Method for generating a connecting web with reduced thickness during cutting of workpiece parts from a plate-shaped workpiece, and corresponding control program product

Abstract

The present invention relates to a method for generating at least one connecting web (21) with a reduced thickness during cutting out workpiece parts (19) from a plate-shaped workpiece (16), the cut-out workpiece parts (19) remaining attached to the remaining grid (26) of the workpiece (16) by means of the connecting web (21). According to the invention, the method comprises the following steps: generating at least one connecting web (21) on the workpiece (16) before cutting out the workpiece parts (19), and squeezing the connecting web (21) in the thickness direction (24) of the workpiece (16), at least in a web section (23) adjacent to the workpiece part (19) that has not yet been cut out, so that the squeezed connecting web (21') recedes against at least one of the two plate sides (16a, 16b) of the workpiece (16) in the direction of the workpiece center, wherein the receding of the squeezed connecting web (21') The method comprises a step of retracting the workpiece (16) edges (25a, 25b) thus formed, which form the edges of the workpiece parts (19) that have not yet been cut out; and a step of cutting separating gaps (22) into the workpiece (16) which correspond to the contour of the workpiece parts (19) and are interrupted along the edges (25a, 25b) formed by the retraction of the pressed connecting webs (21'), whereby the workpiece parts (19) remain attached to the remaining grid (26) of the workpiece (16) by the pressed connecting webs (21').

Description

[Technical Field]

[0001] The present invention relates to a method for generating at least one connecting web with a reduced thickness during cutting of workpiece parts from a plate-shaped workpiece, as well as to a control program product comprising code means adapted to perform the method according to the invention when the program is run on a control system of a suitable machine tool. [Background technology]

[0002] Such a method is known, for example, from EP 3088096 A1.

[0003] During the punching or laser punching process, connecting webs, or so-called "microjoints," are left in place to secure the cut-out workpiece parts, through which they remain connected to the remaining residual grid. The microjoints make it very difficult to manually remove the workpiece parts from the residual grid, especially for sheet thicknesses greater than 2 mm. In addition, because the microjoints extend across the entire workpiece thickness, it is not possible to round or chamfer the edges of the workpiece parts at the microjoint locations.

[0004] In a method known from EP 3088096 A1, workpiece parts are cut out from a plate-shaped workpiece while leaving connecting webs, which are then pressure-formed using a forming tool to reduce the thickness of the connecting webs.

[0005] It is also known from the WO 2022 / 037797(A1) brochure that during laser cutting of workpiece parts from a plate-shaped workpiece, one or more connecting webs are left between the workpiece part and the residual grid, and the cut edges of the workpiece part that are still connected to the residual grid are processed using the laser beam, in particular rounded.

[0006] Summary of the Invention In contrast, the object of the present invention is to provide an alternative method for producing at least one connecting web with a reduced thickness when cutting a workpiece part from a plate-shaped workpiece. In particular, subsequent edge processing along the entire contour of the workpiece part should be possible despite the presence of the connecting web.

[0007] In the method mentioned at the beginning, the object is to provide a method according to the invention comprising the following method steps: - generating at least one connecting web before cutting out the workpiece part; - squeezing the connecting web in the thickness direction of the workpiece, at least in the web section adjacent to the workpiece part that has not yet been cut off, so that the squeezed connecting web is retracted towards the workpiece centre against at least one of the two plate sides of the workpiece, the workpiece edge formed by the retraction of the squeezed connecting web forming the edge of the workpiece part that has not yet been cut off; - cutting separating gaps into the workpiece which correspond to the contours of the workpiece parts and are interrupted along the edges formed by the retraction of the squeezed connecting webs, whereby the workpiece parts remain attached to the remaining grid of the workpiece by the squeezed connecting webs.

[0008] According to the present invention, the connecting webs ("microjoints") are pressed on one or both sides, thereby reducing their thickness and displacing the metal connection points of the connecting webs toward the center of the sheet. Due to the reduced thickness of the pressed connecting webs, the cut-out workpiece parts can be easily removed from the remaining grid, even if the workpiece thickness is greater than 2 mm. The retraction of the pressed connecting webs also creates a straight edge of the future workpiece part in the workpiece, which, together with the subsequent cut edge of the workpiece part, forms a continuous edge of the workpiece part. This continuous edge can then be rounded or chamfered using an edge processing tool in a subsequent processing step.

