Method For Machining a Cutting Insert and Corresponding Device For Machining a Cutting Insert

Abstract

The invention relates to a method for machining a multi-layer workpiece blank (3) by means of a laser beam, comprising the following steps: specifying a machining program for machining the workpiece blank according to an ablation geometry in order to generate a desired edge and/or surface geometry (13) using a laser machining device; tensioning the workpiece blank in the laser machining device and positioning the workpiece holder in a measuring position; measuring a thickness of at least one of the layers of the multi-layer workpiece blank (3); modifying the machining program in order to machine the multi-layer workpiece blank (3) according to the measured layer thickness with an consistent ablation geometry; and machining the tensioned workpiece blank (3) using the modified machining program via a laser of the laser machining device in order to generate the desired edge and/or surface geometry (13) with a cutting edge (12). The invention also relates to a correspondingly configured device.

Claims

1. Method for machining a multi-layer workpiece blank (3) by means of a laser beam, comprising the steps: specifying a machining program for machining the workpiece blank according to an ablation geometry in order to generate a desired edge and/or surface geometry (13) using a laser machining device; tensioning the workpiece blank in the laser machining device and positioning the workpiece holder in a measuring position; measuring a thickness of at least one of the layers of the multi-layer workpiece blank (3); modifying the machining program in order to machine the multi-layer workpiece blank (3) according to the measured layer thick-ness with an consistent ablation geometry; and machining the tensioned work-piece blank (3) using the modified machining program via a laser of the laser machining device in order to generate the desired edge and/or surface geometry (13) with a cutting edge (12).

2. Method for machining a multi-layer workpiece blank by means of a laser beam according to claim 1, characterized in that the step of modifying the machining program comprises the step of adapting the laser control to the measured layer thickness.

3. Method for machining a multi-layer workpiece blank by means of a laser beam according to claim 2, characterized in that the step of modifying the machining program comprises adapting the laser focusing as a function of the measured layer thickness such that the laser does not run out of focus.

4. Method for machining a multi-layer workpiece blank by means of a laser beam according to claim 1, characterized in that the step of modifying the machining program comprises adapting one or more laser parameters and/or the laser guidance as a function of the measured layer thickness.

5. Method for machining a multi-layer workpiece blank by means of a laser beam according to claim 1, characterized in that the step of modifying the machining program comprises the step of adjusting the ablation layer thickness by the laser.

6. Method for machining a multi-layer workpiece blank by means of a laser beam according to claim 1, characterized in that the workpiece blank is a cutting insert blank coated with a hard material and that the method comprises the step of determining the edge position of a cutting edge of the cutting insert blank before measuring the layer thickness, wherein the steps of measuring and machining are carried out in the same position of the tensioned workpiece blank.

7. Laser machining device for machining a multi-layer workpiece blank by means of a laser beam comprising: a memory device for storing a predetermined machining program for machining the workpiece blank as a function of an ablation geometry for generating a desired edge and/or surface geometry by laser machining; a control unit for executing the machining program for machining the workpiece blank as a function of an ablation geometry for generating a desired edge and/or free surface geometry by laser machining; a tensioning device for tensioning the workpiece blank; a positioning device for positioning the workpiece holder in a measuring position; a measuring device for measuring a thickness of at least one layer of the multi-layer workpiece blank; a device for modifying the machining program stored in the memory device for machining the multi-layer workpiece blank as a function of the measured layer thickness with a constant ablation geometry; and a laser device for processing the tensioned workpiece using the modified machining program by means of a laser to generate the desired edge and/or surface geometry (12, 13).

8. Laser device for machining a multi-layer workpiece blank according to claim 7, characterized in that the measuring device for measuring the layer thickness and/or the laser device for machining the tensioned workpiece blank can be tilted relative to the tensioning device by an angular load of up to 120.

9. Laser machining device for machining a multi-layer workpiece blank according to claim 7, characterized in that the control unit (16) is configured to simultaneously perform laser machining and a measurement of the workpiece blank with respect to the layer thickness and/or edge position and/or relative position.

10. Laser machining device for machining a multi-layer workpiece blank according to claim 8, characterized in that the device (18) for modifying the machining program stored in the memory device is configured to automatically adapt the machining program stored in the memory device (17) to the measured layer thickness, laser parameters, laser guidance, laser setting and/or thickness of the ablation layers being adapted by the laser as a function of the layer thickness after measurement of the material layer thickness.

