End mills and methods for machining workpieces with end mills

Abstract

a shaft portion (2) that can be driven to rotate about a longitudinal axis (L) of the end mill (1) and that is designed to be accommodated in a rotary tool holder of a machine tool; a tool head (3) rigidly connected to the shank (2) and comprising a milling section (4) having at least one geometrically defined cutting edge (7) around its periphery centered on a longitudinal axis (L); An end mill (1) comprising: The tool head (3) has a grinding section (5) having abrasive grains (17) of an abrasive material with a cutting edge of irregular geometry bonded to a bonding matrix (18) over an outer periphery centered on a longitudinal axis (L); An end mill characterized by:

Description

[Technical Field]

[0001] The present invention relates to an end mill comprising a shank that can be driven in rotation about its longitudinal axis and is designed to be accommodated in a rotary tool holder of a machine tool, the end mill also comprising a tool head rigidly connected to the shank and comprising at least one milling section having at least one geometrically defined cutting edge over its periphery about the longitudinal axis. [Background technology]

[0002] Such a tool is known from US Pat. No. 5,699,499, in which the tool is designed as a combined drilling, roughing and finishing tool. The drilling tool is driven to rotate about a rotation axis and has a cutting edge at its tip, i.e., in the direction of its longitudinal axis, for cutting material. Since only one tip of the tool comes into contact with the workpiece to be machined, the cutting edge at the tip of the tool also extends conically, making the drilling easier at the start of the drilling process. This form of cutting also improves chip removal. The drilling tool does not have a cutting edge on the periphery of its longitudinal axis. Only a spiral flute is provided to remove chips from the drill hole. The drilling tool therefore has a single machining direction in the direction of its longitudinal axis, which is also the axis of rotation.

[0003] In contrast to drilling tools, milling tools have one or more cutting edges around the periphery of their longitudinal axis. Milling tools may also have secondary cutting edges at the tool tip. In milling tools, the secondary cutting edges at the tool tip are usually arranged in a plane perpendicular to the longitudinal axis to form a flat surface parallel to the feed direction when the feed direction is transverse to the longitudinal axis. Milling tools can therefore machine material in multiple directions. The main working direction is transverse to the longitudinal axis.

[0004] The composite tool described in Patent Document 1 is a combination of a drilling tool and a milling tool. The tool has a cutting edge at the tip that is arranged on a conical surface and a cutting edge that is arranged around the periphery of the longitudinal axis. The cutting edge extends in a spiral shape around the periphery.

[0005] The cutting edge of the tool is provided with a wear protection layer over its longitudinal section, which may contain, for example, nanocrystalline diamond or other hard material. This coating does not change the shape of the geometrically fixed cutting edge, while providing high wear protection. This means that the tool can be used for different machining steps on the same workpiece made from the same material without changing the tool between machining steps. For example, the first section can be designed as a roughing section to machine large amounts of material in a short time at a high feed rate. The second longitudinal section of the tool can be designed as a finishing tool, which can achieve a smooth surface at a low feed rate. The roughing section can have a serrated cutting edge, which is also coated as described above to extend the tool's life. For example, to machine a plate-shaped workpiece, the tool is first positioned longitudinally so that the roughing section is aligned transversely to the plate-shaped workpiece, thereby aligning the longitudinal axis of the tool transversely to the plane of the plate-shaped workpiece. The milling tool is then moved at a high feed rate towards the plane of the plate-shaped workpiece to remove material with the peripheral main cutting edge of the tool, and for the finishing process the tool is moved axially so that the finishing section of the tool is aligned perpendicular to the workpiece so that the workpiece can be machined at a lower feed rate in the subsequent machining step.

[0006] Patent document 2 shows a milling tool with a rotating tool head, whereby at least one cutting edge is provided in an area of ​​the outer circumferential surface of the tool head. Abrasive material is arranged on the outer circumferential surface of the tool head adjacent to the at least one cutting edge in the direction of rotation. The at least one cutting edge and the area provided with the abrasive material thus completely overlap in their axial extent.

