Milling head for a ball track milling cutter, ball track milling cutter with such a milling head, method for producing a cutting edge for a ball track milling cutter, computer program product for carrying out such a method, data carrier with such a computer program product, and grinding machine for carrying out the method

Description

[0001] The invention relates to a milling head for a ball track milling cutter according to the preamble of claim 1, a ball track milling cutter with such a milling head, a method for producing a cutting edge for a ball track milling cutter, a computer program product for implementing such a method, a data carrier with such a computer program product, and a grinding machine for implementing the method. Such a milling head, such a ball track milling cutter, and such a method are known from EP 2 913 132 A1.

[0002] A ball-nose milling cutter of the type discussed here is known, for example, from German patent application DE 10 2014 208 125 A1. A milling head of such a ball-nose milling cutter has an imaginary central axis as well as a first, working-side end and a second, clamping-side end opposite the first end along the central axis. The milling head also has at least one geometrically defined cutting edge, which extends from a first cutting edge end facing the first end of the milling head in the direction of the second end of the milling head to a second cutting edge end facing the second end of the milling head along a cutting edge profile. The at least one cutting edge is formed as an intersection line between a rake face and a flank face, which are each assigned to the cutting edge and which intersect along the cutting edge.The at least one cutting edge is also assigned a negative rake angle, a first clearance angle and a wedge angle.

[0003] Known milling heads have a limited service life, and particularly during extended use, sharp edges develop in the area of ​​at least one cutting edge, which in turn leads to chipping along the cutting edge. Wear is not evenly distributed along the cutting edge, but rather exhibits a distinct wear profile. The at least one cutting edge wears significantly faster and more severely in the area of ​​the second cutting edge end than in the area of ​​the first cutting edge end.

[0004] The invention is based on the object of providing a milling head for a ball track milling cutter, a ball track milling cutter with such a milling head, a method for producing a cutting edge for a ball track milling cutter, a computer program product for carrying out such a method, a data carrier with such a computer program product, and a grinding machine for carrying out the method, wherein the aforementioned disadvantages do not occur.

[0005] The problem is solved by creating the subject matter of the independent claims. Advantageous embodiments emerge from the subclaims.

[0006] The object is achieved in particular by providing a milling head for a ball-and-socket milling cutter according to claim 1, wherein the negative rake angle in the region of the first cutting edge end, in particular at the first cutting edge end, has a different value than in the region of the second cutting edge end, in particular at the second cutting edge end. The first clearance angle also has a different value in the region of the first cutting edge end, in particular at the first cutting edge end, than in the region of the second cutting edge end, in particular at the second cutting edge end. The wedge angle is constant along the cutting edge profile.While the wedge angle remains constant along the cutting edge path from the first cutting edge end to the second cutting edge end, the negative rake angle, on the one hand, and the clearance angle, on the other hand, in the region of the first cutting edge end each have a value that differs from a value present in the region of the second cutting edge end. In this way, the geometric configuration of the at least one cutting edge is adapted in different regions along its cutting edge path to a respective instantaneous engagement situation during machining of a workpiece, thereby reducing wear on the cutting edge and, preferably, vibrations during machining of the workpiece. This also contributes to a longer service life of the milling head.Milling heads and ball track milling cutters of the type discussed here are used primarily for the production of cardan shaft joints, especially for the production of ball raceways for constant velocity joints. They are used, in particular, to produce ball raceways, also known as ball tracks, both in the outer part of such a joint and in its inner part. To machine a ball raceway, such a milling head is positioned at a specific angle of attack relative to a workpiece to be machined. The angle of attack is the angle formed by the imaginary center axis of the milling head relative to a tangent applied to a momentary point of contact between the cutting edge of the milling head and the workpiece surface.The at least one cutting edge makes point-like or at least approximately point-like contact with the workpiece to be machined in the region of the point of contact, whereby this point of contact is not constant on the cutting edge during machining of the workpiece, but rather is displaced along the cutting edge profile. This results in particular, on the one hand, from the finite angle of attack of the milling head and, on the other hand, from the specific relative movement between the milling head and the workpiece to be machined, which is provided for creating a ball bearing surface in the workpiece. On the one hand, there is a relative rotation around the imaginary central axis to create the ball bearing surface along an imaginary circumferential line, and on the other hand, there is a suitable relative displacement between the workpiece and the milling head to create the ball bearing surface along a longitudinal extent of the same - perpendicular to the imaginary circumferential line.Particularly preferably, the milling head is rotated around the imaginary central axis, while at the same time the workpiece is guided—preferably in an elliptical motion—around the imaginary central axis of the milling head in such a way that the ball raceway is formed entirely along its longitudinal extent. During machining of the ball raceway, the at least one cutting edge, starting from the first cutting edge end, plunges into the material of the workpiece to be machined, with the contact point on the cutting edge shifting from the first cutting edge end toward the second cutting edge end during the further course of machining.Where the cutting edge penetrates the material of the ball raceway, which is particularly semicircular, and where it emerges from this material, jumps in the applied cutting force occur, also known as cutting force interruptions, which contribute to undesirable vibrations of the milling head. This has a negative impact on both chip formation and tool life. The adapted geometry of at least one cutting edge proposed here allows it to be adjusted to the shift in the contact point during workpiece machining and, at the same time, reduces the previously described vibrations, thus improving the overall tool life of the milling head.

