Method for producing inclined projections or recesses on a cutting edge of a plate-shaped workpiece and associated computer program product

Description

[0001] The invention relates to a method for producing a recess or a projection on a cutting edge of a plate-shaped workpiece, in particular a sheet metal, when cutting the cutting edge by means of a laser beam which emerges from a laser processing head which can be moved in at least one direction over the workpiece for cutting the cutting edge, and to an associated computer program product.

[0002] From JP 2001246486 A, which forms the basis for the preamble of claim 1, it is known to provide the narrow sides of the workpiece with regularly arranged projections for welding edge preparation for butt joints, which projections have the same shape over the entire thickness of the workpiece and therefore protrude the same distance on the top and bottom sides of the workpiece.

[0003] Furthermore, sheet metal edges with regular, mechanically introduced recesses are also known from US 4,883,937.

[0004] Finally, JP 2009-241083 A discloses a method for producing bevel cuts with microjoints, wherein these structures are produced in several successive steps (cutting processes).

[0005] In general, methods for diagonal cutting using flame cutting machines are also known. For example, DE 29 26 791 A1 describes a method for producing a diagonal cut using a torch unit on a guide machine.

[0006] In contrast, the present invention is based on the object of specifying a method for producing local modifications in the form of a recess or a projection on a cutting edge of a plate-shaped workpiece during laser cutting of the cutting edge, in which the recess or the projection can be cut in one cut, i.e. without having to switch off the laser beam.

[0007] This object is achieved according to the invention by a method for producing local modifications in the form of a recess or a projection on a cutting flank of a plate-shaped workpiece, in particular a sheet metal, when cutting the cutting flank by means of a laser beam which emerges from a laser processing head which can be moved in at least one direction above the workpiece in order to cut the cutting flank and whose longitudinal axis can be inclined in at least one direction, preferably in two directions, with respect to the surface normal of the workpiece or the vertical, wherein when cutting the recess or the projection the laser processing head is inclined and moved in such a way that the laser beam traces contours of different lengths on the two sides of the workpiece facing and facing away from the laser in order to thereby produce an inclined recess or an inclined projection relative to the actual cutting flank.The rotation axes for the pivoting movement of the laser processing head can be located either inside or outside the laser processing head. In the first case, the point of impact of the laser beam on the workpiece surface moves during the pivoting movement of the laser processing head. In the second case, the laser processing head is rotated around a (fixed) point in space that lies on the laser beam axis. This point can be selected either inside or outside the workpiece.

[0008] According to the invention, when laser cutting vertical or angled cut edges, recesses or protrusions can also be integrated into the cut edge in a single laser cut. This allows various types of local modifications to be introduced into the cut edges of workpieces in a simple and variable manner. These recesses or protrusions can fulfill specific functions during further processing of the workpiece, for example, as spacers when welding two workpieces, as positioning aids for connecting components, or as relief cuts for subsequently created bending beads.

[0009] To create the recesses or projections according to the invention, the inclination of the laser processing head is changed during cutting, in particular in a plane perpendicular to the cutting flank or perpendicular to the cutting direction, in order to thereby execute a cut, in particular perpendicular to the cutting flank, which is of different lengths on the two workpiece sides. To this end, at least the angle by which the laser processing head is inclined (tilted) relative to the cutting flank in the direction perpendicular to the cutting flank is changed during cutting of the recess or projection.

[0010] According to the invention, during cutting of the oblique recess or the oblique projection, the laser processing head is inclined and moved in such a way that the laser beam traces a recess or projection contour on one, first side of the workpiece, its beam axis always intersecting the edge of the actual cutting flank provided on the other, second side of the workpiece, so that the oblique recess or the oblique projection on the second side of the workpiece flows into the edge of the actual cutting flank. As a result, this edge of the actual cutting flank is continuous, i.e., not interrupted by the recess or the projection. Furthermore, according to the invention, during cutting of the oblique recess or the oblique projection, the beam axis of the laser beam intersecting the edge of the actual cutting flank remains at a fixed point on this edge.In the case of the fixed point, the laser processing head is preferably pivoted around the fixed point at a constant speed along the entire recess or projection contour traversed by the laser beam on the first side of the workpiece.