[0007] Problems arise with conventional tools when plate-shaped workpieces are made of different materials, with layers of ductile material and layers of brittle, wear-resistant material. In this case, tools with geometrically regular cutting edges wear out quickly in the areas of the brittle, wear-resistant layers of the workpiece, so the tool must be replaced even if the section of the cutting edge that machines the ductile layer of the workpiece is not so worn and can be used for machining. When using tools with geometrically irregular cutting edges, they clog quickly in the areas of the workpiece layers made of ductile material, so the tool life is significantly reduced compared to the areas intended for grinding the brittle layer. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] West German Patent Application Publication No. 10318948 [Patent Document 2] German Patent Application Publication No. 102013000942 Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to provide a tool with which plate-shaped workpieces made of layers of different materials can be machined, which tool has improved wear resistance and therefore an increased service life. [Means for solving the problem]

[0010] According to the invention, the problem is solved by an end mill having a shank that can be driven in rotation about the longitudinal axis of the end mill and that is designed to be accommodated in a rotary tool holder of a machine tool, and a tool head that is rigidly connected to the shank and has at least one milling section that has at least one cutting edge of regular geometry on its periphery about the longitudinal axis. The tool head has a grinding section that has abrasive grains of abrasive material with cutting edges of irregular geometry bonded to a bonding matrix over its periphery about the longitudinal axis and that is spaced apart from the milling section in the direction of the longitudinal axis.

[0011] This results in an end mill suitable for machining layers of different materials of a workpiece constructed in layers in a single machining step. This end mill has a grinding section and can therefore also be referred to as a combined tool for milling and grinding. The geometrically regular cutting edge of the milling section is particularly suitable for machining ductile materials such as plastics, non-ferrous metals, aluminum, and even steel. The geometrically irregular cutting edge of the grinding section is particularly suitable for hard, brittle materials such as silicon carbide, silicon, glass, and ceramics. When machining hard, brittle materials, the abrasive grains have a higher strength than the base material of the milling section, so the geometrically regular cutting edge will wear out faster than the geometrically irregular cutting edge of the grinding section. On the other hand, when machining soft, ductile materials, the geometrically irregular cutting edge of the grinding section clogs very quickly and must be cleaned or replaced at high expense. Therefore, a combined milling section and grinding section is ideal for machining plate-shaped workpieces with layers of different materials in a single machining step.

[0012] For this purpose, the grinding section is arranged at a distance from the milling section in the direction of the longitudinal axis. This includes an arrangement in which the milling section and the grinding section are directly adjacent to each other. The milling section and the grinding section are arranged without overlapping in the circumferential direction about the longitudinal axis. In the circumferential direction, only one of the two sections, either the milling section or the grinding section, is in contact with the workpiece to be machined at a given segment. This does not exclude the possibility that an additional section combining the characteristics of the milling section and the grinding section may be arranged between the milling section and the grinding section.

[0013] The milling section may have only a geometrically regular cutting edge. The grinding section may have a geometrically regular cutting edge or a corresponding contour in addition to a geometrically irregular cutting edge. However, it is also possible for the grinding section to have only a geometrically irregular cutting edge.

[0014] In an embodiment, the grinding section is axially disposed between the shank and the milling section.

[0015] An additional milling section may be arranged between the grinding section and the shank, which has at least one geometrically defined cutting edge around its periphery about the longitudinal axis. The grinding section is therefore arranged between the two milling sections and is particularly suitable for plate-shaped workpieces having two outer layers made of a ductile material and an intermediate layer made of a brittle material, such as semiconductor chips.

[0016] In an exemplary embodiment, the grinding section is formed by a grinding wheel formed from abrasive grains bonded to a bonding matrix, and the milling section is formed by a milling shank made of a metallic material, such as a hard metal, and the grinding wheel and the milling shank are configured to be rigidly connected to each other by material or a press fit. Additionally, the grinding wheel and the shank can also be rigidly connected to each other by material or a press fit.

[0017] For example, an additional milling shank made of a metallic material such as a hard metal and forming an additional milling section can be arranged between the grinding wheel and the shank, so that the additional milling shank can be rigidly connected to the grinding wheel on the one hand and to the shank on the other hand in a material or press-fit manner.

[0018] The grinding wheel may have a shape whose outer contour corresponds to the contour of the grinding section so as to provide a continuous geometrically regular cutting edge of the grinding section.

[0019] According to a further exemplary embodiment, the grinding section is formed by a cylindrical section having an outer circumferential surface to which a bonding matrix having abrasive grains accommodated therein is applied.

[0020] The cylindrical section may be formed by a circumferential groove.

[0021] In all embodiments, the bond matrix may be a metal, ceramic, or synthetic resin-based bond matrix. The abrasive grains may be fully encapsulated in the bond matrix. The abrasive grains may have an average grain size of at least 15 μm. The abrasive material from which the abrasive grains are made may be, for example, cubic boron nitride (CBN), diamond, corundum, zirconium corundum, ceramic corundum, or silicon carbide.

