EP4096883A1

EP4096883A1 - Method and system for automatic cutting of defective portions in a patterned fabric

Info

Publication number: EP4096883A1
Application number: EP21716499.5A
Authority: EP
Inventors: Stéphane BODIVIT; Régis LAINÉ; Cory CRAWFORD; Sébastien DUCHESNE
Original assignee: Lectra SA
Current assignee: Lectra SA
Priority date: 2020-03-26
Filing date: 2021-03-18
Publication date: 2022-12-07
Also published as: WO2021191532A1; BR112022017115A2; FR3108546B1; CN115379935A; MX2022011106A; US20230110371A1; FR3108546A1

Abstract

The invention relates to a method and system for automatic cutting of defective portions in a patterned fabric repeating at a certain interval, comprising the steps of developing a theoretical layout of portions to be cut on a theoretical representation of the fabric whilst respecting layout constraints, spreading out at least one layer of fabric on a cutting table, checking at least one portion of the spread-out fabric to ascertain actual characteristics, modifying the theoretical layout in order to generate an actual layout taking into account the actual characteristics of the fabric, identifying in the actual layout of defective portions that will have defects once cut in the fabric and that will need to be cut again, and automatically allocating each defective portion to a new theoretical layout by adjusting the layout constraints associated with the defective portions depending on the actual layout.

Description

Title of the invention: Method and system for the automatic cutting of faulty parts in a patterned fabric

Technical area

The invention relates to the general field of the automatic cutting of pieces in a fabric with a pattern repeating at a certain pitch, called the pattern pitch. It relates more particularly to the management of faulty parts which will contain defects once cut from the fabric and which will need to be cut.

Fields of application of the invention are in particular the clothing and furniture industries.

Prior art

When the production of articles of clothing or of furnishing elements involves an assembly of pieces cut from a fabric, there are particular constraints if the fabric is patterned. By “patterned fabric” is meant here any flexible sheet textile material printed with a pattern which is repeated with regular and predetermined pitches.

In this case, it is then desirable, or even necessary, to respect the continuity of the pattern between two assembled parts, for example two parts of a garment sewn together, or two parts intended to be adjacent, for example. two pieces of clothing located side by side when the garment is worn, or two sofa cushions placed side by side.

In order to comply with these constraints, it is known practice to associate the parts with absolute or relative position marks and to establish a hierarchy between main parts and secondary parts.

An absolute position mark is normally associated with a main part. It characterizes the absolute positioning of the main piece in relation to the pattern of the fabric. The position of a piece with respect to the pattern is characterized by the fact that a given point on the surface of the piece occupies a determined relative position with respect to the patterns which surround it. Thus, parts whose locations at the fabric surface are deduced from each other by translations of a whole number of pattern pitches occupying the same position relative to the pattern.

Relative position markers are associated with two parts to be assembled taking into account imperatives related to the existence of the pattern. They identify the locations of two tie points to be matched when assembling parts.

For example, in the case of a jacket, a back piece can be a main piece. An absolute position mark is possibly associated with the part of the back, for example when it is desired that a complete pattern be visible in a particular location of this part. A sleeve, the neckline, a front then constitute secondary parts. For each of these, the location of a fitting point is determined to match the location of the associated fitting point on the main part.

In addition, a part with which is associated a relative position mark can also be the main part of one or more other parts. In this case, we are talking about a chain of bonds. Likewise, a part can have an absolute, relative or none position mark in the axis of the weft thread, and another type of position mark (relative, absolute or none) for the axis of the warp thread of the fabric. .

Furthermore, it is known practice to cut tissue automatically. Automatic cutting installations have been marketed by the applicant for many years.

Typically, an automatic cutting process comprises a placing operation which consists in optimally determining the positions of the pieces to be cut in a web of fabric. The placement is chosen so as to minimize the loss of fabric while respecting certain constraints: respect for the right grain, sufficient minimum margin between pieces, etc ... In the case of a patterned fabric, the constraints related to the respect of the positions of the absolute position and relative position markers. Systems allowing an operator to define placements using computer workstations and specialized software are known, including in the case of patterned fabrics.