[0011] It is understood that, to create the recesses or projections according to the invention, the laser processing head is pivoted in the cutting direction, i.e., parallel to the actual cutting flank, during the cutting of the actual cutting flank, so that the desired angle of the laser processing head in the cutting direction is already set when cutting the projection or recess begins. Likewise, the laser processing head can be returned to the cutting direction only after the projection or recess has been cut, while the actual cutting flank continues to be cut. In this way, a continuous transition is achieved between the cutting of the cutting flank and the recess or projection, so that the cutting speed does not have to be reduced excessively.

[0012] Preferably, the cutting speed when cutting the inclined recess or projection is reduced or increased compared to the cutting speed when cutting the cutting flank, by the amount by which the effective sheet thickness for the inclined laser beam increases or decreases. Advantageously, the laser power when cutting the inclined projection or recess is the same as when cutting the actual cutting flank.

[0013] Alternatively, the actual cutting edge can be cut with a laser beam angled perpendicular to the cutting edge. The angle of the laser beam is then changed to cut the recess or projection in order to create a (possibly less) angled recess or projection on the angled cutting edge. Depending on the possibly lower angle of the machining head relative to the surface normal of the workpiece, the cutting speed when cutting the recess or projection can also be higher than when cutting the actual cutting edge.

[0014] To ensure that the effective distance traveled by the laser beam emerging from the laser processing head to the workpiece does not change even when the laser processing head is tilted, when cutting the inclined recess or the inclined projection, the distance between the laser processing head and the workpiece surface, in particular the distance between a cutting gas nozzle of the laser processing head and the workpiece surface, is reduced accordingly if the inclination of the laser processing head relative to the surface normal of the workpiece increases.

[0015] When cutting the oblique recess or the oblique projection, the pressure of a cutting gas escaping from a cutting gas nozzle of the laser processing head can be increased accordingly if the inclination of the processing head is greater due to the then greater effective workpiece thickness.

[0016] The invention also relates to a computer program product which has code means adapted to carry out all steps of the method according to the invention when the program runs on a controller of a laser processing machine.

[0017] Further advantages and advantageous embodiments of the subject matter of the invention will become apparent from the description, the claims, and the drawings. Likewise, the features mentioned above and those listed below can be used individually or in combination in any desired manner. The embodiments shown and described are not to be understood as an exhaustive list, but rather are exemplary in nature for describing the invention.

[0018] They show: Fig. 1 a movable and tiltable laser processing head for laser cutting of workpieces; Figs. 2a-2d the individual steps ( Fign. 2a-2c ) of a first method variant for producing an oblique recess or an oblique projection on a cutting flank of a plate-shaped workpiece ( Fig. 2d ) (not subject of the present claims); Figs. 3a, 3b compared to Fig. 2c modified process step for producing a modified oblique recess or a modified oblique projection on the cutting flank of the plate-shaped workpiece ( Fig. 3b ); Figs. 4a-4d the individual steps ( Fign. 4a-4c ) a second method variant for producing an oblique recess or an oblique projection on a cutting flank of a plate-shaped workpiece ( Fig. 4d ) (not subject of the present claims); Figs. 5a, 5b compared to Fig. 4c modified process step for producing a modified oblique recess or a modified oblique projection on the cutting flank of the plate-shaped workpiece ( Fig. 5b ) (not subject of the present claims); Fig. 6 a plate-shaped workpiece with an inclined projection on the upper side of the workpiece and with an inclined recess on the lower side of the workpiece (not subject of the present claims); and Figs. 7a, 7b a cutting gas nozzle of the laser processing head with the laser processing head tilted and not tilted.

[0019] In the following description of the drawing, identical reference symbols are used for identical or functionally identical components.

