Workpiece holder and method for manufacturing a rotationally symmetrical tool

Abstract

A workpiece holder (3) for coupling a workpiece (2) provided with a reference surface (30) to a machining device (200) for manufacturing a rotationally symmetrical tool (1) having at least one geometrically defined cutting edge (10), the workpiece holder (3) comprising: a machine portion (31) configured to be connectable in releasable rotational fixed manner to the machining device (200); a clamping portion (32) configured to releasably receive and clamp the workpiece (2). The clamping portion (32) of the workpiece holder (3) comprises at least one slot (40) provided at a circumference of the workpiece holder and configured to provide access through the at least one slot to the reference surface (30) of the clamped workpiece (2). The disclosure further relates to a method for manufacturing a rotationally symmetrical tool and a machining device.

Description

TECHNICAL FIELD

[0001] The present invention relates to a workpiece holder for manufacturing a substantially rotationally symmetrical tool, such as a drill and / or a milling cutter, in particular a ball raceway milling cutter for producing a ball raceway in a constant velocity joint. Furthermore, the present invention relates to a method for manufacturing a rotationally symmetrical tool and a machining device. BACKGROUND

[0002] The manufacturing of a rotationally symmetrical tool, such as a drill and / or a milling cutter, e.g. a ball raceway milling cutter and / or a radius end milling cutter, is a multi-step process which is performed in more than one machining device. At least one of these steps comprises the temporary holding of a workpiece, such as a rotationally symmetrical workpiece, in a defined position relative to the rotation axis of the machining device and relative to the machining tool, such as a grinding wheel, during grinding or in a laser unit. The holding device for temporarily holding the workpiece during machining is considered to be a source of multiple errors. In order to machine the workpiece from all sides, the workpiece is rotated around the rotation axis of the machining device, wherein the rotation axis and the longitudinal or central axis of the workpiece are preferably identical. In practice, the parts of the holding device which are held in the clamping mechanism of the machining device exhibit fitting tolerances and other tolerances, and there are tolerances for clamping the workpiece in the holding device. Especially when the workpiece is measured from the outside, the machining process has to be interrupted and the repeatability of the clamping can be another source of errors. Furthermore, thermal effects during machining can change the position of the holding device relative to the clamping mechanism of the machining device and relative to the machining tool. All these effects can affect the repeatability and accuracy of manufacturing a rotationally symmetrical tool of high quality and precision.

[0003] High-precision ball raceway milling cutters are used for machining ball raceways or track profiles for forming bearing balls at the circumferential side of a cylindrical assembly of a homokinetic joint. One type of homokinetic joint comprises a spherical inner shell with grooves or tracks therein and a similar outer shell, wherein each groove or track guides one bearing ball. Homokinetic joints, also called constant velocity joints, are particularly used in the automotive sector to allow a drive shaft to transmit power through variable angles at a constant rotational speed without significantly increasing friction or play.

[0004] Manufacturing a ball path milling tool involves processing a workpiece in different processing devices, for example creating a mounting portion in one processing device and forming a functional portion thereof by grinding, laser or other suitable processing in another processing device. In order to manufacture the functional portion of a ball path milling tool forming a milling head portion, the workpiece can not be held in a tool holder for a milling device, but rather in a temporary holding device. Common methods for avoiding errors and achieving the precise geometry of the functional portion by manufacturing a ball path milling tool include measuring the raw functional portion of the workpiece prior to processing and / or relying on the utmost geometric accuracy of the interface between the pre-fabricated reference surface of the workpiece and the temporary holding device. However, it is known that each interface between the processing device and the workpiece and each change of the holding device causes geometric errors which will limit the achievable precision of the finish machining cutting tool and thus can limit the precision of the performance of the finish machining cutting tool.

[0005] Patent document DE 102005007038 discloses a tool grinder having a workpiece spindle stock to receive a workpiece in a collect to provide compensation for inaccuracies. In order to correct and / or compensate for inaccuracies, the spindle is configured to allow the collect and thus the workpiece to be motorized aligned normal to the spindle axis by mechanically changing the position of the workpiece. However, the adjustment related to the diameter is limited to compensate only for small inaccuracies in a limited degree of freedom.

[0006] An adjustment method for minimizing run-out of a workpiece for a machine tool is described in patent document EP 2311600. The workpiece is held in a workpiece holding mechanism whereby a floating mechanism transmits rotation of a workpiece spindle to the workpiece holding mechanism and allows the workpiece holding mechanism to move relative to the workpiece spindle. The adjustment method includes adjusting the run-out of the workpiece while rotating and adjusting the workpiece and the rotational axis of the processing device horizontally. The adjustment method is complex, delicate and is also limited to only two translational degrees of freedom. Inaccuracies between the clamping diameter and the diameter to be processed cannot be adjusted.