[0009] Particularly preferred are the cut edges of the cut-off workpiece part and the edge of the workpiece part formed by the return retreat of the compressed connecting web, which together form a continuous edge of the workpiece part and are processed by an edge processing tool guided along the contour (overall) of the workpiece part, in particular rounded or chamfered.

[0010] Advantageously, in order to form a predetermined breaking point for the workpiece component at the web end on the workpiece component side, the connecting web can be pressed to a thickness less at the web end on the workpiece component side than at the web end on the remaining grid side. The pressed connecting web preferably has a wedge-shaped cross section, for example in a longitudinal plane extending through its longitudinal direction and its thickness direction, tapering in the direction of the web end on the workpiece component side.

[0011] The connecting webs are particularly preferably compressed on both sides in the thickness direction, at least in the web sections adjacent to the workpiece parts that have not yet been cut, so that the compressed connecting webs are retracted against the two plate sides of the workpiece in the direction of the workpiece center, and the edges of the workpiece formed by the retraction of the compressed connecting webs on both sides each form an edge of the workpiece part that has not yet been cut. The compressed connecting webs are located only in the center of the sheet thickness, which makes it possible to apply continuous edge rounding or chamfering on both sides over the entire contour of the workpiece parts that are still connected to the remaining grid despite the compressed connecting webs.

[0012] Thereafter, the cut edge of the cut-off workpiece part and the edge of the workpiece part formed by the retraction of both sides of the compressed connecting web together form a continuous edge of the workpiece part and are simultaneously machined by an edge machining tool guided along the contour (entire) of the workpiece part, in particular rounded or chamfered.

[0013] Preferably, the connecting web in the workpiece is generated by two spaced apart cutouts, which form a connecting web between them. The separating gaps can open into the cutouts on both sides of the pressed connecting web, specifically into the cutout tips of the cutouts. In this case, the pressed connecting web is connected to the workpiece component only on the front side. If the separating gaps on both sides of the pressed connecting web do not open into the cutouts, the pressed connecting web is also still connected to the remaining grid on both sides. The ideal shape of the cutout is triangular, because in this case the remaining grid can exert a supporting force on the pressed connecting web during subsequent edge processing of the workpiece component with an edge processing tool, and the edge rounding tool is not pushed aside. Cutouts having shapes other than triangular are also conceivable. The cutouts can be punched out of the workpiece or cut out with a processing beam, for example, a laser beam.

[0014] Instead of first creating the connecting web with two cutouts in two separate steps and then squeezing it, this can alternatively be done in one single step, in which the connecting web is simultaneously punched out with a suitable punching tool and squeezed on one or both sides in the thickness direction of the workpiece, at least in the web section adjacent to the workpiece part that has not yet been cut out. Thus, the workpiece is not completely punched out at the point of the connecting web. The squeezed connecting web is preferably located in the lower third of the thickness of the workpiece part.

[0015] Preferably, the separating gap is cut with a machining beam, for example a laser beam, or with a punching tool.

[0016] In a further aspect, the present invention also relates to a control program product comprising code means adapted to perform all the steps of the method according to the present invention when the program is run on a control system of a machine tool suitable for performing all the steps of the method according to the present invention.

[0017] Further advantages of the present invention will become apparent from the description and the drawings. Likewise, the features mentioned above and further presented features can in each case be used individually or together in any desired combination. The illustrated and described embodiments should not be understood as an exhaustive list, but rather as exemplary features for explaining the present invention. [Brief explanation of the drawings]

