WORKPIECE HOLDER AND METHOD FOR MANUFACTURING A ROTATIONAL-SYMMETRICAL TOOL

Abstract

Workpiece holder (3) for coupling a workpiece (2) provided with reference surfaces (30) to a machining device (200) for manufacturing a rotational-symmetrical tool (1) with at least one geometrically defined cutting edge (10), the workpiece holder (3) comprises a machine part (31) configured to be connectable to the machining device (200) in a releasable rotationally fixed manner, a clamping part (32) configured to receive and clamp the workpiece (2) in a releasable manner. The clamping part (32) of the workpiece holder (3) comprises at least one slot (40) provided at a circumference thereof and configured to provide access to the reference surfaces (30) of the clamped workpiece (2) therethrough.

Claims

1. Workpiece holder for coupling a workpiece provided with reference surfaces to a machining device for manufacturing a rotational-symmetrical tool with at least one geometrically defined cutting edge, the workpiece holder comprising: a machine part configured to be connectable to the machining device in a releasable rotationally fixed manner, and a clamping part configured to receive and clamp the workpiece in a releasable rotationally fixed manner, wherein the clamping part of the workpiece holder comprises at least one slot provided at a circumference thereof and configured to provide access to the reference surfaces of the clamped workpiece therethrough.

2. Workpiece holder according to claim 1, wherein the clamping part of the workpiece holder comprises a conical or cylindrical part and a radial flange part configured to form interfaces with compatible formed reference surfaces of the clamped workpiece.

3. Workpiece holder according to claim 1, wherein the at least one slot is configured as an elongated slot extending partly in a direction of a longitudinal axis of the workpiece holder and is configured such that a measuring probe of a measuring device can be inserted therethrough so as to directly contact at least part of the reference surfaces.

4. Workpiece holder according to claim 1, wherein the at least one slot is configured such that a non-contact measuring of the reference surfaces by an optical measuring device is performed.

5. Workpiece holder according to claim 1, said at least one slot comprising a plurality of slots.

6. Workpiece holder according to claim 1, wherein the workpiece holder is configured to hold the workpiece while machining a functional part of the rotational-symmetric tool.

7. Workpiece holder according to claim 1, wherein the workpiece holder is configured to hold the workpiece while machining at least one cutting tip connected to a base body of the workpiece to create the at least one geometrically defined cutting edge of the rotational-symmetrical tool.

8. Workpiece holder according to claim 1, wherein the rotational-symmetrical tool is a ball track milling cutter.

9. Workpiece holder according to claim 1, further comprising at least one cam at a first circumferential diameter and/or a notch (37) at a second circumferential diameter thereof, which cam and/or notch is configured to trigger at least one measurement process in a predetermined position of the workpiece holder in the machining device.

10. Workpiece holder according to claim 9, wherein the workpiece holder provides measurement of a displacement of a rotational axis of the machining device and a workpiece axis.

11. Method for manufacturing a rotational-symmetrical tool with at least one geometrically defined cutting edge using the workpiece holder according to claim 1, the method comprising the following steps: connecting the machine part of the workpiece holder to a clamping system of the machining device in a releasable rotationally fixed manner; connecting a mounting part of the workpiece to the clamping part the workpiece holder in a releasable rotationally fixed manner; performing at least one measurement process and generating measurement data of the clamped workpiece by introducing a measuring probe of a measuring device through said at least one slot provided at the circumference of the workpiece holder to contact the reference surfaces of the clamped workpiece, processing the measurement data to obtain a real orientation of the workpiece axis for correcting detected displacements between a rotational axis of the machining device and the workpiece axis (W), processing the measurement data to obtain a curve of the at least one geometrically defined cutting edge of the rotational-symmetric tool related to the reference surfaces of the workpiece for manufacturing the rotational-symmetrical tool by the machining process.

