Method for determining a free-cutting point when separating a workpiece part from a remaining part and programming device for this purpose

Abstract

Method for determining at least one free-body diagram point (P F ) one from an entry point (20) along a cutting path (18) to the clearance point (P F ) guided cutting jet to close a cutting gap (17) and thereby to separate a workpiece part (12) from a residual part (10), wherein the cutting jet is moved along an approach path (22) at the beginning of the cutting path (18), along a cutting path (24) following the approach path (22) and along a final path (32) at the end of the cutting path (18), wherein the approach path (22) is selected such that it runs outside the workpiece part (12), wherein the cutting jet in the approach path (22) generates an approach cutting edge (26) facing a desired cutting edge (28) and approaching the desired cutting edge (28) and in the end path (32) generates a cutting edge (34) bounding the workpiece part (12) as well as a front cutting flank (36), characterized in that the clearance point (P F ) as the point of contact P B1 the front cutting flank (36) is selected, which, when closing the cutting gap (17), brings the approach cutting edge (26) into contact at a point P B2 touched and that the clearance point and / or the insertion point is chosen in such a way that jam-free removal of the workpiece part or the remaining part is enabled.

Description

[0001] The invention relates to a method for determining at least one clearance point of a cutting beam, in particular a laser beam, guided from an entry point along a cutting path to the clearance point, for separating a workpiece part from a residual part. The cutting beam is guided along an approach path at the beginning of the cutting path, along a cutting path following the approach path, and along a final path at the end of the cutting path. Furthermore, the approach path is selected such that it runs outside the workpiece part, wherein the cutting beam generates an approach cutting edge in the approach path, converging towards the desired cutting edge, and generates a cutting edge bounding the workpiece part and a leading cutting flank in the final path. Ideally, the cutting edge bounding the workpiece part lies on the desired cutting edge.

[0002] From DE 10 2015 211 403 A1, a method for cutting out a workpiece part from a workpiece using a laser beam is known. Before cutting out the workpiece part, the laser beam is moved along at least one of the two cutting edges to generate an auxiliary gap with a focus diameter that is smaller than the focus diameter used for cutting out the workpiece part.

[0003] From EP 0 646 434 A1 it is known to end the cut shortly before the end of the contour, whereby the machining conditions are changed before reaching the clearance point.

[0004] From JP H05 - 269 588 A a programming machine and an associated method are known that processes 2D coordinate data with other data into 3D coordinate data for processing.

[0005] US patent 2015 / 0290801 A1 discloses a system and a method in which multiple units of the system are used to perform a virtual process sequence for machining a workpiece. The actual machining process, in particular the laser cutting process, is also described in US patent 2015 / 0290801 A1.

[0006] US patent 2014 / 0246405 A1 discloses a laser cutting device and a laser cutting method, wherein a control unit of the device monitors the cutting process and makes changes to the feed rate of the laser nozzle, the oxygen concentration in the cutting gas or the frequency of a laser oscillator based on the process sequence and the process viewpoint.

[0007] When cutting workpiece parts from workpieces, it has been found that, particularly for jam-free removal of the workpiece parts, it is desirable to determine the clearance point as precisely as possible. It is known from the prior art to determine the clearance point based on the center point of the cutting jet, or to use this center point as the basis for calculating the cutting path, the entry point, and the clearance point. In practice, however, this has not always led to satisfactory results.

[0008] The present invention is therefore based on the objective of proposing a method for determining at least one free-body diagram point.

[0009] This problem is solved by a method with the features of claim 1. The method according to the invention provides that the point of release is defined as the point of contact P. B1the front cutting flank is selected, which, when the cutting gap is closed, i.e., when the contour of the workpiece part is completed, turns the approach cutting edge into a point of contact P B2 The point of contact is not the center of the cutting jet, but rather the point of contact where, upon closing the cutting gap, the leading edge of the cut touches the approach cutting edge. By determining the point of contact in this way, it is possible to deduce how the cut-out workpiece part ultimately separates from the remaining part. This is particularly important if it is ejected downwards by gravity or driven out by a process gas. From the actual point of contact determined by the method according to the invention, it can be deduced whether the workpiece part might tilt and consequently become jammed in the remaining part.

