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Claims  |
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We claim:
1. Apparatus for cutting pattern pieces from sheet material in accordance
with preprocessed marker data comprising:
an automatically controlled cutting machine including a table that supports
sheet material being cut, a cutter including a cutting tool, controlled
motor means connected with the table and cutter for moving the cutting
tool and sheet material on the table relative to one another in cutting
engagement and control means connected with the motor means for producing
motor command signals to guide the cutting tool along lines of cut in
accordance with program data defined by the pattern pieces in the marker;
and
preprocessing means connected with the control means of the automatically
controlled cutting machine for receiving and processing data defining the
pattern piece in the marker prior to use in the control means of the
cutting machine to identify in the marker data trouble points of high
cutting difficulty including points of close approach, or tangencies and
to generate remedial motor command signals, the preprocessing means
including window comparator means for detecting potential trouble points
of high cutting difficulty from a comparison of rectangular windows about
two adjacent pattern pieces, one of the pattern pieces being cut
subsequent to the other in a predetermined order established by the
program data, and for further identifying critical line segments of the
adjacent pattern pieces in overlapping areas of the rectangular windows.
2. Apparatus for cutting pattern pieces from sheet material as defined in
claim 1 wherein:
the control means in the automatically controlled cutting machine includes
means for establishing the feed rate of the cutting tool and the sheet
material relative to one another; and
the preprocessing means includes means for generating in the processed data
reduced feed rate signals for the cutting tool and material at the trouble
points.
3. Apparatus for cutting pattern pieces from sheet material as defined in
claim 1 wherein:
the cutting tool in the cutting machine comprises a knife blade having a
sharp leading edge which is advanced along a line of cut;
the controlled motor means includes a motor means for orienting the knife
blade relative to the line of cut at each point along the cutting path;
and
the preprocessing means includes means for generating yaw signals for
orienting the knife blade at an angle to the line of cut at the trouble
points.
4. Apparatus for cutting pattern pieces from sheet material as defined in
claim 1 wherein the preprocessing means includes path modification means
for offsetting the line of cut in the vicinity of the trouble points.
5. Apparatus for cutting pattern pieces as defined in claim 4 wherein the
path modification means includes means for smoothly blending the offset
portion of the cutting path in the vicinity of a trouble point with
adjacent portions of the cutting path.
6. Apparatus for cutting pattern pieces from sheet material as defined in
claim 1 wherein the preprocessing means includes means for calculating the
separation of two adjacent lines of cut.
7. Apparatus for cutting pattern pieces from sheet material as defined in
claim 6 wherein the preprocessing means further includes means for
calculating the angular relationships of two cutting paths separated less
than a preset amount; and means for generating remedial motor command
signals when the angular relationships are less than a preset angle.
8. In a system for automatically cutting sheet material with a reciprocated
cutting blade, the blade and material being moved relative to one another
in cutting engagement as the blade is guided along cutting paths defined
by marker data representing a plurality of patterns in a closely packed
array, the improvement comprising: processing means receiving the marker
data for identification of critical cutting paths in the closely packed
array of patterns, the processing means including path separation
calculating means for determining the separation distances of two adjacent
cutting paths of patterns in the array, means for comparing the determined
separation distances with a pre-established minimum separation distance to
identify a critical cutting path having a segment located less than the
minimum separation distance from an adjacent cutting path, and path
modification means for modifying the marker data along identified critical
cutting paths to offset the located segments and establish the minimum
separation distance at each point along the adjacent cutting paths.
9. In a system for automatically cutting sheet material, the improvement of
claim 8 wherein the processing means further includes signal generating
means for producing compensating blade commands for guiding the cutting
blade along critical cutting paths identified by the calculating and
comparing means.
10. In a system for automatically cutting sheet material, the improvement
of claim 9 wherein the signal generating means has a reduced feed rate
generator for reducing the rate of advance of the cutting blade along an
identified critical cutting path.
11. In a system for automatically cutting sheet material, the improvement
of claim 9 wherein the signal generating means comprises a yaw signal
generator for producing signals orienting the blade slightly out of a
position tangent to the critical cutting path and away from the adjacent
cutting path.
12. In a system for automatically cutting sheet material, the improvement
of claim 8 further including in the data processing means means for
calculating the angular relationships of the critical cutting path and the
adjacent cutting path and means for comparing the calculated angular
relationships with a minimum angle to exclude from a critical
classification cutting paths having angular relationships greater than a
specified amount.