12. Method according to claim 11, wherein processing the measurement data includes calculating a virtual plane of a real positioned cutting tip of the workpiece and using the virtual plane of the real positioned cutting tip to obtain the curve of the at least one geometrically defined cutting edge as an intersection line of a predetermined envelope surface of a functional part of the rotational-symmetrical tool with the virtual plane of the real positioned cutting tip of the workpiece.

13. Machining device for manufacturing a rotational-symmetrical tool, comprising: a control unit, a machining tool, a clamping system configured to receive and connect the workpiece holder according to claim 1 in a releasable rotatable fixed manner, and a measuring device comprising a measuring probe configured to be inserted through the at least one slot provided at the circumference of the workpiece holder so as to directly perform measuring of the reference surfaces of the clamped workpiece.

14. Machining device according to claim 13, wherein the machining device is a multiple axis grinding device.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0038] For a more complete understanding of the invention and the advantages thereof, exemplary embodiments of the invention are explained in more detail in the following description with reference to the accompanying figures, in which like reference characters designate like parts and in which:

[0039] FIG. 1 is a schematic perspective view of a rotational-symmetrical cutting tool, in particular a ball track milling cutter;

[0040] FIG. 2 is a schematic perspective view of a workpiece holder according to a first embodiment of the invention;

[0041] FIG. 3 is a schematic longitudinal section view of the workpiece holder according to the first embodiment of the invention and a workpiece inserted therein;

[0042] FIG. 4 is a schematic section view of the workpiece holder of the first embodiment with a mounted workpiece and a measuring probe during a measurement process;

[0043] FIG. 5 is a schematic side view of a ball track milling cutter showing real and ideal positions of cutting tips of a rotational-symmetrical tool with a plurality of geometrical defined cutting edge;

[0044] FIG. 6 is a schematic perspective view of parts of a grinding device to machine a workpiece into a cutting tool showing the workpiece clamped into the workpiece holder according an embodiment shown in FIG. 2;

[0045] FIG. 6a is a detail of the grinding device shown in FIG. 6.

DETAILED DESCRIPTION OF THE DRAWING

[0046] FIG. 1 shows a perspective view of a head part of rotational-symmetrical tool 1 with at least one geometrically defined cutting edge 10, here a total of four geometrically defined cutting edges 10, only one of which is designated. A plurality of cutting edges 10 is evenly spaced in circumferential direction and preferably each geometrically defined cutting edge 10 is identical designed. The cutting edge 10 can be formed as an intersection line between a rake face 10a and a flank face 10b which are respectively associated with the cutting edge 10 and which can include a chamfer 10c.

[0047] The rotational-symmetrical tool 1 can be a ball track milling cutter 100, which is configured to be received and held in a tool holder of a milling device, in particular clamped in a spindle of the milling device. The rotational-symmetrical tool 1 comprises a mounting part 12, referred as well as a shaft portion and a functional part 14 provided with at least one geometrically defined cutting edge 10 at a head portion 18 of the rotational-symmetric tool 1. The head portion 18 includes a base body 16, preferably made of steel or carbide and a plurality of the geometrical defined cutting edges 10 forming the functional part 14 of the tool 1. Hereinafter, the term functional part 14 describes the finished functional part 14 of the tool 1 but as well a raw functional part 14 of a workpiece to be machined into the finished functional part 14 of the tool 1. In the embodiment shown in FIG. 1 the cutting edges 10 are formed on cutting tips 15 connected to the base body 16, preferably by soldering or brazing. The cutting edge 10 comprises or is made of a hard material which can be selected from the group consisting of cubic boron nitride (CBN), polycrystalline cubic boron nitride (PCBN) and polycrystalline diamond (PCD).

[0048] The cutting edges 10 of the functional part 14 can be manufactured by removing material from the connected cutting tip 15 made of hard material by grinding, by means of laser or an erosion process. The cutting edge 10 is machined, preferably ground, on each cutting tip 15 already fastened to the base body 16. The grinding process can be performed in an automated multiple axis grinding machine controlled by a control unit and according to a programmable computer program product. Manufacturing the at least one geometrically defined cutting edge 10 with a defined cutting profile by removing material from the cutting tip 15 is an object of the method of the invention.