[0007] It is possible for the milling head to have only one and precisely one geometrically defined cutting edge. However, in another exemplary embodiment, it is also possible for the milling head to have a plurality of geometrically defined cutting edges, in particular two geometrically defined cutting edges, three geometrically defined cutting edges, four geometrically defined cutting edges, or five geometrically defined cutting edges. Of course, a larger number of geometrically defined cutting edges is also possible. However, the milling head particularly preferably has four geometrically defined cutting edges. Preferably, all geometrically defined cutting edges provided on the milling head are identical and, in particular, designed as explained here and below for the at least one geometrically defined cutting edge.

[0008] The milling head can be formed integrally with other elements of a ball track milling cutter, in particular with a ball track milling cutter base body, so that this is in particular a milling head of a ball track milling cutter. However, it can also be formed in multiple parts with the remaining parts of the ball track milling cutter, whereby it can be connected, for example, to the ball track milling cutter base body via an interface, for example by means of a thread with an adjoining centering cone and a flat surface surrounding the centering cone in the circumferential direction for the precise positional fixation of the milling head to the ball track milling cutter base body. Such single-piece and also multi-part designs, in particular also corresponding interfaces, are known per se, so they will not be discussed in detail here.

[0009] The working end of the milling head is understood to be the end—seen along the imaginary central axis—that is intended to face the workpiece during machining by the milling head. In contrast, the clamping end of the milling head is understood to be the end—seen along the central axis—that is intended to face away from the workpiece during machining, with this end being assigned to a clamping section of the milling head or the ball track milling cutter. As already explained, the milling head can be connected to the clamping section with a ball track milling cutter base body. The ball track milling cutter, in turn, can be connected to a suitably designed clamping section with additional tool elements, such as adapters, spacers, extensions, or the like, or directly to a machine spindle.For this purpose, the ball nose milling cutter can, in particular, have a clamping shank suitable for clamping into another tool part and / or a machine spindle. Such a clamping shank can be cylindrical, conical, for example, a Morse taper, or a hollow shank taper (HSK).

[0010] The fact that the rake face is assigned to the at least one cutting edge means, in particular, that the rake face directly adjoins the at least one cutting edge. Accordingly, the first flank face also directly adjoins the cutting edge. This is particularly evident from the fact that the cutting edge is formed as the intersection line between the rake face and the first flank face.

[0011] The fact that at least one cutting edge is assigned a negative rake angle means, in particular, that the rake face has a negative rake angle. Such a negative rake angle is particularly advantageous for machining hard materials that are machined with a cutting material of great hardness and temperature resistance. Typically, workpieces of the type discussed here are machined with the milling head in an already hardened form. A negative rake angle enables higher cutting forces and shorter chips to be achieved. Due to their internal crystalline structure, suitable, hard cutting materials have the property of being resistant to compressive stresses that occur with a negative rake angle. At the same time, they possess great hardness and temperature resistance.In contrast, a positive rake angle would generate tensile stress during chip breaking, which would cause a correspondingly hard cutting tool material to fail very quickly. Such hard cutting tools exhibit poor behavior in response to tensile stresses, in particular, a low internal tensile resistance of the material. Therefore, they are prone to chipping on the cutting edge at positive rake angles.

[0012] Furthermore, it should be noted that the wedge angle should be selected as large as possible for machining hard, brittle materials in order to guarantee the necessary stability when machining materials with high strength and hardness.

[0013] The rake angle is the angle formed by the rake face with an imaginary plane in which the cutting edge runs, and which is locally perpendicular to a workpiece surface machined by the cutting edge. The rake angle has a positive value if the rake face is set back relative to the imaginary plane—as seen against the machining direction—i.e., it trails the cutting edge. The rake angle has a negative value if the rake face—as seen in the machining direction—leads the cutting edge, i.e., it is positioned in front of the imaginary plane in the machining direction.

[0014] The clearance angle is the angle formed by the flank surface with a machined workpiece plane or a tangential plane adjacent to the workpiece in the area of ​​the cutting edge, with the cutting edge also lying in this workpiece plane or tangential plane. The workpiece plane or tangential plane used to determine the clearance angle, on the one hand, and the imaginary plane used to determine the rake angle, on the other, are perpendicular to each other and intersect at the cutting edge. The clearance angle ensures, in particular, that the milling head is free from the machined workpiece surface, minimizing friction and heating between the cutting edge and the machined material.

[0015] The wedge angle is the angle formed by the rake face on the one hand and the first flank on the other hand.

[0016] The general rule is that the rake angle - taking into account the sign assigned to it -, the first clearance angle and the wedge angle always add up to 90° - based on a full circle of 360°.

[0017] The wedge angle can therefore be calculated from the rake angle—taking its sign into account—and the first clearance angle. Conversely, the first clearance angle is determined from the wedge angle and the rake angle.

[0018] According to a further development of the invention, it is provided that along the cutting edge profile there are no two different points on the at least one cutting edge at which the at least one cutting edge has identical values ​​for the rake angle and / or identical first clearance angles. This means in particular that the value of the negative rake angle and / or the first clearance angle is / are not the same at any two different points along the cutting edge profile on the cutting edge. The value of the negative rake angle is therefore different at every point along the cutting edge profile. Alternatively or additionally, the clearance angle is different at every point along the cutting edge profile. This leads to a particularly favorable cutting geometry for reducing vibrations occurring during machining of a workpiece and for increasing the service life of the milling head.