[0022] Furthermore, the problem is solved by a method for machining a workpiece with an end mill as described above, the workpiece comprising a plurality of planar layers of different materials, the method comprising the following steps: - positioning the end mill so that the longitudinal axis of the end mill is disposed transverse to the plane of the layer; - positioning the end mill so that the milling section is axially positioned in the plane of the first layer and the grinding section is axially positioned in the plane of the second layer of the workpiece; - material removal machining of the workpiece with a rotary driven end mill in a feed direction parallel to the plane of the layer;

[0023] In one embodiment of the method, the milling section may be axially aligned with the plane of a first layer made of a ductile material such as plastic, non-ferrous metal, aluminum, or synthetic resin, and the grinding section may be axially aligned with the plane of a second layer made of a brittle material such as silicon carbide, silicon, glass, or ceramic. [Brief explanation of the drawings]

[0024] Exemplary embodiments are described in more detail below with reference to the figures. [Figure 1] FIG. [Figure 2] FIG. 2 is an enlarged perspective view of the tool tip of the first embodiment of the end mill. [Figure 3] FIG. 10 is an enlarged perspective view of a tool tip of a second embodiment of the end mill. [Figure 4] 1 is a portion of a longitudinal section of an end mill according to the first or second embodiment; [Figure 5] FIG. 5 is an enlarged view of a longitudinal section of the tool tip area of ​​the end mill shown in FIG. 4. [Figure 6] FIG. 6 is an enlarged cross-sectional view of a portion of the grinding wheel of the end mill shown in FIG. 5. [Figure 7] 10 is a portion of a longitudinal section of a third embodiment of an end mill. [Figure 8] 8 is an enlarged view of a longitudinal section of the grinding section area of ​​the end mill shown in FIG. 7. FIG. [Figure 9] 2 shows the arrangement of the end mill according to FIG. 1 on a plate-shaped workpiece for machining; DETAILED DESCRIPTION OF THE INVENTION

[0025] FIG. 1 shows a perspective view of an end mill 1. The end mill 1 has a shank 2 and a tool head 3. The end mill 1 or shank 2 can be driven to rotate about a longitudinal axis L of the end mill 1. For this purpose, the shank 2 is designed to be held in a rotary tool holder (not shown here) of a machine tool. The tool head 3 is rigidly connected to the shank 2. The shank 2 and the tool head 3 can be manufactured as a single piece from a common tool blank. Alternatively, the shank 2 and the tool head 3 can be manufactured from different tool blanks that are later rigidly connected to each other.

[0026] The tool head 3 has a milling section 4, a grinding section 5 longitudinally adjacent thereto, and an additional milling section 6 longitudinally adjacent to the grinding section 5. The milling section 4, the grinding section 5, and the additional milling section 6 are arranged axially spaced apart from one another in the direction of the longitudinal axis L, i.e., they do not overlap in the circumferential direction. In the illustrated design example, the grinding section 5 is located between the milling section 4 and the additional milling section 6, so that the additional milling section 6 is arranged directly adjacent to the shank 2. In principle, it is also conceivable to have only one milling section 4 and only one grinding section 5. It is also conceivable to arrange several milling sections and several grinding sections alternately next to one another along the longitudinal axis L.

[0027] In the design shown, the milling section 4 is arranged at the tool tip 9 facing away from the shank 2. It is also possible for the grinding section 5 to be arranged at the tool tip 9.

[0028] Each of the two milling sections 4, 6 has several geometrically defined cutting edges 7, 8 over its entire circumference, which cutting edges extend in a spiral pattern. Geometrically defined cutting edges are characterized by the fact that the number of cutting edges, their path and the geometry of the cutting edges in cross section (cutting wedge) have a predetermined and well-defined shape.

[0029] The grinding section 5 has abrasive grains bonded to a bonding matrix over its entire periphery about the longitudinal axis L, which consists of an abrasive material with cutting edges of irregular geometry. The irregular geometry cutting edges are characterized by the fact that the number of cutting edges, their path and the geometry of the cutting edges in cross section (cutting wedge) are not predetermined and have no clear definite shape. The abrasive grains consist, in particular, of cubic boron nitride (CBN), diamond, corundum, zirconium corundum, ceramic corundum or silicon carbide.

[0030] 2 shows an enlarged view of the tool head 3 in the area of ​​the tool tip 9 of a first embodiment of the end mill 1 according to FIG. 1, where corresponding components are given the same reference numerals. The first embodiment of the end mill 1 has a grinding section 5 that has only a geometrically irregular cutting edge, i.e., it forms an essentially cylindrical outer periphery. The grinding section 5 is formed by a grinding wheel 12 made of abrasive grains bonded to a bonding matrix. The milling section 4 and the additional milling section 6 form only geometrically regular cutting edges 7, 8. In the illustrated design example, the grinding section 5 is located between the milling section 4 and the additional milling section 6. The milling section 4 is located at the tool tip 9.