[0007] Tool holders for reversibly fastening to a machining device and for reversibly receiving a tool, such as a milling cutter, are known. Such tool holders or collet chucks or collet holders can be implemented in a multi-part form. Typically, the tool holder comprises a machine or holding part for reversibly fastening the tool holder to a machining device, i.e. a machine spindle, and a clamping part for reversibly receiving a tool. Further, the machining part can comprise shaped parts, such as conical parts and radially protruding parts, which provide abutment faces to corresponding counter faces of a clamping mechanism of the machining device. One known type of tool holder is referred to as HSK holder (hollow shank taper), which provides a double contact between the tool holder and the clamping mechanism of the machining device. Known HSK holders provide high repeatability and accuracy as well as fast tool change and are only slightly affected by temperature variations.

[0008] A rotationally symmetrical tool received in the tool holder can comprise at least two parts, such as a mounting part or engagement part having a shaft section, and a functional part or cutting part, such as a milling head, having at least one cutting edge for removing material from a workpiece to be machined. The tool holder, adapter, spacer, extension, etc. for holding the tool or the machine tool spindle itself can be configured to the mounting part of the tool and can vary accordingly. The mounting part of the tool received and securely held in the tool holder forms an interface to the tool holder. For stability, stiffness and dimensional accuracy, the interface between the tool and the tool holder is of great importance. The interface can comprise reference surfaces designed according to vendor specification, for example.

[0009] A function part of a rotationally symmetrical tool, such as a milling cutter, has at least one geometrically defined cutting edge, wherein the cutting edge can be formed as an intersection line between a rake face and a flank face. Different types of milling cutters are known. For example, one type (of milling cutter) is configured as a solid tool comprising a base body, wherein the at least one cutting edge is formed integrally with the base body. Another type is configured such that the cutting edge can be formed on a cutting tip or a cutting plate configured as a single piece of material, which is brazed, soldered, welded or clamped to a base body made of a different material. Preferably, the cutting tip is made of a hard material such as cubic boron nitride (CBN), polycrystalline cubic boron nitride (PCBN) or polycrystalline diamond (PCD), whereby the base body can be made of a material providing toughness, such as steel or carbide. Typically, this type of milling cutter is machined to produce a cutting edge on each individual cutting tip, for example meeting a predetermined envelope surface, which contributes to the final machined surface. SUMMARY

[0010] It is an object of the present invention to provide a workpiece holder for temporarily holding a workpiece. The workpiece holder as a holding device is used in a machining device, in particular a grinding device or a laser device, for manufacturing at least a part of a substantially rotationally symmetrical tool, for example a shank tool or preferably a milling cutter, such as a ball path milling cutter, by grinding and / or laser. The workpiece holder can be received and fastened in the machining device and is configured such that a position and / or orientation of the workpiece in a clamped position can be measured or adjusted to avoid errors in the accuracy of the finished machined tool.

[0011] It is a further object of the present invention to provide a method for manufacturing such a rotationally symmetrical tool, which method comprises a measurement step performed at the workpiece while the workpiece is held in the workpiece holder. The method provides for adapting the machining process such that the position and / or orientation of the workpiece held in the workpiece holder is taken into account while machining the workpiece, in particular while forming a function part of the final rotationally symmetrical tool. The method is configured to reduce run-out errors due to deviations in distance and / or angle.

[0012] It is a further object of the present invention to generate measurement data related to a reference surface of a clamped workpiece, wherein the measurement data can be used for machining a function part of a final rotationally symmetrical tool, in particular for manufacturing a high-precision tool, such as a ball path milling cutter.

[0013] Furthermore, the invention aims to provide a machining device which is configured to manufacture a workpiece to a measured rotationally symmetrical tool which provides a clamped workpiece and to adapt the machining process based on the measured data of the clamped workpiece.

[0014] These objects are achieved according to the embodiments of the present disclosure. Advantageous embodiments of the invention are also disclosed in the attached drawings and in the following content.

[0015] These objects are achieved by a workpiece holder for coupling a workpiece provided with a reference surface to a machining device for manufacturing a rotationally symmetrical tool. Preferably, the workpiece holder is configured to hold a substantially rotationally symmetrical workpiece to be machined to a milling cutter, i.e. a ball path milling cutter.

[0016] The workpiece holder is configured to be connectable to the machining device in a releasable rotational fixed manner. In particular, the workpiece holder can be received and firmly clamped in a clamping system of the machining device. The machine part can be configured to be received in an axially conical accommodation and to be fixed by means of a clamping system or clamping mechanism of the machining device. Due to the geometry of the interface between the workpiece holder and the accommodation of the machining device, a contact between the two compatible shapes is achieved. Thus, the workpiece holder is aligned without play in axial and radial direction with respect to the machining device and furthermore in a releasable rotational fixed manner. Due to the configuration of the machine part of the workpiece holder, an accuracy and a high repeatability of the positioning of the workpiece holder with respect to the machining device, i.e. with respect to the machine tool such as a grinding wheel, as well as a quick variability of the workpiece holder is achieved.