[0020] The Fig. 1 shown laser processing head 1 used for laser cutting of plate-shaped workpieces 2 , such as sheet metal, by means of a laser beam emerging from the laser processing head 1 3. The laser beam 3 is generated in a laser beam source (not shown) and transmitted to the laser processing head 1, for example by means of an optical fiber.

[0021] The laser processing head 1 is parallel to the flat workpiece surface 4 two-dimensionally movable in X and Y directions. In addition, the laser processing head 1 with its longitudinal axis 5 or with the beam axis 6 of the emerging laser beam 3 relative to the surface normal 7 of the workpiece 2 or relative to the vertical in the X and Y directions by an angle α or β and by a point 8 The laser processing head 1 is rotated in the X and / or Y direction along the desired cutting direction at a cutting speed v1 to create a cutting edge in workpiece 2 10 to cut.

[0022] With reference to the Fign. 2a bis 2d In the following, a first method for producing an oblique recess 11 or an oblique projection 12on the cutting edge 10 of the workpiece 2 when cutting the cutting edge 10 by means of the laser beam 3. The method according to the Figuren 2a bis 2d is not the subject of the presently claimed invention.

[0023] Fig. 2a shows the laser cutting of the cutting edge 10 by means of the laser beam 3 striking the workpiece 2 at a right angle, for example, by moving the laser processing head 1 over the workpiece 2 at the cutting speed v1 in the cutting direction (X direction).

[0024] In Fig. 2b the laser beam 3 is deflected within the plane of the cutting edge 10 (in X-direction) by the angle αinclined, either with the laser processing head 1 still moving in the cutting direction or with the laser processing head 1 stationary in the cutting direction. This inclination of the laser processing head 1 is maintained during the subsequent laser cutting of the inclined recess 11 or the inclined projection 12, but could alternatively also be changed during this time.

[0025] In Fig. 2c For laser cutting of the recess 11 or the projection 12, the inclined laser processing head 1 is now moved and at the same time inclined perpendicular to the plane of the cutting flank (in the Y direction) 10 with a changing angle β, so that the laser beam 3 is directed onto the upper side of the workpiece facing the laser 13a and on the underside of the workpiece facing away from the laser 13b contours of different lengths 14a, 14b in order to thereby cut the actual cutting flank 10 in Fig. 2d shown oblique recess 11 or the one in Fig. 2d shown oblique projection 12. The laser processing head 1 is thus rotated around a point in space which lies below the workpiece 2. In the exemplary embodiment shown, the contour traced on the upper side 13a of the workpiece is a semicircle with a larger radius and the contour traced on the lower side 13b of the workpiece is a semicircle with a smaller radius, so that, as in Fig. 2d shown, a truncated cone-shaped recess 11 or a truncated cone-shaped projection 12 is created on the actual cutting flank 10. Finally, by returning the laser processing head 1 by the angle α to the position shown in Fig. 2a In the initial position shown, the laser beam 3 is again positioned perpendicular to the workpiece 2 within the plane of the cutting edge 10 and the cutting edge 10 is further cut by means of the laser beam 3 by moving the laser processing head 1 over the workpiece 2 at the cutting speed v1 in the cutting direction (X-direction). The resetting of the laser processing head 1 can also take place during further cutting. As in Fig. 2d shown, neither of the two top and bottom edges is 15a, 15b the actual cutting flank 10 is not continuous, but is interrupted by the recess 11 or the projection 12.