In order to effect the cut, the fabric is laid out on a cutting table in one or more superimposed layers which can be held by suction through Table. Cutting is performed by means of a tool carried by a head whose movements, relative to the cutting table, are controlled according to the predetermined placement. Cutting can be done by vibrating blade, rotary blade, laser, water jet, etc. Difficulties arise when the fabric used is a patterned fabric. In particular, the problem arises in practice of the non-coincidence between the fabric pattern used for placement and the fabric actually laid out on the cutting table. This non-coincidence is reflected in particular as follows. If we stand on the cutting table at the coordinates of a reference point of a part of the placement, we see that the corresponding point on the spread fabric does not always occupy the desired relative position with respect to the pattern of the real fabric. These differences are more or less large and in practice inevitable. They are due to printing defects, defects in the laying of fabric on the cutting table, variations in the density of the threads of the loom and / or deformations of the fabric which can result in irregularities in the pitch of the loom. repeating the pattern. As a result, the pre-established placement, or theoretical placement, must be modified to match the reality of the spread tissue.

A method for effecting this modification of placement automatically is described in document EP 0,759,708 filed in the name of the applicant. After spreading the patterned fabric on the cutting table, this method provides for detecting a possible offset between the actual pitch of the pattern on the fabric and the theoretical pitch of the latter by capturing images of parts of the spread fabric then a check on the captured images that locations corresponding to stored information occupy desired positions relative to the actual pattern of the spread fabric. If necessary, the theoretical placement of the pieces is modified according to the result of the control in order to adapt it to the real pitch of the pattern on the spread fabric, taking into account the real characteristics of the fabric.

As the actual placement of a group of parts provided on a portion of fabric is generated, the phase of cutting this group of parts is initiated. However, during this phase, many problems are often encountered, especially at the level of the tissue to be cut. Indeed, it is frequent that this one presents in certain places defects, tears, degradations of color of the material, etc. However, when a piece of the placement is cut to these places, it becomes unusable and must therefore be cross-checked. Likewise, changing the placement of parts to be cut sometimes results in repositioning parts in which some adjacent parts overlap. In this situation, these parts become unusable and it is then necessary to cut them. In practice, these problems force the operator to cut all the parts of the placement which are concerned (hereinafter called “faulty parts”) at the end of the cutting phase.

Generally, the faulty parts that need to be cut are manually cut by the operator after cutting the other parts of the placement. In practice, the operator cuts a coupon from the roll of fabric and cuts the faulty part manually. However, this manual re-cut can prove to be particularly complicated when the default part is a child part to which is associated a relative placement constraint with respect to a parent part. Indeed, in this situation, the operator must perform the connection manually by finding the parent part and its connection with the child part to be cut, then transfer this type of constraint manually to the coupon in which the part will be cut. Moreover, it may be necessary to repeat these operations for all the parts having a relative position mark with respect to the cut part.

This manual trimming method has many drawbacks. On the one hand, the automatic part cutting process is interrupted. On the other hand, the use of the material is not optimized (resulting in a waste of fabric) and the quality of the connections with the pattern of the fabric often lacks precision.

Disclosure of the invention

The present invention therefore proposes a method for automatically cutting faulty pieces in a patterned fabric in which the faulty pieces are automatically cut.

According to the invention, this object is achieved by means of a method for automatically cutting faulty pieces in a fabric with a pattern repeating at a certain pitch, called the pattern pitch, comprising the steps of:

- development of a theoretical placement of parts to be cut on a theoretical representation of the fabric while respecting the placement constraints associated with the parts; spreading at least one layer of fabric on a cutting table; acquiring the actual characteristics of at least part of the spread tissue; modification of the theoretical placement to generate an actual placement of the parts on the spread fabric taking into account the real characteristics of the fabric; identification in the actual placement of faulty parts which will contain defects once cut from the fabric and which will need to be cut; and automatically assigning each failing part to a new theoretical placement by adapting the placement constraints associated with the failing parts based on the actual placement.