[0019] According to a further development of the invention, the magnitude of the negative rake angle and / or the first clearance angle varies / vary continuously along the cutting edge profile. A continuous variation is understood in particular to mean a continuous change, very particularly a continuous and differentiable change, in the values ​​for the magnitude of the rake angle and / or the first clearance angle, wherein in particular no jumps occur in the corresponding values. Particularly preferably, the magnitude of the negative rake angle and / or the first clearance angle changes / changes linearly along the cutting edge profile of the at least one cutting edge. This avoids abrupt changes in the cutting geometry, which has a positive effect on preventing vibrations and increasing the service life of the milling head.

[0020] According to a further development of the invention, it is provided that the amount of the negative rake angle is smaller in the region of the first cutting edge end, in particular at the first cutting edge end, than in the region of the second cutting edge end, in particular at the second cutting edge end. Alternatively or additionally, it is preferably provided that the first clearance angle is smaller in the region of the first cutting edge end, in particular at the first cutting edge end, than in the region of the second cutting edge end, in particular at the second cutting edge end. In this way, the resistance and stability of the cutting geometry are coordinated such that the at least one cutting edge has greater stability along its cutting edge profile where it would otherwise be subject to increased wear, while at the same time being designed to be more cutting-efficient where it typically exhibits less wear.This allows wear to be uniformed across the cutting edge, increasing the overall service life of the freehead. The constant wedge angle along the cutting edge ensures that the stability and durability of the cutting geometry are not compromised at any point along the cutting edge due to a reduced wedge angle.

[0021] By varying the negative rake angle and the clearance angle along the cutting edge profile on the one hand, and the constant wedge angle on the other, the cutting geometry is essentially rotated along the cutting edge from the first cutting edge end to the second cutting edge end - viewed in cross-section. In particular, the rake face exhibits a twisted profile along the cutting edge due to the rake angle and clearance angle profiles, with a normal vector of the rake face being essentially rotated along the cutting edge from the first cutting edge end to the second cutting edge end in the direction of an outer circumference of the milling head. This creates increased stability of the cutting geometry, particularly in the area of ​​the second cutting edge end, i.e., where increased wear occurs with conventional milling heads.

[0022] According to a further development of the invention, the magnitude of the negative rake angle along the cutting edge profile—in particular from the first cutting edge end to the second cutting edge end—increases at the same rate as the first clearance angle increases. The magnitude of the rake angle thus increases, in particular, in the same proportion as the value of the first clearance angle.

[0023] For clarification, it should be added that the negative rake angle - everywhere along the cutting edge - becomes smaller and smaller taking into account its sign, i.e. it changes towards more negative values, when its amount increases from the first cutting edge end towards the second cutting edge end.

[0024] According to the invention, it is provided that a width of the rake face in the region of the first cutting edge end, in particular at the first cutting edge end, is greater than in the region of the second cutting edge end, in particular at the second cutting edge end. The width of the rake face preferably changes continuously along the cutting edge profile from the first cutting edge end to the second cutting edge end, particularly preferably linearly with the cutting edge profile. In particular, the width of the rake face preferably decreases continuously, in particular linearly, from the first cutting edge end to the second cutting edge end. This results, for a given contour of the cutting edge, i.e. for a predetermined cutting edge profile, from the development of the rake angle on the one hand and the first clearance angle on the other hand along the cutting edge profile.

[0025] The rake face proposed here, which is variable in width and twisted along its length, is also referred to as a trailing negative chamfer. It enables increased stability of the cutting geometry, particularly in the area of ​​the second cutting edge end, and thus improves the service life of the milling head while simultaneously reducing vibration.

[0026] According to a further development of the invention, the width of the chip face in the region of the first cutting edge end is at most 0.4 mm, preferably at most 0.3 mm, while the width of the chip face in the region of the second cutting edge end is at least 0.1 mm, preferably at least 0.15 mm. With these values, the advantages already described are realized in a special way.

[0027] According to a further development of the invention, the cutting edge profile can be straight, curved and / or spiral. The cutting edge profile can in particular be aligned parallel to the imaginary central axis or enclose a finite angle with the imaginary central axis. This angle can vary along the cutting edge profile or be constant. The design of the cutting edge profile described here relates in particular to an imaginary projection of the actual cutting edge profile in space onto an imaginary, cylindrical circumferential surface that extends concentrically around the central axis. In fact, the cutting edge profile is always curved because the milling head is hemispherical or approximately hemispherical, at least in the region of the at least one cutting edge.However, this curvature disappears when projected onto an imaginary, cylindrical circumferential surface around the central axis, so that in this projection it is particularly easy to assess whether the cutting edge is aligned parallel to the central axis, set at an angle to the central axis or formed spirally around the central axis.

[0028] The milling head therefore has, at least in the region of its working end, a hemispherical or at least approximately hemispherical geometry, the curvature of which is followed by the at least one cutting edge, wherein in particular in this way a ball raceway can be produced, in particular with a diameter which corresponds to the diameter of the imaginary hemisphere.

[0029] According to a further development of the invention, the magnitude of the negative rake angle in the region of the first cutting edge end, in particular at the first cutting edge end, is from at least 10° to at most 19°, preferably from at least 12° to at most 17°, preferably from at least 14° to at most 16°, preferably 15°. Alternatively or additionally, the magnitude of the negative rake angle in the region of the second cutting edge end, in particular at the second cutting edge end, is preferably from at least 20° to at most 30°, preferably from at least 22° to at most 28°, preferably from at least 24° to at most 26°, preferably 25°.

