Method for inserting a laser beam of a laser cutting machine into a plate-like workpiece for cutting out a workpiece part from the workpiece along a predetermined cutting contour on the workpiece

Abstract

The invention relates to a method (100) for inserting a laser beam (40) of a laser cutting machine (10) into a plate-like workpiece (30) for cutting out a workpiece part (32) from the workpiece (30) along a predetermined cutting contour (42) on the workpiece (30), wherein the workpiece (30) rests on a workpiece support (20) having a plurality of supporting regions (24) and the relative positions of the supporting regions (24) in relation to the workpiece (30) are known, wherein predefined surface regions (50) on the workpiece (30) are assigned to the supporting regions (24) on the basis of the known relative positions, and a damage-free insertion point (44, 46) for inserting the laser beam (40) into the workpiece (30) for cutting out the workpiece part (32) is selected, the position of which insertion point lies outside the predefined surface regions (50) such that the laser beam (40) does not pierce any of the supporting regions (24).

Description

[0001] Title: Method for piercing a laser beam of a

[0002] Laser cutting machine in a plate-shaped workpiece for cutting out a workpiece part from the workpiece along a cutting contour specified on the workpiece

[0003] Description

[0004] The invention relates to a method according to the preamble of claim 1 and to a laser cutting machine.

[0005] A method according to the preamble of claim 1 is known, for example, from DE102018126077A1, which shows a method for laser cutting in which the position of a workpiece sheet relative to support webs of a workpiece support is determined and the position of support tips of the support webs is calculated. Support spaces above the support tips and support surrounding spaces are defined, in which a comparison is made with programmed contour lines and puncture points. Depending on the result of the comparison, a nesting of the workpiece parts to be cut is optimized in a control program for the cutting process, i.e. the position of contours / workpiece parts to be cut on the workpiece sheet is shifted to prevent cutting contours or puncture points from lying exactly on web tips, which would otherwise cause damage to the web tips by the laser beam.

[0006] The known method reliably prevents damage to the workpiece support. However, the method is complex because the nesting must be optimized to meet a further restriction. Other restrictions also exist, such as minimizing waste of the remaining workpiece, which must also be taken into account, and therefore optimization with multiple restrictions is challenging. It is difficult to provide a nesting that optimally meets all restrictions, for example, one hundred percent prevents damage to support webs and at the same time allows for minimal waste of the remaining workpiece. These are just two of many possible additional restrictions.

[0007] The object of the invention is therefore to provide a method which is improved compared to the prior art and which reliably prevents damage when laser cutting workpiece parts from a plate-shaped workpiece in a simple manner and with as few restrictions as possible. This object is achieved by a method according to claim 1. Accordingly, a method is proposed for piercing a laser beam from a laser cutting machine into a plate-shaped workpiece in order to cut out a workpiece part from the workpiece along a cutting contour predetermined on the workpiece, wherein the workpiece rests in a workpiece support having a plurality of support areas and the relative positions of the support areas in relation to the workpiece are known (or are determined). Predefined surface areas on the workpiece are (or are) assigned to the support areas on the basis of the known relative positions.In addition, a damage-free piercing point is selected for piercing the laser beam into the workpiece to cut out the workpiece part, the position of which lies outside the predefined surface areas, so that the laser beam does not penetrate into any of the support areas.

[0008] The method according to the invention therefore achieves the object mentioned at the outset in that the method selects a piercing point for piercing the laser beam into the workpiece before the workpiece part is actually cut out therefrom, which piercing point or whose position is not in the support areas of the workpiece support, so that these cannot be damaged by the piercing. This piercing point is referred to herein as the damage-free piercing point. The surface areas are predefined by the known relative position of the workpiece to the support areas of the workpiece support or vice versa, in each case where damage to the workpiece support can occur during piercing. Since piercing into support areas requires a lot of energy and time, the method according to the invention not only prevents damage to the workpiece support, but also saves time and energy.By comparing the relative position of the workpiece with the support areas and the insertion point, it is possible to avoid the need to laboriously change a nesting plan to the position of the workpiece on the support areas.

[0009] The process applies only to one workpiece part on the workpiece. Typically, however, a large number of workpiece parts are cut out of one workpiece.

[0010] Accordingly, the method can be applied to several or all workpiece parts of a workpiece, whereby a damage-free penetration point is selected for each of the workpiece parts.

