Field of the invention
[0001] This invention relates the manufacturing of garments, upholstery and other items
from fabric or other flexible sheet material. In particular, the present invention
deals with an innovative method and apparatus for spreading and cutting flexible sheet
materials from rolls or other supply of the same on to a work table preparatory to
cutting or other operation.
Background of the invention
[0002] A process for fabricating products related to garments, upholstery and other sheet
material includes a number of steps and utilizes complex machinery. Typically, the
system has a flow line layout consisting of three stages, connected by a linear conveyor.
Each stage corresponds respectively to a spreader, a cutting machine and an unloading
stage, where a human operator picks cut-out pieces.
In the first stage the sheet material is spread one ply at a time to form a lay-up
having a certain length. (Each ply spread has a different length thus implying that
the length of the lay-up is equal to the length of ply or plies with the maximum length.)
The spreader worktable is connected to the cutting table by a linear conveyor. The
cutting stage consists in cutting out pieces in compliance with a pre-established
layout, said cutting pattern.
Therefore, the cutting pattern outline the shapes of the parts to cut-out. Frequently,
it is advantageous to form a single lay-up (i.e. a sequence of cutting patterns) with
varying heights of spread plies for each cutting pattern, different typologies of
sheet materials, i.e. different colored fabric. In the sequel, the area of lay-up
corresponding to a single cutting pattern is referred to as cutting position.
A lay-up consists of a sequence of cutting positions each of them characterized by
a stack of plies. Moreover, each cutting position joins at least one spreading operation
with the contiguous cutting positions. The linear conveyor advances so that to bring
in the cutting zone one cutting position at a time. Pieces related to a cutting pattern
are obtained by means of a tool which penetrates into the lay-up while the sheet material
is held against the table by suction.
The cutting tool is typically a knife and is moved according to the current cutting
pattern. Downstream from the cutting out zone there is the unloading stage. To each
shape of the cutting pattern corresponds a single piece or a stack of pieces cut out.
In the unloading phase there is an operator designated to distinguish pieces cut out
correctly, during the pick-up phase.
[0003] To optimize productivity in the manufacturing of a assigned quantity of parts, i.e.
the workload, that must be delivered to the following operations within an assigned
due date, the minimization of the workload make-span (i.e. the time between the starting
time of the spreading operation of the first part and the end of the unloading operation
of the last cutting position) may be considered as the main goal.
Given the workload of the machinery, in order to reach the goal two important contributors
are: the ability to shorten the time spent by cut-out pieces in the unloading zone
and the ability to maximize the length and height of each spread lay-ups , given both
the spreader work-table length and the maximum number of plies that can be cut at
once.
[0004] The first contributor is related to advances in fabric cutting technology and to
those solutions that can be proposed to support the picking operator in order to distinguish
in a correct manner shapes of the cutting pattern as well as different groups of layers
in the lay-up. In
US patent 6,521,074 it has been proposed a solution to the presence of off-cuts that are complementary
respect to the shape of the cut-out pieces set.
Such off-cuts clutter up the unloading zone and they can complicate the identification
of the pieces to be unloaded, in particular when at least some of the pieces are difficult
to distinguish from the off-cuts. To overcome this difficulty, in
US patent 6,521,074, a scaling film is applied over the surface of a stack, prior to the sucking phase.
The scaling film is cut together with the sheet material.
The off-cuts of the scaling film are referred to as "skeleton". The skeleton is diverted
from the path of sheet material in the unloading zone so as to be recovered automatically
and separately from the cut-out pieces. The absence of the skeleton can make it easier
to identify the pieces to be unloaded because they are the only portions of the sheet
material that remain covered with the scaling film.
Another difficulty related to recognition of the cut-out pieces concerns the presence
in the cutting pattern of similar shapes but in different sizes. This issue is typically
encountered in clothing manufacturing, where similar shapes are related to the same
article of clothing, but in different sizes. In
GB-A-2 364 293, it has been proposed a solution to distinguish visually shapes.
In the cutting phase each shape is automatically labeled. Labels typically include
information regarding part name, description and size as well as model identification
and name.
The above solution is incomplete, if there exist "similar" articles sharing the cutting
pattern but following different processing phases downstream the unloading phase.
In clothing industry, this is true when the pieces cut-out are related to article
differing only in terms of fitting.
This issue is difficult to be managed in the spreading phase, since, in general, each
cutting position in the lay-up could be characterized by a different vertical partitioning
of plies. Therefore applying a separating film in the spreading phase, by means of
standard spreader, might require a huge number of roll changes. Often the actual solution
to this difficulty is to spread sheet material so that to cut out "similar" articles
in different cutting positions.
Therefore in this case, the system performance, measured by the parameter make-span,
are worsted.
[0005] In
DE 199 06 304 A1 which is the closest prior art for the invention, during spreading phase a film ply
is deposited over each sheet material ply. The goal is to expedite the picking phase
by means of a film ply, that reduces the friction between sheet material plies, i.e.
the piece to be unloaded slides over the film ply, without hooking or discomposing
sheet material plies stacked below. In the solution proposed in
DE 199 06 304 A1, the spreading mechanism deposits as many film plies as many the sheet material plies
are. Moreover, the film and the sheet material detaching operations are synchronous:
the length of the sheet material equals the length of the film ply. Therefore, given
a spread sheet material ply and the set of cutting positions covered by it, there
is no way of spreading different shorter film ply, covering any combination of said
cutting positions.
[0006] The second contributor deals with solutions related to the planning of the spreading
operations that determine the number of spread lay-ups, as well as the length and
the height of each them. The solutions proposed in the state of art relate to the
hardware optimization of the spreader. In particular, it has been made considerable
progress toward decreasing the slowdown due to the set-up operations of the spreading
phase. Therefore, in real-world applications characterized by a great variety of sheet
materials, the spreader has been provided by automated apparatus for roll changes
(XM3000 BKR).
Another setup operation is related to the overturning of the plies. Overturning operations
are useful when the sheet material has a geometric design and there exist mirror cutting
patterns. For example, in upholstery manufacture some articles might be the right
or the left version of the same model, i.e. a sofa model requires either the right
arm or the left one. In this case, left and right versions can be cut out at once,
adopting the left version cutting pattern and overturning the plies related to the
right version.
An example of automated mechanism to overturn rolls is (ST4000T). In absence of the
cutting side the overlapping of mirror cutting patterns can take place without overturning
ply in the spreading phase, but overturning cut out pieces during the unloading one.
In this case, plies related to two mirror cutting patterns are stacked in a single
cutting position and separated in the unloading phase.
Given the above automatisms, the overall system is only controlled by computer based
on software written so that to aid an operator to compose the lay-up on the basis
of the current work load. Given a number of parts to be produced, the daily system
productivity performance is the result of the operator's ability to group parts to
be produced in the minimum number of lay-ups, where each position is characterized
by a number of spread plies as higher as possible.
[0007] From this discussion of the art state in automated apparatus for processing flexible
sheet materials, it may be seen that even if a considerable progress has been made
toward increasing efficiency, there remains an unmeet need for a system that provides
an automated solution for distinguishing layer groups among plies stacked in each
cutting positions and a system that automatically provides high system productivity
for unpredictable combinations of product requests.
Indeed, there remains an unmeet need for a system operating method for efficiently
completing unpredictable combinations of products which require a great variety of
sheet materials and cutting patterns.
Brief description of the drawings
[0008] Other features and advantages of the invention appear from reading the following
description given by way of non-limiting example and with reference to the accompanying
drawings.
Fig.1 is a perspective view of an apparatus embodying the present invention and used
in practicing the methods of the present invention.
Fig.2 is a simplified schematic illustration of cutting patterns performed by system
in Fig.1, where Fig.2(a) shows a couple of mirror cutting patterns, whilst Fig.2(b)Fig.2(c)
and Fig.2(d) are related to a symmetric cutting pattern.
Fig.3 is a side elevational view of a lay-up composed by apparatus in Fig.1.
Fig.4 and Fig.5 are a somewhat schematic fragmentary perspective and side elevational
view of the apparatus shown in Fig.1.
Fig. 6 is side elevational view of a lay-up composed by apparatus in Fig.1, where
the overturning operations involves mirror and symmetric cutting patterns.
Fig. 7 is a flow chart in accordance with the system operating method of the present
invention.
Fig.8 side elevational view of a lay-up composed by apparatus in Fig.1, constrained
to end all spreading operations at the same point on the worktable.
Fig.9 reports both side elevational view of two lay-ups composed by apparatus in Fig.1
and the schematic diagram illustrating the cutting job similarity in accordance with
the method of Fig.7.
Detailed description of preferred embodiments of the invention
[0009] Turning now to Fig.1, a typical apparatus embodying the present invention and used
in practicing methods of the invention is indicated by the reference E. The illustrated
apparatus E consists of a sheet material supporting surface 16, a sheet material spreader
12 having a supply roll S and movable to and from longitudinally relative to the table
to spread a ply F, as it is dispensed from the roll S and a rotary cutting device
20.