Description

[0053] Further details and advantages of the invention result from the embodiments described below in connection with the drawing. Therein:

[0054] FIG. 1 shows a cutting insert blank tensioned on a workpiece table of a laser machining device in accordance with the invention,

[0055] FIG. 2 shows a view of the cutting insert from FIG. 1,

[0056] FIG. 3 shows a schematic side view of the cutting insert from FIG. 1,

[0057] FIGS. 4a and b show a side view of a cutting insert blank before its edge processing (FIG. 4a) and a cutting insert after exposure of a free surface by means of a laser (FIG. 4b),

[0058] FIGS. 5a and b show a side view of a cutting insert blank before its edge processing (FIG. 5a) and a cutting insert after exposure of a free surface by means of a laser (FIG. 5b) according to a method known in the state of the art.

[0059] FIG. 1 shows an embodiment of a laser machining device according to the invention for machining a multi-layer workpiece blank 3, which is tensioned on a workpiece table 2 of the laser machining device 1.

[0060] The present embodiment, the laser machining device is a machine tool which is configured for 5-axis machining. Accordingly, the three linear axes XYZ and the two rotary axes A, C are drawn in FIG. 1. The machine tool has a control unit 16 which can be used to control a machining program stored in the memory device 17 for laser machining of the insert blank by a laser 9. For this purpose, the machining program stored in the memory device 17 comprises the conventional NC program, which includes the ablation geometry, as well as the necessary laser path guidance and parameterization. The laser parameters for controlling laser settings, such as laser power, laser frequency, pulse duration and feed rate and track speed of the laser are specified according to the ablation geometry.

[0061] In FIG. 1, reference sign 6 identifies a camera which can be used to determine the position of the layers to be machined on the workpiece blank 3 and the position of the blank relative to the workpiece table. Thus, in this embodiment, the machine tool can automatically measure the position of the cutting insert blanks and simultaneously control the laser according to this position alignment. In this way, the machine tool of the present embodiment combines modern 5-axis CNC machining with laser measurement of the workpiece. In this way, the cutting edge, free angle cutting grooves in cutting inserts and end mills, especially those made of PCD or CVD, can be measured and machined in one tensioning so that the productivity is also significantly increased by the method according to the invention. With this type of machining, the free angle can be freely varied within wide limits between 9 and 35. The minimum cutting edge radius can be up to 1 m.

[0062] Due to the exact control according to the actually available layer thickness, optimized cutting edges without chipping result which can contribute considerably to the service life extension of the resulting tools without having to accept losses with regard to cutting edge radius or free angle.

[0063] For the purpose of adapting the machining program, the control unit has an automatic program generation device 18 which cannot only create the original machining program from 3D CAD data, but can also modify the machining program subsequently on the basis of the measured layer thicknesses, also in an automated manner.

[0064] By means of relevant image processing algorithms which are also stored in the memory device 17 and executed by the control unit 16, the correct relative cutting edge position can be determined exactly on the basis of the contrasts of the different material layers of the cutting edge blank. Due to the movability within the scope of 5-axis machining, it is possible without further ado that the cutting insert blank is tilted by 90 for measurement, so that the camera is directed directly to the side area.

[0065] FIG. 2 shows a view of the cutting insert blank from above, wherein position A corresponds to a nominal position on the workpiece table 2 and position B (edges marked with horizontal lines) corresponds to an actual position.

[0066] The image field of the camera 6 is dimensioned such that the cutting insert blank 3, i.e. the preceding face of the cutting surface 4, is scanned by means of this camera 6 or the camera is moved along the edges and the edge position and the position of the corresponding cutting insert blank 3 is determined with high accuracy by means of image processing.

[0067] After determining the position, the cutting insert blank is moved from the actual position B to the nominal position A, for example by moving or tilting the workpiece table 2.

[0068] After this, as schematically shown in FIG. 3, the camera 6 and the cutting insert blank 3 are pivoted 90 relative to each other so that the camera 6 is directed essentially perpendicular to the preceding face of the free surface 5. Both in FIG. 2 and in FIG. 3, the positions at which the respective edge or layer thickness determination is carried out with the camera are marked with a crossed circle.

[0069] The camera 6 detects the hard material layer 7 and the base material 8 by means of relevant image processing algorithms on the basis of the different contrast of these layers and the control unit can thus precisely determine the layer thickness of the hard material layer 7.