[0010] Furthermore, the clearance point and / or the entry point are selected to ensure jam-free ejection of the workpiece part or the remaining part. Depending on the clearance point, it can be determined whether the workpiece part will tilt relative to the remaining part. It can also be determined whether this tilting will cause the workpiece part to jam within the remaining part. Tilting of the workpiece part ultimately depends, in particular, on the choice of the clearance point, the workpiece part geometry, and its moment of inertia. The cutting gas pressure of a cutting gas used in the cutting process can also influence tilting. Ultimately, the clearance point is selected to prevent any disruptive tilting and to ensure that the workpiece part—or the remaining part, depending on the configuration—can be safely ejected from the remaining part or the workpiece part, respectively.

[0011] According to the invention, it can further be provided that the cutting gap is not closed by the cutting jet to form at least one connecting bridge, also referred to as a microjoint. Particularly with larger workpiece parts, it is advantageous to provide such connecting bridges to prevent the workpiece part from unintentionally separating prematurely from the remaining part. In the case of providing such connecting bridges, the clearance cut point is referred to as the contact point P. B1 the front cutting flank is selected, which, when closing the cutting gap, brings the approach cutting edge into a point of contact P B2 would touch, in the event that the cut gap, especially on the direct path to the approach road, were to be closed. For the connecting web, a web dimension is then calculated with the distance between the contact points P. B1 and P B2The web dimension is selected. It is crucial for the stability of the connecting web and for the subsequent removal of the workpiece part. Therefore, it is important to determine the web dimension correctly. According to the described method, a web dimension can be determined that corresponds to, or very closely approximates, the actual conditions.

[0012] According to a further embodiment of the invention, it is advantageous if the point of contact P B1 The cutting edge lies on the front edge of the cutting jet, in the area furthest from the cutting edge. This results in favorable conditions. Furthermore, the clearance point can be selected relatively easily and efficiently.

[0013] In one variant of the procedure, the approach path runs along an approach radius, so that the approach cutting edge runs along a circular segment, with the point of contact P B2the approach cutting edge lies in the circular section.

[0014] Furthermore, it is conceivable that the approach track runs along an approach straight line, so that the approach cutting edge runs along a straight section, with the point of contact P B2 The approach cutting edge lies within the straight section. Depending on the angle between the straight section and the end path, the point of release is located in different positions. If the angle between the straight section and the end path is relatively small, the release occurs relatively early, resulting in a different position of the point of release than if the angle is relatively large.

[0015] Furthermore, it is possible that the approach path initially runs along an approach straight line and then transitions into an approach radius, so that the approach cutting edge runs along a straight section and a subsequent circular section, with the point of contact P B2The approach cut edge can then lie between the straight section and the circular section.

[0016] The method according to the invention can be used in a programming device for a laser cutting machine, in which a control program for a control unit for regulating and controlling the cutting beam to generate the cutting path, which includes a penetration point and a clearance point, is generated. In such a programming device, which is typically implemented on an industrial PC, the clearance point can therefore be determined in such a way as to ensure favorable ejection of the respective workpiece part, and this clearance point can be output to the control unit of the machine, for example as a parameter in a control program, or transferred to the control unit.

[0017] The invention also relates to a computer program product comprising code means adapted to carry out the method according to the invention when the program runs as part of a programming system implemented on an industrial PC.

[0018] Further details and advantageous embodiments of the invention can be found in the following description, which describes and explains different exemplary embodiments of the invention in more detail. The figures show: Fig. 1 a section of a top view of a remaining part with a cutting path that has an entry point and a clearance point; Fig. 2 an enlarged section from Fig. 1; Fig. 3 and Fig. 4 two further excerpts of top view of workpieces; Fig. 5 a section of a top view of a workpiece in which a connecting web remains between the free cutting point and the approach track.

[0019] In the Fig. Figure 1 shows a remaining part 10 that is separated from a workpiece part 12, i.e., cut free by means of a laser beam 14. In the Fig. In the top view shown in Figure 1, the laser beam 14 has a diameter d and a beam center 16. The laser beam 14 creates a cutting gap 17 with a width equal to the diameter d of the laser beam 14.