13. In a system for automatically cutting sheet material with a
reciprocating cutting blade the improvement of claim 8 wherein the data
processing means includes a window comparator identifying patterns in the
array having potentially critical cutting paths separated by less than the
minimum separation distance from an adjacent pattern, the window
comparator being connected in the data processing means to receive the
pattern data prior to the path separation calculating means.
14. In a system for automatically cutting sheet material, the improvement
as defined in claim 13 wherein: the window comparator includes means for
establishing windows defined by the limits of the pattern pieces in two
coordinate directions, and means for comparing the windows of one pattern
piece with another for overlap.
15. In a system for cutting sheet material as defined in claim 14, the
improvement wherein the window comparator and the path separation
calculating means cooperate to limit calculations of the separation
distances to the portions of the cutting paths lying within the window
overlap.
16. A method of cutting pattern pieces from sheet material with a cutting
blade and preprocessed marker data defining the pattern pieces in a
closely packed array comprising:
reducing the pattern pieces in the marker array to machine readable data
defining the shapes and positioning of the patteren pieces in the array in
terms of rectangular coordinates;
preprocessing the machine readable data by comparing the data of one
pattern piece with another in a data processor to determine the separation
between the pieces in the array, and identifying in the data processor
critical segments of a cutting path for a pattern piece which segments are
located closer to an adjacent pattern piece than a predetermined amount,
the step of identifying including defining rectangular windows around
adjacent pattern pieces by means of the maximum and minimum coordinates
along each coordinate axis, and examining the distance between the pattern
pieces along those segments of the cutting paths falling within any area
of a rectangular window overlapping an adjacent window;
generating basic command signals from the machine readable data for guiding
the cutting blade along cutting paths defined by the shapes and
positioning of the pattern pieces in the array;
generating remedial command signals for guiding the cutting blade past the
identified critical segments; and
cutting the pattern pieces from the sheet material by guiding the cutting
blade along cutting paths defined by the shapes and positioning of the
pattern pieces with the basic and remedial command signals.
17. A method of cutting pattern pieces from sheet material with a cutting
blade as defined in claim 16 wherein:
the step of generating basic command signals from the machine readable data
comprises generating basic command signals controlling the feed rate of
the cutting blade along a cutting path; and
the step of generating remedial command signals comprises generating
signals which reduce the feed rate established by the basic command
signals along the identified critical segments of a cutting path.
18. A method of cutting pattern pieces from sheet material with a cutting
blade as defined in claim 16 wherein:
the step of generating basic command signals from the machine readable data
comprises generating command signals for orienting the cutting blade
tangentially of a cutting path at each point along the path; and
the step of generating remedial command signals comprises generating yaw
signals for rotating the cutting blade slightly out of the tangent
position and away from an adjacent pattern piece along the identified
critical segments of a cutting path.
19. A method of cutting pattern pieces from sheet material as defined in
claim 16 wherein the step of generating remedial command signals comprises
generating signals for guiding the cutting blade along a cutting path
offset from the adjacent pattern piece by a limited amount at an
identified critical segment.
20. A method of cutting pattern pieces from sheet material as defined in
claim 19 wherein the step of generating signals for guiding along an
offset cutting path includes generating a new cutting path offset from an
identified critical segment in an old cutting path by a fixed amount and
blending the new cutting path into the old cutting path at the opposite
ends of the critical segment.
21. A method of cutting pattern pieces from sheet material with a cutting
blade as defined in claim 16 wherein the step of comparing one pattern
piece with another in the data processor to determine and identify
critical segments of a cutting path comprises establishing an order in
which the pattern pieces in the marker are to be cut in the array, and
comparing the data of one pattern piece only with the data of pattern
pieces to be cut prior to said one pattern piece to identify critical
segments.
22. A method of cutting pattern pieces from sheet material as defined in
claim 16 wherein the step of examining includes comparing the two maximum
values of the point data in each coordinate for two pattern pieces, and
comparing the two minimum values of the point data in each coordinate for
the same two pieces to establish the overlapping area of the rectangular
windows.