[0049] The head portion 18 has an imaginary center axis M which corresponds to a rotational axis of the tool 1 during the intended machining of workpiece in a tool device. Furthermore, the head portion 18 has a working-end side 19 and a clamping-end side 20 as the mounting part 12 opposite the working-end side 19 along the central axis M. The working-end side 19 of the ball track milling cutter 100 shown in FIG. 1 faces the workpiece intended to be machined by a milling device.

[0050] On the opposite end to the working-end side 19 of the rotational-symmetrical tool 1, preferably the ball track milling cutter 100, i.e. at the clamping-end side 20 the mounting part 12 is provided, preferably configured as the shaft portion. It is mentioned that the mounting part 12 including the clamping-end side 20 of the tool 1 is manufactured previous to manufacturing the functional part 14 thereof., Therefore, the mounting part 12 of a workpiece 2 (not shown in FIG. 1) corresponds to the finished tool 1. In the embodiment shown, the mounting part 12 is cylindrical but can be as well configured conical in the direction to the clamping-end side 20. The clamping-end side 20 can include an internal thread 21 connectable to a complementary thread part provided by holding means of the machining device. The clamping-end side 20 can be configured in different forms such as providing an external thread or the like wherein the clamping-end side 20 can be fastened to the holding means securely and in a releasable rotationally fixed manner.

[0051] The mounting part 12 including the shaft portion which can be integrally attached to the head part 18 of the tool 1 comprises towards the head part 18 a first seating face 23, which in the clamped position bears against an end face of the holding means (not shown). The first seating face 23 can be configured as a radial portion merging to the shaft portion 12 and configured as a conical or annular face providing a shoulder. Between the first seating face 23 and the clamping-end side 20 a conical or cylindrical formed second seating face 24 is provided. The conical or cylindrical second seating face 24 and the first seating face 23 form interfaces in axial and radial direction with compatible formed portions of the holding means when the mounting part 12 is inserted and fastened into the holding means of the machining device. The conical or cylindrical second seating face 24 and the radial formed first seating face 23 form reference surfaces 30 of the tool 1 and as explained of the workpiece 2 (not shown in FIG. 1).

[0052] However, manufacturing the rotational-symmetrical tool 1 is a multiple step process. In a previous step the rotational-symmetrical workpiece 2 (not shown in FIG. 1) with a central workpiece axis W (not shown in FIG. 1) is processed to form the clamping-end side 20, the first seating face 23 and the second seating face 24 providing the reference surfaces 30 and configured to be connectable to holding means such as a workpiece holder 3 (not shown in FIG. 1).

[0053] FIG. 2 shows a perspective view of the workpiece holder 3 of a preferred embodiment. The workpiece holder 3 comprises a machine part 31 and a clamping part 32. In accordance with the shown embodiment of the workpiece holder 3, the machine part 31 is insertable into a clamping system (not shown in FIG. 2) of a machining device. The rotational-symmetrical workpiece 2 (not shown in FIG. 2) may be attached to the clamping part 32 of the workpiece holder 3 in a releasable rotationally fixed manner. The workpiece holder 3 comprises on the machine part 31 a conical or cylindrical portion 33 and a radial flange portion 34. As shown in FIG. 2 the radial flange portion 34 is located between the machine part 31 and the clamping part 32. The conical or cylindrical portion 33 extends along a longitudinal axis WH of the workpiece holder 3. In the case of a conical shaped portion 33, the conical shape is inclined in a predetermined angle and assists in centering the workpiece holder 3 in the clamping system of the machining device. The radial flange portion 34 may be formed as a shoulder providing an end surface 34a perpendicular to the longitudinal axis WH of the workpiece holder 3 and forming an abutment or bearing face with the clamping system of the machining device when the workpiece holder 3 is clamped.