[0017] The workpiece holder comprises a clamping portion configured to releasably receive and clamp a workpiece. The clamping portion of the workpiece holder can be configured to be compatible with a mounting portion of the workpiece having a reference surface, such that the workpiece is firmly clamped and an original functional portion of the workpiece can be machined. The mounting portion of the workpiece can be machined in at least one previously performed machining process. The mounting portion can be of any shape suitable to provide a seating or bearing surface that bears against a compatible face of a holding device, in particular of the workpiece holder, in order to provide axial and / or radial positioning and orientation of the clamped workpiece. The mounting portion of the workpiece can comprise a shaft portion as a first seating surface. The shaft portion can have a (circular) conical or (circular) cylindrical shape to provide a firm seating by radial positioning in the workpiece holder. The conical or cylindrical shape can have a circular cross-section over the entire length of the shaft portion, or alternatively a rounded polygonal cross-section. The shaft portion can form a transition to a radial portion configured to bear against a surface of a compatible configuration of the workpiece holder for firm seating by axial positioning. The radial portion can be configured to provide a conical or annular ring of a shoulder portion. The workpiece holder can be configured to provide a radial portion and a conical or cylindrical portion to accommodate the mounting portion of the workpiece. The clamping portion can be individual according to the specifications related to the tool. Furthermore, to firmly hold the mounting portion of the workpiece in the workpiece holder and / or another holding device, the clamping end side of the shaft portion can be configured to provide a threaded clamping or a pressure clamping.

[0018] However, the mounting portion of the workpiece is configured to provide a firm seating in the holding device, but also a reference surface. The reference surface can be at least a portion of the cylindrical or conical shaft portion and the adjacent radial portion, which can be formed as an annular or tapered portion.

[0019] The workpiece holder comprises a clamping portion to clamp a workpiece in releasable rotational fixation. The clamping portion of the workpiece holder is configured such that a mounting portion of the workpiece is firmly seated by an interface formed between a face of the workpiece holder and a compatible configuration of the mounting portion of the workpiece in axial and radial direction. Thus, during manufacturing of a functional portion of a precision machined rotationally symmetrical tool, such as a head portion of a milling cutter, such as a ball path milling cutter, having at least one geometrically defined cutting edge for removing material, the workpiece holder firmly holds the workpiece.

[0020] According to the present invention, the clamping portion of the workpiece holder comprises at least one slot arranged at its circumference, which is configured to provide access, preferably from the outside, to the reference surface of the clamped workpiece. In the following, the slot generally means an opening, which can be configured in various forms, such as a hole, a recess, etc.

[0021] In some cases, clamping of the workpiece in the workpiece holder through the mounting portion of the workpiece can be performed so that at least a part of the mounting portion of the workpiece, i.e. at least a part of the shaft portion, extends beyond the workpiece holder. Thus, the reference surface of the workpiece can be accessible for direct measurement by the measuring device. In a laser unit, a short clamping of the workpiece at the rear can be chosen. When manufacturing a function portion of a rotationally symmetrical tool by means of laser, there is almost no force acting on the clamped workpiece. In this particular case, the measurement of the reference surface of the clamped workpiece can be performed directly without having to pass through the openings or slots provided by the workpiece holder. The generated measurement data can be used as described below, i.e. for exact tolerances related to dimensional, shape and / or position accuracy.

[0022] Since direct measurement can be performed at the clamped workpiece, it is not necessary to repeatedly perform the following steps: mounting of the workpiece into the workpiece holder; machining of the workpiece in the machining device; re-chucking of the workpiece holder; and transporting of the workpiece holder with the clamped workpiece to an external measuring device for measuring the processed workpiece; and repeating these steps until the final geometry of the function portion is achieved. The repeated re-chucking is in any case a potential source of error, since it can lead to the well-known chucking errors, so that even an exact tool guidance cannot ensure that high and very high accuracy is achieved. The repeated steps, including e.g. measurement, grinding, measurement, etc. in several iterative steps of manufacturing a high-precision tool, lead to high scrap rates and high machining times.

[0023] A direct measurement of the position and / or orientation of the clamped workpiece is achieved by accessing a previously established reference surface on the workpiece, i.e. at its mounting portion, through at least one slot or another opening, such as a hole, a groove or a recess, provided at the circumference of the workpiece holder. The workpiece to be clamped in the workpiece holder comprises a defined reference surface established beforehand. Advantageously, the at least one slot is configured as an elongated slot extending partially in the direction of the longitudinal axis of the workpiece holder and is configured such that a measurement probe of a measurement device can be inserted therethrough, preferably from the outside, to directly contact at least a portion of the reference surface of the clamped workpiece. The measurement or probing by contacting the reference surface broadly contemplates the use of non-contacting probe tips, such as laser probes and electrostatic probes. Furthermore, advantageously, the at least one slot is configured such that a measurement of the reference surface is provided. According to one embodiment, this measurement can be performed by an optical measurement device, such as a camera or a laser system or other measurement device that can be integrated or mounted on the machining device. Preferably, the opening or slot is configured to provide a tactile measurement. Thus, the measurement probe can be inserted and can be moved along a defined direction while contacting the reference surface.