23. A method of preprocessing data defining a marker of pattern pieces to
be cut from a layup of sheet material with an automatically controlled
knife blade comprising the steps of:
reading data defining the marker of pattern pieces into a data processor
with the periphery of each pattern piece and the positioning of the pieces
within the marker fully defined by the data;
comparing the data of each pattern piece with the data of each other
pattern piece in the processor to identify critical segments of the
pattern peripheries lying closer to adjacent pattern pieces than a
predetermined minimum separation distance; and
selectively modifying the marker data defining the pattern pieces by
calculating from the data identified as a critical segment new data
defining a cutting path for the blade offset from the identified critical
segment and away from a closely adjacent pattern piece to establish a
separation not less than the predetermined minimum.
24. A method of preprocessing data defining a marker of pattern pieces as
defined in claim 23 wherein the step of comparing comprises scanning the
data for each pattern piece for the limits of the peripheries in two known
coordinate directions and comparing the limits of the pieces to establish
the potential for critical segments having less than the minimum
separation.
25. A method of preprocessing data defining a marker of pattern pieces as
defined in claim 23 wherein the step of modifying the marker data
additionally includes adding to the data identified as a critical segment
a yaw command to orient the knife blade out of a position tangent to the
cutting path and away from an adjacent pattern piece.
26. A method of preprocessing data defining a marker of pattern pieces as
defined in claim 23 further including the step of adding to the modified
marker data a reduced feed rate command to slow the rate at which the
knife blade advances along the offset cutting path in a cutting process. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
This invention relates to a method and apparatus for cutting sheet material
and is concerned more particularly with problems that arise in automated
cutting machines when a plurality of pattern pieces in a closely packed
array are cut from limp sheet material.
Numerically controlled cutting machines such as disclosed in U.S. Pat. No.
3,495,492, having the same assignee as the present invention, are well
known in the art and are widely accepted in industry for cutting various
limp sheet materials such as woven or nonwoven fabrics, vinyl and other
plastics, paper, cardboard, leather and others. The machines frequently
are used to cut pattern pieces of various shapes in a predefined marker. A
marker is an array of pattern pieces arranged as cut in closely spaced and
sometimes contacting relationship in order to minimize the total quantity
of material used. In the automatically controlled cutting machine of U.S.
Pat. No. 3,495,492, a reciprocating cutting blade is guided along cutting
paths defined by the pattern piece peripheries by means of a numerical or
other control that responds to program data defining the shapes and
positioning of the pattern pieces in the marker array.
A phenomenon that exists in cutting limp sheet materials in contrast to
cutting in other arts is the fact that a blade having a sharp leading
knife edge severs the material as the blade advances along a cutting path
but does not remove material to any significant extent. As a result the
material is pushed aside by the advancing blade and generally flows around
the cutting blade in pressing engagement. Because of the engagement of the
blade and material, and also because limp sheet materials are pliable even
in a multi-ply layup compacted by vacuum as disclosed in the referenced
patent, significant forces can be developed against the blade and cause
the blade to depart from the programmed line of cut regardless of the
accuracy with which the blade positioning mechanism is operated.
In cutting multi-ply layups of sheet material with a cantilevered knife
blade, pattern pieces cut from the upper plies of the layup may have
slightly different shapes and dimensions than the same pieces in the lower
plies where the disturbing forces applied to the blade by the material
cause the blade to bend. Such forces and the resulting bending are
attributable to a number of factors, some of which are known and others of
which are unknown. However, it is known that the forces frequently arise
in connection with points of tangency or close approach in a closely
packed marker array. When a cutting blade passes in close proximity to an
adjacent pattern piece that was cut at an earlier stage in the operation,
the kerf created by the previous cut interrupts the continuity of the limp
sheet material and allows the material at one side of the knife blade to
yield more easily to the blade than at the opposite side. As a result the
blade experiences unbalanced lateral loading. Naturally, the closer the
cutting path approaches a previous cut, the greater the unbalanced loading
will be on the blade and the greater the blade bending. The blade may
eventually break or jump completely into the kerf of the previous cut.
Inaccuracies or damage to the machine are the ultimate consequences.
Several techniques have been developed to overcome the difficulties that
are associated with tangencies and points of close approach in marker
arrays. U.S. Pat. Nos. 3,855,887 and 3,864,997 having the same assignee as
the present invention, reveal that a reciprocated knife blade may be
slowed down with reduced feet rate signals in such critical cutting areas,
and yaw signals may be applied to rotate the blade out of a tangent
position at the same time. Until now, however, the introduction of
compensating or remedial commands such as the reduced feed rate and yaw
signals was left to the experience and skill of the person who digitized
the marker array and prepared the cutting program in a basically manual
process.