[0026] The Figuren 3a und 3b show a laser cutting process according to the invention. In contrast to Fig. 2c will be in Fig. 3a During the laser cutting of the recess 11 or the projection 12, the inclined laser processing head 1 is moved and simultaneously pivoted in such a way that the laser beam 3 on the upper side 13a of the workpiece follows the desired recess or projection contour 14a and in doing so always intersects with its beam axis 6 the edge 15b of the actual cutting flank 10 provided on the lower side 13b of the workpiece, so that the laser-cut recess 11 or the laser-cut projection 12 on the lower side 13b of the workpiece ends in this edge 15b of the actual cutting flank 10 ( Fig. 3b ). In the example shown, during the laser cutting of the recess 11 or the projection 12, the beam axis 6 of the laser beam 3 intersecting the edge 15b of the actual cutting flank 10 remains at a fixed point 16 on this edge 15b, as in Fig. 3a is shown. The laser processing head 1 is moved at a constant speed along the entire recess or projection contour 14a traversed by the laser beam 3 on the first workpiece side 13a v2, which is lower than the cutting speed v1 during laser cutting of the cutting edge 10, is pivoted around the fixed point 16. Alternatively, the beam axis 6 could also wander on this edge 15b during laser cutting of the recess 11 or the projection 12, which leads to a contour as shown in Fig. 5b shown (The alternative according to Fig. 5b is not the subject of the present claims).

[0027] As in Fig. 3b As shown, the underside edge 15b of the actual cutting flank 10 is now continuous, i.e. not interrupted by the recess 11 or the projection 12.

[0028] With reference to the Fign. 4a bis 4d A second method (which does not fall within the scope of the present claims) for producing an oblique recess 11 or an oblique projection 12 on the cutting flank 10 of the workpiece 2 when cutting the cutting flank 10 by means of the laser beam 3 is described below.

[0029] Fig. 4a shows the laser cutting of the cutting edge 10 by means of the laser beam 3 striking the workpiece 2 at a right angle, for example, by moving the laser processing head 1 over the workpiece 2 at the cutting speed v1 in the cutting direction (X direction).

[0030] When the laser processing head 1 is stationary in the cutting direction, Fig. 4b the laser processing head 1 is inclined by the angle β in a plane perpendicular to the cutting edge 10 (in the Y direction) in order to thereby produce a cut perpendicular to the cutting edge 10 17which is longer on the upper side 13a of the workpiece than on the lower side 13b of the workpiece. For this purpose, the laser processing head 1 can be inclined at an increasing angle during the cutting of the cut 17 until the point 18 the maximum inclination of the laser processing head 1 is set on the workpiece underside 13b. Alternatively, the laser processing head 1 can first be moved in a perpendicular alignment to the workpiece surface 13a up to point 18 and then pivoted around point 18 in the Y direction until the final inclination is reached.

[0031] In Fig. 4c the inclined laser processing head 1 is moved further in the cutting direction (X-direction) at a speed v2, which is lower than the cutting speed v1 during laser cutting of the cutting flank 10, in order to thereby carry out a cut parallel to the actual cutting flank 10, which cut is of equal length on the upper and lower surfaces 13a, 13b of the workpiece. Subsequently, with the laser processing head 1 stationary in the cutting direction, the laser processing head 1 is moved back by the angle β in a plane perpendicular to the cutting flank 10 into its Fig. 4a shown starting position, in order to perform a cut perpendicular to the cutting flank 10, which is longer on the upper side 13a of the workpiece than on the lower side 13b of the workpiece. The pivoting movement of the laser processing head 1 can take place before or during the travel movement in the Y direction. The recess or projection contour 14a traced by the laser beam 3 on the upper side 13a of the workpiece is thus shorter than the recess or projection contour 14b traced on the lower side 13b of the workpiece. Thus, on the actual cutting flank 10, the Fig. 4d shown oblique recess 11 or the one in Fig. 2d shown oblique projection 12 is created. Finally, the cutting flank 10 is further cut by means of the laser beam 3 by moving the laser processing head 1 over the workpiece 2 at the cutting speed v1 in the cutting direction.

[0032] As in Fig. 4d As shown, neither of the two upper and lower edges 15a, 15b of the actual cutting flank 10 is continuous, but is interrupted by the recess 11 or the projection 12.

[0033] In contrast to Fig. 4b cuts into Fig. 5a the inclined laser processing head 1, during its travel movement in the X direction, with its beam axis 6, the edge 15b of the actual cutting flank 10 provided on the underside 13b of the workpiece. When the laser processing head 1 moves in the cutting direction, the beam axis 6 moves on this edge 15b along the contour line 14b, while the laser beam 3 travels along the desired recess or projection contour 14a on the upper side 13a of the workpiece.