The method according to the invention is remarkable in that it provides for the automatic cutting of the faulty parts by assigning them to a new placement, this assignment being carried out so as to keep their placement constraints in order to adapt them according to the placement. real. In other words, the method according to the invention provides for recording the placement constraints on the spread fabric of the faulty pieces in order to translate them into positioning constraints for the new placement from which the faulty pieces will be cut.

The method according to the invention is thus particularly advantageous in that the process for re-cutting faulty parts is fully automated. In this way, the automatic part cutting process does not need to be interrupted. This automation also makes it possible to optimize the material to limit waste and to guarantee high precision in the quality of the connections with the pattern of the fabric. Preferably, each part to be cut is associated with a reference point and a placement constraint on the fabric chosen from: a) absolute constraint for which the position of the reference point of the part with respect to the pattern of the fabric is determined so that a pattern of the fabric appears at a desired location in the room; b) relative constraint for which the position of the reference point of the part, called the child part, is determined with respect to a connection point of another part, called parent part, so that the position of the reference point of the child part with respect to the fabric pattern is the same as the position of the connection point of the parent part; c) relative symmetry constraint for which the position of the reference point of the part, called the child part, is determined with respect to a connection point of another part, called the parent part, so that the position of the point reference point of the child piece with respect to the pattern of the fabric is symmetrical with respect to the pattern of the position of the point of connection of the parent piece; and d) free stress for which the position of the part reference point with respect to the fabric pattern is free.

When the default part is a part to which is associated an absolute constraint (case a) above), the automatic assignment of the part to the new theoretical placement advantageously comprises the conservation in the new theoretical placement of this absolute constraint with respect to to the fabric pattern.

When the default part is a child part to which is associated a relative constraint or a relative symmetry constraint with respect to a parent part that does not need to be cut (case b) or c) above), the assignment automatic operation of the part at the new theoretical placement advantageously comprises the transformation in the new theoretical placement of the relative stress into an absolute stress so that the position of the reference point of said child part with respect to the pattern of the fabric remains the same as what she was in the actual placement.

When the default part is a parent part to which is associated at least one relative constraint or at least one relative symmetry constraint with respect to one or more child parts (case b) or c) above), the automatic assignment of the part to the new theoretical placement also advantageously includes the automatic allocation of the child part (s) to the new theoretical placement.

Finally, when the faulty part is a part with which is associated a free constraint, the automatic assignment of the part to a new theoretical placement advantageously includes the absence in the new theoretical placement of a position constraint of the reference point of the piece in relation to the fabric pattern. The new theoretical placement of the failed parts can be calculated and cut into an area at the end of the actual placement in the direction of the fabric feed on the cutting table.

Alternatively, the new theoretical placement of the faulty parts can be incorporated into a subsequent placement in the direction of the fabric feed on the cutting table.

The faulty part can be: a part which, after generation of the actual placement, is positioned on a defect in the spread fabric; or a part which, after generating the actual placement, overlaps another part of the placement; or a part which, after generation of the actual placement, is positioned on an area of the spread fabric which exhibits significant deformation; or a part which, after generation of the actual placement, cannot be entirely cut from the spread fabric; or a part which, after generation of the actual placement and after cutting, has a cutting defect; or a part which, after generation of the actual placement, exhibits a geometric defect; or a child part to which is associated a relative constraint or a relative symmetry constraint with respect to a parent part in default requiring to be cut.

The faulty part may not be cut from the spread fabric.

The subject of the invention is also a system for automatically cutting faulty pieces in a fabric with a pattern repeating at a certain pitch, called the pattern pitch, comprising: means for developing a theoretical placement of pieces to be cut on a theoretical representation of the fabric while respecting the placement constraints associated with the parts; - a cutting table on which can be spread at least one layer of fabric;

- Means for acquiring the real characteristics of at least part of the spread fabric;

means for modifying the theoretical placement to generate a real placement of the pieces on the spread fabric taking into account the real characteristics of the fabric;

- Means for identifying in the actual placement of faulty parts which will contain defects once cut from the fabric and which will need to be cut; and

means for automatically assigning each faulty part to a new theoretical placement by adapting the placement constraints associated with the faulty parts according to the actual placement.