It is, accordingly, a general object of the present invention to provide
method and apparatus for automatically preprocessing data defining a
marker to identify tangencies, points of close approach and other critical
cutting conditions, and to develop compensating or remedial commands for
guiding a cutting blade past such cutting conditions without sacrificing
accuracy or damaging the machine due to excessive blade loading.
SUMMARY OF THE INVENTION
The present invention resides in a method and apparatus for cutting pattern
pieces from sheet material in accordance with preprocessed marker data.
The apparatus which is employed in carrying out the method includes an
automatically controlled cutting machine having a cutting table that
supports limp sheet material during the cutting operation. A cutter,
including a cutting tool such as a reciprocated knife blade is guided
along a programmed cutting path by means of drive motors and motor control
means producing command signals in accordance with program data defined by
the pattern pieces in a marker.
Prior to developing the command signals, however, the program data is
operated upon in a preprocessing means connected with the control means
for the machine. The preprocessing means receives and processes the data
defining the pattern pieces and identifies in the marker data critical
points of high cutting difficulty including points of close approach or
tangencies. Once such critical points have been identified, the processing
means further generates remedial motor command signals such as reduced
feed rates, yaw commands, and translational commands that guide the
cutting blade along a path offset slightly from a path at a pattern
periphery.
As a result, the preprocessing means produces a program of cutting commands
that not only define the shapes and the positioning of the pattern pieces,
but also include compensating command signals for guiding the cutting
blade through difficult cutting situations that would otherwise result in
inaccurate cutting or damage to the cutting blade or machine. Typically,
the preprocessing means would be a microprocessor that handles a large
volume of data at speeds far beyond human capabilities and with more
completeness and accuracy than is possible or practical during the
digitizing process. A more complete analysis of a marker is made and a
more precise product is produced by the automatically controlled cutting
machine.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a cutting system having an automatically
controlled cutting machine in which the present invention is employed.
FIG. 2 is an overall diagram of the cutting system including the
preprocessor of the present invention.
FIG. 3 is a marker of pattern pieces showing the positional relationship of
the various pieces as they are cut from a layup of sheet material.
FIG. 4 is a block diagram illustrating the functional components of the
preprocessor in one embodiment.
FIG. 5 is a diagram illustrating a typical feed rate program produced by
the slowdown generator.
FIG. 6 is a diagram illustrating a typical yaw program produced by the yaw
generator.
FIG. 7 is a diagram showing two pattern pieces in the marker array in close
proximity to one another and the technique of locating critical cutting
segments by means of the window comparator.
FIG. 8 is a table illustrating the comparisons made by the window
comparator to establish no overlap.
FIGS. 9-12 are window diagrams representing the geometric relationships
established by the comparisons in the table of FIG. 8.
FIG. 13 is a table illustrating the comparisons made by the window
comparator to locate the overlapping sides of the windows.
FIGS. 14-17 are window diagrams representing the geometric relationships
established by the comparisons in the table of FIG. 13.
FIG. 18 is an enlarged fragmentary view of the pattern pieces in FIG. 7 at
a critical cutting area.
FIG. 19 is a fragmentary view of a critical path in FIG. 18 and shows the
directional offset of the cutting path.
FIG. 20 is a flow diagram illustrating the logic of the path modifier in
the preprocessor.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates an automatically controlled cutting machine, generally
designated 10 of the type shown and described in greater detail in U.S.
Pat. No. 3,495,492 referenced above. The machine 10 is utilized to cut a
multi-ply layup of a sheet material including woven and nonwoven fabrics,
paper, cardboard, leather, rubber and synthetic materials. The machine is
numerically controlled, and for this purpose is connected to a numerical
controller 12 by means of cable 14 which transmits other signals between
the controller and machine. Attached to the controller 12 is a data
processor 15 which preprocesses program data utilized by the controller to
produce command signals for a cutting operation. The processor 15 receives
input data from a cutting program tape 16 and processes that data before
it is utilized by the controller 12 to command the cutting machine. As
described in greater detail below, the preprocessor analyzes the cutting
data to identify critical segments of cutting paths that could lead to
cutting difficulties due to the closely packed arrangement of the pattern
pieces in a marker to be cut. The preprocessed data is then transmitted to
the controller 12 which converts that data into machine commands for
guiding a reciprocating cutting blade 20 along various cutting paths P
through the sheet material. The resulting pattern pieces may be used, for
example, in the manufacture of garments or upholstery products. The
preprocessed data, which controls the eventual motions of the cutting
blade 20, permits the close packing of pattern pieces in a marker array to
be maintained because the data includes compensating commands for guiding
the cutting blade through difficult cutting situations attributed to the
close packing without loss of cutting accuracy.