The system is provided by a controller 22 which sends and receives signals to the
cutting device and the spreader. The controller includes a PC computer with sufficient
memory and other peripheral hardware to perform the functions set forth herein.
The spreader 12 is provided by drive motors and other electromechanical devices widely
used in the flexible sheet material manufacturing and designed to pay-off material
from the roll S at linear rate, generally corresponding to the linear rate at which
the sheet material is spread on the supporting surface. The spreader operates in response
to command signals sent by the controller. Each spreading command corresponds to a
distance D respect to the spreader zero position and a spreading length of L (so that
D-L>0). Let us suppose that the length unit is millimeter. The distances D and (D-L)
corresponds to the beginning and ending spreading positions on the supporting table
16, respectively. In response to the command signal a setup operation takes place,
that is the spreader moves toward the right end, when the longitudinal movement ends,
the distance between the spreader and the spreader zero position is D. Then the spreading
operation begins when the spreader moves toward left and operates to pay-off the material
on to the supporting surface. When the advancing spreader is at (D-L) mm from the
left end of the supporting table 16, the sheet material is cut to separate the material
spread on the supporting surface from the supply roll S. A suitable cutting mechanism
(not shown) may be mounted on the spreader for this purpose. If a multi-plies lay-up
is desired, the spreading mode hereinbefore described may be repeated to build a lay-up
which includes a plurality of stacked plies of sheet materials.
Moreover, in order to exploit mirror cutting patterns, spreader is provided by an
automatic mechanism to overturn the supply roll S. Fig.2(a) is a simplified schematic
illustrations of two mirror cutting patterns. Hereinafter, given the cutting pattern
symbol, the mirror feature is denoted by M (i.e. A and A
M are mirror cutting patterns).
The spreading operations of a lay-up might require set up operations, due to supply
roll changes. Roll changes may be related to real applications where there are different
typologies of sheet materials and each typologies is characterized by a set of variants.
For example, in the case of cloth manufacturing and upholstery, variants are colour
and/or design. Hereinafter the terms variant and colour will be considered as equivalent.
Table I reports an illustrative example of products requests, each of them detailed
in terms of cutting patterns, length of spreading operation, colours and quantity.
Fig.3 details a lay-up 100 corresponding to Table I, where dotted lines refers to
overturned plies. There are three cutting positions, related to the cutting pattern
CP
1,CP
2,CP
3. The cutting operations are scheduled from right to left, that is the right most
position is the first one and the left most position is the last one. In each cutting
position, at least one spreading operation is joined with contiguous positions. Table
II details the command signals of spreading operations related to the lay-up 100 in
Fig.3. The schematic picture in Fig.3 is not representative of a flexible sheet material.
Indeed, as the spreading operations proceed, spread sheet material could encounter
one or more stairs of plies (for example, the three spreading operations related to
command signals 4 in Table II). The feasibility of the spreading operations can be
compromised by too high stairs. Therefore, spreading a ply on one or more stairs is
admissible if stairs do not exceed a threshold value. Unfeasible spreading operations
due too high stairs can be overcome by splitting the spreading operations, i.e. command
signals 4 in Table II are splitted into three command signals with D and L value equal
to (200mm, 200 mm), (300mm, 100mm) and (350 mm, 50 mm), respectively.
Even if not shown in Fig.1, the spreader can be provided by automatic mechanism for
supply rolls change (XM300 BKR).
Immediately upon the completion of the lay-up spreading operations, the lay-up is
transferred in the area of the cutting machine and the cutting activity is started.
Cutting position are processed one at a time, that is the cutting device processes
stacked plies according to the related cutting pattern.
[0010] The technological features, hereinbefore stated, are widely adopted in the art of
automatic apparatus for manufacturing flexible sheet materials. The two main innovative
aspects related to the present invention are: innovative solution for applying a separating
film between groups of plies of the lay-up and an innovative operating method for
composing lay-ups so that to complete in an efficient manner unpredictable combinations
of products which require a great variety of sheet materials and cutting patterns.
The first goal of the present invention concerns a system that provides an automated
solution for distinguishing groups of layers in a single cutting position. In particular,
the system is provided by a spreader paying-off a film in order to separated plies
belonging to the same cutting position that is efficient and does not increases sheet
material spreading time. In Fig.4 and Fig.5, a typical apparatus embodying the present
invention and used in practicing methods of the invention is indicated by the reference
12.
Table I
Color Requests |
Cutting Pattern |
White |
Gray |
Black |
Lenght |
CP1 |
8 |
3 |
- |
200 mm |
CP2 |
3 |
2 |
- |
100 mm |
CP2M |
3 |
- |
- |
100 mm |
CP3 |
6 |
1 |
3 |
50 mm |
Table II
Command |
Roll |
D |
L |
Overturned |
Number of runs |
1 |
Gray |
350 mm |
350mm |
No |
1 |
2 |
Gray |
3 00 mm |
3 00 mm |
No |
1 |
3 |
Gray |
200 mm |
200 mm |
No |
1 |
4 |
White |
350 mm |
350mm |
No |
3 |
5 |
White |
200 mm |
200 mm |
No |
5 |
6 |
White |
350 mm |
50 mm |
No |
3 |
7 |
White |
300 mm |
100 mm |
Yes |
3 |
8 |
Black |
350 mm |
50 mm |
No |
3 |
[0011] The spreader 12 is provided by drive motors, a programmable controller 22 and the
other electromechanical devices widely used in spreading flexible sheet material and
designed to pay-off material from the roll S at a linear rate, generally corresponding
to the linear rate at which the sheet material is spread on the supporting surface.
A drive motor 46 receives command signal from controller 22 and drives the supply
roll S to pay-off flexible sheet material. At least one feed roller is controlled
for rotation around an axis parallel to the axis of the supply roll S, but preferably,
and as shown in Fig.4 and Fig.5 the apparatus includes feed rollers 47, 48, 49. The
feed rollers 47,48,49 are driven in timed relation to supply roll S and to each other
by a drive mechanism 50, which receives command signals from controller 22 so that
to spread out flexible sheet on the working table 16. A means is provided to move
longitudinally the overall carriage, to overturn the sheet material and to separate
the material spread from the supply roll S. The separation of the ply F prom the sheet
material on the supply roll F takes place by means of solution widely used in spreading
flexible sheet material, but preferably, and as shown in Fig.4 Fig.5, by the cutter
17. Since the details of such a carriage construction are not essential to an understanding
of the present invention, the carriage structure will not be further described. Further
and in accordance with the invention means are provided for spreading a film ply Q
separating sheet material plies stacked upper and below the film ply Q. As the sheet
material spreading operation, hereinafter referred as the main spreading operation,
goes on in response to signals sent by controller 22 the supply roll 2 operates to
unroll the separating film Q. A drive motor 52 receives command signal from controller
22 and drives the supply roll 2 to pay-off separating film. The feed rollers 3 and
4 are driven in timed relation to supply roll 2 and to each other by a drive mechanism
51 and functions to spread out separating film on the working table 16. During the
film spreading operation, hereinafter referred as the secondary spreading operation,
the bars 5 and 6 are opened. The bars 5 and 6 extend transversely of the spreader
carriage and substantially across the entire width of the carriage so that when bars
are closed the film is tighten between them along its entire width. A drive motor
53 receives command signal from controller 22 and drives the bars 5 and 6 in the opening
and closing operations.
The separating film Q and the main sheet material F (e.g. the fabric) are simultaneously
dispensed from two different supply rolls S and 2. For each main spreading operation
there might be one or more secondary spreading operations. Indeed, the separating
film can be dispensed on any combination of cutting positions covered by the concomitant
main spreading operation. The secondary spreading operation means to separate two
different groups of plies stacked one on each other in order to make, at the unloading
phase, visually distinguishable the plies stacked below, from the ones stacked over
the spread separating film ply. Said separating film ply can be spread during the
first spreading operation of the upper stacked plies and below the sheet material
ply concurrently spread, or during the last spreading operation of the lower stacked
plies and on the sheet material ply concurrently spread. As shown in Fig.4 and Fig.5
it should be preferable to couple up the separating film spreading operation with
the first main spreading operation of the upper stacked plies.
To obtain an efficient system for spreading the separating film, the sequence of operations
necessary to spread the separating film is designed in the present invention in order
to require neither the stop of the overall carriage nor the stop of the main spreading
operation.
Preferably, and as shown in Fig.4 and Fig.5, feed roller 49 corresponds to the engagement
point between the separating film Q and the main sheet material F. The separation
of the spread film from the supply roll 2 is obtained by a tearing pattern set on
the separating film Q. In practising methods for spreading film ply Q, the tearing
pattern be chosen among those ones that enable a correct tearing operation. One possible
choice is a zig-zag pattern and it is shown in Figure 4 as W. The idea is similar
to the one adopted for block notes where sheets are tore accordingly to a fixed tearing
pattern, typically a straight line. The idea is to pay-off the separating film by
a tearing operation instead of a cutting one.