[0011] Piercing points are points into which the laser beam is inserted in order to trace the cutting contour and thus the workpiece part in the workpiece. Piercing is therefore part of the cutting process, which, however, precedes the actual cutting of the workpiece part from the workpiece. The piercing points can be located outside the actual cutting contour. The piercing points can approach the cutting contour of the workpiece part in a predefined path or a cut-in, in particular in an arc-shaped path or an arc-shaped cut-in.

[0012] The fact that the insertion point is selected means, in particular, that its position on the workpiece is selected or determined. The insertion point can be freely positioned, for example, or selected from predetermined and thus predefined insertion points, as will be explained in more detail later.

[0013] In the present case, a plate-shaped workpiece is understood to mean in particular a workpiece plate or workpiece panel which has its greatest extent in a horizontal plane and is designed with a thickness in the vertical plane orthogonal thereto. Such a workpiece panel can in particular be a workpiece sheet. Workpiece parts are cut out of such a workpiece panel (hereinafter also referred to as "workpiece") by laser cutting. It can be provided that the workpiece parts remain connected to the workpiece by one or more predetermined breaking points, from which they are subsequently detached. Such a predetermined breaking point can in particular be designed in the form of a web between the workpiece part and the workpiece or a remaining residual workpiece.

[0014] The laser cutting machine for laser cutting the workpieces can in particular be a flatbed machine tool, i.e. a laser cutting flatbed machine tool, in particular a 2D laser flatbed machine. However, the flatbed machine tool can also be a combination machine that can carry out further cutting processes and / or further processing steps such as deburring, bending, folding, welding, drilling, thread cutting, etc. The laser cutting machine cuts out the workpiece parts, the shape of which is specified to the laser cutting machine, from the workpiece or the remaining workpiece by means of laser cutting. The cutting contours can be specified according to a nesting plan, which can be specified, for example, by a control device of the laser cutting machine. A corresponding laser processing head of the laser cutting machine then moves the laser beam along the specified cutting contours.

[0015] The relative positions of the support areas with respect to the workpiece are known in the method. Of course, the method according to the invention can for this purpose comprise a prior step of detecting the relative positions of the support areas with respect to the workpieces. The geometry or arrangement of the support areas with respect to one another can be known, since it is typically rigid and does not move. However, the position of a workpiece on the workpiece support and thus the support areas can change. How the detection of a workpiece with respect to the workpiece support can take place, for example by sensory detection, will be explained in more detail later using an example.

[0016] The workpiece support can, for example, comprise a pallet or the like. The workpiece support can also comprise a plurality of support webs. The support webs can, in particular, run parallel to one another. The support areas can each be arranged along the support webs. The support areas can, in particular, be support elevations, very particularly in the form of support tips. The workpiece can thus rest on the support areas of the support webs at defined distances between the support areas of the same support web and different support webs. The support webs can, for example, be part of the pallet, be arranged on the pallet or between an edge of the pallet and be firmly connected to the laser cutting machine, in particular to a pallet changer thereof. The support areas can offer a point-shaped or, preferably, flat support surface for the workpiece.The support elevations, in particular support tips, particularly with a flat support surface for the workpiece, can be formed by serrated sections on the support webs, with each serrated section forming a support elevation. Accordingly, it is now possible to protect the support areas, in particular the support tips of the support webs, from damage and wear. Accordingly, only the support areas, in particular support tips, can be taken into account when predefining the surface areas. This improves the quality of the workpiece because undamaged support tips always enable the same positionally accurate support and thus the relative position of the workpiece in relation to the workpiece support. It is also avoided that the support webs have to be replaced, so the process can be carried out cost-effectively.

[0017] It can be advantageous if two penetration points for the workpiece part are (or will be) predefined in a nesting plan of the laser cutting machine and the damage-free penetration point is selected from the two predefined penetration points by comparing the predefined penetration points with the predefined surface areas. This means that the nesting planning does not have to take into account the coincidence of penetration points and support areas. Instead, only two penetration points are defined in the nesting plan. The nesting plan specifies the so-called nesting or

[0018] Distribution of the workpiece parts on the workpiece and thus the cutting contours and the puncture points.