The cutting machine 10 includes a table 22 having a penetrable bed 24
defining the support surface for the layup L during cutting. The bed 24
may be comprised of a Styrofoam material or preferably a bed of bristles
which are easily penetrated by the reciprocating cutting blade 20 without
damage to either while the cutting path P is traversed. The bed may also
employ a vacuum system such as illustrated and described in greater detail
in the above referenced U.S. Pat. No. 3,495,492 for holding the layup
firmly in position.
The cutting blade 20 in a preferred embodiment is a knife blade suspended
above the support surface of the table 22 by means of an X-carriage 26 and
a Y-carriage 28. The X-carriage 26 translates back and forth in the
illustrated X coordinate direction on a set of racks 30 and 32 which are
engaged by an X-drive motor 34 energized by command signals from the
controller 12. The Y-carriage 28 is mounted on the X-carriage 26 for
movement relative to the X-carriage in the Y coordinate direction and is
translated by the Y-drive motor 36 and a lead screw 38 connected between
the motor and carriage. Like the drive motor 34, the drive motor 36 is
also energized by command signals from the controller 12. Thus coordinated
movements of the carriages 26 and 28 can translate the cutting blade 20
along a cutting path over any area of the table 22.
The cutting blade 20 is suspended in cantilever fashion from a platform 40
attached to the projecting end of the Y-carriage 28 for elevating the
sharp, leading cutting edge of the blade into and out of cutting
engagement with the layup of sheet material on the table 22. The blade 20
is reciprocated by means of a drive motor 42 also supported on the
platform 40.
In order to cut pattern pieces in a marker by means of any automatically
controlled machine, it is necessary to reduce the contours or peripheries
of each pattern piece to a machine-readable form. For a numerically
controlled machine, such as the machine 10 in FIG. 1, it is customary to
reduce the contours of the pattern piece peripheries to point data by
means of a coordinate digitizer. The digitizer is operated manually or in
more automated systems, line followers can be employed for the same
purpose. In either event, a sufficient sampling of data points lying on
the pattern piece peripheries is recorded by Cartesian coordinates so that
the locations of the patterns within the marker array as well as the
individual contours of the pieces are well defined. From such data, the
controller 12 generates the command signals that cause the X- and
Y-carriages 26 and 28 in FIG. 1 to translate the cutting blade in cutting
engagement with the sheet material along corresponding cutting paths.
It is apparent from the marker illustrated in FIG. 3 that a plurality of
pattern pieces forming a marker present difficult cutting situations due
to their irregular configurations and close packing which brings the
pieces into close proximity or contacting relationship with one another at
random points. The markers themselves are generated in this closely packed
configuration either manually or by automatic or semi-automatic marker
generators such as described in the reference Patent 3,855,887.
FIG. 2 illustrates in an overall block diagram the interrelationship of the
various components which control the operation of the cutting machine 10.
Basic marker data defining the positioning and contours of the pattern
pieces in a marker array, such as illustrated in FIG. 3, is stored in
digital form in the program tape 16 and is fed as an input to the data
processor 15. After the data has been analyzed in the processor 15 for
difficult cutting conditions at points of tangency or close approach, the
data together with any remedial command signals is transmitted to the
controller 12. The controller 12 is preferably a numerically controlled
computer which converts the digitized data and remedial commands into
motor command signals in accordance with conventional servo and curve
algorithms. Those signals are then transmitted to the drive motors in the
machine 10 to guide the cutting blade along programmed lines of cut.
FIG. 7 illustrates two pattern pieces, A and B, which are positioned in the
marker in such a manner that the upper edge of the pattern piece A is
located in close proximity to the lower edge of pattern piece B in the
vicinity of a point 50 located on the periphery of pattern piece B. The
separation of the pattern pieces at the point 50 is at a minimum and such
point is therefore referred to as the point of closest approach.
