METHOD AND DEVICE FOR CUTTING A WORKPIECE

Abstract

The invention relates inter alia to a method for cutting a workpiece, in particular a blank or a component, comprising the following steps: inserting the workpiece (3) into a cutting device, wherein the cutting device comprises a first tool half (1) having at least one workpiece holder (12) and at least one first cutting means (11), which comprises a first cutting edge (111) and a contact surface (112), and a second tool half (2) having at least one second cutting means (21) having a second cutting edge (211) and a contact surface (212), clamping the workpiece (3) by means of the workpiece holder (12) and the contact surface (212) of the second cutting means, cutting the workpiece (3) by means of the cutting means (11, 21), the workpiece (3) undergoes, prior to cutting, both a first prebending, which is produced substantially in the opposite direction counter to the cutting direction, and thereafter a second prebending in the cutting direction.

Claims

1. A method for cutting a workpiece, in particular a blank or a component, comprising the following steps: inserting the workpiece (3) into a cutting device, in particular into a device as claimed in one of claims 10 to 15, wherein the cutting device comprises a first tool half (1) having at least one workpiece holder (12) and at least one first cutting means (11), which comprises a first cutting edge (111) and a contact surface (112), and a second tool half (2) having at least one second cutting means (21) having a second cutting edge (211) and a contact surface (212), clamping the workpiece (3) by means of the workpiece holder (12) and the contact surface (212) of the second cutting means, cutting the workpiece (3) by means of the cutting means (11, 21), characterized in that the workpiece (3) undergoes, prior to cutting, both a first prebending, which is produced substantially counter to the cutting direction, and a second prebending in the cutting direction.

2. The method as claimed in claim 1, characterized in that the tensile stress in the workpiece (3) that is produced by the first prebending is less than its yield point, substantially corresponds to its yield point or is greater than its yield point.

3. The method as claimed in claim 1 or 2, characterized in that the workpiece (3) undergoes the first prebending during clamping between the workpiece holder (12) and the contact surface (212) of the second cutting means (21).

4. The method as claimed in one of claims 1 to 3, characterized in that the workpiece (3) undergoes the second prebending during lowering of the first cutting means (11) and while the contact surface (112) of the first cutting means (11) comes into contact with the workpiece (3).

5. The method as claimed in one of claims 1 to 4, characterized in that the first and/or the second prebend are/is elastic.

6. The method as claimed in one of claims 1 to 5, characterized in that the second prebending of the workpiece (3) occurs in the opposite direction to the first prebending.

7. The method as claimed in one of claims 1 to 6, characterized in that an open cut is produced by the cutting operation by means of the cutting means (11, 21).

8. The method as claimed in one of claims 1 to 6, characterized in that a closed cut is produced by the cutting operation by means of the cutting means (11, 21).

9. The method as claimed in one of claims 1 to 8, characterized in that the method is a one-stage method.

10. A device for cutting a workpiece, in particular a blank or a component to be trimmed, in particular for carrying out a method as claimed in one of claims 1 to 9, having a first tool half (1) and a second tool half (2), wherein the first tool half (1) comprises at least one workpiece holder (12) and at least one first cutting means (11) having a first cutting edge (111) and a contact surface (112), and wherein the second tool half (2) comprises at least one second cutting means (21) having a second cutting edge (211) and a contact surface (212), characterized in that the contact surface (212) of the second cutting means (21) rises from a substantially planar level, forms a convex region (213) and falls again toward the second cutting edge (211) of the second cutting means (21).

11. The device as claimed in claim 10, characterized in that the contact surface (211) of the first cutting means (11) is of oblique design.

12. The device as claimed in one of claims 10 to 11, characterized in that the first cutting edge (111) and/or the second cutting edge (211) have/has an obtuse angle, wherein, for the open cut, the angle of the first cutting edge (111) preferably corresponds to that of the second cutting edge (112).

13. The device as claimed in one of claims 10 to 12, characterized in that the first cutting edge (111) and/or the second cutting edge (112) have/has an obtuse angle, wherein, for the closed cut, the angle of the first cutting edge (111) is preferably less than the angle of the second cutting edge (112).

14. The device as claimed in one of claims 10 to 13, characterized in that the first and/or the second cutting edge (111, 112) are/is rounded, wherein preferably the first and the second cutting edge (111, 112) are differently rounded.

15. The device as claimed in one of claims 10 to 14, characterized in that a gap is provided between the workpiece holder (12) and the first cutting means (11), wherein the gap is preferably chosen to be of such size that the workpiece holder (12) is situated behind the highest point of the convex region (213) of the contact surface (212).

16. The device as claimed in one of claims 10 to 15, characterized in that the contact surface of the workpiece holder (12) is designed to be complementary and/or offset in relation to the shape of the contact surface (212) of the second cutting means (21).

