System comprising a cutting device for cutting out objects from a material web that is at least partially two layers thick

Abstract

System for cutting out an object from a material web that is at least partially two layers thick (1), wherein the at least two layers of material are at least partially connected to each other in a linear, strip-like and / or planar manner in circumferential areas of the object to be cut out (3), the system comprising: a cutting device (2); a camera system (12) which is set up to acquire contactless data which are assigned to the position of the object (3) in the material web (1) and which assigns these data to the coordinates of the cutting device as cutting coordinates, and wherein the cutting device (2) is set up to cut out the respective object (3) based on the cutting coordinates, characterized in that the camera system is further configured to detect structural changes in the material that are part of the object (3) resulting from those areas in the material web (1) that are connected to each other in a linear, strip-like and / or planar manner, and to determine the position of the respective object (3) in the material web (1) without contact, at least on the basis of previously defined and stored, distinctive and spaced-apart geometric sub-forms of the areas of the object (3) that are connected to each other in a linear, strip-like and / or planar manner.

Description

[0001] The present invention relates to a system for cutting out objects from a material web that is at least partially two-layered using a cutting device according to the preamble of claim 1. A method for cutting out objects from a material web that is at least partially two-layered using a cutting device is also described.

[0002] The system is specifically designed to cut bag- or pouch-shaped objects, including airbag blanks, from such a two-layer material web. Preferably, the cutting device is a laser cutting device.

[0003] Such a material web, from which the objects are to be cut, consists of at least two layers of material that are partially connected to each other, at least in the circumferential areas of the respective object to be cut, either linearly, in strips, and / or across the entire surface. This connection can consist of gluing, welding, or weaving the two material webs together. Weaving the two material webs together is used particularly in the production of airbag blanks.

[0004] In some applications, such as the production of airbag components, the parts must be cut with extreme precision to ensure all safety-relevant aspects of the airbags' durability when deployed under high pressure. Specifically, the interwoven or intertwined areas of the two material layers must not be damaged or weakened during the cutting process. The exception to this is the interwoven or intertwined areas that form the airbag's retaining loops or tabs, which are shaped into their final form during the cutting process. Ultimately, the airbag must be cut precisely according to specifications.

[0005] One problem that arises when cutting objects from a web of material, and especially from a two-layer web, is that the webs exhibit distortion due to the manufacturing process and the material itself and its treatment. This distortion can vary significantly from web to web and even within a single web. If the objects are cut using fixed cutting data predefined in the cutting device relative to the cutting table of the cutting system, the distortion in the web will prevent the objects from being cut along their defined contours.

[0006] To detect such distortion in a material web, a method is used to mark the web during its production with markers that are directly linked to the objects to be cut. These markers are optically detected by the cutting device to determine the degree of distortion based on their positions on the material web. Correction values ​​are derived from the deviations between the target positions of the markers (corresponding to their positions during production) and their actual positions at the cutting device. These correction values ​​are then used to adjust the cutting coordinates for the objects, ensuring that the objects are cut precisely along the specified contours despite any distortion in the material web.

[0007] Markings can include, for example, periodically repeating grids formed by lines running lengthwise and crosswise along the material web, or dots or crosses visible on the surface of the material web. If the material web is woven or knitted, identification threads or marking threads are incorporated into the material, which contrast with the material web in color.

[0008] Typically, the markings are detected optically, i.e., without contact, and the position of the objects in the material web is derived from the location and position of the markings. These positions are then assigned to the coordinates of a cutting device as cutting coordinates. The respective object is cut out using the cutting device based on these cutting coordinates.

[0009] The procedure described above requires that, in every case, the two- or multi-layered material web must first be marked with the markings, which must be printed on at least one side of the web or, in the case of a woven or knitted material web, incorporated as identification threads. If errors such as discontinuities occur during printing or incorporating the identification threads, an exact match between the cut-out items and these markings is not possible, resulting in rejects. Furthermore, printing or incorporating identification threads involves additional effort and therefore additional costs in the production of the items.