It has been determined from experience that when the points of close
approach are separated by certain minimum distances depending upon the
type of material being cut, the depth of the layup and other factors, an
automatically controlled cutting blade experiences great difficulty in
following the programmed line of cut when the adjacent pattern piece has
been previously cut. For example, if pattern piece A is cut prior to
pattern piece B, when the cutting blade 20 advances along the periphery of
pattern piece B generally parallel to the upper side of pattern piece A
and comes in the vicinity of point 50, lateral forces developed by the
material and applied to the blade may cause the blade to "jump" into the
previous cut even though the X- and Y-carriages attempt to track the
cutting blade accurately along the programmed line of cut through the
point 50. Alternatively, as the blade passes point 50, lateral forces on
the blade may have increased to a point which causes the blade to fracture
or, if the blade has jumped into the previous cut, the reaction to the
forces by the blade may cause the material to be displaced until the
cutting edge cuts back into the material and continues along the remaining
portions of the periphery of pattern piece B. The obvious results are that
pattern piece B as cut does not conform to the programmed profile for that
pattern piece. Similar consequences result when the pattern pieces are
actually tangent to one another.
Such cutting problems usually arise only when the cutting paths are
generally parallel and the angular relationship of the adjacent cutting
paths is less than a predetermined amount, for example, 30 degrees. With
larger angles lateral loading applied to the blade is not as severe and
there are no segments of the cutting paths which tend to approach a
parallel relationship with one another.
In accordance with the present invention, the data defining the marker is
analyzed by the processor 15 to identify points of tangency or close
approach. More specifically, the pattern pieces are analyzed to identify
critical cutting paths which have separation distances less than a
preestablished minimum separation distance. When such cutting paths are
located, the processor also generates remedial or compensating command
signals to guide the blade effectively past the critical cut without the
difficulties mentioned above.
FIG. 4 illustrates the components of the data processor 15 in one
embodiment. Typically the processor is part of the data input equipment
for the control 12 and may include software or firmware programs or have a
hard wired construction. One commercially available processor suitable for
the purpose is a Hewlett-Packard 21MXE series, model 2113.
As shown in FIG. 4, the digitized marker data defining the contours and
locations of each of the pattern pieces in the marker is transmitted from
the program tape 16 into a marker memory 56 at the input of the processor.
The point data defining each pattern piece is loaded sequentially into the
memory in the order in which the pattern pieces are cut from the layup,
and it is preferable that the marker memory have a storage capacity
sufficient to hold all of the pattern pieces in the marker or at least a
sufficient number of pattern pieces to conduct an analysis for all points
of tangency or close approach of the pieces in one general location of the
marker.
A window comparator 58 in the processor performs a preliminary analysis of
the data stored in the marker memory 56 to determine if potentially
critical cutting paths may be defined by the marker data. Such preliminary
analysis is performed by comparing the maximum and minimum coordinates of
a given pattern piece with the maximum and minimum coordinates of all
previously cut pattern pieces. Since the data defining the patterns is
stored in the marker memory in the order which the pattern pieces are cut,
the analysis of the coordinates according to that order is possible.
In order to more clearly understand how the window comparator 58 operates
and the comparison steps performed, one of the pattern pieces illustrated
in the marker of FIG. 3 has been framed in a "window" that has boundaries
or limits established by the maximum and minimum coordinates along both
the X and Y axes. The lower and upper limits along the X-coordinate axis
are designated by the abscissas XL and XU, respectively. Correspondingly,
the lower and upper limits along the Y-coordinate axis are designated by
the ordinates YL and YU, respectively. These limits are located in the
point data of the marker memory 56 by scanning all of the coordinate data
defining a particular pattern piece under investigation and selecting the
maximum and minumum values for each coordinate axis. Such scanning and
selecting of the maximum or minimum value from an identified group of data
is an elementary function for data processors.
Once the window of a given pattern piece is defined by the comparator 58,
the window is compared with the windows of every other pattern piece cut
prior to the given piece to determine if the windows overlap. If the
comparator finds no overlap, then there will be no overlap of the pattern
pieces and the comparator proceeds to examine the next pattern piece in
the cutting sequence. If the comparator determines there is an overlap,
then the comparator locates the sides of the windows which define the
overlap area, and other components of the processor perform more detailed
analyses on the data within the overlap area to determine if there is in
fact a difficult cutting condition.
FIG. 7 illustrates the two windows associated with the pattern pieces A, B.