[0030] Alternatively or additionally, the first clearance angle in the region of the first cutting edge end, in particular at the first cutting edge end, is from at least 5° to at most 10°, preferably from at least 6° to at most 8°, preferably 7°. Alternatively or additionally, the first clearance angle in the region of the second cutting edge end, preferably at the second cutting edge end, is from at least 15° to at most 20°, preferably from at least 16° to at most 18°, preferably 17°.

[0031] With the values ​​given here for the amount of the negative rake angle and / or the first clearance angle, the previously described advantages of the milling head are realized in a special way.

[0032] According to a further development of the invention, a second flank surface, which is associated with a second clearance angle, adjoins the first flank surface on the circumferential side. The term "circumferential" refers in particular to a circumferential line that concentrically encompasses the imaginary central axis. The second flank surface is in particular directly adjacent to the first flank surface, with the first flank surface being arranged between the cutting edge and the second flank surface.

[0033] Preferably, the second clearance angle is larger than the first clearance angle everywhere along the cutting edge.

[0034] According to a further development of the invention, the second clearance angle is constant along the cutting edge profile. In particular, it is preferably from at least 16° to at most 21°, preferably from at least 17° to at most 19°, preferably 18°.

[0035] The second flank, which slopes down more sharply than the first flank - seen opposite to the machining direction - enables improved clearance and reduced friction and heating between the cutting edge and the machined material while maintaining a stable cutting geometry.

[0036] According to a further development of the invention, the milling head comprises a base body. It is possible for the at least one cutting edge to be formed directly on the base body, in particular machined from the base body. Alternatively, it is possible for the at least one cutting edge to be formed on a cutting insert connected to the base body.

[0037] The base body preferably comprises a solid carbide or consists of a solid carbide. In the case where the cutting edge is formed directly on the base body, the base body preferably has a hard material layer, preferably made of cubic boron nitride (CBN), polycrystalline cubic boron nitride (PCBN), or polycrystalline diamond (BKD), applied, in particular pressed, to at least some regions of the solid carbide. The at least one cutting edge is formed on the hard material layer, in particular machined from the hard material layer.If, on the other hand, the at least one cutting edge is formed on a cutting insert connected to the base body, the base body can in particular consist of solid hard metal, wherein the cutting insert preferably comprises a hard material or is formed from a hard material, wherein the cutting insert in particular comprises or consists of a material selected from a group consisting of cubic boron nitride (CBN), polycrystalline cubic boron nitride (PCBN), and polycrystalline diamond (PKD).

[0038] The cutting insert is preferably connected to the base body by soldering, preferably by brazing. In particular, it is possible for the cutting insert to be soldered into the base body.

[0039] It is also possible, in principle, to attach the cutting insert to the base body in another way, for example by screw clamping, which makes it particularly easy to replace it with a new cutting insert once its service life has ended. However, this results in shorter service life due to the less stable arrangement of the cutting insert compared to soldering and the resulting inaccuracies when changing. In addition, replaceable cutting inserts can lead to increased inaccuracies during machining and ultimately to larger tolerance deviations in the machined workpiece. In contrast, permanently soldered cutting inserts significantly increase service life and avoid inaccuracies when changing, thus also increasing machining accuracy and improving the achievable tolerances on the machined workpiece.

[0040] The object is also achieved by creating a ball track milling cutter according to claim 12, which has a milling head according to one of the previously described embodiments. In this case, the advantages already explained in connection with the milling head are particularly realized in connection with the ball track milling cutter. As also already explained, the milling head can be formed integrally with the remaining parts of the ball track milling cutter, in particular with a ball track milling cutter base body. However, it is also possible for the milling head to be formed in several pieces with the ball track milling cutter base body and to be fastened to the latter by means of a suitable interface. This design has the advantage that the milling head can be easily replaced at the end of its service life without the ball track milling cutter base body having to be disposed of and replaced at the same time.

[0041] The object is also achieved by providing a method for producing a cutting edge for a ball-and-socket milling cutter according to claim 13, in which the cutting edge is produced by grinding directly on a base body of a milling head or on a cutting insert for a milling head, wherein the cutting edge is produced as a cutting line between a rake face and a clearance face, wherein the cutting edge is formed with a negative rake angle, the amount of which has a different value in the region of a first cutting edge end, which is intended to face a working-side end of the milling head, than in the region of a second cutting edge end, which is intended to face a clamping-side end of the milling head, wherein the cutting edge is formed with a clearance angle which has a different value in the region of the first cutting edge end than in the region of the second cutting edge end,and wherein the cutting edge is formed with a wedge angle that is constant along a cutting edge profile of the cutting edge between the first cutting edge end and the second cutting edge end. In connection with the method, the advantages already explained in connection with the milling head on the one hand and the ball track milling cutter on the other hand are realized in particular.

[0042] In particular, the base body or the cutting insert is ground, whereby the cutting edge is produced by grinding the base body or the cutting insert as a cutting line between the rake face and the flank face.

[0043] In particular, the cutting edge is produced by grinding at least one surface selected from the rake face and the flank face, preferably by grinding the rake face and the flank face, as a cutting line between the flank face and the rake face.

[0044] If the cutting edge is produced on a cutting insert for a milling head, this preferably occurs according to a first embodiment of the method after the cutting insert has been attached to a milling head, in particular after the cutting insert has been soldered or brazed to the milling head or into the milling head. The cutting insert is / is preferably brazed to the milling head. Alternatively, according to another embodiment of the method, it is possible for the cutting insert to be ground before being attached to the milling head, thereby producing the cutting edge. However, it is possible for the cutting edge to be reworked after the cutting insert has been attached to the milling head, in particular to ensure the dimensional accuracy of the cutting edge.