Brief description of the drawings

[Fig. 1] FIG. 1 is a schematic view of an example of a fabric with repeating patterns to which the invention applies.

[Fig. 2] FIG. 2 represents an example of theoretical placement of parts to be cut.

[Fig. 3] Figure 3 shows how the theoretical placement of Figure 2 can be changed to generate an actual placement.

[Fig. 4] Figure 4 shows an example of automatic assignment of a default part (having a free constraint) from the actual placement of Figure 3 to a new theoretical placement.

[Fig. 5] FIG. 5 shows an example of automatic assignment of another part failing (having a relative constraint) from the actual placement of FIG. 3 to the new theoretical placement.

[Fig. 6] Figure 6 shows an example of automatic assignment of two faulty parts linked from the actual placement of Figure 3 to the new theoretical placement.

Description of the embodiments The invention relates to the cutting of a placement of a group of pieces in a fabric with repeating patterns, for example by means of an automatic cutting installation such as that described in the publication EP 0,759,708.

The invention relates more precisely to the automatic cutting of so-called “faulty” pieces in a fabric with a pattern repeating at a certain pitch.

The preliminary step of such a process consists in characterizing the fabric from which the pieces will be cut. This step can be accomplished by taking manual measurements on the fabric, based on information provided by the manufacturer or by scanning a strip of material to automatically recognize the pattern and characterize it; number of grids, not in warp, not in weft, offsets, etc.

An example of a fabric with repeating patterns to which the invention applies is shown in FIG. 1.

In this figure 1 is shown a fabric T with repeating patterns M having a main grid G1 and two secondary grids G2, G3, these grids G1 to G3 having offsets in the weft direction and in the warp direction with respect to each other (the direction warp being shown schematically by the X axis and the weft direction by the Y axis). The M patterns are characterized in particular by their P-C warp pitch and their P-T weft pitch.

The information extracted from the characterization of the tissue T is recorded to define a theoretical grid which is used to develop a theoretical placement of the parts.

The development of a theoretical placement consists in determining on the theoretical grid the locations of the parts to be cut so as to minimize material loss, while respecting certain constraints (respect for grain, minimum spacing between the parts to be cut, etc. .).

In the case of a fabric with repeating patterns, aesthetic imperatives may impose, on the one hand, for certain parts, the presence of a complete pattern in a particular place of the part, on the other hand, for two parts intended for to be assembled, a section of these parts ensuring, for example, the continuity of the pattern after assembly.

To this end, it is known to characterize each part of the placement by assigning it an initial contour, a reference point, and at least one placement constraint. Once the information relating to the theoretical characteristics of the fabric and the different parts of the placement has been determined and recorded, the theoretical placement of the parts is developed while respecting the placement constraints associated with the parts.

FIG. 2 represents an example of theoretical placement developed for four pieces P-1 to P-4 to be cut from a fabric T having in particular as a pattern a weft M1, M2, M3, etc. repeating at a predetermined step p.

Each of the parts P-1 to P-4 is assigned an initial contour, respectively Ci-1, Ci-2, Ci-3 and Ci-4. These initial contours are typically defined by computer aided design (CAD) software without any margins. They are represented by a polygon (in this case here by rectangles).

Each part of the placement P-1 to P-4 is also associated with a reference point, respectively O-1, O-2, O-3 and O-4, and at least one constraint of placing the part on the fabric .

The reference point of each part is defined by the operator regardless of the placement constraint used. This is an important point on the part to position.

The placement constraint is chosen by the operator from one of the following placement constraints:

1 / Absolute constraint:

This constraint is associated with a piece that must be positioned on the fabric at a specific location for a pattern of the fabric to appear at a desired location in the room.