It is readily apparent that the windows fall in overlapping relationship
due to the close proximity of the pattern pieces particularly in the
vicinity of point 50. The upper and lower limits of the windows for the
respective pattern pieces are illustrated by dotted lines and bear
suffices associated with the respective pattern pieces. It is assumed that
the pattern piece B is cut in sequence after pattern piece A, and in
accordance with a preferred embodiment of the invention, the window of
pattern piece B has been enlarged by a proximity tolerance T. That
tolerance T is selected by means of the proximity preset 66 in FIG. 4 and
is added to the maximum coordinate values and subtracted from the minimum
coordinate values of a pattern piece for the purpose of insuring that no
two pattern pieces will escape examination if they are closer to one
another than the proximity tolerance. For example, if the maximum Y
coordinate of pattern piece B also happened to lie at the point of closest
approach of the two pattern pieces, the windows defined at those
coordinates would not overlap. Nevertheless a difficult cut could exist
with the pieces in such proximity. The proximity tolerance insures that a
potential cutting problem is identified if the pieces are closer together
than the distance T. Typically, such a tolerance for woven fabric material
would be one quarter to one third inch.
FIG. 8 illustrates the preliminary data processing steps performed within
the window comparator 58 to determine if any two pattern pieces, or more
specifically the windows of any two pattern pieces, are not in overlapping
relationship. The first comparison step illustrated in block 70 determines
if the right-hand edge of the window for pattern piece B does not overlap
the left-hand edge of the window for the previously cut pattern piece A.
Stated otherwise, the comparison in block 70 determines if any potential
for overlap exists at the referenced sides of the windows. The diagram in
FIG. 9 illustrates this comparison schematically. If XLA is larger than
XUB, there can be no overlap of the windows A and B as shown in FIG. 9,
and an affirmative response is output by the window comparator 58. The
data processor then proceeds to compare the window of pattern piece B with
another previously cut pattern piece and the process is repeated until all
previously cut pattern pieces have been examined.
If the result of the comparison indicated in block 70 is negative, a
potential for overlap exists and then the window comparator conducts a
further comparison step indicated at block 72. The comparison performed in
block 72 determines if the left-hand edge of the window for pattern piece
B does not overlap the right-hand edge of the window for pattern piece A.
If XUA is less than XLB, then there is no overlap of the pattern pieces as
indicated in FIG. 10, and the comparator 58 then proceeds to analyze the
coordinates of another previously cut pattern piece. If the comparison in
block 72 is negative, then it is necessary for the comparator to perform
the further comparison step illustrated in block 74. The comparison of
block 74 corresponds to the diagram in FIG. 11 and determines if the upper
edge of the window for pattern piece B does not overlap the lower edge of
the window for pattern piece A. Again if the comparison of block 74
produces an affirmative indication, the window comparator advances to an
analysis of another previously cut pattern piece, but if a negative
indication is given, the comparator conducts one further comparison
indicated at block 76. The comparison indicated at block 76 is illustrated
in FIG. 12 and determines if the lower edge of the window for pattern
piece B does not overlap the upper edge of the window for pattern piece A.
If the result of the comparison at block 76 is affirmative, then no
overlap exists and other previously cut patterns are examined. A negative
indication at this stage of analysis indicates an overlap.
As a result of the comparisons performed at blocks 70-76, there will be at
least one affirmative response if the windows of the two pattern pieces
under consideration do not overlap. If no affirmative response is received
from any of the comparisons, then the existence of an overlap of the
windows is confirmed.
FIG. 13 illustrates a table of four additional comparisons utilized to find
the side or sides of the window for pattern piece B which overlap the
window of pattern piece A. An affirmative response to the comparison
illustrated in block 80 indicates that the windows of pattern pieces A and
B overlap at the left and right sides respectively as indicated in FIG.
14. Correspondingly, affirmative indications from the comparisons
identified in blocks 82, 84, and 86 identify overlaps in the pattern piece
windows as shown in FIGS. 15, 16 and 17, respectively. It should be
understood that when an overlap does exist in the windows, there will
normally be two affirmative responses, one relating to the two X-limits of
the windows and another for the two Y-limits. The four limits associated
with the affirmative responses define the overlapping region of the
windows and all further analysis of the pattern piece peripheries for
critical cutting segments can, therefore, be limited to data points
falling within the overlap area.
It will be understood that the window comparator 58 eliminates the need for
determining the separation between the peripheries of pattern pieces which
do not lie closer to one another than the proximity tolerance T. In a
marker with fifty or more pattern pieces, there are generally not more
than four or five pattern pieces in close proximity to any given pie | | |