[0045] By means of the method, in particular by producing the cutting edge directly on the base body of the milling head or on the cutting insert, a milling head according to the invention or a milling head according to one of the previously described embodiments is preferably obtained. If necessary, the cutting insert is also attached to the milling head after grinding, in particular by soldering, preferably by brazing.

[0046] The object is also achieved by creating a computer program product according to claim 15, which has machine-readable instructions on the basis of which a method according to the invention or a method according to one of the previously described embodiments is carried out when the computer program product runs on a computing device configured to control a grinding machine and preferably operatively connected to the grinding machine for its control. Based on the machine-readable instructions, the computing device then controls, in particular, the grinding machine such that the cutting edge is produced. In connection with the computer program product, the advantages already explained in connection with the milling head and / or the ball track milling cutter arise in particular.

[0047] In particular, the computer program product comprises machine-readable instructions based on which a base body of a milling head arranged on or in the grinding machine, or a cutting insert for such a milling head, is ground by means of the grinding machine. The cutting edge is produced by grinding a cutting line between a rake face and a flank face, in particular by grinding at least one surface selected from the flank face and the rake face by the grinding machine. Preferably, the flank face and the rake face are ground by the grinding machine.

[0048] The object is also achieved by providing a data carrier according to claim 16, on which a computer program product according to the invention or a computer program product according to one of the previously described embodiments is stored. The data carrier is preferably designed as a volatile or non-volatile data carrier. The data carrier can be, in particular, a working memory of a computing device, a read-only memory, in particular a hard disk or hard disk device of the computing device, or a mobile data carrier, for example a tape storage device, a floppy disk, a CD-ROM, a DVD, a USB stick, a memory card, or the like. The data carrier can also be designed as a data cloud, that is to say, in particular, as a network storage device comprising a plurality of computing devices, in particular as a so-called cloud.

[0049] In connection with the data carrier, the advantages already explained in connection with the milling head or the ball track milling cutter are realized in particular.

[0050] Finally, the object is also achieved by providing a grinding machine according to claim 17, which is configured to carry out a method according to the invention or a method according to one of the previously described embodiments. In connection with the grinding machine, the advantages already explained in connection with the milling head or the ball track milling cutter are particularly evident.

[0051] According to the invention, the grinding machine comprises a computing device on which a computer program product according to the invention or a computer program product according to one of the previously described embodiments runs. Alternatively or additionally, the grinding machine preferably comprises a data carrier according to the invention or a data carrier according to one of the previously described embodiments.

[0052] The method is particularly intended for producing a milling head according to the invention or a milling head according to one of the previously described embodiments. In this respect, the method preferably comprises at least one method step that is determined by at least one feature or a combination of features of the milling head according to the invention or of a milling head according to one of the described embodiments. In particular, method steps that were explicitly or implicitly explained in connection with the milling head are preferably, individually or in combination with one another, steps of a preferred embodiment of the method.

[0053] The invention is explained in more detail below with reference to the drawings, which show: Figure 1 shows a detailed representation of an embodiment of a milling head for a ball track milling cutter; Figure 2 shows a first detailed cross-sectional view along a Figure 1shown first section line AA, and Figure 3 a second detailed cross-sectional view along a Figure 1 shown second section line BB.

[0054] Figure 1 shows a detailed illustration of a first exemplary embodiment of a milling head 1 for a ball-and-socket milling cutter 3 (not shown in detail beyond the milling head 1). The milling head 1 has an imaginary central axis M, which corresponds to a rotational axis of the milling head 1 and also of the ball-and-socket milling cutter 3 during the intended machining of a workpiece (not shown). The milling head 1 and, in particular, the ball-and-socket milling cutter 3 are thus preferably rotated around the central axis M during the machining of a workpiece.

[0055] The milling head 1 has a first, working-side end 5 and a second, clamping-side end 7 opposite the first end 5 along the central axis M, which is shown here in the detailed illustration of Figure 1is no longer shown, wherein the first end 5 is intended to face the workpiece during machining of a workpiece, wherein the second end 7 faces a clamping section of the ball track milling cutter 3 or has a clamping section of the milling head 1.

[0056] The milling head 1 also has at least one geometrically defined cutting edge, here a total of four geometrically defined cutting edges, of which only one is designated by the reference number 9 for the sake of clarity.

[0057] Everything explained below for the geometrically defined cutting edge 9 explicitly designated here also applies equally to the remaining three geometrically defined cutting edges of the milling head 1, which are not specifically designated for the sake of clarity. The four geometrically defined cutting edges 9 are therefore all identically designed. For the sake of simplicity, only one geometrically defined cutting edge 9 will be described in detail below.

[0058] The geometrically defined cutting edge 9 extends from a first cutting edge end 11 facing the first end 5 in the direction of the second end 7 to a second cutting edge end 13 along a cutting edge profile, wherein the term "cutting edge profile" refers to the profile of the geometrically defined cutting edge 9 starting from the first cutting edge end 11 to the second cutting edge end 13.

[0059] The cutting edge 9 is formed as a cutting line between a rake face 15 and a first flank 17, which are each assigned to the cutting edge 9. The rake face 15 has a negative rake angle. In addition to the negative rake angle, the cutting edge 9 is assigned a first clearance angle and a wedge angle, which, in conjunction with the Figures 2 and 3 be explained in more detail.