[0010] DE 602 17 280 T2 relates to a device for cutting shapes which are contained in a continuous sequence of a plate-shaped material according to the preamble of claim 1.

[0011] DE 103 41 318 A1 relates to a method for checking quality criteria of flat, multi-layered textile structures knitted or sewn along a specified web and having cutouts or holes.

[0012] FR 2 911 807 A1 relates to a method for cutting predefined parts from a multi-layered material with automatic control of the part dimensions.

[0013] DE 102 45 730 A1 relates to another device for cutting textiles.

[0014] DE 40 13 837 A1 relates to a method for cutting to match the pattern.

[0015] DE 196 40 023 A1 relates to a device for correction of distortion during the processing of a web of goods printed with a pattern or otherwise provided with optically recognizable patterns.

[0016] The present invention is based on the objective of providing a system of the type mentioned at the outset which enables the precise cutting of objects from a material web of at least two layers without the need to first provide the material web with markings.

[0017] This problem is solved by a system with the features of claim 1. Advantageous embodiments of the method result from the dependent claims.

[0018] The system is characterized by its contactless detection of the object's position by analyzing structural changes within the material itself. These changes arise from the interconnected areas of the material web, whether linear, strip-like, or planar. The object's position is determined by predefined and stored, distinct, and spaced geometric sub-forms of these interconnected areas. This allows the system to detect distortion and rotation of the object within the material web, resulting from any distortion of the material itself.A particular advantage of the method according to the invention is that it is not necessary to capture the entire geometric shape of the object or all surface areas in which the connected structures of the two material webs are located, although this would of course be possible; however, this would unnecessarily increase the computational effort in order to convert the captured coordinates into the cutting coordinates.

[0019] Preferably, only geometric sub-shapes of the connected structures are captured, and these geometric sub-shapes are then connected and / or supplemented based on the stored geometric shape of the object. The geometric sub-shape of the object that is assigned to the connected structures of the two material webs is predefined. In particular, the geometric sub-shapes are those that are especially distinctive due to their geometry. Such distinctive geometric sub-shapes include, for example, areas with strongly curved contours and tab-like formations, regardless of whether these distinctive geometric shapes are located in the area of ​​the outer contour or in the area of ​​an inner surface region of the object to be cut out.

[0020] These distinctive geometric shapes can already be sufficient to derive the actual position of the object in the material web when it is on the cutting table, in order to then cut out the object with corrected cutting data according to the existing distortion in the material web.

[0021] As already mentioned, the distinctive geometric sub-forms can be supplemented based on stored geometry and contour data of the object, in order to then determine the position of the respective object in the material path for the cutting process from the supplemented geometric forms of the respective object and subsequently assign the cutting coordinates according to the position of the object and cut out the object with the cutting coordinates.

[0022] The non-contact detection of structural changes in the material is preferably carried out using at least one photographic device; this method is particularly advantageous when woven or knitted structures in the area where the two material webs are joined are to be detected. Especially when the photographic device is positioned at a relatively large distance above the material web, i.e., at a distance of up to 15 mm, preferably at a distance of approximately 800 to 1000 mm, photographic images are obtained in which the woven or knitted structures to be detected are captured with high resolution.

[0023] Several individual images can be combined to form a complete image, from which the structural changes in the material can then be captured across a large area of ​​the material web. These individual images form a kind of panoramic image, whereby the individual images can also be arranged two-dimensionally in rows and lines.

[0024] To enhance the contrast between the interconnected areas of the two layers of the material web, the web is illuminated. This makes the structural changes even more apparent. This illumination can be provided from the top side, from which the photographic images are also taken. However, it is also possible, and in certain applications preferred, to illuminate the material web for non-contact detection of the structural changes, preferably from the side of the material web opposite a photographic device, typically the underside of the material web.