[0034] As in Fig. 5b As shown, the laser-cut recess 11 or the laser-cut projection 12 on the workpiece underside 13b ends in the edge 15b of the actual cutting flank 10, so that this underside edge 15b of the actual cutting flank 10 is continuous, i.e., not interrupted by the recess 11 or the projection 12. The method according to the Figuren 5a und 5b also does not fall within the scope of the present claims.

[0035] In Fig. 6 A further method variant is shown (which also does not fall within the scope of the present claims), in which the fixed point 16, around which the laser cutting head 1 is rotated during cutting of the local cutting edge modification, is positioned approximately in the center of the workpiece. In this way, a conical projection 12 is created on the workpiece upper side 13a and a conical recess 11 is created on the workpiece lower side 13b. Such edge modifications are advantageous for compensating for material expansion or compression during a subsequent bending process: During bending, the workpiece 2 is expanded on the workpiece upper side (outside) 13a and compressed on the workpiece lower side (inside) 13b. The resulting material displacement is at least partially compensated for by the previously introduced edge modification.

[0036] In Fign. 7a, 7b is a cutting gas nozzle 19of the laser processing head 1, from whose nozzle opening 20 the laser beam 3 together with a cutting gas 21 in the direction of the workpiece 2. Fig. 7a shows the cutting gas nozzle 19 with the laser processing head 1 not tilted and Fig. 7b the cutting gas nozzle 19 with the laser processing head 1 tilted. As in Fig. 7b shown, the distance A between cutting gas nozzle 19 and workpiece 2 when the laser processing head 1 is inclined, since otherwise the effective distance A eff, which is traveled by the laser beam 3 emerging from the cutting gas nozzle 19 to the workpiece 2, would increase. Ideally, the effective distance A eff should remain constant along the entire travel distance. The focus position of the laser beam 3 on the workpiece 2 can be adjusted according to the change in distance A and the effective sheet thickness, so that the position of the focus point relative to the workpiece surface 4 remains unchanged. In practice, adjustment of the focus position is often not necessary.

[0037] Preferably, when cutting the oblique recess 11 or the oblique projection 12, the pressure of the cutting gas exiting from a cutting gas nozzle 19 is increased in order to take into account the larger effective workpiece thickness.

[0038] When laser cutting the recess 11 or the projection 12, the cutting speed is preferably reduced by the amount by which the effective sheet thickness increases. For example, when laser cutting a 12 mm thick workpiece 2 with a (temporary) angle of attack of 37°, the effective workpiece thickness increases to 15 mm. The feed rate is therefore reduced to the value typically used for laser cutting a 15 mm thick workpiece. However, the feed rate should not be reduced too much (typically not to < 60%), since otherwise the cutting quality deteriorates in the area of the excessively high energy per unit length (i.e. over the shorter path).

[0039] If possible, the laser power remains constant during laser cutting of the recess 11 or the projection 12. However, if the laser power used for laser cutting is below the rated power for the effective workpiece thickness, it is advantageous to increase the laser power in accordance with the increasing effective sheet thickness.

[0040] All of the parameters described above are adjusted depending on the inclination angle of the laser processing head 1. Therefore, a local path change on the top / bottom of the workpiece also results in a local change in these parameters. For small angle changes, parameter adjustment is not necessarily required, or individual parameters can remain unchanged, even with a loss of quality.

[0041] Instead of using a laser beam 3 incident at a right angle as shown in the figures, the cutting edge 10 can also be cut with an inclined laser beam 3, the inclination of which is then changed for laser cutting the recess 11 or the projection 12 in order to create an inclined recess 11 or an inclined projection 12 on the inclined cutting edge 10. If the inclination of the laser processing head 1 is reduced during cutting of the recess 11 or the projection 12, the cutting speed when cutting the recess 11 or the projection 12 can also be higher than when cutting the cutting edge 10.