[0070] In this embodiment, the position of the cutting insert blank 3, its edge positions and the layer thickness of the hard material layer are determined by means of the same camera 6 in one tensioning of the workpiece blank.

[0071] The camera 6 can be pivotally mounted and/or the entire positioning device or only parts thereof, e.g. the workpiece table 2. This ensures that the cutting insert blank 3 can be tilted in relation to the camera 6.

[0072] After the position of the cutting insert blank 3 on the workpiece table 2 and its edge position and also its layer thickness of the hard material layer are known, a laser beam which is not shown in FIGS. 2 and 3 and which is provided with reference sign 9 in FIG. 4a is now directed from the side of the preceding face of the cutting surface 4 of the cutting insert blank 3 onto a region of the preceding edge of the cutting insert 10 (cf. FIG. 4a) and guided along the preceding edge of the cutting edge 10 substantially parallel to the preceding face of the free surface 11 (cf. FIG. 4a). Here the laser can be moved and/or the cutting insert blank can be moved using the positioning device of the workpiece table shown in FIG. 1.

[0073] FIG. 4a shows a cross-sectional view of the cutting insert blank 3, in which the preceding edge of the cutting edge 10, the preceding face of the free surface 5 and the preceding face of the cutting surface 4, which are formed on the cutting insert blank 3 at a predetermined angle prior to edge machining, are shown schematically, and the respective cutting edge 12, the free surface 13 and the cutting surface 14 which are provided in the finished cutting insert 11, are shown schematically.

[0074] As shown in FIG. 4a, the laser beam 9 is guided along the preceding edge of the cutting edge 10 (perpendicular to the paper plane) and removes material of width b1 in longitudinal direction to the preceding edge of the cutting edge 10 layer by layer (in depth direction).

[0075] When the laser arrives at the interface between the hard material layer 7 and the base material 8, the laser track, the focus position and the thickness of the ablation layer are changed on the basis of the measured layer thickness of the hard material layer 7 according to the machining program of the control unit 16 shown in FIG. 1 and adapted to the material properties of the base material 8.

[0076] By the ablation of the material width b1, the finished cutting insert geometry 11 schematically shown in FIG. 4b in its cross-sectional view is generated with the cutting surface 14, the free surface 13, and the cutting edge 12.

[0077] By adapting the laser guidance to the respective insert blank 3 on the basis of the layer thickness information, a comparatively small offset can be generated or, as shown in FIG. 4b, an offset between hard material layer 7 and base material 8 can be completely avoided.

[0078] The hard material layer preferably consists of polycrystalline diamond, other hard materials can be: cubic BN, TiC, TiV WC, TaC. The hard material layer is preferably a ceramic layer.

[0079] A carbide metal is preferably used as the base material. Materials for the base material can be: hardened steel, high-strength alloys.

[0080] The thickness of the hard material layer is preferably between 30 and 1000 m, in particular 50 and 800 m, preferably 100 to 700 m, in particular approx. 400 m.

[0081] As an alternative to a single layer of a base material, one or more further layers may also be provided between the base material 8 and the hard material layer 7. In this case, the laser parameters or laser guidance of the machining program can be adapted to the thickness of at least one or more layers, or each corresponding layer, and an analogous procedure as described above for the two-layer material can be carried out.

REFERENCE SIGN LIST

[0082] 1 edge machining device

[0083] 2 workpiece table

[0084] 3 workpiece blank

[0085] 4 preceding face of the cutting surface

[0086] 5 preceding face of the free surface

[0087] 6 camera

[0088] 7 hard material layer

[0089] 8 base material

[0090] 9 laser

[0091] 9a laser beam

[0092] 10 preceding edge of the cutting edge

[0093] 11 cutting insert

[0094] 12 cutting edge

[0095] 13 free surface

[0096] 14 cutting surface

[0097] 15 interface

[0098] 16 control unit

[0099] 17 memory device

[0100] 18 machining program generation device

[0101] 100 cutting insert blank

[0102] 101 base material layer

[0103] 102 hard material layer

[0104] 103 preceding face of the cutting surface

[0105] 104 preceding edge of the cutting edge

[0106] 106 laser beam

[0107] 107 offset

[0108] 108 offset

[0109] B actual position

[0110] A nominal Position

[0111] b1 material width