[0018] [Figure 1] 1 shows a machine tool for sheet processing having a cutting station and a forming station. [Figure 2] 1 shows a perspective top view of a sheet with two cutouts forming a connecting web between them. [Figure 3] 3a-3c show a perspective top view of a sheet with squeezed connecting webs (FIG. 3a) as well as a perspective cross-sectional view (FIG. 3b) and a longitudinal cross-sectional view (FIG. 3c) of the squeezed connecting webs. [Figure 4] Figures 4a to 4c show a sheet with workpiece components cut out apart from the pressed connecting web in a perspective top view (Figure 4a), and the pressed connecting web in a top view (Figure 4b) and a perspective cross-sectional view (Figure 4c). [Figure 5] 5a to 5c show edge rounding by an edge rounding tool of a workpiece part cut out apart from the pressed connecting web in a top perspective view (FIG. 5a) as well as in a longitudinal cross-sectional view (FIG. 5b) and a cross-sectional perspective view (FIG. 5c). [Figure 6] The completed workpiece part is shown in a perspective top view. DETAILED DESCRIPTION OF THE INVENTION

[0019] The machine tool 1 shown in Figure 1 is designed as a combined punching and laser cutting machine. The machine frame 2 of the machine tool 1 has a C-shape and comprises an upper frame leg 3 and a lower frame leg 4. At the free ends of the upper and lower frame legs 3, 4, a laser cutting station 5 and a forming station 6 are provided.

[0020] The laser cutting station 5 comprises a laser cutting head 7 on the upper frame leg 3 and a laser beam holder 8 on the lower frame leg 4. The forming station 6 has an upper tool holder 9 on the upper frame leg 3 and a lower tool holder 10 on the lower frame leg 4. An upper tool designed as a punching die 11 can be inserted into the upper tool holder 9 and a lower tool designed as a die 12 can be inserted into the lower tool holder 10. The punching die 11 and the die 12 are tool parts of a forming or punching tool 13.

[0021] A conventional lift drive allows the punch 11 to be raised and lowered longitudinally along a stroke axis 14 relative to the die 12. The upper tool holder 9 and the lower tool holder 10, together with the punch 11 and the die 12, are rotatably adjustable about the stroke axis 14 (double arrow in Figure 1). All functions of the machine tool 1 are controlled by a programmable numerical control system 15.

[0022] A plate-shaped workpiece 16, in the illustrated embodiment, sheet metal, is processed in the laser cutting station 5 and the forming station 6. For processing, the sheet 16 is moved in two-axis horizontal motion on a workpiece support 18 of the machine tool 1 by a conventional coordinate guide 17, thereby moving it relative to the laser cutting head 7 and laser beam holder 8 and relative to the forming tool 13. In FIG. 1, the sheet 16 is shown cut away, allowing the laser beam holder 8 and the lower tool holder 10 with the forming die 12 of the forming tool 13 to be seen. Due to the movement of the sheet 16 generated by the coordinate guide 17, the laser beam directed from the laser cutting head 7 to the sheet 16 cuts out the sheet part (e.g., the finished part) while leaving a connecting web ("microjoint"). As a result of the creation of a residual connection via the connecting web, the residual grid and the sheet part are only incompletely separated from each other. Instead of a laser cutting beam, a different type of cutting tool can also be used, in particular a punching tool inserted in the forming station 6, for the incomplete separation of the remaining grid and sheet parts.

[0023] 2 to 6 show the method steps of the processing method according to the invention, which are carried out on a machine tool 1 to cut a workpiece part 19 (FIG. 6), hereafter referred to as the finished part, from a sheet 16 (e.g., 2 mm mild steel) and to machine the edge of the finished part 19 along the entire finished part contour while the finished part 19 is still connected to the remaining grid of the sheet 16 via connecting webs having a reduced thickness.

[0024] In a first method step, two spaced-apart recesses or cutouts 20 are punched into the sheet 16 using a corresponding punching tool 13, forming a connecting web ("micro-joint") 21 between them (FIG. 2). This allows material to flow laterally into the two cutouts 20 during the subsequent formation of the connecting web 21. Preferably, the cutouts 20 open into the not-yet-created separating gaps 22. Alternatively, the cutouts 20 can be introduced with the laser beam of the laser cutting head 7. The cutouts 20 are, for example, specifically designed as triangles with rounded corners, forming connecting webs 21 between opposing sides of the triangle, each opening into the not-yet-created separating gaps 22 at the tip of the triangle.