[0024] In one embodiment, the preferred elongated slot can be configured such that at least a portion of a 3D measurement probe of a measurement device can be inserted therethrough. The dimensions of the at least one slot can be configured such that a measurement head of the measurement probe can be inserted with a play. For example, by using a spherical measurement head, the width of the at least one slot can be 0.5 mm to 1 mm larger than the diameter of the spherical measurement head. Advantageously, a plurality of slots can be provided at the circumference of the workpiece holder. The number and arrangement of the slots at the circumference of the workpiece holder can vary within a certain range, but preferably, the number of slots can be 3 or more, unless the mechanical stability of the clamping of the workpiece given is still compromised.

[0025] According to one aspect of the present invention, the workpiece holder is configured to hold the workpiece while machining a functional portion of a rotationally symmetrical tool.

[0026] According to one embodiment, 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 establish a geometrically defined cutting edge of a rotationally symmetrical tool. Preferably, the rotationally symmetrical tool is a ball nose end mill.

[0027] Generally, a type of rotationally symmetrical tool comprises a base body and a cutting tip or a cutting plate connected to the base body and providing the at least one geometrically defined cutting edge. For example, a ball groove milling cutter can be configured with a bonded cutting tip or blade made of a hard material. In order to manufacture a high-precision ball groove milling cutter from a workpiece with a bonded cutting tip, an exact grinding process and / or a laser process are required to meet very high surface and dimensional requirements. In order to achieve the predetermined plane running accuracy of the finished tool, careful measurements must be made so that the usually excessive manufacturing tolerances of the functional part of the ball groove milling cutter are corrected to the plane running accuracy necessary for the finished ball groove milling cutter.

[0028] According to a further embodiment of the present application, the workpiece holder comprises at least one cam or notch provided at its outer circumferential diameter. The at least one cam or notch is configured to trigger at least one measurement process at a predetermined position of the workpiece holder in the machining device. The triggering activates a measurement device, in particular a 3D measurement probe, comprising a measurement probe to be inserted into the at least one slot and to directly contact a reference surface of a workpiece held in the workpiece holder. Furthermore, the provided cam or notch can be used to position the workpiece holder relative to the machining device in a clamping system. If the workpiece holder is connected to the machining device, the workpiece holder can be rotated around a rotational axis, for example a so-called B-axis, to a predetermined position.

[0029] According to one embodiment, the workpiece holder provides a measurement of a displacement of a rotational axis of the machining device and a longitudinal axis of the workpiece holder. The displacement can comprise a displacement of the longitudinal axis of the workpiece holder relative to the rotational axis of the machining device and / or relative to the workpiece axis. Due to the direct access to the clamped workpiece, preferably from the outside to the reference surface of the clamped workpiece, the relationship between the reference surface of the clamped workpiece and the reference point and / or reference axis of the machining device can be used to verify the positioning and / or orientation of the clamped workpiece. Furthermore, the measurement data can be used to generate a reliable coordinate system based on which the manufacturing of the functional part of the rotationally symmetrical tool can be performed.

[0030] Due to the direct measurement from the outside, deviations caused by set-up errors of the machining device, the workpiece holder and / or the workpiece relative to each other can be detected. Thus, set-up errors can be corrected before the machining process or can be taken into account by adjusting the machining process. The adjustment of the machining process can comprise settings regarding rotation, pitch and planar movement, thereby avoiding a slight jumping of the workpiece due to a displacement or deviation of the axis at each workpiece rotation.

[0031] An advantage of the workpiece holder according to the present invention is the accessibility of the measurement probes to the reference surface of the clamped workpiece. Measurements of the clamped workpiece can be performed to determine the axis displacement of the rotational axis of the machining device, in particular the B-axis and / or the workpiece axis, further including the displacement of the workpiece axis and the longitudinal axis of the workpiece holder, and / or the longitudinal axis of the workpiece holder and the rotational axis of the machining device (which can be corrected based on the measurements), so that the position of the workpiece axis can be corrected and fixed in the desired position relative to the rotational machine axis.

[0032] According to one embodiment of the present invention, a method for manufacturing a rotationally symmetrical tool having at least one geometrically defined cutting edge is provided, which uses a workpiece holder according to the present invention for holding a workpiece. The workpiece provides a reference surface and preferably comprises at least one cutting tip at its original functional part. The method comprises the steps of connecting the workpiece holder in releasable rotational fixed manner to a clamping system of a machining device, connecting a mounting part of the workpiece to the workpiece holder, performing at least one measurement process by introducing a measurement probe of a measurement device through at least one slot provided at the circumference of the workpiece holder to contact the reference surface of the clamped workpiece, to generate measurement data, correcting a detected displacement between the rotational axis of the machining device and the workpiece axis, and processing the measurement data to obtain a curve of the at least one geometrically defined cutting edge of the rotationally symmetrical tool relative to the reference surface of the workpiece for manufacturing the rotationally symmetrical tool by a machining process.