[0019] It is preferred if the two penetration points are specified with a predefined penetration point distance from one another on a workpiece plane of the workpiece, wherein the predefined penetration point distance is selected such that at most one of the two penetration points falls into one of the predefined surface areas when the geometry of the support areas in the workpiece plane is known. This ensures that one of the two penetration points for a workpiece part, which is provided according to the nesting plan, can always be used for damage-free piercing by the laser beam. For this purpose, the geometry of the support areas must be known. Geometry refers in particular to the arrangement and / or size of the support areas in the workpiece plane.

[0020] For this purpose, the piercing point distance in a first extension direction of the workpiece plane, along which the support areas are spaced from one another, can be different from a support area distance between each two support areas.

[0021] For this purpose, the support areas can also be arranged on support webs of the workpiece support, wherein the support webs are arranged parallel to one another in a second extension direction of the workpiece plane running perpendicular to the first extension direction and the puncture point distance in the second extension direction is different from a support web distance between each two support webs.

[0022] Finally, it can also be provided that the puncture point distance in the first extension direction is further greater than a length of the surface areas in the first extension direction and / or the puncture point distance in the second extension direction is further greater than a length of the surface areas in the second extension direction.

[0023] Preferably, the predefined surface areas are larger in area than the support areas. The advantage of this is that damage to the area of ​​the workpiece support surrounding the support area, particularly to the flanks of the support tips of the support webs, can be easily prevented.

[0024] It is advantageous if the predefined surface areas are round. This is a beneficial geometry for the surface areas because it ensures a high degree of damage-freeness around a peripheral area surrounding the support areas. A diameter of at least 5 mm, at least 6 mm, or at least 7 mm for the round surface areas has proven particularly advantageous.

[0025] It is also advantageous if the relative positions of the support areas with respect to the workpiece are specified by at least one stop for the workpiece. This stop can be located, for example, on the workpiece support itself and / or on a pallet for the workpiece. Multiple stops can also be provided. This ensures that the workpiece is always in a defined position with respect to the workpiece support. The stop can also be used for improved sensor-based determination of the relative position and / or for a double determination of the relative position.

[0026] Alternatively or additionally, the relative positions of the support areas with respect to the workpiece can be determined by measuring the workpiece and / or the workpiece support, in particular at least one reference element on the workpiece support. Since the geometry of the workpiece support, in particular the arrangement of the support areas with respect to one another, is known, measuring the workpiece with respect to the reference element of the workpiece support can be sufficient. The measurement can be carried out by one or more sensors and / or one or more cameras. The relative position of the workpiece support, in particular the relative positions of the support areas, can be determined in a simple manner, for example during operation.The measurement can be performed, for example, using a sensor system on the laser cutting machine, in particular a capacitive distance sensor system for detecting the distance between the laser processing head of the laser cutting machine and the workpiece. Generally, at least a subset of the support webs and / or the web tips can be detected, and optionally, the positions of non-detected webs can be measured.

[0027] Support bars and / or bar tips can be calculated by interpolation. Other possible measurement options are based, for example, on optical sensors that use at least one of the following methods:

[0028] Image processing method based on a

[0029] Area image recording, a laser light section method, a striped light projection method, a light field camera, a 3D camera, e.g. a time-of-flight (TOF) camera, in particular for detecting the distance and / or depth of web depressions, the condition recording of the geometric shape for an accompanying assessment of wear of a support web and / or a web tip, and / or on an ultrasonic sensor system, which uses ultrasonic sensors in particular on a cutting head of the flatbed machine tool.

[0030] The object mentioned at the outset is further achieved by a laser cutting machine according to claim 11. The laser cutting machine is equipped with a workpiece support for supporting a workpiece thereon, a laser processing head for emitting a laser beam, and a control device for selecting a piercing point for piercing the laser beam, the laser cutting machine being set up to carry out the method according to the invention.

[0031] In this case, features which are described herein with reference to the method according to the invention apply equally with reference to the laser cutting machine and vice versa.

[0032] The method according to the invention can in particular be controllable by appropriate control of the laser cutting machine by the control device. The control device can have a memory on which a computer program is stored which is executed by a CPU of the control device in order to carry out the method according to the invention on the laser cutting machine. The control device or the computer program selects the piercing point or predetermines its position on the workpiece. The control device can of course also perform other tasks, such as measuring the relative positions, planning the nesting of the workpiece parts on the workpiece, controlling the cutting out of the workpiece part from the workpiece, etc.

