Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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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
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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
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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.
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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
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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
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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.
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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.
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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
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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.
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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
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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
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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.
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