[0060] In the milling head 1, it is provided in particular that an amount of the negative rake angle in the region of the first cutting edge end 11 has a different value than in the region of the second cutting edge end 13, wherein the first clearance angle in the region of the first cutting edge end 11 has a different value than in the region of the second cutting edge end 13. The wedge angle is constant along the cutting edge profile from the first cutting edge end 11 to the second cutting edge end 13.

[0061] In particular, the cutting edge 9 does not have two different points along the cutting edge profile at which the values ​​for the negative rake angle and / or the first clearance angle would be equal. Particularly preferably, the values ​​of the rake angle and / or the first clearance angle vary continuously, in particular linearly, along the cutting edge profile of the cutting edge 9.

[0062] The magnitude of the negative rake angle is preferably smaller in the region of the first cutting edge end 11, in particular at the first cutting edge end 11, than in the region of the second cutting edge end 13, in particular at the first cutting edge end 13. Alternatively or additionally, the first clearance angle is preferably smaller in the region of the first cutting edge end 11, in particular at the first cutting edge end 11, than in the region of the second cutting edge end 13, in particular at the second cutting edge end 13.

[0063] The magnitude of the negative rake angle increases along the cutting edge profile from the first cutting edge end 11 to the second cutting edge end 13, in particular to the extent that the first clearance angle also increases. The magnitude of the negative rake angle and the first clearance angle therefore increase in the same proportion.

[0064] Based on Figure 1 It is also already clear that the width of the rake face 15 in the region of the first cutting edge end 11, in particular at the first cutting edge end 11, is greater than in the region of the second cutting edge end 13, in particular at the second cutting edge end 13. The width of the rake face 15 also preferably varies continuously along the cutting edge profile, in particular it decreases linearly from the first cutting edge end 11 to the second cutting edge end 13. The rake face 15 can therefore also be referred to as a trailing negative chamfer.

[0065] Preferably, the width of the chip surface 15 in the region of the second cutting edge end 13 is at least 0.1 mm, preferably at least 0.15 mm, wherein the width of the chip surface 15 in the region of the first cutting edge end 11 is at most 0.4 mm, preferably at most 0.3 mm.

[0066] Based on Figure 1 It also becomes clear that the chip surface 15, starting from the first cutting edge end 11 to the second cutting edge end 13, takes a quasi-twisted course, wherein an imaginary normal vector of the chip surface 15 is twisted outwards in the direction of an external environment of the milling head 1 in the course from the first cutting edge end 11 to the second cutting edge end 13.

[0067] It is possible for the cutting edge 9 to have a straight, curved, and / or spiral profile—particularly in a projection onto a cylindrical circumferential surface encompassing the central axis M. It can, in particular, be aligned parallel to the imaginary central axis or enclose a finite angle with it.

[0068] In the embodiment illustrated here, the milling head 1 has a base body 19, which preferably comprises or consists of solid carbide. The cutting edge 9 is formed here on a cutting insert 21 connected to the base body 19, in particular soldered to the base body 19—preferably by brazing. In particular, a separate cutting insert 21 is provided for each of the four cutting edges 9. This preferably applies regardless of how many cutting edges 9 the milling head 1 actually has. Thus, each cutting edge 9 is preferably always assigned its own cutting insert 21.

[0069] The cutting insert 21 preferably comprises or consists of a material selected from a group consisting of cubic boron nitride (CBN), polycrystalline cubic boron nitride (PCBN), and polycrystalline diamond (PCD).

[0070] Alternatively, it is also possible for the cutting edge 9 to be formed directly on the base body 19, in particular machined therefrom. In this case, the base body 19 preferably comprises a solid carbide body and a hard material layer pressed onto the solid carbide body, from which the cutting edge 9 is machined. This hard material layer preferably comprises or consists of a material selected from a group consisting of cubic boron nitride (CBN), polycrystalline cubic boron nitride (PCBN), and polycrystalline diamond (PCD).

[0071] Figure 2 shows a detailed cross-sectional view according to a Figure 1 shown first section line AA. The Figure 2 The first cross-sectional plane shown is arranged closer to the first cutting edge end 11 than a plane shown in Figure 3 shown, second cross-sectional plane, which in Figure 1by a second section line BB, the detailed cross-sectional view being shown in accordance with Figure 3 is arranged closer to the second cutting edge end 13.

[0072] Identical and functionally identical elements are provided with the same reference symbols in all figures, so that reference is made to the preceding description in each case.

[0073] In Figure 2In particular, an imaginary workpiece plane 23, which can also be designed as a tangential plane to the machined workpiece, and an imaginary plane 25 are shown, wherein the imaginary plane 25 is perpendicular to the imaginary workpiece plane 23, and wherein the imaginary workpiece plane 23 and the imaginary plane 25 intersect at the cutting edge 9. During the machining of a workpiece, the cutting edge 9 touches the latter in particular at a point of contact which lies both in the imaginary workpiece plane 23 and in the imaginary plane 25, wherein the imaginary workpiece plane 23 is designed in particular as a tangential plane to the workpiece at the point of contact.

[0074] The rake angle 15 is the angle formed by the rake face 15 and the imaginary plane 25. For simplicity, an angle α that is numerically identical to the rake angle is shown here. The identity between the illustrated angle α and the rake angle results from simple geometric considerations. For simplicity, the rake angle will therefore also be referred to as rake angle α below.

[0075] An arrow P1 represents a machining direction of the milling head 1, along which the cutting edge 9 is displaced relative to a workpiece. It is clear that the rake face 15 leads the imaginary plane 25 and also the cutting edge 9 in the machining direction. Therefore, the rake angle α is assigned a negative sign.