[0025] It is also provided that the material web is guided through a scanner device at the inlet side of the cutting device. This scanner device, positioned at a short distance from the material web, non-contactly scans the surface of the material web or the contrast revealed when the material web is illuminated, preferably from the opposite side. Such a scanner device is fixedly aligned with the cutting table or the cutting coordinates of the cutting device, so that any distortion in the material web, and thus the actual position of the linearly, strip-wise, and / or planarly connected areas of the object, or at least geometric sub-shapes thereof, are detected and transferred to the coordinates of the cutting device.

[0026] The described method also allows for the detection of structural changes in the material that are not attributable to the parts of the object to be cut out, such as where the two material layers are joined linearly, in strips, and / or across a surface. These changes can then be checked as potential material defects. If a material defect is associated with an area of ​​an object to be cut out, that object is inspected, and a decision is made as to whether the defect affects only an optical aspect of the object or another aspect, such as a safety-related aspect, that is unacceptable. The object identified as defective is then not cut out of the material web.

[0027] Further details and features of the invention will become apparent from the following description of an exemplary embodiment with reference to the drawing. The drawing shows Fig. 1 a flowchart, referred to as the main program, which represents the individual process steps of the process according to the invention, Fig. 2 a subroutine that inserts into the main program of the Fig. 1 inserts, Fig. 3A to Fig. 3C cuts an object from a web of material in three process stages, which correspond to the flowchart of the Fig. are assigned to 1, Fig. 4 a cutting system with which the method according to the invention can be carried out, Fig. 5A a schematic representation of a material web with a multitude of objects that are visible in the material web through structural changes in the material, and Fig. 5B the items of the Fig. 5A, as described by the device of Fig. 4 can be cut out.

[0028] The method according to the invention relates to cutting out objects from a material web 1 that is at least partially two-layered, as described in the Fig. 5A and Fig. 5B is shown, by means of a cutting device which is in the Fig. 4 and Fig. 5B is designated with reference numeral 2. These material webs 1 comprise at least two material layers which, at least in the circumferential areas of an object 3 to be cut out, are partially connected to each other in a linear, strip-like and / or planar manner. Such objects 3 can be bags, pouches, sacks, but also more complex parts, such as airbags. Such an object 3 in the form of an airbag is shown in Fig. 3A is shown and its production is described below using the figures.

[0029] These airbags, hereinafter generally referred to by reference numeral 3, are typically manufactured from a woven or knitted web of material consisting of at least two superimposed layers of material that are woven and / or intertwined in certain areas. These woven or intertwined areas of the airbag are described in the Fig. 3A to Fig. 3C is represented by the black areas. These black areas partly form a frame-shaped structure, designated by reference numeral 4, tab-shaped sections, some of which are connected to the frame-shaped structure 4 and designated by reference numeral 5, and island-shaped sections within the frame-shaped structure 4, designated by reference numeral 6. At least the frame-shaped structure 4 lies within an outer contour line 7 of the airbag 3, along which the airbag is to be cut from the material web 1.

[0030] Ideally, the connected structures of the material web 1 are aligned in the xy direction of a rectangular coordinate system, as shown in Fig. 3A, also indicated by the broken line 8. However, it becomes apparent that the material web 1 exhibits distortion or twisting when it runs over a cutting table 9 for various reasons, e.g., manufacturing-related ones, which can manifest itself, for example, as elongation or shrinkage in the x and / or y direction. Such distortion is clearly visible in Fig. 5A can be identified.

[0031] In order to cut out the airbags 3 using the cutting device 2, despite the altered position of the material web 1 on the cutting table 9 due to distortion, this distortion must be taken into account. Otherwise, there is a risk that the airbag 3 will not be cut along the outer contour line 7, and consequently, damage to the safety-relevant interwoven or intertwined structures 4 and 5 in the area of ​​the outer contour of the airbag 3 may occur. The tab-shaped sections 5, which serve, among other things, to secure the airbag in a vehicle, are an exception to this; these tab-shaped sections 5, in which the two material layers of the material web 1 are interwoven or intertwined, can be brought into their final shape when cutting out the airbag 3.