[0054] For connecting the workpiece holder 3 to the machining device the damping system thereof can comprise drawback fingers or segmented collets which are configured with clamping surfaces structured and arranged to engage an inner surface of the workpiece holder 3. The drawback fingers can be forced radially outwards to clamp for example a hollow shank workpiece holder 3 in the damping system of the machining device. The hollow shank workpiece holder 3 may be designed as a known hollow shank tool holder HSK.

[0055] According to FIG. 2 the workpiece holder 3 comprises at an outer circumferential diameter 35a a cam 36 protruding from the circumferential diameter 35a. Furthermore, in the embodiment shown, a notch 37 is provided at a second circumferential diameter 35b. When the workpiece holder 3 is received and securely connected by the clamping system of the machining device in a releasable rotationally fixed manner the workpiece holder 3 as well as the cam 36 and/or the notch 37 can be rotated about the longitudinal axis WH of the workpiece holder 3. At a predetermined position the cam 36 and/or the notch 37 triggers a measuring device 50 (not shown in FIG. 2) comprising a measuring probe 51 (not shown in FIG. 2) to be moved from a rest position to a measuring position. In the measuring position the measuring probe 51 gets direct contact to the reference surfaces 30 of the clamped workpiece 2. The movement of the measuring probe 51 can be controlled by a controller (not shown in FIG. 2).

[0056] As shown in FIG. 2, the workpiece holder 3 comprises at the clamping part 32 a series of slots 40 arranged at a circumference, preferably evenly arranged around the circumference and identical designed. Each slot 40 extends about a predeterminable length from a clamping part end 32a towards the machine part 31 parallel to the longitudinal axis WH of the workpiece holder 3. In one preferred embodiment, each slot 40 has a width 41 adequate to allow passage of the measuring probe 51 to contact portions of the clamped workpiece 2, in particular to get direct access to the reference surfaces 30 of the workpiece 2. The number and arrangement of the slots 40 can vary, preferably the number is at least 3 slots 40 which can be distributed evenly about the circumference of the workpiece holder 3.

[0057] FIG. 3 shows a schematic longitudinal section view of the workpiece holder 3 shown with the workpiece 2 inserted and clamped by the clamping part 32 of the workpiece holder 3. The machine part 31 of the workpiece holder 3 is configured with an opening 31a at the end configured and arranged to receive parts of the clamping system of the machining device. The workpiece 2 including the reference surfaces 30, in particular the first seating face 23 extending in radial direction and the second seating face 24 extending in axial direction seen from the central workpiece axis W is inserted in the workpiece holder 3 such the first seating face 23 and the second seating face 24 forms interfaces with complementary formed faces of the workpiece holder 3, respectively. Therefore, the workpiece holder 3 provides at his clamping part 32 a radial part and a conical or cylindrical part at least partially formed complementary to the first seating face 23 and the second seating face 24 of the workpiece 2 such that a secure seating of the workpiece 2 in the workpiece holder 3 is provided. The radial part and the conical or cylindrical part of the workpiece holder 3 is not visible in FIG. 3.

[0058] The workpiece 2 is fastened in the workpiece holder 3 by means of fixation means 38 provided by the workpiece holder 3. The fixation means 38 can be configured with a thread to be connectable to the thread formed at the clamping-end side 20 of the workpiece 2.

[0059] FIG. 4 shows a longitudinal section view of the workpiece holder 3 with the inserted and damped workpiece 2 and a measuring probe 51 during a measuring process. As can be seen in FIG. 4, the workpiece 2 is in axial and radial direction positioned in the workpiece holder 3 such that the longitudinal axis WH of the workpiece holder 3 and the central axis W of the workpiece 2 are aligned.