[0033] Further details and advantageous embodiments of the invention can be found in the following description, on the basis of which embodiments of the invention are described and explained in more detail.

[0034] They show schematically:

[0035] Figure 1 is a perspective view of a

[0036] Laser cutting machine according to an embodiment of the invention;

[0037] Figure 2 is a perspective view of a support web of a workpiece support of the laser cutting machine of Figure 1;

[0038] Figure 3 is a schematic view of a main body of the laser cutting machine of Figure 1;

[0039] Figure 4 is a schematic view of a method according to an embodiment of the invention for laser cutting workpiece parts from a plate-shaped workpiece using the laser cutting machine of Figure 1; Figure 5 is a schematic plan view of a workpiece to be machined with support areas and predefined surface areas.

[0040] In the following description and in the figures, the same reference symbols are used for identical or corresponding features.

[0041] Figure 1 shows a laser cutting machine 10 in the form of a laser cutting flatbed machine tool with a main housing 12 in which a laser cutting process is carried out with a laser beam 40 (see Fig. 3). In particular, a focus of the laser beam 40 is guided by a control device 11 (see Fig. 3) along predetermined cutting contours 42 arranged in a processing area over a plate-shaped workpiece 30, in particular a sheet metal extending essentially two-dimensionally, in order to cut out workpiece parts 30 with specific shapes predetermined according to a nesting plan.

[0042] The laser cutting machine 10 also includes a pallet changer 14. The pallet changer 14 is designed to position one or more pallets 18 during production. A workpiece 30 to be cut (as raw or starting material), in particular a workpiece panel, can be placed and stored on a pallet 18 and introduced into the main housing 12 for the laser cutting process. After the cutting process is completed, the pallet 18 can be moved out of the main housing 12 with a cut workpiece 30, as shown in Fig. 1, so that the cut workpiece parts 32 can be sorted from the remaining workpiece 30.

[0043] Figure 3 shows the laser cutting process in the main housing 12. The laser processing head 13, which emits the laser beam 40 for cutting out the workpiece parts 32 from the workpiece 30 onto the workpiece 30, can be freely positioned in the processing area so that the laser beam 40 can be guided essentially along any desired two-dimensional cutting contours over the workpiece 30 to be cut. A cutting contour 42 for the laser beam 40 is predetermined in each case on the basis of a nesting plan in the control device 11 in order to cut out the workpiece parts 32 from the workpiece 30. The nesting plan specifies the arrangements of the individual workpiece parts 32 in the workpiece 30, as can be seen in Fig. 1. In addition, the nesting plan includes the specification of piercing points 44, 46 and predetermined gates 48 for piercing the laser beam 40 and guiding the laser beam along the gate 48 to the cutting contour 42 (see Fig. 5).

[0044] During laser cutting, the laser beam 40 heats the metal of the workpiece 30 along the predetermined cutting contours 42 until it melts. A gas jet, usually nitrogen or oxygen, usually emerges from the laser processing head 13 in the region of the laser beam 40 and forces the molten material of the workpiece 30 downwards and out of the gap that is formed. The workpiece 30 is thus completely severed by the laser beam 40 during cutting. To cut out a workpiece part 32, the laser beam 40 is moved along the predetermined cutting contours 42 of the respective workpiece 32. This starts at one of the piercing points 44, 46, which lie outside the workpiece 30, and then approaches the contour of the workpiece 30, in particular in an arc-shaped cut 48.

[0045] In the illustrated embodiment, the pallet 18 has a workpiece support 20. The workpiece support 20 has a plurality of support webs 22 extending transversely, in particular perpendicularly, to the insertion direction of the workpiece 30 into the main housing 12 and aligned parallel to one another.

[0046] A part of a support web 22 is shown in perspective in Figure 2. By way of example, the support webs 22 are spaced apart from one another by, for example, 20 mm to 100 mm. The support webs 22 form support regions 24 on which the workpiece 30 is placed or laid down. The support regions 24 usually form grid points which can be spaced apart by, for example, 5 mm to 50 mm along the support webs 22, wherein a support web 22 can have a thickness of, for example, 1 mm to 5 mm. The support regions 24 thus form a grid of regions which can influence the cutting process of the workpiece 30 lying on them. The regions of the support webs 22 which influence the cutting process can moreover extend to regions which are directly adjacent to the support regions 24 which are in contact with the workpiece 30, e.g. the flanks of the support webs 22 leading to the support areas 24 .As shown, the support areas 24 here are tips of repeating tooth sections 26 of the support webs 22.