[0033] In another embodiment of the present invention, the step of processing the measurement data to obtain the curve of the geometrically defined cutting edge uses a predetermined envelope surface of the functional part of the rotationally symmetrical tool. The measurement data can comprise data related to the position of the at least one connected cutting tip relative to a coordinate system, preferably related to the position of each of the plurality of cutting tips. The coordinate system can be related to the reference surface of each individual clamped workpiece.

[0034] For each rotationally symmetrical tool, a predetermined ideal envelope surface is known. The envelope surface of a tool such as a milling cutter can be seen as a combination of multiple sections of an individual envelope surface of each cutting edge, which contribute to the predetermined final machined surface. The individual envelope surface of each cutting edge can be generated as a rotational surface by rotating around the machining axis. Deviations from the ideal position of the cutting edge and the presence of run-out thus result in an effective envelope surface which differs from the predetermined ideal envelope surface. By machining a geometrically defined cutting edge at each cutting tip, the measurement data determined at each cutting tip can be used to generate a machining process which is adapted to establish the ideal cutting edge relative to the predetermined ideal envelope surface.

[0035] However, each of the plurality of cutting tips will be measured individually to determine the measurement data of that cutting tip to be processed to calculate the ideal or effective cutting edge. The measurement process of each individual cutting tip can comprise determining the position of the cutting tip by using a measurement probe of the measuring device. Preferably, the measurement determining the actual position of the individual cutting tip is performed even if the workpiece is precisely oriented in the workpiece holder. The measurement probe is inserted into at least one slot of the workpiece holder and determines the rough position of the cutting tip by contact or not directly by contact. After determining the rough position of the cutting tip, measurements are taken at different measurement points on the cutting tip, preferably at least at 3 measurement points, using the measurement probe. The obtained measurement data comprises the true and precise position of the cutting tip and can be processed to generate or calculate a virtual plane of the actually positioned cutting tip.

[0036] The calculated shape, in particular the curve, of the geometrically defined cutting edge can be seen as the intersection line of the predetermined ideal envelope surface and the virtual plane of the actually positioned cutting tip. By processing the measurement data and by calculating the intersection line for each individual cutting edge defining the machining path, it is possible to manufacture the functional part of the cutting tool with high precision, e.g. with its chamfer.

[0037] Another aspect of the present invention relates to a machining device configured to manufacture a workpiece to a rotationally symmetrical tool. The machining device can be a generally known multi-axis grinding device comprising at least a control unit or controller, a clamping system according to the present invention for holding a workpiece holder and a measuring device adapted to perform measurements at the clamped workpiece. BRIEF DESCRIPTION OF DRAWINGS

[0038] For a more complete understanding of the present invention, and for further features and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals indicate like parts and in which:

[0039] Figure 1 is a schematic perspective view of a rotationally symmetrical cutting tool, in particular a ball nose end mill;

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

[0041] Figure 3 is a schematic longitudinal sectional view of a workpiece holder according to a first embodiment of the present invention and a workpiece inserted therein;

[0042] Figure 4 is a schematic sectional view of the workpiece holder of the first embodiment and a measurement probe installed with a workpiece during a measurement process;

[0043] Figure 5 is a schematic side view of a ball nose milling cutter showing the real and ideal position of the cutting tip of a rotationally symmetrical tool with a plurality of geometrically defined cutting edges;

[0044] Figure 6 is a schematic perspective view of the individual parts of a grinding device for machining a workpiece into a cutting tool showing the workpiece according to Figure 2 a workpiece clamped into a workpiece holder according to the embodiment shown;

[0045] Figure 6a is a detail of the grinding device shown in Figure 6 DETAILED DESCRIPTION

[0046] Figure 1 A perspective view of the head of a rotationally symmetrical tool 1 is shown, which has at least one geometrically defined cutting edge 10, here a total of four geometrically defined cutting edges 10, of which only one is designated (in the drawing). The plurality of cutting edges 10 is uniformly spaced in the circumferential direction, and preferably each geometrically defined cutting edge 10 is designed identically. The cutting edge 10 can be formed as an intersection line between a rake face 10a and a relief face 10b, which are associated with the cutting edge 10, respectively, and can include a chamfer 10c.

[0047] The rotationally symmetrical tool 1 can be a ball nose 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 a milling device. The rotationally symmetrical tool 1 comprises a mounting portion 12, also referred to as a shaft portion, and a functional portion 14, which is provided with at least one geometrically defined cutting edge 10 at a head 18 of the rotationally symmetrical tool 1. The head 18 comprises a base body 16, preferably made of steel or carbide, and a plurality of geometrically defined cutting edges 10 forming the functional portion 14 of the tool 1. In the following, the term "functional portion 14" describes the finished functional portion 14 of the tool 1, but also the original functional portion 14 of the workpiece to be machined into the finished functional portion 14 of the tool 1. In the following, the term "workpiece" describes the original workpiece to be machined into the finished functional portion 14 of the tool 1, but also the workpiece to be machined into the finished functional portion 14 of the tool 1. Figure 1 In the embodiment shown, the cutting edge 10 is formed on a cutting tip 15, which is 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 edge 10 of the functional part 14 can be manufactured by grinding, by means of a laser or a corrosion process, removing material from the connected cutting tip 15 made of hard material. The cutting edge 10 is machined, preferably ground, on each cutting tip 15 that has been fastened to the base body 16. The grinding process can be performed in an automated multi-axis grinding machine controlled by a control unit and according to a programmable computer program product. Manufacturing at least one geometrically defined cutting edge 10 with a defined cutting profile by removing material from the cutting tip 15 is the object of the method of the present application.