The separating film Q is provided by a equally spaced tearing patterns. A tearing
operation consists of the following steps: bars 5-6 are closed and, simultaneously
feed rollers 3-4 and supply roll 2 stop; feed rollers 47-48-49 continue to rotate,
so that a tension force is applied along the part of separating film positioned between
bars 5-6 and feed roller 49. This tearing operation allows an immediate separation
of the spread film from the supply roll 2 and it requires to stop neither the carriage
nor the main spreading operation.
At the end of each tearing operation, the two edges of only one tearing pattern has
been separated: one ending the film wound on the supply roll 2 and one ending the
dispensed film ply. The distance between bars 5-6 and the feed roller 49 is set in
order to make feasible both the tearing operation and the joining operation between
the film and the sheet material that will take place in correspondence to the beginning
of next film spreading operation. Preferably, and as shown, bearings 60 extend transversely
of the spreader carriage and substantially across the entire width of the carriage
so that the edge of the separating film wound on the supply roll 2 is correctly positioned
for starting a new film spreading operation.
When a new film spreading operation is started, the bars are re-opened and the film
feeding activity can be started, by re-starting the rotation of feed rollers 3, 4
and the supply roll 2. Each film spreading operation is size-dependent. In particular
it is required that the film ply covers the corresponding cutting positions in a significant
manner. There is no need that the length and the width of the sheet material ply equals
those of the separating film ply, i.e. the film ply can be longer or/and shorter than
the corresponding sheet material ply. Indeed, the main goal is that each separating
film ply significantly covers the corresponding cutting positions and, during the
unloading phase, there is no ambiguity between the cutting positions covered by the
film ply and the contiguous ones.
Another approach is to dispense a separating film ply as long as the concomitant sheet
material one. In this way the separating film covers as many contiguous cutting positions
as the concomitant sheet material ply does. At the unloading phase, a work note, or
any other suitable communication mean solution, can be used to detail to the human
operator which separating plies have to be considered in each cutting positions (for
example in the second cutting position, the second group of stacked plies is limited
by the third and sixth film plies). The main advantage of this alternative solution
consists in the opportunity to separate from the corresponding supply rolls both the
film ply and the sheet material at the same time.
The second goal of the invention is to provide a method for operating an automatic
apparatus E in a manner that achieves low make-span irregardless of the mix of product
requests, that is the workload.
The processing time of each lay-up is obtained by the overall cutting time and the
overall spreading time. Therefore, low make-span is obtained when the overall cutting
time as well as the overall spreading time are minimized. Since cutting patterns are
pre-assigned, the lower the overall number of cutting positions are, the lower the
overall cutting time is. The overall spreading time is minimized if the number of
spreading operations are minimized. This is true because of the acceleration during
spreading phase (i.e. spreading one 2L length ply requires less time then spreading
two different L length plies). Moreover, joining the spreading operations of several
cutting positions decreases the number of roll changes as well as the number of overturning
operations. In the viewpoint of make-span optimization, there are two key features:
cutting patterns partitioning in to three groups, and an optimization algorithm oriented
to compose lay-ups.
The proposed operating method consists of two key feature. The first key feature includes
partitioning cutting patterns into a number of groups accordingly to the symmetry
property respect to ply overturning.
All cutting patterns are defined respect to one of the two ply sides and called the
cutting side. The ply is overturned if the upper ply side is not the cutting side.
The cutting patterns are separated into three distinct groups defining if the ply
overturning is feasible and if it requires or not a concomitant cutting pattern overturning.
Fig.2 reports illustrative examples. The first group of cutting patterns (Symmetric-type)
consisting of all those cutting patterns indistinguishable from its overturned version
and where a ply overturning operation is feasible and requires no cutting pattern
overturning operation. Fig.2(b) represents the pieces cut-out when the cutting side
is the one characterized by a geometric design. Fig.2(c) reports the pieces cut-out
when the ply is overturned. Fig.2(d) details Fig.2(c) respect to the opposite side.
The second group (Mirror-type) consisting of pair of cutting patterns ((A, A
M)), where one is the overturned version of the other and the first cutting pattern
(A) is adopted to obtain shapes of cutting pattern A
M when the ply is overturned respect to cutting side. Vice versa the second cutting
pattern (A
M) is adopted to obtain shapes of cutting pattern A when the ply is overturned respect
to cutting side. See Fig.2(a) for an example. The third group (Asymmetric-type) comprises
all cutting patterns except those in said first group and said second group. It should
be understood that all cutting patterns have to be considered as asymmetric if the
sheet material sides are undistinguishable and are both suitable for cutting. In particular,
each couple of mirror cutting patterns is exhaustively represents by only one of them,
i.e. the cutting pattern
A. Indeed, the cut-out pieces related to the cutting pattern
AM are overturned in the unloading phase. In this case the system operating method organizes
the spreader activity so that to apply in the corresponding cutting positions the
separating film between the plies related to and the plies related to
AM. In all other cases, the stated groups help spreading and cutting time optimization
since the ply overturning is allowed for the first and second grouping. Overturning
plies in the second group helps to reduce the number of cutting positions: cutting
patterns A and A
M can be cut out in the same cutting position. At the same time, the overturned ply
spreading operation could be exploited to cover groups of contiguous cutting positions
where there are a symmetric-type cutting patterns as well as a mirror cutting-patterns.
In this way, set up time due to overturning operations is decreased. The cutting pattern
partitioning can be exploited in order to reduce the time spent to spread plies of
a lay-up. The lay-up 101 in Fig.6 is an illustrative example where cutting patterns
CP
1 and
CP
3 are symmetric and asymmetric respectively, whilst the cutting pattern CP
2 is mirror type. The overturned plies in CP
2 cutting position are due to a not null requests for the CP
2M cutting pattern. The overturned plies spreading operations can be exploited to cover
both the CP
2 cutting position. This is possible for the symmetric property of CP
1.
In the present invention, the second key feature of the system operating method is
an optimization algorithm minimizing both the number of cutting positions and the
number of spreading operations. Fig.7 is a flow chart detailing the decision-making
steps executed by the system operating method in order to compose a lay-up.
[0012] Let H
max denote the maximum number of plies stackable in a cutting position. If there exist
cutting patterns with H
max-overflowing demands, minimizing the number of cutting positions as well as the number
of spreading operations might become conflicting objectives. Indeed, given the generic
H
max-overflowing cutting pattern
i (i=1,..,N) the computation of the minimum number of cutting positions related to
it, i.e. P
i, is a straightforward arithmetic operation (see (111) and (112) and Table III). The
minimization of the number of spreading operations might require a number of cutting
positions greater than P
i.
Since the system performance are almost influenced by the number of cutting positions,
a trade-off is rejected and the highest priority is given to the optimization of cutting
positions. Indeed, the apparatus E is typically provided by a lay-up buffer between
the spreading and the cutting stages. In this case, in the production there might
be more than one lay-up in process. Consequently, the cutting machine and the spreader
work in parallel. Since the cutting phase is the last one, the system performance
are almost influenced by the cutting time: the number of cutting positions must be
minimized, firstly (the first step 80 in Fig.7). Table III reports a notation related
to technological constraints and product requests.
Table III
Symbol |
Description |
Hmax |
Maximum number of stackable plies |
Lmax |
Spreader work-table length |
NS |
Number of symmetric cutting patterns |
NA |
Number of asymmetric cutting patterns |
NM |
Number of pairs of mirroring cutting patterns |
N = (NS + NA + NM) |
Number of distinct cutting patterns |
K |
Number of distinct colours |
i∈[1,..,NS]∪[(NS+1),..,(NA+NS)]∪ ∪ [(NS+NA+1),.., (NS+NA+NM)] |
Cutting pattern index i=1,..,N |
(i,iM) |
Pair of mirroring cutting patterns(i=NA+1,..,N) |
K |
Colour index (k=1,..,M) |
Cik |
Number of requests for cutting patterns i-th with colour k. (k=1,..,M i=1,..,N) |
CiMk |
Number of requests for iM that is the mirror cutting pattern related to i-th with colour k. (k=1,..,M i=NA+1,..,N) |
Pi |
Number of cutting positions of the i-th cutting pattern (i=1,..,N) |
P |
Maximum number of cutting positions in a lay-up |
j |
Cutting positions index j=1,.,P |
[0013] The minimum number of cutting positions P
i is determined as follows
where
┌·┐denotes
the minimum integer value greater or equal.
[0014] Cutting patterns with a P
i value greater than 1 will be denoted as H
max-overflowing cutting patterns.