[0047] Fig. 1 further shows a camera 16 of the laser cutting system 10, which is arranged, for example, on the main housing 12. The camera 16 can be designed, among other things, for image capture of the pallet 18, the support webs 22 and support areas 24 as well as the relative position of the workpiece 30 with respect to the pallet 18 (and possibly the support webs 22 and support areas 24) and is connected to an image evaluation unit of the control device 11. Consequently, the control device 11 can determine at least the relative position of the workpiece 30 with respect to the support areas 24 or the relative positions of the support areas 24 with respect to the workpiece 30. The arrangement of the support areas 24 is already known due to their geometry. It is therefore sufficient to detect the relative position of the workpiece 30 with respect to a reference element (not shown), in particular on the workpiece support 20.The control device 11 can predefine these support areas 24 as surface areas 50, as shown in Fig. 5, or can define enlarged surface areas 50, in particular round surface areas 50, around the support areas 24, as is also shown purely by way of example for the surface areas 50 of the support web 22 shown at the bottom of Fig. 5.

[0048] The method 100 shown schematically in Figure 4 is now carried out by means of the laser cutting system 10, as explained with reference to Figures 1 to 3. In a first method step 102, the relative positions of the workpiece 30 with respect to the support regions 24 are determined, as described above. In a second method step 104, the surface regions 50 are defined based on the support regions 24. The surface regions 50 comprise at least the regions in which the workpiece 30 rests on the support regions 24, and preferably also an adjacent region in which the flanks of the support webs 22 branch off from the support regions 24.

[0049] Subsequently, in a third method step 106, one of two predefined puncture points 44, 46 is selected based on a comparison of the predefined puncture points 44, 46 with the predefined surface areas 50. In this case, the puncture point 44, 46 that is arranged outside the predefined surface areas is selected as the damage-free puncture point 44, 46 and pierced into its position with the laser beam 40. This can prevent the support webs 22 from being damaged at their support areas 24 by the laser beam 40.

[0050] In the fourth method step 108 of the method 100, the workpiece parts 32 are finally cut out of the workpiece 30 along the predetermined cutting contours 42, wherein the laser beam 40, after piercing the damage-free piercing point 44, 46, passes over the gate 48 to the cutting contour 42 and travels along this in order to cut out the workpiece part 32.

[0051] Figure 5 shows a schematic plan view of a workpiece 30 with a highly simplified nesting plan, in which only one workpiece part 32 is present or considered for cutting out, which also has an exemplary simple rectangular geometry. The workpiece 30 and the

[0052] Workpiece support 20 are here in a common

[0053] Workpiece plane 34 is viewed in which the workpiece 30 rests on the workpiece support 20, i.e. just in contact between the two.

[0054] The support areas 24, in particular support tips, of the support webs 22 of the workpiece support 20 are located beneath the workpiece 30. The surfaces of the support areas 24 are predefined as the surface areas 50, as described above. A cutting contour 42 for cutting out the workpiece part 32 from the workpiece 30 is predefined along two surface areas 50.

[0055] 5 shows the two previously mentioned penetration points 44, 46 which are predefined for the penetration according to the nesting plan in the control device 11. The two penetration points 44, 46 are located at a predefined penetration point distance A from one another. The penetration point distance A is smaller in a first extension direction Y on the workpiece plane 34 than a support area distance B between adjacent support areas 24 in the first extension direction Y. At the same time, the penetration point distance A in the first extension direction Y is greater than a length of the surface areas 50 in the first extension direction Y. In addition, the penetration point distance A in a second extension direction X on the workpiece plane 34, which is perpendicular to the first extension direction Y, is smaller than a support web distance C between adjacent support webs 22 in the second extension direction X.At the same time, the puncture point distance A in the second extension direction X is greater than a length of the surface areas 50 in the second extension direction X .