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

[0050] On the opposite end of the rotationally symmetrical tool 1, preferably the raceway milling cutter 100, i.e. at the clamping end side 20, a mounting part 12 is provided, which is preferably configured as a shaft portion. It is mentioned that the mounting part 12, including the clamping end side 20 of the tool 1, is manufactured before the functional part 14 thereof. Thus, the mounting part 12 of the workpiece 2 (not shown in Figure 1 The mounting part 12, in the shown embodiment cylindrical, but can also be configured conically in the direction of the clamping end side 20, can include an internal thread 21, which is connectable to a complementary threaded portion provided by a holding device of a machining device. The clamping end side 20 can be configured in different forms, such as provided with an external thread, etc., wherein the clamping end side 20 can be fastened to the holding device firmly and in a releasable rotational fixed manner.

[0051] The mounting part 12, including the shaft portion, which can be integrally attached to the head 18 of the tool 1, comprises a first seating face 23 towards the head 18, which supports against an end face of a holding device (not shown) in the clamped position. The first seating face 23 can be configured as a radial portion merged with the shaft portion 12 and as a conical or annular face providing a shoulder. Between the first seating face 23 and the clamping end side 20 a second seating face 24 of conical or cylindrical shape is provided. When the mounting part 12 is inserted and fastened into the holding device of a machining device, the conical or cylindrical second seating face 24 and the first seating face 23 form an interface with compatible shape portions of the holding device in axial and radial direction. The conical or cylindrical second seating face 24 and the radially formed first seating face 23 form a reference surface 30 of the tool 1 and, as the workpiece 2 (not shown in Figure 1As illustrated in (not shown in the image).

[0052] However, manufacturing rotationally symmetric tool 1 is a multi-step process. In the previous step, the workpiece's central axis W (in...) Figure 1 Rotationally symmetric workpiece 2 (not shown in the image) Figure 1 (Not shown in the image) is processed to form a clamping end side 20, a first mounting surface 23, and a second mounting surface 24, providing a reference surface 30 and being configured to connect to, for example, a workpiece retainer 3 (in... Figure 1 (Not shown in the image) Holding device.

[0053] Figure 2 A perspective view of a workpiece holder 3 according to a preferred embodiment is shown. The workpiece holder 3 includes a machine part 31 and a clamping part 32. According to the illustrated embodiment of the workpiece holder 3, the machine part 31 can be inserted into the clamping system of the processing apparatus. Figure 2 (Not shown in the image). Rotationally symmetric workpiece 2 ( Figure 2 (Not shown) It can be releasably and rotatably attached to the clamping portion 32 of the workpiece holder 3. The workpiece holder 3 includes a tapered or cylindrical portion 33 and a radial flange portion 34 on the machine part 31. Figure 2 As shown, the radial flange portion 34 is located between the machine portion 31 and the clamping portion 32. A tapered or cylindrical portion 33 extends along the longitudinal axis WH of the workpiece holder 3. In the case of the tapered portion 33, the tapered shape is inclined at a predetermined angle and facilitates centering of the workpiece holder 3 within the clamping system of the machining apparatus. 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 surface or support surface with the clamping system of the machining apparatus when the workpiece holder 3 is clamped.

[0054] To connect the workpiece holder 3 to the machining apparatus, its clamping system may include a drawback finger or a segmented collector configured with clamping surfaces, these clamping surfaces being constructed and arranged to engage the inner surface of the workpiece holder 3. The drawback finger can be forced radially outward to clamp, for example, the hollow shank workpiece holder 3 into the clamping system of the machining apparatus. The hollow shank workpiece holder 3 may be designed as a known hollow shank tool holder (HSK).

[0055] according to Figure 2The workpiece holder 3 comprises at the outer circumferential diameter 35a a cam 36 protruding from this circumferential diameter 35a. Further, in the shown embodiment a notch 37 is provided at a second circumferential diameter 35b. When the workpiece holder 3 is received in releasable rotational fixed manner by the clamping system of the machining device and firmly connected, the workpiece holder 3 and the cam 36 and / or the notch 37 can be rotated around the longitudinal axis WH of the workpiece holder 3. At a predetermined position the cam 36 and / or the notch 37 triggers a movement of a measuring device 50 (not shown in Figure 2 ) comprising a measuring probe 51 (not shown in Figure 2 ) from a rest position to a measuring position. In the measuring position the measuring probe 51 directly contacts the reference surface 30 of the clamped workpiece 2. The movement of the measuring probe 51 can be controlled by a controller (not shown in Figure 2 ).