Once determined the P
i's values, i.e. the minimum number of cutting positions, the second step 81 in Fig.7,
and, the third step 82 in Fig.7, are devoted to determine the minimal cutting job
set (i.e. for each cutting pattern i is determined how to arrange the coloured requests
in P
i positions, each arrangement will correspond to a cutting job) and to sequence its
elements in order to minimize the number of spreading operations. In accordance with
the present invention the second step 81 determines, for each of the P
i cutting jobs, how many requests of the C
ik demand has to be included, i.e. how many k-th colour plies are included. There are
two constraints to be satisfied: each cutting position will not include more than
H
max plies and the overall sum of k-th coloured plies included in the P
i cutting jobs will be equal to C
ik. The output of the second step 81 is the minimal set of jobs to be processed by the
cutting device, i.e. the cutting job, and the corresponding similarity sequencing
matrix. Each matrix element assigns a "pair values", i.e. distance between jobs, based
upon colour similarity. Indeed, each possible pairing of jobs receives a similarity
pair value, providing a measure of how many spreading operations could be joined together
in each cutting job pair. In alternative, each pair of jobs can be valued by a measure
of their dissimilarity, i.e. how many spreading operations cannot be joined together.
The third step 82 exploits the similarity (dissimilarity) matrix in order to solve
a sequencing problem, subject to L
max constraint and product requests C
ik constraints.
The objectives of the second step 81 and the third step 82 are the same: minimizing
the number of spreading operations. This goal is obtained through the maximization
of job sequence similarity or the minimization of job sequence dissimilarity. Since
the shared optimization goal the second step 81 and the third step 82 can be simultaneously
tackled in a unique framework. However, due to the combinatorial nature of the considered
optimization problems there might be the need to execute each step separately accordingly
to the hierarchical order shown in Fig.7. An object of the present invention is an
optimal algorithm as well as a near-optimal algorithm to solve combinatorial aspects
related to the second step 81 and the third step 82.
Since these decisional steps involves mathematical operations which can be cast in
widely different but mathematically equivalent expressions, the scope of the present
invention is defined in terms of equivalent of a particular expression. Those skilled
in the art will recognize that equivalent formalizations can use different number
of steps, different combinations of operations with steps, and different expressions
for operations. Mathematical technique can resolve unambiguously the question of mathematical
equivalence of method for the purpose of determining the scope of the present invention.
Given the products request the system controller elaborates the lay-up according to
the flowchart of Fig.7. The resulting lay-up is converted into a list of command signals
and sent to the spreader and the cutting device. The complete system, from proper
lay-up determination to actual manufacturing, can operates completely under computer
control, essentially free from human intervention.
Formalization: general lay-up composition problem
[0015] Given the spreader work table length L
max, the maximum number of cutting positions in the lay-up is:
[0017] Expression (114) maximizes the total similarity between positions in the determined
lay-up. An alternative optimization goal can be the minimization of the total dissimilarity
between positions in the determined lay-up.
[0018] Expressions (115) state that for each position the number of stacked plies cannot
exceed H
max.
Expressions (116)-(117) state that for each cutting pattern i and for each colour
k the number of allocated plies have not to exceed product request C
ik.
Expressions (118) assure that the number of cutting positions is minimized according
to P
i values determined at the first step 80.
Expressions (119) state the relationship between X's and Y's variables for the symmetric
and asymmetric cutting patterns.
Expressions (110) and (111) state that, for each cutting pattern i, plies have to
be overturned or not if at each position j it has been placed the cutting pattern
i
M (i.e.
YiMj=1) or the cutting pattern i (i.e. Y
ij=1).
The same considerations apply to each cutting pattern
iM by means of expressions (111) and (113).
Expressions (114) state that for each position j at most one cutting pattern can be
placed.
Expressions (118) state that the lay-up length cannot exceed the spreader work-table
length,
Lmax. Expressions (116)-(117)-(118)-(119) state the relationship among
Z's, T's and
X's decision variables.
Expressions (120)-(132) state that there does not exist a mirror cutting pattern for
asymmetric and symmetric cutting patterns.
Expressions (121) state that overturning operations cannot be applied to Asymmetric-type
cutting patterns.
Expressions (122)-(131) state the nature of decision variables.
In the state of art there are apparatus for spreading and cutting sheet material,
where all spreading operations are constrained all to end at the same point of the
work table (typically at the spreader zero position). This means that the difference
D-L of each command spreading signal must be equal to zero. In these system the heights
of cutting positions in a single must have a not increasing profile from the left
most cutting position (i.e. the last cutting position) to the right most one (i.e.
the first cutting position). The lay-up 102 in Fig.8 is an illustrative example. This
technological constraint can be embedded in the formulation of (114)-(132) by adding
the set of linear inequalities (133)-(134):
[0019] The second and third decisional steps(i.e. the second step 81 and the third step
82) of Fig. 7 can be recast using the described mathematical formalism.
[0020] The second step 81. The X's decision variable values determine unambiguously the similarity matrix for
cutting jobs included into the current lay-up.
[0021] The X's values determine position by position the number of plies to be spread each
of them characterized in terms of colour and overturning operation. The Expression
(118) guarantee that each cutting pattern i will be processed exploiting no more than
P
i cutting positions. In particular the left hand side represents for each cutting pattern
the number of plies not allocated in the current lay-up. The right hand side computes
the maximum number of plies that can be allocated in further lay-ups without violating
the P
i cutting position constraint. Expressions (115) represent
the
Hmax―constraint. Expressions (116) and (117) guarantee that the
X's values are consistent with product requests. Expressions (116)-(119) model the concept
of similarity between positions.
[0022] The third step 82. The Y's decision variable values detail the cutting job sequence related to the current
lay-up. Expressions (119)-(115) take into account the mirror cutting pattern concept,
the overturning operation, the L
max- constraint. Given the cutting job sequence the expression (114) expresses the related
similarity value. The max operator represents the search algorithm valued on the basis
of Expression (114). Maximizing the sequence similarity is equivalent to minimize
the number of spreading operations.
Implementation issues
[0023] The implementation details related to lay-up composition deal with the computational
complexity inherent the adopted solution algorithm. If an optimal solution is required,
given the formalization in (111)-(132) or an equivalent one, the lay-up composition
can be obtained by means of an optimal solution algorithm. Computational issues might
guide the choice between a general purpose optimal algorithm for mixed-integer linear
programs (a commercial software may be ILOG Cplex 9.0) and a special purpose optimal
solution algorithm. If the optimal approach is unfit, i.e. too long time is required
to obtain at least a good feasible solution, heuristic methods can be adopted. The
heuristic method can tackle the second step 81 and the third step 82 by means of a
decomposition approach. In the following some approaches are presented as examples.
Dillenberger, Ch., L.F. Escudero, A. Wollensak and W. Zhang in "On practical resource
allocation for production planning and scheduling with period overlapping setups",
European Journal of Operational Research 75, 275-286 1994, propose the Fix-and-relax methodology as decomposition method to solve a large scale
mixed integer programming (MIP). The approach decomposes the original problem into
a number of smaller MIP sub-problems. The limited size of these sub-problems allows
using exact methods for their solution, which would be impossible for the entire problem,
in a reasonable amount of time. The number and the size of the sub-problems define
the computational burden and the solution quality of the heuristic procedures. The
Fix and Relax approach is based on a partition of the integer decision variable set.
The method requires as many iterations as the determined sub-set are. Moreover the
sequence by which the sub-problem are solved and the variables partition has to be
defined so that to guarantee the determination of a feasible solution. To each subset
is associated a mixed integer programming sub-problem, fixing variables related to
previously solved sub-problems, declaring integer variables related to the current
sub-problem and relaxing the integral constraints related to the remaining integer
variable subsets. The defined sub-problem is solved optimally and the integer variable
values are used for the fixing related to the next sub-problem. The final solution
is determined by the variable values provided by solving the last sub-problem (including
those fixed by precedence steps).
The main issues of this approach are: the partitioning policy and the sub-problem
feasibility. A decomposition approach for the lay-up composition problem, a position
based-partition policy can be considered: each partition sub-set consists of variables
related to contiguous cutting positions. For example if there are two subsets V
1, V
2 such that |V
1| +|V
2| =P: the integer variables indexed from j=1 ,.., |V
1| are related to V
1, integer variables indexed from j=|V
1+1| ,.., |P| are related to V
2. There exists no matter about sub-problem feasibility, since fixing decision variables
position by position results in a lay-up consisting at least of one position.
Another decomposition approach concerns dealing with the decisional the second step
81 and the third step 82, one at time.
[0024] The combinatorial nature of the second step 81 is due to: requests for multi-coloured
H
max― overflowing cutting patterns, i.e. there are different colour requests for H
max―overflowing cutting patterns; and/or requests for symmetric cutting patterns and
for mirror cutting patterns. In both cases the main issues is to value between any
pair of cutting positions. However given the hereinbefore mentioned requests, the
similarity matrix as well as the dissimilarity matrix cannot be determined a-priori
respect to the job sequence (the job sequence will be computed in the next step 82).