[0025] In a second method step, the connecting web 21 is pressed by a corresponding forming tool (embossing tool) 13 in the thickness direction 24 of the sheet 16 onto the web section 23 adjacent to the not-yet-separated future finished part 19 (or alternatively, over its entire web length), moving the connecting web 21 back toward the center of the workpiece against one of the two plate sides 16a, 16b of the sheet 16, or, as shown, against both plate sides 16a, 16b (Figures 3a-3c). The pressed connecting web or web section is designated 21' and forms, for example, a so-called nanojoint. Excess material from the pressing process flows into the previously created notch 20. The pressed connecting web 21' is located here in the center of the sheet thickness, preferably up to one-third of the sheet thickness. The linear upper and lower edges 25a, 25b formed by the retraction of the pressed connecting web 21' on the future finished part 19 correspond to the contour of the future finished part 19.

[0026] As shown in Fig. 3c, the connecting web 21 is more strongly compressed at its web end 21a on the side of the finished part 19 connected to the future finished part 19 than at its web end 21b on the side of the remaining grid 26 connected to the future remaining grid. Thereby, the compressed connecting web 21' tapers in the direction of the web end 21a on the side of the finished part in the longitudinal plane extending by its longitudinal direction and its thickness direction 24, and here has a wedge-shaped cross section. The web thickness d1 of the web end 21a on the side of the finished part is smaller than the web thickness d2 of the web end 21b on the side of the remaining part, that is, d1 < d2, and a predetermined breaking point is formed at the web end 21a on the side of the workpiece part for the finished part 19.

[0027] Instead of first creating and then compressing the connecting web 21 in two separate steps, this can alternatively be done in a single step by simultaneously punching and compressing the connecting web 21 using a suitable punching tool. Thus, the sheet 16 is not completely punched at the point of the connecting web 21. The compressed connecting web 21' is preferably located in the lower third of the sheet thickness.

[0028] In a third method step, a separation gap 22 corresponding to the contour of the finished part 19, interrupted along the compressed connecting web 21' or the upper edge and the lower edge 25a, 25b, is cut into the sheet 16 (Figs. 4a - 4c). The separation gap 22 opens into the notches 20 on both sides of the compressed connecting web 21', whereby the finished part 19 is only held on the remaining grid 26 by the compressed connecting web 21'. The separation gap 22 is cut out using a laser beam or alternatively created using a punching tool 13. Preferably, the laser beam should be used to cut the contour as a cutting gap having a size of a fraction of a millimeter, and then have an ideal shape for the edge processing tool to be used subsequently.

[0029] In an optional fourth method step, the edges of the finished part 19 are processed, e.g., rounded, along the entire contour of the finished part 19, i.e., along the upper and lower cut edges 27a, 27b and along the upper and lower edges 25a, 25b, by an edge processing tool 28 inserted instead of the forming or punching tool 13 (FIGS. 5a-5c). The edge processing tool 28 is shown here as an example as a roller pinch tool with an upper tool roller 28a in the upper tool and a lower tool roller 28b in the lower tool. This means that edge rounding can be performed simultaneously on both the upper and lower sides of the sheet. The tool rollers 28a, 28b have annular rounding projections 29a, 29b with a rounding radius (e.g., 0.5 mm or less) on their outer periphery and engage in the separation gap 22. The tool rollers 28a, 28b are displaced or forced in the separation gap 22 toward the finished part 19 to round the upper and lower edges 25a, 25b and the cut edges 27a, 27b of the finished part 19. An upper tool punch presses the upper tool roller 28a to generate the required contact pressure. The punch is spring-loaded and can therefore compensate for variations in sheet thickness. Instead of the illustrated double-sided component rounding, only the upper edges 25a, 27a or only the lower edges 25b, 27b can alternatively be processed, e.g., rounded, using a corresponding edge processing tool (single-sided component rounding). For example, a ball deburring tool could also be used as the edge processing tool 28 to round the edges 25a, 25b and 27a, 27b by roller deburring.

[0030] The finished part 19 is now complete and can be removed from the machine tool 1 (FIG. 6). For this purpose, the pressed connecting webs 21′ can be punched out in the machine tool 1 or cut open by a laser beam, after which the free finished part 19 is removed via a part chute. Alternatively, the finished part 19 can remain attached to the remaining grid 26 and can be later removed from the remaining grid 26 by breaking open the pressed connecting webs 21′, either manually or with mechanical assistance.