For this constraint, the position of the part reference point relative to the fabric pattern is predetermined. Thus, in the example of figure 2, the parts P-1 and P-2 have an absolute placement constraint: the reference point O-1 of the part P-1 is positioned on the grid M3, while the Reference point O-2 of part P-2 is positioned on frame M5.

2 / Relative stress:

This constraint is associated with a first part, called “child part”, the position of which on the fabric is determined as a function of the position of a second part, called “parent part”. For this constraint, the position of the reference point of the child part is determined with respect to a connection point L of the parent part so that the position of the reference point of the child part with respect to the pattern of the fabric is the same as the position of the connection point of the parent part.

In the example of Figure 2, part P-3 is a child part for part P-2 (parent part). For this purpose, the parent part P-2 has a connection point L-2 which allows the positioning of the reference point O-3 of the child part P-3.

Point L-2 is located at distance d from frame M11, at 75% of the pitch between M11 and M12. Point O-3 must therefore also be positioned at the distance d of a frame. In our example, it is positioned between the frames M3 and M4, at the distance d from the frame M3.

Likewise, still in the example of figure 2, the part P-4 is a child part for the part P-3 (parent part) so that the parent part P-3 has a connection point L-3 which allows to position the reference point O-4 of the child part P-4.

It should be noted that the same part can contain several connection points because it can be the parent of several child parts.

3 / Relative stress of symmetry:

This constraint is also associated with a first part, called “child part”, the position of which on the fabric is determined as a function of the position of a second part, called “parent part”.

Relative to a relative placement constraint, the position of the child part's reference point is determined to be symmetrical about the pattern of the parent part's tie point position.

4 / Free constraint:

This constraint is associated with a part whose position relative to the fabric pattern is free (i.e. absence of relative or absolute constraint).

For this constraint, the position of the part's reference point relative to the fabric pattern is free. Once the information relating to the theoretical characteristics of the fabric and the different parts of the placement has been determined and recorded, the theoretical placement of the parts is developed while respecting the placement constraints associated with the parts. The characterization of each part and the development of the theoretical placement of the parts are usually carried out by an operator using a computer workstation equipped with suitable software. The theoretical placement and the characteristics of the parts are memorized.

The next step in the process is to lay out on the cutting table at least one layer of fabric T from which the placement will be cut, then to check at least part of the spread fabric to determine if the theoretical placement thus established is correct. and, if necessary, to correct it.

The check is typically carried out by positioning itself on the laid fabric, at the stored coordinates of the characteristic points associated with reference points and the connection points and by checking whether any characteristic points of the pattern of the laid fabric are indeed found at these locations.

If not, each time the closest characteristic point is sought on the spread fabric and the difference between the memorized theoretical position and the closest real position represents the offset to be corrected for the corresponding part in the placement.

In practice, the control of the fabric spread in order to acquire the real characteristics thereof is carried out for example by taking and then analyzing an image of a part of the surface of the fabric spread around a characteristic point of the pattern. Reference may be made to the publication EP 0,759,708 which describes an example of checking and correcting the theoretical placement in order to take into account the real characteristics of the fabric.

At the end of this checking step, the theoretical placement of the parts is modified to take into account the real characteristics of the fabric spread on the cutting table. Changing the theoretical placement thus generates an actual placement of the parts on the spread fabric. Figure 3 shows an example of the actual placement generated from the theoretical placement of Figure 2. In this example, the control of the spread tissue allowed to note that the pitch p 'of matter has increased compared to the theoretical pitch p (ie p' is strictly greater than p).

The position of parts P-1 and P-2, which each have an absolute placement constraint, is modified so that their respective reference points O-1 and O- 2 are positioned on the real frames M3 '(for part P-1 ) and M5 '(for part P-2) of the spread fabric.

The repositioning of the reference point O-2 and the value of the pitch p 'cause the link point L-2 to be located on the actual placement at a distance d' from the frame M11 representing 50% of the pitch p 'between the frames real M11 'and M12'.