The second step 81 can be tackled by any heuristic approach oriented to maximize some
average measures of similarity matrix elements (or minimize some average measures
of dissimilarity matrix elements).
Other approaches are to deal with H
max-overflowing cutting patterns by : relaxing the H
max constraint and considering a unique cutting job for each H
max-overflowing cutting pattern. Given the cutting jobs, the feasibility respect to the
relaxed constraint is recovered by post-processing procedure in the third step 82.
In particular, even relaxing the H
max constraint, the similarity matrix could not be unambiguously determined due to requests
of mirror cutting patterns and symmetric cutting patterns. That is, the overturning
operations of a symmetric cutting job is determined only when the job is inserted
into a sequence. The sequencing problem to be solved at the third step 82 is a historical
set-up sequence dependent problem. This problem is typically encountered in Flexible
Manufacturing System and it is often formalized as a generalization of the Travelling
Salesman Problem as stated by
Tang, C. and Denardo, E. in "Models Arising from Flexible Manufacturing Machine, Part
I: Minimization of the Number of Tool Switches" Operation Research Vol. 36, No. 5,
pp.767-777,1988 and by
Laporte,G. Salazar-Gonzalez, J., Semet, F. in "Exact algorithms for the job sequencing
and tool switching problem". The classical TSP stipulates that a salesperson must visit a sequence of cities
one at a time, never visiting the city twice. The optimization goal is to minimize
the total distance travelled.
The cutting job set can be mapped on an undirected graph G(N,V), where N is the set
of nodes and V the set of edges. Each node corresponds to a cutting job and is characterized
by a cost coefficient, i.e. the cutting pattern length. Edge has a gain coefficient
corresponding to sequencing the two end nodes. Each gain coefficient is equal to deterministic
value if any end node is a symmetric job. On the contrary, if at least one end node
is a symmetric job the edge cost is a function of the actual sequence or it is an
estimated value of such function value. Given the graph G, the algorithm determines
a job sequence by selecting a subset of edges, such that to form a chain of nodes,
not exceeding the L
max threshold. Moreover, for each pair of mirror cutting patterns there exits a cluster
of nodes in G, i.e. there are two nodes in G representing the two alternative way
of processing the mirroring cutting job. Only one of node in the cluster can be included
in the output sequence. Under this respect, the solution is made of a sequence of
node cluster, each cluster consisting of one or two nodes.
The stated sequencing problem must take into account the resource constraints implied
by the L
max constraint. The algorithm designed to solve this sequencing problem can be derived
by any algorithm designed for the generalized-TSSP+1 problem, the problem of finding
a maximum profit cluster sequence in a graph under a one additional constraint.
The adopted algorithm can be taken from literature and further properly modified in
order to take into account that some similarity matrix elements (those related to
symmetric job) is a function of the actual sequence. Feillet,D., Dejax,P., Gendreau,
M. in "Travelling Salesman problem with profits: an overview" provide an overview
for the TSSP+1. The lay-ups 103 and 105 in Fig.9(a) and Fig.9(b) illustrate that it
is not possible to determine a priori the similarity between the symmetric cutting
job of the second position (labelled CP
2) and the mirroring cutting job of the first position (labelled CP
1) (see Table I for product request details of CP
1, CP
2, CP
3). The cutting job labelled CP
3 and CP
4 are asymmetric. The graph 104 and 106 in Fig.9a and Fig.9b report the similarity
values to be considered: the sequencing value of CP
1 and CP
2 cannot be determined a-priori to the determination of the overall sequence.
1. A method for an apparatus designed to spread and to cut flexible sheet material wound
on a supply roll, said apparatus provided by means for depositing one or more plies
of sheet material onto a working surface table in order to automatically compose a
lay-up consisting of stacked plies, said plies deposited by a spreader which performs
a size-dependent movements in one and opposite direction longitudinally of said working
surface with arbitrary starting and ending points; said spreader provided by means
for depositing and detaching one or more plies from said sheet material supply roll
in order to automatically form a single lay-up with varying heights, said spreader
provided by means to spread automatically overturned plies; said apparatus provided
by means to hold the lay-up or one portion of it against the table by suction; said
apparatus provided by a tool passing through the stacked plies in order to cut-out
sets of predetermined shapes, called cutting patterns, according to a sequence of
cutting sessions, each said cutting session
characterized by one and only one cutting pattern and one and only one cutting area, called cutting
position, each said cutting position related to one and only one cutting session;
said apparatus provided by means for unloading pieces cut-out; the method comprising:
o depositing automatically one or more plies of a separating film at different heights
of said sheet material lay-up, each film ply separating lower stacked plies from the
upper stacked plies;
o depositing said separating film ply during the sheet material spreading operation
without stopping nor reducing the speed of the sheet material spreader;
o said separating film wound on a supply roll and pre-pricked off along a predetermined
pattern, called tearing pattern, that extends transversely across the entire width
and that is repeated periodically longitudinally the film roll.
o depositing automatically a separating film ply covering one or more contiguous cutting
positions, in order to make, at the unloading phase, visually distinguishable the
plies stacked below, from the ones stacked over the spread film ply;
o spreading said film ply either during the first spreading operation of the upper
stacked plies and below the sheet material ply concurrently spread, or during the
last spreading operation of the lower stacked plies and on the sheet material ply
concurrently spread;
o depositing during the concomitant sheet material spreading operation one or more
separating film plies, each of them covering one or more contiguous cutting positions;
o depositing a separating film ply over one or more contiguous cutting positions,
so that the covered area points out with no ambiguity which are the cutting positions
where the upper and lower stacked plies has to be distinguished at the unloading phase;
o detaching the separating film from the film supply roll by a cutting operation or
by applying two opposite tension forces along said tearing patterns; said tearing
operation allowing an immediate separation of the spread film from the supply roll
and requiring to stop neither the carriage movement nor the main spreading operation;
o cutting out shapes according to a predetermined cutting pattern by means of a tool
passing through the separating film plies and the sheet material plies stacked in
each cutting positions.
2. A method of operating an apparatus as set forth in claim 1 that is capable of machining
a plurality of jobs, each one requiring both one different cutting operation according
to a cutting pattern defined respect to one of the two ply sides and called the cutting
side, and a set of spreading operations
characterized by a plurality of sheet material variants, the method comprising:
o partitioning the cutting patterns into three separate groups defining if the ply
overturning is feasible and if it requires a concomitant cutting pattern overturning,
where the first group of cutting patterns (Symmetric-type) consisting of all those
cutting patterns indistinguishable from its overturned version and where a ply overturning
operation is feasible and requires no cutting pattern overturning operation; the second
group (Mirroring-type) consisting of pair of cutting patterns ((A, AM)), where one is the overturned version of the other and the first cutting pattern
(A) can be adopted to obtain shapes of cutting pattern AM when the ply is overturned respect to cutting side of A; viceversa the second cutting pattern (AM) can be adopted to obtain shapes of cutting pattern A when the ply is overturned respect to cutting side of AM, the third group (Asymmetric-type) comprising of all cutting patterns except those
in said first group and said second group;
o operating the apparatus so that each spreading operations depositing overturned
ply can cover one or more cutting positions if and only if the related cutting patterns
do not belong to the third group of said three groups;
o operating the apparatus so that each spreading operation depositing overturned ply
can cover one or more cutting positions if and only if the related cutting patterns
belong to the first or second group of said three groups.
3. A method of operating an apparatus as set forth in claim 1 that is capable of arranging
in one or more lay-ups a plurality of product batches, each
characterized by a different cutting pattern and a set of product requests each of said requests
characterized by a sheet material variant and a number of items to be produced; the method composing
a single lay-up one at time, as set forth in claim 1 and 2, as a sequence of cutting
positions by comprising:
o determining, for each batch or equivalently for each cutting pattern, the minimum
number of cutting positions, computed as the minimum integer value greater or equal
to the ratio between the total number of requests related to the considered batch
and the maximum number of stacked plies that can be cut out at once by the cutting
tool, said H_max;
o partitioning product batches into two groups, where the first group, called H_max
overflowing group, comprises those batches, characterized by a total number of product requests greater than said H_max; the second group comprises
all batches except those in said first group;
o determining a first sequence of cutting positions, as said in claim 1 and 2, each
of them characterized by a cutting pattern, and said sequence determined so that its length does not exceed
the length of spreader working surface, said L_max;
o defining a cutting job for each cutting position in the first sequence by assigning
a plurality of items, chosen among those ones to be cut out according to the cutting
pattern assigned to said cutting position, the number of said items determined so
that said H_max value is not exceeded and the minimal number of cutting positions
for the considered cutting pattern is not increased;
o calculating said first sequence value by assigning a pair value to each pair of
cutting jobs in the first sequence, the pair value being a monotonic function of how
many spreading operations could be joined together in the sequence taking into account
the three groups partition set forth in claim 2;
o determining the sequence of command signals to be executed by the apparatus of claim
1, in order to compose and to cut out the determined sequence of cutting jobs;
o causing the apparatus to compose the lay-up and to cut-out the stacked plies in
each cutting position in the order of the determined cutting job sequence;
o decreasing the number of items requested in each said product batches according
to the determined cutting job sequence.