[0032] For the foregoing reasons, the method according to the invention is applied, the course of which is shown in the flowchart of the Fig. 1 is shown.

[0033] According to the inventive method, the position of the airbag 3 in the material web 1 is determined by non-contact detection of structural changes in the material web 1, as indicated by step 101. Such structural changes in the material web 1 result from weaving or knitted structures visible on the surface of the material web 1, in the area where the two material layers of the material web 1 are interwoven or intertwined. Such structural changes could also result from areas of the material web 1 where two material layers are bonded together or otherwise connected.

[0034] The geometry of the objects to be cut out 3, i.e., in this case the airbags to be cut out, with all contour data and structures, for example the frame-shaped structures 4, the flap-shaped sections 5, the island-shaped sections 6, and the outer contour line 7, which are specified, is subdivided into geometric sub-forms in step 102. Such geometric sub-forms are in the Fig. 3A and Fig. 3B is marked by rectangles 10. As geometric sub-forms 10, those geometric areas of the airbag 3 that are particularly distinctive are preferably selected; these include, for example, the tab-shaped sections 5, the island-shaped sections 6, or at least parts thereof, as well as the parts of the frame-shaped structure 4 that have a small radius of curvature.

[0035] The xy coordinates and the dashed line 8 serve as an example to indicate that the structures visible in the material path differ from the ideal position data due to the interconnected areas of the material layers. Fig. 3A by an angle 11 due to a distortion of the material path 1 along the cutting table 9 to the x-axis (see also Fig. 5A) is shifted. A distortion also occurs with respect to the y-axis, which is not shown.

[0036] In step 103, therefore, a comparison of the position of the recorded geometric sub-forms is performed, which are in Fig. 3B, designated with reference symbols 4, 5 or 6, supplemented by a superscript line, with the stored geometric subforms 4, 5 or 6 (see Fig. 3A) compared.

[0037] In step 104, it is determined whether the captured geometric sub-forms 4', 5', 6' can be assigned to a stored geometric form or stored geometric sub-forms 4, 5, 6. If this is the case, in step 105 the captured geometric sub-forms 10 (4', 5', 6') are computationally linked together based on stored data of the airbag structure.

[0038] It should be noted that preferably only a portion of the geometric sub-forms of the airbag 3, or of the structures 4' and the tab-shaped and island-shaped sections 5', 6', which are marked with a rectangle 10, are captured, in order to minimize the computational effort required to determine the position of the airbag 3 in the distorted material web 3. However, it is also possible to capture all the structural lines that emerge in the structure of the material web 1 and to determine their position in the material web 1.

[0039] In step 106, the position of the object's geometric shape in the material path 1 is assigned to cutting coordinates of the cutting device 2, and finally, in step 107, the respective object is cut according to its position in the material path 1 with the cutting coordinates, in the case of the airbags shown in the figures along the outer contour line 7, which are based on the stored data of the airbag cut (see Fig. 3A) can be determined, as this the Fig. 3C shows, cut out.

[0040] To detect structural changes in the material web 1 without contact, a camera system 12 is arranged on the inlet side of the material web 1 into the cutting device 2; in addition, the material web 1 is illuminated from above with a suitable light source 13 transversely (y-direction) to the direction of travel (x-direction). Fig. 5A marked area 14 illuminated; however, it is also possible, alternatively or additionally, to illuminate the material web 1 with a light source 15 from the underside 1, opposite the camera system 12, so that the camera system 12 can detect a stronger contrast between light and dark areas.

[0041] While in the Fig. 3B and Fig. 3C shows the detection of the position of a single airbag in the material web, the Fig. 5A and Fig. 5B the material web 1, over whose length and width a large number of airbags 3, which are to be detected and cut out, are distributed.