For part P-3 which is the child part of parent part P-2, the actual placement is changed so as to keep the positioning constraint between points L-2 and O-3. This causes a positioning of the reference point O-3 of the child part P-3 between the real wefts M3 'and M4' at a ratio of 50% of the pitch p 'of the fabric spread between these real wefts (instead of 75% of the pitch p on the theoretical grid) which corresponds in FIG. 3 to a distance d ′ from the real frame M3 ′.

Likewise, for part P-4 which is the child part of parent part P-3, the actual placement is changed to keep the same relative position with respect to the pattern of points L-3 and O-4. This causes a positioning of the reference point O-4 of the child part P-4 between the real wefts M8 'and M9' at a ratio of 50% of the pitch p 'of the fabric spread between these real wefts (instead of 90% of the pitch p on the theoretical grid) which corresponds in FIG. 3 to a distance e 'from the real frame M8'.

The actual placement which has thus been generated from the theoretical placement of Figure 2 presents some problems for the cutting of the parts, and in particular for the overlapping parts P-1 and P-3.

Indeed, if, following the step of generating the actual placement, the program for automatically cutting the parts of the placement was launched (as is customary in the state of the art), the parts P-1 and P-3 would become parts failing which it would then be necessary to cut.

The object of the method according to the invention is to propose an automatic cutting of these faulty parts regardless of the placement constraint associated with these parts. In general, the method provides for this purpose to identify in the actual placement the faulty parts which will contain defects once cut from the fabric and which will need to be cut (typically parts P-1 and P-3 of the actual placement of figure 3), then automatically assign each defaulting part to a new theoretical placement by adapting the placement constraints associated with the defaulting parts according to the actual placement.

By "default part" is meant here parts of the placement which will contain defects once cut from the fabric and which will need to be cut.

In a non-exhaustive manner, the following parts are considered to be faulty parts within the meaning of the invention:

- a part which, after generation of the actual placement, is positioned on a defect in the spread fabric

- a part which, after generation of the real placement, overlaps another part of the placement (case of parts P-1 and P-3 in figure 3)

- a part which, after generation of the actual placement, is positioned on an area of the spread fabric which exhibits significant deformation

- a part which, after generation of the actual placement, cannot be cut entirely from the spread fabric

- a part which, after generation of the actual placement and after cutting, has a cutting defect

- a part which, after generation of the actual placement, has a geometric defect

- a child part to which is associated a relative constraint or a relative constraint of symmetry with respect to a parent part in the absence of which needs to be cut

The identification in the actual placement of the faulty parts can be carried out automatically before cutting (by analyzing the overlapping parts, detecting a defect on the material or a material coupon that is too short) or manually. by an operator when unloading parts and inspecting cut parts. In this case, the operator preferably has a graphical interface fitted to the cutting machine allowing him to manually select the faulty parts in the placement. More generally, this graphical interface allows to display the placement during cutting and to select the parts to be cut.

The automatic allocation of the faulty parts in a new theoretical placement is implemented by means of an algorithm for repositioning the faulty parts, this algorithm being implemented on a computer on board the cutting machine or separate from it.

We will now describe the way in which this repositioning algorithm works, taking as examples the faulty parts P-1 and P-3 of the actual placement of figure 2.

The case of the faulty part P-1 is relatively simple to deal with. This P-1 part has an absolute placement constraint and has no child parts. In this case, the method according to the invention provides for the automatic allocation of this part P-1 to the new theoretical placement while keeping in the new theoretical placement its absolute constraint with respect to the pattern of the fabric.

As shown in the example of FIG. 4, this assignment results in the transfer of the reference point O-1 of the part P-1 onto a new weft of the fabric (in this case the weft M18) so that the fabric pattern appears in the same location of the part as on the actual placement.

On the other hand, the case of the faulty part P-3 is more complicated to deal with because it is a part which is a child of the parent part P-2.