4. A method as set forth in claim 3 where in the method further comprises:
o if the monotonic function is not decreasing, finding the optimal cutting job sequence
by repeating the determining, the defining and the calculating steps for each plurality
of different possible cutting job sequences and selecting the sequence which has the
largest sequence value;
o if the monotonic function is not increasing, finding the optimal cutting job sequence
by repeating the determining, the defining and the calculating steps for each plurality
of different possible cutting job sequences and selecting the sequence which has the
smallest sequence value.
5. A method of operating an apparatus as set forth in claim 1,2,3 and 4, that decomposes
the decision problem of determining a cutting job sequence, sub-optimal respect to
a monotonic function as said forth in claims 3 and 4, into a sequence of smaller decision
sub-problems, each of said sub-problem determining a portion of the sequence of cutting
jobs.
6. A method of operating an apparatus as set forth in claim 1,2,3,4, and 5, that decomposes
the decision problem of determining a cutting job sequence, sub-optimal respect to
a monotonic function as said forth in claims 3 and 4, into three consecutive steps
comprising:
o assigning a pair value to each pair of product batches, as said in claims 3 and
4, the pair value being a monotonic function of how many spreading operations could
be joined together in each product batch pair;
o arranging the product batches in a sequence determined by evaluating a generalized
sub-tour travelling salesman problem with knapsack constraints, with the sequencing
value determined in the previous step and properly modifying the travelling salesman
problem algorithm in order to determine unambiguously the sequencing cost of each
batch related to a symmetric cutting pattern as set forth in claim 2;
o determining for each position of the sequence evaluated in the arranging step, the
plurality of items determined ,as said in claim 3, so that the H_max value is not
exceeded and the minimal number of cutting positions for the considered cutting pattern
is not increased.
1. Eine Methode für eine Apparatur zum Ausbreiten und Schneiden von biegsamem, auf Zufuhrrollen
aufgewickeltem Folienmaterial. Diese Apparatur ist mit Mitteln zum Ablegen von einer
oder mehreren Lagen des Folienmaterials auf einem Arbeitstisch ausgestattet, um
dadurch automatisch Lagen zusammen zu stellen, die aus aufeinander gestapelten Lagen bestehen.
Diese Lagen werden von einer Breitstreckvorrichtung abgelegt, die von der Größe abhängige
Längsbewegungen in die eine Richtung und in die Gegenrichtung auf der Arbeitsfläche
ausführt, wobei Anfangs- und Endpunkt beliebig eingestellt werden können. Die besagte
Breitstreckvorrichtung ist mit Mitteln für das Ablegen und das Abziehen von einer
oder mehreren Lagen von der besagten Zufuhrrolle mit Folienmaterial ausgestattet,
um automatisch eine einzelne Schichtanordnung in verschiedenen Höhen zu bilden. Die
besagte Breitstreckvorrichtung ist auch mit Mitteln ausgestattet, umgekantete Lagen
automatisch auszubreiten. Die genannte Apparatur ist mit Mitteln ausgestattet, die
Schichtanordnung oder einen Teil davon mittels Ansaugung gegen den Tisch zu halten.
Weiter ist die genannte Apparatur mit einem Werkzeug ausgestattet, das sich durch
die aufgestapelten Lagen bewegt, um Sets mit vorher festgelegten Formen auszuschneiden,
so genannte Schnittmuster, wobei jeweils eine Abfolge von Schneidevorgängen ausgeführt
werden. Jeder von diesen Schneidevorgängen ist durch ein und nur ein Schnittmuster
und einen und nur einen Schnittbereich
gekennzeichnet, was als Schnittposition bezeichnet wird. Jede dieser Schnittpositionen bezieht sich
nur auf jeweils einen Schneidevorgang. Die besagte Apparatur ist mit Mitteln zum Entnehmen
der ausgeschnittenen Werkstücke ausgestattet. Die Methode umfasst folgendes:
• automatisches Ablegen einer oder mehrerer Lagen einer Trennfolie auf verschiedenen
Höhen der besagten Schichtanordnung von Folienmaterial, wobei jede Trennfolie die
darunter aufgestapelten Lagen von den weiter oben aufgestapelten Lagen trennt,
• Ablage der besagten Trennfolie während des Ausbreitvorgangs am Folienmaterial, ohne
dass dadurch die Breitstreckvorrichtung gestoppt oder ihre Geschwindigkeit verringert wird,
• die besagte Trennfolie ist auf einer Zufuhrrolle aufgewickelt und wird entlang eines
vorher festgelegten Musters, das als Abrissmuster bezeichnet wird, vorher abgerissen.
Dieses Abrissmuster erstreckt sich quer über die gesamte Breite und wird periodisch
in Längsrichtung der Folienrolle wiederholt,
• automatisches Ablegen einer Trennfolienlage, die eine oder mehrere zusammenhängende
Schnittpositionen abdeckt, um in der Entnahmephase die unten gestapelten Lagen visuell
von den über der ausgebreiteten Folienlage gestapelten unterscheidbar zu machen,
• Ausbreiten der besagten Folienlage entweder während des ersten Ausbreitvorgangs
der oberen gestapelten Lagen und unterhalb des Folienmaterials, das gleichzeitig ausgebreitet
wird, oder während des letzten Ausbreitvorgangs der unteren gestapelten Lagen und
auf der Folienmateriallage, die gleichzeitig ausgebreitet wird,
• Ausbreiten von einer oder mehreren Trennfolienlagen während des gleichzeitig ablaufenden
Ausbreitvorgangs des Folienmaterials, wobei jede Trennfolienlage eine oder mehrere
zusammenhängende Schnittpositionen abdeckt,
• Ablegen einer Trennfolienlage über eine oder mehrere zusammenhängende Schnittpositionen,
so dass der abgedeckte Bereich eindeutig anzeigt, welche die Schnittpositionen sind,
wenn die oberen und die unteren gestapelten Lagen in der Entnahmephase voneinander
unterschieden werden müssen,
• Abtrennen der Trennfolie von der Folienzufuhrrolle durch einen Schneidevorgang,
• oder durch Anwendung von zwei entgegengesetzten Zugkräften entlang der besagten
Abrissmuster, wobei der besagte Abreißvorgang eine sofortige Trennung der Folie von
der Zufuhrrolle ermöglicht, ohne dass die Wagenbewegung oder der Hauptvorgang des
Ausbreitens gestoppt werden muss,
• das Ausschneiden von Formen nach einem vorher festgelegten Schnittmuster mittels
eines Werkzeugs, das durch die Trennfolienlagen und die aufeinander gestapelten Lagen
auf jeder der Schnittpositionen hindurchgeführt wird.
2. Eine Methode für den Betrieb einer Apparatur, wie sie in den Ansprüchen 1 dargelegt
ist, die eine Maschinenbearbeitung einer Vielzahl von Jobs durchführen kann, von denen
jeder sowohl einen verschiedenen Schneidevorgang gemäß einem für eine der beiden Seiten
der Lage, der so genannten Schnittseite, festgelegtes Schnittmuster, als auch eine
Reihe von Ausbreitvorgängen erfordert, die durch eine Vielzahl von Varianten des Folienmaterials
gekennzeichnet sind. Die Methode umfasst folgendes:
• Aufteilung der Schnittmuster in drei separate Gruppen, wobei festgelegt wird, ob
ein Umkanten der Lage machbar ist, und ob dies ein gleichzeitiges Umkanten des Schnittmusters
erfordert. Dabei besteht die erste Schnittmustergruppe (vom symmetrischen Typ) aus
all den Schnittmustern, die von ihrer umgekanteten Version nicht unterscheidbar sind,
und wo ein Umkantvorgang der Lage machbar ist und keinen Umkantvorgang des Schnittmusters
erfordert. Die zweite Gruppe (Spiegeltyp) besteht aus einem Paar von Schnittmustern
((A, AM)), bei denen eines die umgekantete Version des anderen ist und bei denen das erste
Schnittmuster (A) verwendet werden kann, um Formen vom Schnittmuster AM zu erhalten, bei dem die Lage zur Schnittseite von A hin umgekantet ist. Umgekehrt kann das zweite Schnittmuster (AM) verwendet werden, um Formen vom Schnittmuster A zu erhalten, wenn die Lage zur Schnittseite von AM hin umgekantet ist. Die dritte Gruppe (asymmetrischer Typ) enthält alle Schnittmuster
mit Ausnahme der in der oben genannten ersten und der oben genannten zweiten Gruppe.