[0076] The first clearance angle β is the angle which the clearance surface 17 encloses with the imaginary workpiece plane 23.

[0077] Finally, the wedge angle γ is the angle that the rake face 15 makes with the flank face 17.

[0078] The equation applies that the rake angle α - taking into account its sign -, the wedge angle γ and the first clearance angle β add up to 90°, whereby the degree specification refers to a full circle of 360°.

[0079] For example, here the sum of the wedge angle γ and the first clearance angle β is greater than 90° by exactly the amount of the negative rake angle α, so that exactly 90° results when the amount of the rake angle - due to the negative sign assigned to the rake angle - is subtracted from the sum of the wedge angle γ and the first clearance angle β.

[0080] In Figure 2 a width b of the chip surface 15 is also shown.

[0081] Figure 3 shows - as already mentioned - a second detailed cross-sectional view along the Figure 1shown second section line BB.

[0082] A comparison of the Figures 2 and 3 shows that both the amount of the negative rake angle α and the amount of the first clearance angle β are smaller in the area of ​​the first cutting edge end 11 than in the area of ​​the second cutting edge end 13. In particular, they have in the cutting plane according to Figure 2 first values ​​α1, β1 which are smaller than the second values ​​α2, β2 according to the cutting plane of Figure 3 . However, the change in the rake angle α on the one hand and the clearance angle β on the other hand is such that the wedge angle γ is constant.

[0083] Overall, a comparison of the Figures 2 and 3 also that the cutting geometry is virtually twisted from the first cutting edge end 11 to the second cutting edge end 13, here in a clockwise direction.

[0084] At the same time, with a given cutting edge profile of the cutting edge 9, the width b of the chip surface 15 decreases from the first cutting edge end 11 to the second cutting edge end 13. In this respect, the chip surface 15 has Figure 2 a first, larger width b1 and in Figure 3 a second, smaller width b2.

[0085] The magnitude of the negative rake angle α described here in the region of the first cutting edge end 11, in particular at the first cutting edge end 11, is preferably from at least 10° to at most 19°, preferably from at least 12° to at most 17°, preferably from at least 14° to at most 16°, preferably 15°. In the region of the second cutting edge end 13, in particular at the second cutting edge end 13, it is preferably from at least 20° to at most 30°, preferably from at least 22° to at most 28°, preferably from at least 24° to at most 26°, preferably 25°.

[0086] The first clearance angle β is preferably at least 5° to at most 10°, preferably at least 6° to at most 8°, preferably 7°, in the region of the first cutting edge end 11, in particular at the first cutting edge end 11. It is preferably at least 15° to at most 20°, preferably at least 16° to at most 18°, preferably 17°, in the region of the second cutting edge end 13, in particular at the second cutting edge end 13.

[0087] In a manner not shown, a second flank surface preferably adjoins the first flank surface 17 circumferentially, to which a second clearance angle is assigned. This second clearance angle is preferably greater than the first clearance angle β everywhere along the cutting edge profile of the cutting edge 9 and is particularly preferably constant along the cutting edge profile. It preferably has a value of at least 16° to at most 21°, preferably of at least 17° to at most 19°, preferably of 18°.

[0088] The cutting geometry of the milling head 1 shown here proves to be particularly stable, particularly by creating uniform wear across the cutting edge 9, thus increasing the service life of the milling head 1. In addition, vibrations during machining of a workpiece are reduced, which also has a beneficial effect on the service life of the milling head 1.

[0089] The cutting edge 9 is preferably produced by directly grinding the base body 19 or the cutting insert 21, in particular by grinding at least one surface selected from the rake face 15 and the first flank face 17. Preferably, both the rake face 15 and the first flank face 17 are ground to produce the cutting edge 9 as a cutting line between the rake face 15 and the first flank face 17.

[0090] If the cutting insert 21 is ground, this is preferably done while the cutting insert 21 is already attached to the base body 19. Alternatively, the cutting insert can also be ground before being attached to the base body 19.

[0091] By producing the cutting edge 9, the milling head 1 is preferably obtained. If necessary, only a fastening, in particular a soldering, of the cutting insert 21 to the base body 19 is additionally required if the cutting insert 21 is ground before being fastened to the base body 19.

[0092] Grinding is preferably carried out using an automated, in particular programmable, grinding machine. In particular, a computer program product is provided for controlling the grinding machine. This computer program product has machine-readable instructions based on which a previously described method for producing the cutting edge 9 is carried out on the grinding machine when the computer program product is running on a computing device configured to control the grinding machine.

Claims

1. Milling head (1) for a ball track milling cutter (3), comprising - an imaginary centre axis (M), - a first, working-side end (5) and a second, clamping-side end (7) opposite the first end (5) when viewed along the centre axis (M), and comprising - at least one geometrically defined cutting edge (9) extending along a cutting edge profile of the cutting edge (9) from a first cutting edge end (11) facing the first end (5) of the milling head (1) in the direction of the second end (7) of the milling head (1) to a second cutting edge end (13) facing the second end (7) of the milling head (1), wherein - the at least one cutting edge (9) is designed as an intersecting line between a rake face (15) associated with the at least one cutting edge (9) and a first flank face (17) associated with the at least one cutting edge (9), wherein - a negative rake angle (α), a first clearance angle (β), and a wedge angle (γ) are assigned to the at least one cutting edge (9), wherein - an absolute value of the negative rake angle (α) has a different value in the region of the first cutting edge end (11) than in the region of the second cutting edge end (13), und wherein - the first clearance angle (β) has a different value in the region of the first cutting edge end (11) than in the region of the second cutting edge end (13), characterised in that - the wedge angle (γ) is constant along the cutting edge profile, and in that - a width of the rake face (15) is greater in the region of the first cutting edge end (11) than in the region of the second cutting edge end (13).