To find in the new theoretical placement the same final position of this part P-3, the position of its reference point O-3 in relation to the pattern of the fabric must be the same as the position of the connection point L-2 of the parent part P-2 relative to the fabric pattern, that is to say the distance d 'from the actual weft which is equal to 50% of the pitch p' of the spread fabric.

As represented in FIG. 5, the assignment of the part P-3 to the new theoretical placement thus consists in transferring the reference point O-3 of this part a distance çT from the new chosen frame (here the frame M15) which corresponds at the same percentage of the pitch of the fabric, that is to say at 50% of the pitch p of the fabric.

In some situations, it may be necessary to have to (or choose to) intersect multiple parts that are linked together by a relative placement constraint. If we take the example of parts P-3 and P-4 which are linked together by a relative placement constraint (part P-3 is a parent part for child part P-4), the assignment Automatic of these two parts failing at the new theoretical placement is carried out as follows.

In the actual placement (figure 3), the part P-3 is placed so that its reference point O-3 is positioned between the real frames M3 'and M4' at the distance d 'from the real screen M3' equal to 50% of the pitch p 'of the spread fabric.

As for the part P-4, it is placed in the real placement (figure 3) so that its reference point O-4 is positioned between the real frames M8 'and M9' at the distance e from the real frame M8 ' equal to 50% of the pitch p 'of the spread fabric.

In the new theoretical placement (Figure 6), part P-3 is placed so that its relative placement constraint is maintained.

For this purpose, as shown in figure 6, the position of its reference point O-3 relative to the pattern of the spread fabric must be the same as the position of the connection point of the parent part (part P-2) by compared to the pattern of the spread fabric, namely between the new wefts M15 and M16 at a distance d '' from the weft M16 which corresponds to the same percentage of the pitch of the fabric, ie 50% of the pitch p.

Even if it does not present a defect that would require re-cutting, it may be deemed necessary by the operator to re-cut part P-4 (child part of parent part P-3 if not).

To this end, as represented in FIG. 6, the repositioning algorithm recalculates the position of the connection point L-3 of the parent part P-3 with respect to the distance e '' between the new frames M17 and M18. This distance e '' is then reused to calculate the position of the reference point O-4 of the part P-4.

Automatic assignment is thus carried out for each faulty part regardless of its placement constraint in order to generate a new theoretical placement comprising all of the faulty parts.

Note that the repositioning algorithm operates in the same way for a faulty part which is associated with a relative symmetry constraint: in the new theoretical placement, the relative symmetry constraint is transformed into an absolute constraint so that the part reference point position child relative to the fabric pattern remains the same as it was in the actual placement.

Note also that, when the default part is a parent part to which is associated at least one relative constraint or at least one relative symmetry constraint with respect to one or more child parts, the algorithm for repositioning the part to the new theoretical placement can also include the automatic assignment of the child part (s) to the new theoretical placement.

The new theoretical placement of the faulty parts thus generated can then be cut in an area at the end of the actual placement in the direction of the fabric feed on the cutting table. This can be a specific fabric coupon from the same roll that was used for cutting the actual placement and located either after the actual placement or further downstream depending on the cutting strategy.

Of course, if one or more faulty parts were identified when cutting the new placement, the operation of automatically assigning these faulty parts to a new theoretical placement would be repeated.

Claims

[Claim 1] A method for automatically cutting faulty pieces in a fabric with a pattern repeating at a certain pitch, called the pattern pitch, comprising the steps of:

- development of a theoretical placement of parts to be cut (P-1 to P-4) on a theoretical representation of the fabric (T) while respecting the placement constraints associated with the parts;

- spreading at least one layer of fabric on a cutting table;

- acquisition of the real characteristics of at least part of the spread tissue;

- modification of the theoretical placement to generate a real placement of the pieces on the spread fabric taking into account the real characteristics of the fabric;

- identification in the actual placement of faulty parts (P-1, P-2) which will contain defects once cut from the fabric and which will need to be cut; and

- automatic assignment of each faulty part to a new theoretical placement by adapting the placement constraints associated with the faulty parts according to the actual placement.