• Betrieb der Apparatur auf eine Weise, dass jeder Ausbreitvorgang beim Ablegen einer
umgekanteten Lage dann und nur dann eine oder mehrere Schnittpositionen abdecken kann,
wenn die betreffenden Schnittmuster nicht zur dritten Gruppe der besagten drei Gruppen
gehören.
• Betrieb der Apparatur auf eine Weise, dass jeder Ausbreitvorgang beim Ablegen einer
umgekanteten Lage dann und nur dann eine oder mehrere Schnittpositionen abdecken kann,
wenn die betreffenden Schnittmuster zur ersten oder zweiten Gruppe der besagten drei
Gruppen gehören.
3. Eine Methode für den Betrieb einer Apparatur wie in Anspruch 1 dargelegt, die eine
Vielzahl von Produktstapeln in einer oder mehreren Schichtanordnungen anordnen kann,
von denen jede durch ein verschiedenes Schnittmuster und durch eine Reihe von Produktanforderungen
gekennzeichnet ist. Dabei ist jede der besagten Anforderungen durch eine Variante des Folienmaterials
und durch eine Anzahl von Elementen
gekennzeichnet, die hergestellt werden sollen. Die Methode zum Zusammenstellen jeweils einer einzigen
Schichtanordnung als einer Abfolge von Schnittpositionen, wie in den Ansprüchen 1
und 2 dargelegt, umfasst folgendes:
• Festlegung der Mindestanzahl von Schnittpositionen für Stapel oder in gleicher Weise
für jedes Schnittmuster, der Mindestanzahl von Schnittpositionen, wobei diese als
der mindeste Ganzzahlwert größer oder gleich wie das Verhältnis zwischen der Gesamtanzahl
an Anforderungen hinsichtlich des betreffenden Stapels und der maximalen Anzahl an
gestapelten Lagen berechnet wird, die vom Schneidewerkzeug auf einmal ausgeschnitten
werden können. Diese wird als • H_max bezeichnet.
• Aufteilung von Produktstapeln in zwei Gruppen, wobei die als Überlaufgruppe von
H_max bezeichnete erste Gruppe die Stapel enthält, die durch eine Gesamtanzahl an
Produktanforderungen gekennzeichnet sind, welche größer als das besagte H_max ist. Die zweite Gruppe enthält alle Stapel
mit Ausnahme der in der besagten ersten Gruppe.
• Festlegung einer ersten Abfolge von Schnittpositionen, wie in den Ansprüchen 1 und
2 gesagt, wobei jede von ihnen durch ein Schnittmuster gekennzeichnet ist. Die besagte Abfolge wird so festgelegt, dass ihre Länge die Länge der Arbeitsfläche
der Breitstreckvorrichtung nicht übersteigt, die als L_max bezeichnet wird.
• Festlegung eines Schneidejobs für jede Schnittposition in der ersten Abfolge durch
Zuweisung einer Vielzahl von Elementen, die aus denen ausgewählt werden, die gemäß
dem Schnittmuster ausgeschnitten werden sollen, das der besagten Schnittposition zugewiesen
ist. Die Anzahl der besagten Elemente wird so festgelegt, dass der besagte Wert H_max
nicht überschritten wird und die Mindestanzahl an Schnittpositionen für das betreffende
Schnittmuster nicht erhöht wird.
• Berechnung des besagten Werts der ersten Abfolge durch Zuweisung eines Paarwerts
an jedes Paar von Schneidejobs in der ersten Abfolge. Dabei ist der Paarwert eine
monotone Funktion dessen, wie viele Ausbreitvorgänge in der Abfolge unter Berücksichtigung
der in Anspruch 2 genannten Aufteilung in drei Gruppen zusammengefasst werden können.
• Festlegung der Abfolge von Befehlssignalen, die von der Apparatur von Anspruch 1
ausgeführt werden soll, um die festgelegte Abfolge von Schneidejobs zusammen zu stellen
und auszuschneiden.
• Veranlassung der Apparatur, die Schichtanordnung zusammen zu stellen und die gestapelten
Lagen in jeder Schnittposition in der Reihenfolge der festgelegten Abfolge des Schneidejobs
auszuschneiden.
• Verringerung der Anzahl von Elementen, die in jedem der besagten Produktstapel gemäß
der festgelegten Abfolge des Schneidejobs angefordert werden.
4. Eine Methode, wie in Anspruch 3 dargelegt, wobei die Methode weiter folgendes umfasst:
• Wenn sich die monotone Funktion nicht verringert, das Finden der optimalen Abfolge
des Schneidejobs durch Wiederholung der Festlegung, der Definitions- und Berechnungsschritte
für jede Vielzahl von verschiedenen möglichen Abfolgen von Schneidejobs und der Auswahl
der Abfolge, die den größten Abfolgewert hat.
• Wenn sich die monotone Funktion nicht erhöht, das Finden der optimalen Abfolge des
Schneidejobs durch Wiederholung der Festlegung, der Definitions- und Berechnungsschritte
für jede Vielzahl von verschiedenen möglichen Abfolgen von Schneidejobs und der Auswahl
der Abfolge, die den kleinsten Abfolgewert hat.
5. Eine Methode für den Betrieb einer Apparatur wie in den Ansprüchen 1, 2, 3 und 4 dargelegt,
welche das Entscheidungsproblem bei der Festlegung der Abfolge von Schneidejobs suboptimal
hinsichtlich einer monotonen Funktion wie in den Ansprüchen 3 und 4 dargelegt in eine
Reihe von Entscheidungen von kleineren Unterproblemen aufgliedert, wobei jedes dieser
Unterprobleme einen Teil der Abfolge von Schneidejobs festlegt.
6. Eine Methode für den Betrieb einer Apparatur wie in den Ansprüchen 1, 2, 3, 4 und
5 dargelegt, die das Entscheidungsproblem bei der Festlegung der Abfolge von Schneidejobs
suboptimal hinsichtlich einer monotonen Funktion wie in den Ansprüchen 3 und 4 dargelegt
in drei aufeinander folgende Schritte aufgliedert, die folgendes umfassen:
• Zuweisung eines Paarwerts an jedes Paar von Produktstapeln wie in den Ansprüchen
3 und 4 dargelegt, wobei der Paarwert eine monotone Funktion dessen ist, wie viele
Ausbreitvorgänge in jedem Produktstapelpaar zusammengefasst werden können.
• Anordnung der Produktstapel in einer Abfolge, die durch Bewertung des Problems eines
allgemeinen reisenden Vertreters festgelegt wird, der beschränkten Platz in seinem
Rucksack hat. Dabei wird der Abfolgewert im vorhergehenden Schritt festgestellt und
der Algorithmus des Problems des reisenden Vertreters entsprechend modifiziert, um
die Kosten der Erstellung der Abfolge für jeden Stapel in Verbindung mit einem symmetrischen
Schnittmuster wie in Anspruch 2 dargelegt eindeutig festzustellen.
• Festlegung der im Anordnungsschritt bewerteten Abfolge für jede Position, wobei
die Vielzahl der Elemente wie in Anspruch 3 dargelegt so festgelegt wird, dass der
Wert H_max nicht überschritten und die Mindestanzahl von Schnittpositionen für das
betreffende Schnittmuster nicht erhöht wird.
1. Une méthode pour un appareil servant à déployer et couper des feuilles souples enroulées
sur un rouleau d'approvisionnement. Cet appareil dispose de moyens pour déposer une
ou plusieurs couches de feuilles sur une table de travail afin de former automatiquement
une superposition de couches. Ces couches sont déposées par un extenseur qui exécute
des mouvements selon le format dans un sens et dans l'autre longitudinalement à la
surface de travail avec des points de début et de fin pouvant être définis arbitrairement.
Ledit extenseur dispose de moyens pour déposer et détacher une ou plusieurs couches
dudit rouleau d'approvisionnement de feuilles afin de former automatiquement une seule
superposition de couches de différentes hauteurs. Ledit extenseur dispose de moyens
pour déployer automatiquement des couches retournées. Ledit appareil dispose de moyens
pour maintenir la superposition de couches ou une partie contre la table par aspiration.
En outre, ledit appareil est muni d'un outil qui se déplace à travers les couches
superposées afin de découper des jeux de formes prédéterminées, appelées patrons,
conformément à une suite d'opérations de coupe. Chacune de ces opérations de coupe
est
caractérisée par un seul et unique patron et une seule et unique zone de coupe, appelée position de
coupe. Chacune de ces positions de coupe ne porte que sur une seule et unique opération
de coupe. Ledit appareil dispose de moyens permettant de décharger les pièces découpées.
La méthode comprend :
• le dépôt automatique d'une ou plusieurs couches de film de séparation sur différentes
hauteurs de ladite superposition de couches de feuilles, où chaque couche de film
sépare les couches superposées inférieures des couches superposées supérieures ;
• le dépôt de ladite couche de film de séparation pendant l'opération de déploiement
des feuilles, sans que l'extenseur ne s'arrête ou ne ralentisse ;
• ledit film de séparation est enroulé sur un rouleau d'approvisionnement et est préalablement
déchiré le long d'un patron prédéterminé, appelé modèle de déchirure. Ce modèle de
déchirure s'étend sur toute la largeur et se répète périodiquement longitudinalement
au rouleau de feuilles.
