coordinate system for the blank 2-1. The marker points 1.1 and 1.4 form a corresponding coordinate system for the hole A-1. The same applies to the blanks 2-2 and 2-3. In addition, it is also possible to define an overall coordinate system by way of all the points 1.1 to 3.3, e.g., in order to establish all three blanks 2-l, 2-2, and 2-3. The tolerance bands for differing geometrical elements can be established differently for all the variants set out above. In addition, the generation of tolerance bands can be carried out adaptively, so that matching the size of the tolerance bands is to current process conditions or external influences.

Claims

1. Cutting installation (1) for cutting out fabric blanks (2), with a carrier (24) to accommodate a stack (3) of fabric pieces (4) that are to be cut out, with a sensing device (22) for recording the positions of marker points P(i, j) on the pieces of fabric (4), with a separator (9) to cut a piece of fabric (4) off a web of fabric (6), with a conveyor (26) for transferring pieces of fabric (4) onto the carrier (24), forming the stack (3), with a controller (23) for controlling the carrier (24) and/or the conveyor (26) when the pieces of fabric (4) are transferred to the carrier (26), whilst minimizing the positional deviations of the marker points (P(i, j)) of the pieces of fabric (4) that are stacked one above the other in the stack (3).

2. Cutting installation as defined in Claim 1, characterized in that the controller (23) is equipped to sense the position and/or the distortion of a piece of fabric (4) from the positions of the marker points, and to check whether or not the particular piece of fabric (4) matches the pieces of fabric that have already been laid on the stack.

3. Cutting installation as defined in Claim 1, characterized in that the controller (23) is equipped to determine correction values for adapting the predetermined cut outlines to existing distortions from the sensed positions of the marker points (P(i, j)).

4. Cutting installation as defined in Claim 1, characterized in that a pull-off device is provided to tension the web of fabric (6) before a piece of fabric is cut off it.

5. Cutting installation as defined in Claim 1, characterized in that the controller (23) activates the sensing device (22) ahead of the separator (9) in order to sense the positions of the marker points (P(i, j)) before separation of the piece of fabric (4), when the web of material (6) is stretched.

6. Cutting installation as defined in Claim 1, characterized in that the controller (23) is equipped to convert the positions of the marker points (P (i, j)) of the stretched web of fabric (6) into positions that they will take up when relaxed, by using fabric parameters.

7. Cutting installation as defined in Claim 1, characterized in that the carrier (24) is connected to a positioning device (29) that is controlled by using deviations of the marker points (P (i, j)) of the current piece of material (4) from positions of the marker points of at least one of the pieces of fabric (4) that has already been laid down, or from set positions.

8. Cutting installation as defined in Claim 1, characterized in that the separator permits a variably adjustable line of separation.

9. Method for cutting out patterned fabrics, which comprises the following steps:
Recording the positions of marker points on a web of fabric or a piece of fabric, Comparison of these positions with predetermined desired positions, Determination of the amount and direction of possible existing deviations, Determination of a target position in which the deviations of the positions of the marker points from the desired position are minimal, Placing the piece of fabric in the previously determined target position.

10. Method as defined in Claim 9, characterized in that the desired positions are determined by the positions of the maker points of a previously sensed piece of fabric.

11. Method as defined in Claim 9, characterized in that the cut outlines are matched to the sensed positions of the marker points.

12. Method for cutting out patterned fabrics, which comprises the following steps:
Recording the positions of marker points on a web of fabric or on a piece of fabric, Placing individual pieces of fabric on a carrier so as to form a stack of pieces of fabric with conforming marker points, Matching at least one predetermined cut outline to the positions of the marker points that have been sensed.

13. Method as defined in Claim 9 and Claim 11, characterized in that the possible deviations are compared with predetermined maximal deviations; and that the piece of fabric is only placed on the preceding piece if the deviations are below a maximal size, whereas the current piece of fabric is used as the first layer of a new stack if the maximal deviations fall short of the maximal deviations.

14. Method as defined in Claim 9 and Claim 11, characterized in that a plurality of blanks are associated with a web of material.

15. Method as defined in Claim 9 and Claim 11, characterized in that a plurality of cut outlines that form different geometric elements are associated with a blank, its own marker points being associated with each such geometric element.

16. Method as defined in Claim 15, characterized in that their own coordinate systems and their own tolerance bands are associated with the geometric elements.