[0056] As shown in Figure 2 , the workpiece holder 3 comprises at the clamping portion 32 a series of slots 40 arranged at the circumference, preferably evenly arranged around the circumference and identically designed. Each slot 40 extends from the clamping portion end 32a towards the machine portion 31 parallel to the longitudinal axis WH of the workpiece holder 3 for a predetermined length. In one preferred embodiment each slot 40 has a width 41 sufficient to allow the measuring probe 51 to pass through to contact a portion of the clamped workpiece 2, in particular to directly access the reference surface 30 of the workpiece 2. The number and arrangement of the slots 40 can vary, preferably the number of slots 40 is at least 3 which can be evenly distributed around the circumference of the workpiece holder 3.

[0057] Figure 3 A schematic longitudinal section of the workpiece holder 3 is shown, wherein a workpiece 2 is inserted and clamped by the clamping portion 32 of the workpiece holder 3. The machine portion 31 of the workpiece holder 3 is configured at the end with an opening 31a configured and arranged to receive a portion of the clamping system of the machining device. The workpiece 2 is inserted into the workpiece holder 3, wherein the workpiece 2 comprises a reference surface 30, in particular a first seating face 23 extending in radial direction and a second seating face 24 extending in axial direction as seen from the workpiece center axis W, such that the first seating face 23 and the second seating face 24 form an interface to complementary formed faces of the workpiece holder 3, respectively. Thus, the workpiece holder 3 provides at its clamping portion 32 a radial portion and a conical or cylindrical portion at least partially formed complementary to the first seating face 23 and the second seating face 24 of the workpiece 2, thereby providing a firm seating of the workpiece 2 in the workpiece holder 3. The radial portion and the conical or cylindrical portion of the workpiece holder 3 are not visible in Figure 3 .

[0058] The workpiece 2 is fastened in the workpiece holder 3 by means of a fixing device 38 provided by the workpiece holder 3. The fixing device 38 can be configured with a thread in order to be able to be connected to a thread formed at the clamping end side 20 of the workpiece 2.

[0059] Figure 4 A longitudinal sectional view of the workpiece holder 3 with the inserted and clamped workpiece 2 and the measuring probe 51 during the measurement process is shown. As Figure 4 shown, the workpiece 2 is positioned in the workpiece holder 3 in an axial direction and a radial direction, such that the longitudinal axis WH of the workpiece holder 3 is aligned with the central axis W of the workpiece 2.

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

[0061] By measuring at different points 52, a virtual plane of the actually positioned cutting tip and / or a virtual centrum of the workpiece central axis W of the clamped workpiece 2 can be calculated from the measurement data. In order to ensure a correct orientation of the workpiece 2 clamped in the workpiece holder 3, the rotation of the workpiece 2 around the axis of the machining device can be simulated and monitored by the inserted measuring probe 51 and calculated by the controller. Furthermore, by measuring at at least three measurement points 52 on the cutting tip 15, the actual position of the cutting tip 15 can be determined. The measurement data can be used to calculate a geometrically defined cutting edge 10 of the ideal shape and positioning and to manufacture this geometrically defined cutting edge 10 by grinding or laser machining.

[0062] Figure 5A schematic side view of the raceway milling cutter 100 is shown, which shows the actual position 60 of the cutting tip 15 and / or the cutting edge 10 and the ideal position 70 of the cutting tip 15 and / or the cutting edge 10. The actual position 60 of the cutting tip 15 can be seen as a result of the joining process (e.g. by soldering or brazing) of the cutting tip 15 to the base body 16 and the original form of the cutting tip 15 to be joined. According to one embodiment, the geometrically defined cutting edge 10 is produced on the cutting tip 15 after joining the cutting tip 15 to the base body 16. The cutting tip 15 joined to the base body 16 usually has a circular or elliptical shape and provides sufficient material (which can be removed) to obtain the ideal profile of the geometrically defined cutting edge 10.

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

[0064] Figure 6 is a schematic perspective view of parts of the machining device 200, in particular of a grinding machine having a grinding wheel 201. The grinding machine 200 in particular comprises a clamping system 202 to receive and clamp the workpiece holder 3. The workpiece holder 3 is configured to be releasably rotationally fixed to the grinding device 200, in particular to the clamping system 202. The workpiece 2 is inserted and held 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 (as shown) to a measuring position, in which the measuring probe 51 is partially inserted through at least one slot 40 or opening 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 Figure 6 shown, the machining device 200 comprises a control unit 210, which is configured to control the performance of the machining device 200 and to control the measuring process of the measuring 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 these axes will be measured by the measuring probe 51 and can be taken into account by processing the measurement data according to the method.

[0065] Figure 6aA detail of the clamped workpiece 2 held in the workpiece holder 3 is shown. The groove 40 provided at the workpiece holder 3 is arranged and configured such that the reference surface 30 can be measured even if at least a portion of the reference surface 30 is covered by the workpiece holder 3.