[0060] By triggering the measuring process performed in a controlled manner by the measuring device 50 the measuring probe 51, preferably a 3D measuring probe with a spherical measuring head, is moved from a rest position to a so measuring position. In one of the measuring positions the measuring probe 51 is partially inserted into the at least one slots 40 provided at the workpiece holder 3 and configured to allow partial passage of the measuring probe 51 therethrough to directly contact the reference surfaces 30 of the clamped workpiece 2. The inserted measuring probe 51 contacting the reference surfaces 30 of the clamped workpiece 2 allows measurements in different directions and in different orientations not only by contacting the reference surfaces 30 but as well by moving on the reference surfaces 30. Different measurement points 52 are shown, wherein a plurality of the measurement points 52 can be located at the reference surfaces 30, in particular the first seating face 23 and the second seating face 24 of the workpiece 2, and a plurality of measuring points 52 can be located at the raw functional part 14 of the workpiece 2, in particular at different positions on the cutting tip 15.

[0061] By measuring at different points 52 the virtual plane of the real positioned cutting tip and/or a virtual centrum of the central workpiece axis W of the clamped workpiece 2 may be calculated from the measurement data. To ensure correct orientation of the workpiece 2 clamped in the workpiece holder 3 the rotation of the workpiece 2 about an axis of the machining device may be simulated and monitored by the inserted measuring probe 51 as well as calculated by a controller. Furthermore, by measuring on the cutting tip 15 on at least 3 measuring points 52 the real position of the cutting tip 15 can be determined. The measuring data can be used for calculating an ideal shaped and positioned geometrical defined cutting edge 10 and for manufacturing this geometrically defined cutting edge 10 by grinding or lasering.

[0062] FIG. 5 shows a schematic side view of the ball track milling cutter 100 showing a real position 60 of the cutting tip 15 and/or the cutting edge 10 and an ideal position 70 of the cutting tip 15 and/or the cutting edge 10. The real position 60 of the cutting tip 15 can be seen as a result of the connecting process of the cutting tip 15 to the base body 16, for example by soldering or brazing as well as of the original form of the cutting tip 15 to be connected. According to one embodiment, the geometrically defined cutting edge 10 is produced on the cutting tip 15, preferably after connecting the cutting tip 15 to the base body 16. The cutting tip 15 connected to the base body 16 usually have a circular or oval form and provides enough material which can be removed to for an ideal profile of the geometrically defined cutting edge 10.

[0063] Manufacturing the cutting edge 10 can be performed by a method according to the invention including measuring the real position 60 of the cutting tip 15. The method can be controlled by a control unit such that a computer program product is running on the control unit or another computing device set up for controlling a machining device such as a grinding device and operatively connected with the machining device. The machining device preferably comprises the control unit or computing device that runs the computer program and a data storage device.

[0064] FIG. 6 is a schematical perspective view of parts of a machining device 200, in particular a grinding machine with a grinding wheel 201. The grinding machine 200 comprises inter alia a clamping system 202 to receive and clamp the workpiece holder 3. The workpiece holder 3 is configured to be releasable rotatable fixed to the grinding device 200, in particular to the clamping system 202. The workpiece 2 is inserted and hold in the workpiece holder 3. Furthermore the measuring device 50 is arranged such that the measuring probe 51 of the measuring device 50 can be moved from a rest position (shown) into a measuring position, wherein the measuring probe 51 is partially inserted through at least one slot 40 or openings provided at the workpiece holder 3. The at least one slot 40 is provided such that the measuring probe 51 can contact reference surfaces 30 provided at the workpiece 2 which are at least partially covered by the workpiece holder 3. As indicated in the FIG. 6 the machine device 200 comprises a control unit 210, configured to control the performance of the machining device 200 but as well as controlling measurement process of the measurement device 50. The central axis W of the workpiece 2 and the longitudinal axis WH of the workpiece holder 3 are aligned with the rotational axis M of the machining device 200. Small misalignments of the axes will be measured by the measuring probe 51 and can be considered by processing the measurement data according to the method described.

[0065] FIG. 6a shows a detail of the clamped workpiece 2 hold in the workpiece holder 3. The slots 40 provided at the workpiece holder 3 are arranged and configured that measurement of the reference surfaces 30 are possible even if at least part of the reference surfaces 30 are covered by the workpiece holder 3.