[Claim 2] A method according to claim 1, wherein each piece to be cut (P-1 to P-4) is associated with a reference point (O-1 to O-4) and a placement constraint on the selected fabric. from: a) absolute stress for which the position of the reference point of the part with respect to the pattern of the fabric is determined so that a pattern of the fabric appears at a desired location of the part; b) relative constraint for which the position of the part's reference point, called the child part, is determined relative to a connection point (L- 2, L-3) of another part, called the parent part, so that the position of the reference point of the child part relative to the fabric pattern is the same as the position of the tie point of the parent part; c) relative symmetry constraint for which the position of the reference point of the part, called the child part, is determined with respect to a connection point of another part, called the parent part, so that the position of the point reference point of the child piece with respect to the pattern of the fabric is symmetrical with respect to the pattern of the position of the point of connection of the parent piece; and d) free stress for which the position of the reference point of the part with respect to the pattern of the fabric is free.

[Claim 3] The method of claim 2, wherein, when the faulty part is a part with which is associated an absolute constraint, the automatic assignment of the part to the new theoretical placement comprises keeping this in the new theoretical placement. absolute stress with respect to the fabric pattern.

[Claim 4] The method of claim 2, wherein, when the default part is a child part with which is associated a relative stress or a relative stress of symmetry with respect to a parent part not requiring to be cut, the The automatic assignment of the part to the new theoretical placement includes the transformation in the new theoretical placement of the relative stress into an absolute stress so that the position of the reference point of said child part with respect to the pattern of the fabric remains the same as what 'she was in the actual placement.

[Claim 5] The method of claim 2, wherein, when the default part is a parent part with which is associated at least one relative constraint or at least one relative constraint of symmetry with respect to one or more child parts, the Automatic assignment of the part to the new theoretical placement also includes the automatic assignment of the child part (s) to the new theoretical placement.

[Claim 6] The method of claim 2, wherein, when the faulty part is a part with which is associated a free constraint, the automatic assignment of the part to a new theoretical placement comprises the absence in the new theoretical placement. position constraint of the part's reference point relative to the fabric pattern.

[Claim 7] A method as claimed in any one of claims 1 to 6, wherein the new theoretical placement of the faulty parts is calculated and cut into an area at the end of the actual placement in the direction of fabric feed on the table. cutting.

[Claim 8] A method according to any one of claims 1 to 6, wherein the new theoretical placement of the faulty parts is integrated with a subsequent placement in the direction of advance of the fabric on the cutting table.

[Claim 9] A method according to any one of claims 1 to 8, wherein the faulty part is:

- a part which, after generation of the actual placement, is positioned on a defect in the spread fabric; Where

- a part which, after generation of the actual placement, overlaps another part of the placement; Where

- a part which, after generation of the actual placement, is positioned on an area of the spread fabric which exhibits significant deformation; Where

- a part which, after generation of the actual placement, cannot be cut entirely from the spread fabric; Where

- a part which, after generation of the actual placement and after cutting, has a cutting defect; Where

- a part which, after generation of the actual placement, exhibits a geometric defect; Where

- a child part to which is associated a relative constraint or a relative constraint of symmetry with respect to a parent part in the absence of which needs to be cut.

[Claim 10] A method according to any one of claims 1 to 9, wherein the faulty part is not cut from the spread fabric.

[Claim 11] System for the automatic cutting of faulty pieces in a fabric with a pattern repeating at a certain pitch, said pitch of the pattern, comprising:

- Means for developing a theoretical placement of parts to be cut (P- 1 to P-4) on a theoretical representation of the fabric (T) while respecting the placement constraints associated with the parts; - a cutting table on which can be spread at least one layer of fabric;

- Means for acquiring the real characteristics of at least part of the spread fabric; means for modifying the theoretical placement to generate a real placement of the pieces on the spread fabric taking into account the real characteristics of the fabric;

- Means for identifying in the actual placement of faulty parts (P-1, P-2) which will contain defects once cut from the fabric and which will need to be cut; and