• le dépôt automatique d'une couche de film de séparation couvrant une ou plusieurs
positions de coupe contiguës, afin de pouvoir distinguer visuellement, lors de la
phase de déchargement, les couches superposées inférieures des couches superposées
au-dessus de la couche de film déployée ;
• le déploiement dudit film soit au cours de la première opération de déploiement
des couches superposées supérieures et au-dessous de la couche de feuilles déployée
simultanément, ou au cours de la dernière opération de déploiement des couches superposées
inférieures et sur la couche de feuilles déployée simultanément ;
• le dépôt pendant l'opération simultanée de déploiement de feuille d'une ou plusieurs
couches de film de séparation, chacune d'elles couvrant une ou plusieurs positions
de coupe contiguës ;
• le dépôt d'une couche de film de séparation sur une ou plusieurs positions de coupe
contiguës, de sorte que la surface couverte montre sans ambiguïté quelles sont les
positions de coupe, lorsqu'il faut distinguer les couches superposées inférieures
et supérieures au cours de la phase de déchargement ;
• le détachement du film de séparation du rouleau d'approvisionnement de feuilles
au moyen d'une opération de coupe ou de l'application de deux forces de tension opposées
le long desdits modèles de déchirure ; ladite opération de déchirure permettant de
séparer immédiatement le film déployé du rouleau d'approvisionnement, sans que le
mouvement du chariot, ni l'opération principale de déploiement, ne requiert un arrêt
;
• le découpage de formes selon un patron prédéterminé au moyen d'un outil se
• déplaçant à travers les couches de film de séparation et les couches de feuilles
superposées sur chacune des positions de coupe.
2. Une méthode pour le fonctionnement d'un appareil, tel qu'il est énoncé dans les revendication
1, qui est capable d'exécuter plusieurs tâches, chacune d'elles demandant à la fois
une opération de coupe différente selon un patron précis pour l'un des deux côtés
de la couche, appelé le côté de coupe, et un ensemble d'opérations de déploiement
caractérisées par plusieurs variantes de feuilles. La méthode comprend :
• la répartition des patrons en trois groupes séparés où il est défini si le retournement
de la couche est faisable et si cela demande un retournement simultané du patron.
Ainsi le premier groupe de patrons (de type symétrique) se compose de tous ces patrons
indiscernables de leur version retournée et où une opération de retournement de la
couche est faisable et ne requiert pas d'opération de retournement du patron. Le second
groupe (de type miroir) consiste en une paire de patrons ((A, AM)), où l'un est la version retournée de l'autre et où le premier patron (A) peut être employé pour obtenir des formes du patron AM, où la couche est retournée par rapport au côté de coupe de A. Inversement le second patron (AM) peut être employé pour obtenir des formes du patron A, lorsque la couche est retournée par rapport au côté de coupe de AM. Le troisième groupe (de type asymétrique) comprend tous les patrons, à l'exception
de ceux mentionnés ci-dessus dans le premier et deuxième groupe ;
• le fonctionnement de l'appareil de sorte que chaque opération de déploiement lors
du dépôt d'une couche retournée puisse couvrir une ou plusieurs positions de coupe
uniquement si les patrons concernés n'appartiennent pas au troisième groupe des trois
groupes en question ;
• le fonctionnement de l'appareil de sorte que chaque opération de déploiement lors
du dépôt d'une couche retournée puisse couvrir une ou plusieurs positions de coupe
uniquement si les patrons concernés appartiennent au premier ou au second groupe des
trois groupes en question.
3. Une méthode pour le fonctionnement d'un appareil, tel qu'il est énoncé dans la revendication
1, qui est en mesure de disposer en une ou plusieurs superpositions de couches plusieurs
lots de produits, chacun d'eux étant
caractérisé par un patron différent et une série de demandes de produits. Chacune de ces demandes
est
caractérisée par une variante de feuille et un certain nombre d'articles à produire. La méthode pour
composer à chaque fois une seule superposition de couches en une suite de positions
de coupe, comme énoncé aux revendications 1 et 2, comprend :
• la détermination, pour chaque lot ou de la même manière pour chaque patron, du nombre
minimum de positions de coupe, calculé comme la valeur entière minimale supérieure
ou égale au rapport entre le nombre total de demandes liées au lot considéré et le
nombre maximal de couches superposées pouvant être coupées en une fois par l'outil
de coupe. Cette valeur est appelée H_max ;
• la répartition des lots de produits en deux groupes, où le premier groupe caractérisé comme groupe de dépassement H_max comprend les lots, caractérisés par un nombre total de demandes de produits supérieures à ladite valeur H_max. Le second
groupe comprend tous les lots, à l'exception de ceux dudit premier groupe ;
• la détermination d'une première suite de positions de coupe, comme énoncé dans les
revendications 1 et 2, où chacune d'elles est caractérisée par un patron. Ladite suite est définie de sorte que sa longueur ne dépasse pas la longueur
de la surface de travail de l'extenseur, appelée L_max ;
• la définition d'une tâche de coupe pour chaque position de coupe dans la première
• suite en attribuant plusieurs éléments choisis parmi ceux devant être coupés selon
le patron attribué à ladite position de coupe. Le nombre desdits éléments sera déterminé
de sorte que ladite valeur H_max ne soit pas dépassée et que le nombre minimum de
positions de coupe pour le patron considéré ne soit pas augmenté ;
• le calcul de ladite valeur de la première suite au moyen de l'attribution d'une
valeur paire à chaque paire de tâches de coupe dans la première suite. Ainsi la valeur
paire est une fonction monotone démontrant comment de nombreuses opérations de déploiement
peuvent être assemblées dans la suite en tenant compte de la répartition en trois
groupes mentionnée dans la revendication 2;
• la détermination de la suite des signaux de commande qui doivent être exécutés par
l'appareil de la revendication 1, afin de réunir et découper la suite déterminée des
tâches de coupe ;
• encourager l'appareil à réunir la superposition de couches et à découper les couches
superposées dans chaque position de coupe dans l'ordre de la suite déterminée de tâches
de coupe ;
• la diminution du nombre d'éléments demandés dans chaque lot de produits selon la
suite déterminée de tâches de coupe.
4. Une méthode, comme énoncé dans la revendication 3, où la méthode comprend en outre
:
• si la fonction monotone ne diminue pas, la recherche de la meilleure suite de tâches
de coupe au moyen de la répétition des étapes de détermination, de définition et de
calcul pour chaque variété de différentes suites de tâches de coupe possibles et la
sélection de la suite ayant la plus grande valeur de suite ;
• si la fonction monotone n'augmente pas, la recherche de la meilleure suite de tâches
de coupe au moyen de la répétition des étapes de détermination, de définition et de
calcul pour chaque variété de différentes suites de tâches de coupe possibles, et
la sélection de la suite ayant la plus petite valeur de suite.
5. Une méthode pour le fonctionnement d'un appareil, tel qu'énoncé dans les revendications
1, 2, 3 et 4, qui décompose le problème de décision lors de la détermination de la
suite de tâches de coupe par rapport à une fonction monotone comme énoncé dans les
revendications 3 et 4, en une série de sous-problèmes plus petits, chacun de ces sous-problèmes
déterminant une partie de la suite des tâches de coupe.
6. Une méthode pour le fonctionnement d'un appareil, tel qu'énoncé dans les revendications
1, 2, 3, 4 et 5, qui décompose le problème de décision lors de la détermination de
la suite de tâches de coupe, par rapport à une fonction monotone comme énoncé dans
les revendications 3 et 4, en trois étapes consécutives comprenant :
• l'attribution d'une valeur paire à chaque paire de lots de produits, comme énoncé
aux revendications 3 et 4, où la valeur paire est une fonction monotone démontrant
combien d'opérations de déploiement peuvent être réunies dans chaque paire de lots
de produits ;
• la disposition des lots de produits dans une suite déterminée par l'évaluation du
problème d'un représentant commercial en déplacement dont l'espace dans le sac à dos
est limité. Ainsi la valeur de la suite aura été déterminée à l'étape précédente et
l'algorithme du problème du représentant commercial sera modifié, afin de déterminer
sans ambiguïté le coût de l'élaboration de la suite pour chaque lot lié à un patron
symétrique comme énoncé dans la revendication 2 ;
• la détermination pour chaque position de la suite évaluée dans l'étape d'organisation,
où la variété des éléments est déterminée, comme énoncé dans la revendication 3, de
sorte que la valeur H_max ne soit pas dépassée et que le nombre minimum de positions
de coupe pour le patron considéré ne soit pas augmenté.