Description

[0047] The invention will be further explained below on the basis of an exemplary embodiment with reference to the drawing, in which

[0048] FIG. 1 shows a full section of an exemplary embodiment of a device according to the invention in a schematic illustration during the method step of insertion,

[0049] FIG. 2 shows a full section of the device in a schematic illustration during the method step of clamping and of introducing a first prebend in the workpiece to be cut,

[0050] FIG. 3 shows a full section of the device in a schematic illustration during the application of the first cutting means to a workpiece to be cut,

[0051] FIG. 4 shows a full section of the device in a schematic illustration during the further lowering of the first cutting means and the introduction of a second prebend into the workpiece to be cut,

[0052] FIG. 5 shows a full section of the device in a schematic illustration during the common impingement of the first and second cutting edge on the workpiece,

[0053] FIG. 6 shows a full section of the device in a schematic illustration directly after the method step of cutting, and

[0054] FIG. 7 shows a full section of the device in a schematic illustration during the method step of removal.

[0055] FIG. 1 shows a full section of an exemplary embodiment of a device according to the invention in a schematic illustration during the method step of insertion. The device carries out an exemplary embodiment of a method according to the invention. The device has a first upper tool half 1 having a first cutting means 11 in the form of an upper blade, which comprises a first cutting edge 111 and a contact surface 112, and a workpiece holder 12 in the form of a holding-down means. In addition, the device has a second tool half 2 having a second cutting means 21 in the form of a lower blade, which comprises a second cutting edge 211 and a contact surface 212. The first tool half 1 preferably consists of a lowerable composite part which is as solid as possible and which can be lowered in a substantially vertical movement. Here, the workpiece holder 12 and the first cutting means 11, wherein the first cutting edge 111 adjoins the contact surface 112, can be lowered vertically separately from one another. The second tool half 2 is substantially in one piece, wherein the second cutting edge 211 adjoins the contact surface 212, which has a convex region 213.

[0056] Furthermore, the first tool half 1 preferably has guide elements (not shown) which allow an exact relative movement and cutting gap setting between the two tool halves 1 and 2. A workpiece 3 in the form of a sheet metal blank is inserted into the device. The contact surface 212 of the second cutting means 21 rises starting from a substantially planar level, in particular the region directed away from the cutting edge 211 (right part of the second cutting means 21), forms, in particular close to or in the region directed toward the cutting edge 211 (left part of the second cutting means 21), a convex region, and falls again toward the second cutting edge 211 of the second cutting means 21. The contact surface 112 of the first cutting means 11 starts substantially from a planar level, in particular the region directed away from the cutting edge 111 (left part of the first cutting means 11), and transitions into an inclined region in particular close to or directed toward the cutting edge 111 (left part of the first cutting means 11).

[0057] When carrying out the cutting operation, as illustrated in FIG. 2 and following figures, at first the tool holder 12 is applied to the workpiece 3 and presses it with sufficiently large pressing force against the contact surface 212 such that the workpiece 3 to be cut is fixed in such a way that slipping or cold flow is substantially prevented. With the lowering of the workpiece holder 12, the workpiece 3 simultaneously undergoes a first, preferably elastic upward prebending.

[0058] Then, as illustrated in FIG. 3, the first cutting means 11 moves further downward while the workpiece holder 12 remains applied to the workpiece 3. By virtue of the oblique shape of the first cutting means 11, the latter initially impinges the workpiece 3 by way of a contact surface 112 which leads in relation to the first cutting edge 111 and bends the workpiece 3 downward in its further downward movement (second prebending).

[0059] FIG. 4 shows the intermediate state during lowering of the cutting means 11. It is evident that even at this time there is still no contact between the two cutting edges 111, 211 and the workpiece 3 although the workpiece 3 is already in a relatively intensely prebent state.

[0060] The described bending stresses produce an increasing, particularly high bending stress in the region of the cut contour to be produced, both in the effective region of the first and of the second cutting means 11, 21. With further downward movement. the tensile stress increases, with the tensile stress produced preferably being less than the tensile strength of the workpiece or being able to be preferably close thereto.

[0061] As illustrated in FIG. 5, the first and the second cutting edge 111, 211 then impinge the workpiece 3 and begin to apply a shear stress thereto. The shear stress, together with the introduced tensile stress, produces an equivalent stress which leads to material separation. This is illustrated in FIG. 6. Upon conclusion of the separating operation, the previously bent workpiece portions 31, 32 relax again until, ideally, they finally completely spring back again into their initial shape, as shown in the removal position in FIG. 7.

[0062] The cutting operation described in this respect is accompanied by low forces on the cutting edges and by little tool wear. High separating surface or cut face qualities are achieved. The illustrated cutting device is preferably integrated into the deep-drawing and trimming operations of a press that are necessary in any case.