[0056] The above-specified selection of the insertion point distance A between each two insertion points 44, 46 in the first extension direction Y and in the second extension direction X in the nesting plan ensures that at least one of the two predefined insertion points 44, 46 of a workpiece part 34 is always located outside the predefined surface areas 50 and can be selected as a damage-free insertion point 44, 46.

[0057] In Fig. 5, for example, the predefined penetration point 44 is located in the workpiece plane 34 above the support web 22. Because of the workpiece 30, it cannot be seen that the penetration point 44 is actually located on a predefined surface area 50 or a support area 24. This penetration point 44 cannot therefore be selected without avoiding damage to the support area 24. However, the predefined penetration point 46 is arranged outside the predefined surface areas 50 due to the selected penetration point spacing A, as can be seen from Fig. 5. Consequently, the piercing point 46 is a damage-free piercing point 46 through which the laser beam 40 can penetrate into the workpiece 30, can be moved along its leading edge 48 to the cutting contour 42, and can traverse the cutting contour 42 in order to cut the workpiece part 32 out of the workpiece 30.

Claims

Claims Method (100) for piercing a laser beam (40) of a laser cutting machine (10) into a plate-shaped workpiece (30) for cutting out a workpiece part (32) from the workpiece (30) along a cutting contour (42) predetermined on the workpiece (30), wherein the workpiece (30) is placed on a workpiece support (20) with several The support areas (24) rest on the workpiece (30) and the relative positions of the support areas (24) to the workpiece (30) are known, characterized in that predefined surface areas (50) on the workpiece (30) are assigned to the support areas (24) based on the known relative positions and a damage-free entry point (44, 46) is selected for the laser beam (40) to penetrate the workpiece (30) to cut out the workpiece part (32), the position of which lies outside the predefined surface areas (50), so that the laser beam (40) does not penetrate any of the support areas (24).Method (100) according to claim 1, wherein two insertion points (44, 46) for the workpiece part (32) are predefined in a nesting plan of the laser cutting machine (10) and the damage-free insertion point (44, 46) is selected from the two predefined insertion points (44, 46) by comparing the predefined insertion points (44, 46) with the predefined surface areas (50). Method (100) according to claim 2, wherein the two Insertion points (44, 46) with a predefined insertion point distance (A) from each other are specified in a workpiece plane (34) of the workpiece (30), wherein the predefined insertion point distance (A) is chosen such that at most one of the two The insertion points (44, 46) fall within one of the predefined surface areas (50) in the workpiece plane (34) given a known geometry of the support areas (24). Method (100) according to claim 3, wherein the insertion point spacing (A) is determined in a first extension direction (Y) of the workpiece plane (34), along which the support areas (24) are spaced apart from each other, and the distance (B) between any two support areas (24) differs from the distance (B) between them. Method (100) according to claim 4, wherein the support areas (24) are arranged on support ribs (22) of the workpiece support (20), wherein the support ribs (22) are arranged parallel to each other in a second extension direction (X) of the workpiece plane (34) perpendicular to the first extension direction (Y), and the insertion point spacing (A) in the second extension direction (X) differs from a support rib spacing (C) between any two support ribs (22). Method (100) according to claim 5, wherein the insertion point spacing (A) in the first extension direction (Y) is furthermore greater than a length of the surface areas (50) in the first extension direction (Y) and / or the The spacing of the insertion points (A) in the second extension direction (X) is furthermore greater than the length of the surface areas (50) in the second extension direction (X). Method (100) according to one of the preceding claims, wherein the predefined surface areas (50) are larger in area than the support areas (24). Method (100) according to claim 6, wherein the predefined Surface areas (50) are round. Method (100) according to one of the preceding claims, wherein the relative positions of the support areas (24) with respect to the workpiece (30) are predetermined by at least one stop for the workpiece (30). Method (100) according to one of the preceding claims, wherein the relative positions of the support areas (24) with respect to the workpiece (30) are determined by measuring the workpiece (30) and / or the workpiece support (20), in particular at least one reference element on the workpiece support (20). Laser cutting machine (10) with a workpiece support (20) for supporting a workpiece (30) thereon, a laser processing head (13) for emitting a laser beam (40), and a control device (11) for selecting an entry point (44, 46) for the entry of the laser beam (40), wherein the laser cutting machine (10) is set up to carry out the procedure (100) according to one of the preceding claims.

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