Claims

1. A workpiece holder (3) for coupling a workpiece (2) provided with a reference surface (30) to a machining device (200) for manufacturing a rotationally symmetrical tool (1) having at least one geometrically defined cutting edge (10), the workpiece holder (3) comprising: - a machine portion (31) configured to be connectable to the machining device (200) in releasable rotational fixation, - a clamping portion (32) configured to receive and clamp the workpiece (2) in releasable rotational fixation, characterized in that the clamping portion (32) of the workpiece holder (3) comprises at least one slot (40) provided at the circumference of the workpiece holder and configured to provide access through the at least one slot to the reference surface (30) of the clamped workpiece (2), wherein the workpiece holder (3) comprises at least one cam (36) at a first circumferential diameter (35a) thereof and / or a recess (37) at a second circumferential diameter (35b) thereof, the cam (36) and / or recess (37) being configured to trigger at least one measuring process in the machining device (200) at a predetermined position of the workpiece holder (3).

2. A workpiece holder (3) according to claim 1, characterized in that The clamping portion (32) of the workpiece holder (3) comprises a conical or cylindrical portion and a radial portion configured to form an interface with a compatibly formed reference surface (30) of the clamped workpiece.

3. A workpiece holder (3) according to claim 1 or 2, characterized in that The at least one slot (40) is configured as an elongated slot (40) extending partially in the direction of the longitudinal axis (WH) of the workpiece holder (3) and configured to be insertable through it by a measuring probe (51) of a measuring device (50) for direct contact with at least a portion of the reference surface (30).

4. A workpiece holder (3) according to claim 1 or 2, characterized in that The at least one slot (40) is configured such that a non-contact measurement of the reference surface (30) is performed by an optical measuring device (50).

5. A workpiece holder (3) according to claim 1 or 2, characterized in that A plurality of slots (40) is provided.

6. A workpiece holder (3) according to claim 1 or 2, characterized in that The workpiece holder (3) is configured to hold the workpiece (2) while machining a functional portion (14) of the rotationally symmetrical tool (1).

7. A workpiece holder (3) according to claim 1 or 2, characterized in that The workpiece holder (3) is configured to hold the workpiece (2) while machining at least one cutting tip (15) connected to a base body (16) of the workpiece (2) to establish the geometrically defined cutting edge (10) of the rotationally symmetrical tool (1).

8. A workpiece holder (3) according to claim 1 or 2, characterized in that The rotationally symmetrical tool (1) is a ball path milling cutter (100).

9. A workpiece holder (3) according to claim 1 or 2, characterized in that The workpiece holder (3) provides a measurement of the displacement of the rotational axis (M) of the machining device (200) and the workpiece axis (W).

10. A method for manufacturing a rotationally symmetrical tool (1) having at least one geometrically defined cutting edge (10), the method using a workpiece holder (3) according to any one of claims 1 to 9 for coupling a workpiece (2) provided with a reference surface (30) to a machining device (200), the method comprising the following steps: - connecting a machine portion (31) of the workpiece holder (3) in releasable rotational fixed manner to a clamping system (202) of the machining device (200); - connecting a mounting portion (12) of the workpiece (2) in releasable rotational fixed manner to a clamping portion (32) of the workpiece holder (3); - performing at least one measuring process and generating measuring data of the workpiece (2) being clamped by introducing a measuring probe (51) of a measuring device (50) through at least one slot (40) provided at a circumference of the workpiece holder (3) to contact a reference surface (30) of the workpiece (2) being clamped; - processing the measuring data to obtain a true orientation of a workpiece axis (W) for correcting a detected displacement between a rotational axis of the machining device (M) and the workpiece axis (W); - processing the measuring data to obtain a curve of at least one geometrically defined cutting edge (10) of the rotationally symmetrical tool (1) relative to the reference surface (30) of the workpiece (2) for manufacturing the rotationally symmetrical tool (1) by a machining process.

11. The method of claim 10, wherein, Processing the measuring data comprises calculating a virtual plane of an actually positioned cutting tip (15) of the workpiece (2) and using the virtual plane of the actually positioned cutting tip (15) to obtain the curve of the at least one geometrically defined cutting edge (10) as an intersection line of a predetermined envelope surface of a functional portion (14) of the rotationally symmetrical tool (1) and the virtual plane of the actually positioned cutting tip (15) of the workpiece (2).

12. A machining device (200) for manufacturing a rotationally symmetrical tool (1) by a method according to claim 10 or 11, the machining device comprising: - a control unit (210); - a machining tool; - a clamping system (202) configured to receive and connect a workpiece holder (3) according to any one of claims 1 to 9 in releasable rotational fixed manner; - a measuring device (50) comprising a measuring probe (51) configured to be inserted through at least one slot (40) provided at a circumference of the workpiece holder (3) to directly measure a reference surface (30) of the workpiece (2) being clamped.

13. The processing device (200) according to claim 12, characterized in that The machining device (200) is a multi-axis grinding device.

14. The machining device (200) according to claim 12 or 13, characterized in that the machining tool is a grinding wheel (201).

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