[0020] The laser beam 14, or rather its beam center 16, is guided along a cutting path 18 to cut out the workpiece part 12. For this purpose, the laser beam 14 first pierces a penetration point 20 with its beam center 16. The laser beam 14 is then guided along a approach path 22 at the beginning of the cutting path 18. Following the approach path 22, the laser beam 14 is guided along a cutting path 24. The approach path 22 is selected such that it runs within the remaining part 10 and that the cutting beam generates an approach cutting edge 26 in the approach path 22, which approaches a target cutting edge 28 that ultimately defines the boundary of the workpiece part 12. Fig. 1 The approach cutting edge 26 transitions into the target cutting edge 28 at the transition point 30.

[0021] In the Fig. Figure 1 shows the final path 32 of the cutting path 24. The cutting path therefore moves in the Fig. The cutting beam 14 moves to the right of the image until it finally reappears on the left. In the final path 32, the cutting beam 14 creates a cutting edge 34 that defines the workpiece part 12, as well as a front, essentially semicircular cutting flank 36.

[0022] As the free section point P F Now the point of contact P will be B1 the front cutting edge 36 selected, which when closing the cutting gap, as described in Fig. As shown in 1, the approach cutting edge 26 is at a point of contact P B2 touched.

[0023] Fig. Figure 2 shows an excerpt from Fig. 1, specifically shortly before reaching the point of free cutting P F The point of contact P is clearly visible. B1 the front cutting edge 36, which points to the contact point P B2 approaching the approach cutting edge 26. As seen from Fig. 1 and Fig. As becomes clear in point 2, the point of contact is P. B1the front cutting flank 36 in the area of ​​the front cutting flank 36 of the cutting jet 14 facing away from the cutting edge 34.

[0024] Will the in Fig. 1. Shown free section point P F When the front cutting edge 36 touches the approach cutting edge 26, the workpiece part 12 detaches from the remaining part 10. To remove the workpiece part 12, it is regularly guided downwards by gravity. In another embodiment, not shown, it is conceivable that the remaining part 10 is detached from the workpiece part 12.

[0025] In the known prior art, the actual contours, i.e., neither the approach cutting edge 26 nor the cutting flank 36, are taken into account for calculating the clearance point. Rather, only the center of the jet 16 is used in each case. In the embodiment according to Fig. 1 This means that, according to the state of the art, the center of the jet P1 is taken into account at the transition from the approach path 22 to the cutting path 24, and it is calculated when the center of the jet 16 of the cutting jet 14 reaches this point P1 in the final path 32. As from Fig. As becomes clear in Figure 1, however, the workpiece part 12 is already cut free and thus falls out when the center of the blast 16 in the final path 32 still has a distance X1 to point P1. Such a calculation, known from the prior art, therefore leads to a distorted result. It is not reliably possible to infer the tipping behavior of the workpiece part from the cut-free point determined in this way.

[0026] In the Fig. 1 and Fig. In the embodiment shown in Figure 2, the approach track 22 runs along an approach radius r. The approach cutting edge 26 then runs along a circular segment.

[0027] In the Fig. Figure 3 shows similar relationships, with corresponding components marked with appropriate reference symbols. In contrast to the Fig. 1 the approach lane 22 runs in Fig. 3 along an approach straight line, wherein the approach cutting edge 26 runs along a straight segment. The point of contact P B2 the approach cutting edge 26, or the clearance point P F , lies in the straight section of the approach cutting edge 26. Depending on the angle α between the approach track 22 and the end track 32, the free section point P is located F earlier in time (further to the left in Fig. 3) or later (further to the right in Fig. 3) At very shallow angles α, the point of freedom P moves F in Fig. 3 to the left. At a relatively large angle α, the point of freedom P moves. F further to the right.

[0028] Unlike the Fig. 3 runs in Fig. 4. The approach lane 22 initially runs along a straight approach path and then transitions into an approach radius R. The point of free intersection P F or the point of contact P B2 The approach cutting edge 26 is chosen such that it lies in the circular segment of the approach cutting edge 26.