[0042] With the camera system 12, a larger area of ​​the material web 1 can be captured by combining several individual images into a complete image in order to capture the structural changes in the material web 1.

[0043] There is a possibility that in step 104 of the flowchart, which is in Fig. As shown in Figure 1, it follows that the captured geometric sub-forms 10 cannot be assigned to a stored geometric form or geometric sub-form. If this is the case, the main program branches Fig. 1 to a subroutine that is in Fig. 2 is shown.

[0044] In step 108 of the subroutine, any structural change that cannot be assigned to a geometric shape or geometric sub-shape is checked to determine, as shown in step 109, whether this structural change can be attributed to a material defect and whether this structural change / material defect lies within an object 3 to be cut out (step 110). If this structural change / material defect does not lie within an object 3 to be cut out, it is ignored (step 111) because, being outside the object 3 to be cut out, it cannot have any effect on the object 3.

[0045] If in step 110 it is determined that the structural change / material defect is located within the item 3 to be cut out, in step 112 this item is marked as defective, and in step 113 the cutting device 1 is instructed not to cut out this item, as it is defective, in order to save machine runtime.

Claims

[1] System for cutting out an object from a material web that is at least partially two layers thick (1), wherein the at least two layers of material are at least in circumferential areas of the object to be cut out (3) partially connected to each other in a linear, strip-like and / or planar manner, the system comprising: a cutting device (2); a camera system (12) which is set up to acquire contactless data which are assigned to the position of the object (3) in the material web (1) and which assigns these data to the coordinates of the cutting device as cutting coordinates, and wherein the cutting device (2) is set up to cut out the respective object (3) based on the cutting coordinates, characterized by, that the camera system is further equipped to detect structural changes in the material that are part of the object (3) resulting from those areas in the material web (1) that are connected to each other in a linear, strip-like and / or planar manner, and to determine the position of the respective object (3) in the material web (1) without contact, at least on the basis of previously defined and stored, distinctive and spaced-apart geometric sub-forms of the areas of the object (3) that are connected to each other in a linear, strip-like and / or planar manner. [2] System according to claim 1, characterized by , that the camera system (12) is further equipped to combine and / or supplement the geometric sub-forms after their detection based on the stored geometric form of the object (3). [3] System according to claim 2, characterized by, that the camera system (12) is further equipped to determine the position of the respective object (3) in the material web (1) for the cutting process from the supplemented geometric shape of the respective object (3), in order to subsequently assign the cutting coordinates according to the position of the object (3) and to cut out the object (3) with the cutting coordinates. [4] System according to any one of claims 1 to 3, characterized by , that the camera system (12) comprises a photographic device for non-contact detection of structural changes in the material. [5] System according to any one of claims 1 to 4, characterized by , that the camera system (12) is further configured to detect structural changes in the material from several individual images which are combined to form a complete image. [6] System according to one of claims 1 to 5, further comprising a first light source (13) for illuminating the material web (1), in particular the top side of the material web (1), for the non-contact detection of structural changes in the material. [7] System according to one of claims 1 to 6, further comprising a second light source (15) arranged opposite the camera system (12) for illuminating the underside of the material web (1) for non-contact detection of structural changes in the material. [8] System according to any one of claims 1 to 7, characterized by , that the camera system (12) is further equipped to check for possible material defects any structural changes in the material that are detected which cannot be attributed to the parts of the object to be cut out (3) where the two layers of material are connected in a linear, strip-like and / or planar manner. [9] System according to claim 8, characterized by , that the camera system (12) is further configured to instruct the cutting device (2) not to cut out an object (3) to which a material defect is associated from the material web (1). [10] System according to one of the preceding claims, further comprising a cutting table (9) for providing the material web (1), wherein the camera system (12) further comprises a scanner device for determining the position of the object (3) in the material web, wherein the scanner device is arranged in a fixed association with the cutting table (9).

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