Claims

1. 1. A method for producing at least one connecting web (21) having a reduced thickness during cutting of a workpiece part (19) from a plate-shaped workpiece (16), wherein the cut-out workpiece part (19) remains attached to a remaining grid (26) of the workpiece (16) by means of the connecting web (21), The method steps are as follows: - generating said at least one connecting web (21) on said workpiece (16) before cutting out said workpiece part (19); - squeezing the connecting web (21) in the thickness direction (24) of the workpiece (16), at least in the web section (23) adjacent to the workpiece part (19) that has not yet been cut off, so that the squeezed connecting web (21') recedes against at least one of the two plate sides (16a, 16b) of the workpiece (16) in the direction of the workpiece center, so that the workpiece (16) edges (25a, 25b) formed by the receding squeezed connecting web (21') form the edges of the workpiece part (19) that has not yet been cut off; - cutting separating gaps (22) into the workpiece (16) which correspond to the contour of the workpiece parts (19) and are interrupted along the edges (25a, 25b) formed by the retraction of the squeezed connecting webs (21'), whereby the workpiece parts (19) remain attached to the remaining grid (26) of the workpiece (16) by the squeezed connecting webs (21').

2. 2. The method according to claim 1, characterized in that the cut edges (27a, 27b) of the cut-off workpiece part (19) and the edges (25a, 25b) of the workpiece part (19) formed by the retraction of the compressed connecting web (21') are machined by an edge machining tool (28) guided along the contour of the workpiece part (19).

3. 3. The method according to claim 1, wherein the connecting web (21) is pressed to a thickness less at the web end (21a) on the workpiece component side than at the web end (21b) on the remaining grid side.

4. 4. The method according to claim 1, wherein the pressed connecting web (21') has, in a longitudinal plane spanned by its longitudinal direction and its thickness direction (24), a cross section that tapers in the direction of the web end (21a) on the workpiece component side.

5. 5. The method according to claim 1, wherein the connecting web (21) is squeezed on both sides in the thickness direction (24) at least in the web section (23) adjacent to the workpiece part (19) that has not yet been cut off, so that the squeezed connecting web (21') is pushed back against the two plate sides (16a, 16b) of the workpiece (16) towards the workpiece center, and the edges (25a, 25b) of the workpiece (16) formed by the pushback on both sides of the squeezed connecting web (21') each form an edge of the workpiece part (19) that has not yet been cut off.

6. 6. The method according to claim 5, characterized in that the cut edges (27a, 27b) of the cut workpiece part (19) and the edges (25a, 25b) of the workpiece part (19) formed by the retraction of the sides of the compressed connecting web (21') are simultaneously machined by an edge machining tool (28) guided along the contour of the workpiece part (19).

7. 7. The method according to claim 1, wherein the connecting web (21) in the workpiece (16) is generated by two spaced apart cutouts (20), the two spaced apart cutouts (20) forming the connecting web (21) between them.

8. 8. A method according to claim 7, characterized in that the separating gaps (22) open into the notches (20) on both sides of the pressed connecting webs (21').

9. 9. A method according to claim 7 or 8, characterized in that the separating gaps (22) open into the notch tips of the notches (20) on both sides of the squeezed connecting web (21').

10. 10. The method according to any one of claims 7 to 9, characterized in that the cutouts (20) are designed as triangles and form the connecting webs (21) between opposing triangle sides.

11. Method according to any one of claims 7 to 10, characterized in that the notch (20) in the workpiece (16) is punched or cut out using a processing beam.

12. 7. The method according to claim 1, wherein the connecting web (21) is simultaneously punched out with a punching tool (13) and is pressed on one or both sides in the thickness direction (24) of the workpiece (16), at least in the web section (23) adjacent to the workpiece part (19) that has not yet been cut off.

13. Method according to any one of the preceding claims, characterized in that the separating gap (22) is cut out using a machining beam or a punching tool.

14. A control program product comprising code means adapted to perform all the steps of the method according to any one of claims 1 to 13 when the control program is run on a control system (15) of a machine tool (1) suitable for performing all the steps of the method according to any one of claims 1 to 13.

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