[0029] In the Fig. Figure 5 shows an embodiment in which the cutting gap 17 is not closed to form a connecting web 40. The corresponding components are marked with appropriate reference numerals.

[0030] In the Fig. Figure 5 shows the entry point 20, from which the laser beam 14 is guided along the approach path 22 to the cutting path 24. The end path 32 is also shown. The end path 32 terminates at an end cutting point 42, where the laser beam is switched off. The connecting bridge 40 lies between the front cutting edge 36 of the end cutting point 42 and the approach cutting edge 26 of the approach path 22.

[0031] To determine the length of the connecting web 40, the web dimension X2 is used, which is derived from the distance of the point of contact P. B1 the front cutting edge 36 to the point of contact P B2 in the approach cut edge 26 would result if the cutting gap along the end path 32 had been closed. If this web dimension X2 is used, a dimension is obtained that corresponds to reality or comes very close to it.

[0032] If the web dimension is calculated according to the state of the art, the blasting center point P1 at the transition from the approach track 22 to the cutting track 24 is used, as well as the blasting center point at the final intersection point 42. This results in a dimension X3 that does not correspond to the actual conditions.

[0033] According to the invention, a free-body point P can therefore be FThe dimensions of a connecting web can be determined relatively easily and with relative accuracy. Accordingly, the web dimension of a connecting web can be determined with corresponding precision. By selecting a suitable relief point or web dimension, optimal removal of the workpiece part 12 from the remaining part 10 can ultimately be achieved.

Claims

[1] Method for determining at least one free-body diagram point (P F ) one from an entry point (20) along a cutting path (18) to the clearance point (P F ) guided cutting jet to close a cutting gap (17) and thereby to separate a workpiece part (12) from a residual part (10), wherein the cutting jet is moved along an approach path (22) at the beginning of the cutting path (18), along a cutting path (24) following the approach path (22) and along a final path (32) at the end of the cutting path (18), wherein the approach path (22) is selected such that it runs outside the workpiece part (12), wherein the cutting jet in the approach path (22) generates an approach cutting edge (26) facing a desired cutting edge (28) and approaching the desired cutting edge (28) and in the end path (32) generates a cutting edge (34) limiting the workpiece part (12) as well as a front cutting flank (36), characterized by, that the free-body point (P F ) as the point of contact P B1 the front cutting flank (36) is selected, which, when closing the cutting gap (17), brings the approach cutting edge (26) into contact at a point P B2 touched and that the clearance point and / or the insertion point is chosen in such a way that jam-free removal of the workpiece part or the remaining part is enabled. [2] Method according to claim 1, characterized by , that the cutting gap (17) is not closed by the cutting ray to form at least one connecting bridge (40), whereby the free cutting point (P F ) as point of contact P B1 the front cutting flank (36) is selected, which, when the cutting gap (17) is closed, the approach cutting edge (26) is at a contact point P B2 would touch, wherein for the connecting web (40) a web dimension (X1) with the distance between the contact points P B1 and P B2 is chosen. [3] Method according to claim 1 or 2, characterized by , that the point of contact P B1 in the area of ​​the front cutting flank (36) of the cutting jet facing away from the cutting edge (34). [4] Method according to claim 1, 2 or 3, characterized by , that the approach track (22) runs along an approach radius (r) such that the approach cutting edge (26) runs along a circular segment, with the point of contact P B2 lies within the district. [5] Method according to any one of claims 1 to 3, characterized by , that the approach track (22) runs along an approach straight line, such that the approach cutting edge (26) runs along a straight segment, with the point of contact P B2 lies in the straight line segment. [6] Programming device for a cutting machine (20), comprising a control device (22) for controlling the cutting steel and generating the cutting path (17) with an insertion point (20) and a clearance point (P) F ) is set up, wherein the programming device is set up to carry out the method according to one of the preceding claims and to output the cut-out point to the control and regulating device (22). [7] Computer program product comprising code means adapted to carry out the method according to any one of claims 1 to 5 when the program is running on a control and regulating device of a cutting machine.

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