2. Milling head (1) according to claim 1, characterised in that along the cutting edge profile, there are no two distinct points on the cutting edge (9) where the cutting edge (9) has identical absolute values for the negative rake angle (α) and / or identical first clearance angles (β).

3. Milling head (1) according to one of the preceding claims, characterised in that the absolute value of the negative rake angle (α) and / or the first clearance angle (β) vary continuously, preferably linearly, along the cutting edge profile of the at least one cutting edge (9).

4. Milling head (1) according to one of the preceding claims, characterised in that the absolute value of the negative rake angle (α) is smaller in the region of the first cutting edge end (11) than in the region of the second cutting edge end (13), and / or the first clearance angle (β) is smaller in the region of the first cutting edge end (11) than in the region of the second cutting edge end (13).

5. Milling head (1) according to one of the preceding claims, characterised in that the absolute value of the negative rake angle (α) increases along the cutting edge profile of the at least one cutting edge (9) to the extent to which the first clearance angle (β) increases also.

6. Milling head (1) according to one of the preceding claims, characterised in that the width of the rake face (15) in the region of the first cutting edge end (11) is at most 0.4 mm, preferably at most 0.3 mm, and / or that the width of the rake face (15) in the region of the second cutting edge end (13) is at least 0.1 mm, preferably at least 0.15 mm.

7. Milling head (1) according to one of the preceding claims, characterised in that the cutting edge profile of the at least one cutting edge (9) is formed straight, curved, and / or spiral, wherein said cutting edge profile extends in particular parallel to the imaginary centre axis (M) or comprises a finite angle with the imaginary centre axis (M).

8. Milling head (1) according to one of the preceding claims, characterised in that a) the absolute value of the negative rake angle (α) is in the region of the first cutting edge end (11) from at least 10° to at most 19°, preferably from at least 12° to at most 17°, preferably from at least 14° to at most 16°, preferably 15°, and / or is in the region of the second cutting edge end (13) from at least 20° to at most 30°, preferably from at least 22° to at most 28°, preferably from at least 24° to at most 26°, preferably 25°; and / or that b) the first clearance angle (β) is in the region of the first cutting edge end (11) from at least 5° to at most 10°, preferably at least 6° to at most 8°, preferably 7°, and / or is in the region of the second cutting edge end (13) from at least 15° to at most 20°, preferably from at least 16° to at most 18°, preferably 17°.

9. Milling head (1) according to one of the preceding claims, characterised in that a second flank face adjoins the first flank face (17) on the circumference, to which a second clearance angle is assigned, which is preferably greater than the first clearance angle (β) everywhere along the cutting edge profile.

10. Milling head (1) according to claim 9, characterised in that the second clearance angle is constant along the cutting edge profile and is preferably from at least 16° to at most 21°, preferably from at least 17° to at most 19°, preferably 18°.

11. Milling head (1) according to one of the preceding claims, characterised in that< / b> the milling head (1) comprises a main body (19), wherein the at least one cutting edge (9) is formed a) directly on the main body (19), or b) on a cutting insert (21) connected to the main body (19), preferably soldered to the main body (19).

12. Ball track milling cutter (3), comprising a milling head (1) according to one of claims 1 to 11.

13. Method for producing a cutting edge (9) for a ball track milling cutter (3), wherein - the cutting edge (9) is produced by grinding directly on a main body (19) of a milling head (1) or on a cutting insert (21) for a milling head (1), wherein - the cutting edge (9) is produced as an intersecting line between a rake face (15) and a flank face (17), wherein - the cutting edge (9) is formed with a negative rake angle (α) whose absolute value has a different value in the region of a first cutting edge end (11) facing a working-side end (5) of the milling head (1) than in the region of a second cutting edge end (13) facing a clamping-side end (7) of the milling head (1), wherein - the cutting edge (9) is produced with a clearance angle (β) that has a different value in the region of the first cutting edge end (11) than in the region of the second cutting edge end (13), and wherein - the cutting edge (9) is produced with a wedge angle (γ) that is constant along a cutting edge profile of the cutting edge (9) between the first cutting edge end (11) and the second cutting edge end (13), and wherein - the rake face (15) is produced such that a width of the rake face (15) is greater in the region of the first cutting edge end (11) than in the region of the second cutting edge end (13).

14. Method according to claim 13, characterised in that a milling head (1) according to one of claims 1 to 11 is obtained by manufacturing the cutting edge (9).

15. Computer program product comprising machine-readable instructions, on the basis of which a method according to one of claims 13 or 14 is carried out when the computer program product runs on a computer set up to control a grinding machine.

16. Data carrier comprising a computer program product according to claim 15, which is stored on the data carrier.

17. Grinding machine for producing a cutting edge (9) for a ball track milling cutter (3), wherein the cutting edge (9) is produced by grinding directly on a main body (19) of a milling head (1) or on a cutting insert (21) for a milling head (1), wherein the grinding machine is adapted for carrying out a method according to one of claims 13 or 14, comprising a computing device on which runs a computer program product according to claim 15.