[0042] The process can be used to produce various functional elements: Local protrusions for setting a defined joint gap geometry: Locally angled protrusions on the cutting flank ensure a defined distance from the joining partner during subsequent welding of such flanks (for V-seams) without significantly reducing the volume of the weld joint. This is advantageous compared to local vertical protrusions created with equally long trajectories on the top and bottom of the workpiece, as such protrusions reduce the weld seam volume. Clamping of joints: Especially with thick sheets, locally angled protrusions on the cutting edge can be used to create force-locking connections that do not act across the entire sheet thickness. This allows for joining with tolerances or with minimal force application. Horizontal alignment of joining partners: Opposing bevel cuts (male / female) prevent the components from sagging.Prevent tilting during cutting: A slanted protrusion with a larger extension on the top side of the sheet can prevent a cut component from sinking into the scrap skeleton. Free cuts / contour correction during bending: Bending bulges that occur during bending can be avoided by appropriate slanted recesses and protrusions introduced before bending.

Claims

1. A method for producing a recess (11) or a projection (12) on a cut edge (10) of a plate-shaped workpiece (2), in particular a metal sheet, characterized by the following steps: cutting the cut edge (10) by means of a laser beam (3) which emerges from a laser processing head (1) that can be moved above the workpiece (2) in at least one direction (X, Y) in order to cut the cut edge (10) and whose longitudinal axis (5) can be set at an angle to the surface normal (7) of the workpiece (2), wherein, when cutting the recess (11) or the projection (12), the laser processing head (1) is positioned and moved at an angle such that the laser beam (3) moves along contours (14a, 14b) of different lengths on the two workpiece sides (13a, 13b) facing the laser and facing away from the laser, so that, as a result, an inclined recess (11) or an inclined projection (12) is produced relative to the actual cut edge (10), wherein, during the cutting of the inclined recess (11) or of the inclined projection (12), the laser processing head (1) is positioned and moved at an angle such that the laser beam (3) moves along a recess or projection contour (14a) on the one, first workpiece side (13a) and, in doing so, always cuts the actual cut edge (10) with its beam axis (6) on the edge (15b) provided on the other, second workpiece side (13b), so that the inclined recess (11) or the inclined projection (12) on the second workpiece side (13b) ends in the edge (15b) of the actual cut edge (10), and wherein, during the cutting of the inclined recess (11) or the inclined projection (12), the beam axis (6) of the laser beam (3) that cuts the edge (15b) of the actual cut edge (10) remains in a fixed point (16) on this edge (15b).

2. The method according to claim 1, characterized in that during the cutting of the inclined recess (11) or the inclined projection (12), the inclined position of the laser processing head (1), in particular in a plane perpendicular to the cut edge (10), is changed.

3. The method according to claim 1 or 2, characterized in that the laser processing head (1) is pivoted at a constant speed about the fixed point (16) along the entire recess or projection contour (14a) traversed by the laser beam (3) on the first workpiece side (13a).

4. The method according to one of the preceding claims, characterized in that the cutting speed (v2) when cutting the inclined recess (11) or the inclined projection (12) is reduced or increased relative to the cutting speed (v1) when cutting the cut edge (10).

5. The method according to one of the preceding claims, characterized in that, when cutting the inclined recess (11) or the inclined projection (12), the laser power has the same value as when cutting the cut edge (10).

6. The method according to one of the preceding claims, characterized in that, when cutting the inclined recess (11) or the inclined projection (12), the distance between the laser processing head (1) and the workpiece surface (4), in particular the distance (A) between a cutting gas nozzle (19) of the laser processing head (1) and the workpiece surface (4), is reduced with an increasing inclined position of the laser processing head (1).

7. The method according to one of the preceding claims, characterized in that, when cutting the inclined recess (11) or the inclined projection (12), the pressure of a cutting gas (21) emerging from a cutting gas nozzle (19) of the laser processing head (1) is increased with an increasing inclined position of the laser processing head (1).