[0031] 3 shows an enlarged view of the tool head 3 in the area of ​​the tool tip 9 of a second embodiment of the end mill 1 according to FIG. 1, where corresponding components are given the same reference numerals. The second embodiment of the end mill 1 has a grinding section 5 that forms a cutting edge with an irregular geometry and has an additional shape so that a geometrically defined cutting edge 10 is formed. The grinding section 5 is formed by a grinding wheel 12 made of abrasive grains bonded to a bonding matrix. As in the first embodiment, the grinding section 5 is arranged between the milling section 4 and the additional milling section 6. The geometrically defined cutting edges 7, 8, 10 can be axially aligned with one another.

[0032] 4 and 5 show different views of parts of the longitudinal sections of the first and second embodiments. It can be seen that the milling section 4 is formed by a milling shank 11. The additional milling section 6 is formed by an additional milling shank 13. The two milling shafts 11, 13 are designed as separate components. In the illustrated design example, the additional milling shank 13 is connected to the shank 2 integrally, i.e., as a single unit. Alternatively, the additional milling shank 13 can be designed as a component independent of the shank 2, and is rigidly connected to the shank 2 in a material- or form-fit manner, for example by soldering. This has the advantage that the additional milling shank 13, like the milling shank 11, can be made of hard metal, while the shank 2 can be made of steel. The grinding wheel 12 is placed between the milling shank 11 and the other milling shank 13 and is rigidly connected to them in a material- or form-fit manner. For example, the grinding wheel 12 can be bonded or soldered to the two milling shanks 11, 13. In order that the milling shanks 11, 13 and the grinding wheel 12 can be connected to each other in a centered manner relative to each other and to the longitudinal axis L, each of the milling shanks 11, 13 has a central centering protrusion 19, 20 facing the grinding wheel 12, each of which protrudes into a centering recess 21, 22 of the grinding wheel 12. In principle, it is also conceivable that the milling shanks 11, 13 do not have a centering protrusion and that the grinding wheel 12 correspondingly does not have a centering recess.

[0033] For production purposes, it is possible to first form a continuous tool blank with a geometrically defined cutting edge 8. The tool tip 9 is then cut off, and a grinding wheel 12 can then be rigidly connected between the milling shank 11 formed by the cutting off and another milling shank 13.

[0034] Alternatively, a tool blank without a geometrically defined cutting edge yet formed can first be used for production. The tool tip 9 is then cut off or prepared as an independent component. A grinding wheel 12 is then positioned between and rigidly connected to the two milling shanks 11, 13. The geometrically defined cutting edge can then be continuously ground via the two milling sections 4, 6 and the grinding section 5.

[0035] As shown diagrammatically in Figure 6, the grinding wheel 12 comprises a metal, ceramic or synthetic resin based bonding matrix 18 to which are bonded abrasive grains 17. The abrasive grains 17 consist of an abrasive material with a cutting edge of irregular geometry.

[0036] 7 and 8 show different views of a third embodiment of the end mill 1 according to FIG. 1, where corresponding components are given the same reference numerals. The grinding section 5 is formed by a cylindrical section 14 with an outer circumferential surface 15. The outer circumferential surface 15 is coated with abrasive grains 27 held in a bonding matrix 28. Here, the outer circumferential surface 15 is formed by an outer circumferential groove 16, which is located between the milling section 4 and the additional milling section 6. In this embodiment, the milling sections 4, 6, the grinding section 5 and the shank 2 are manufactured from a common tool blank.

[0037] The abrasive grains 27 are housed in a bonding matrix 28, which may protrude outward from or be surrounded by it. The bonding matrix 28 is an electrochemical, e.g., galvanic, bonding matrix made of nickel material. The abrasive grains 27 may be made of the same materials as those in the first two embodiments. For cutting removal, the abrasive grains 17 have a geometrically irregular cutting edge in the form of an edge 29.

[0038] 9 shows the positioning of the end mill 1 when used to machine a workpiece 23. The workpiece 23 is a plate-shaped component, such as a semiconductor chip. The workpiece 23 comprises a first layer 24, a second layer 25, and a third layer 26, with the second layer 25 being disposed between the first layer 24 and the third layer 26. The first layer 24 and the third layer 26 are made of a ductile or soft material, such as plastic or synthetic resin. The second layer 25 disposed therebetween is made of a brittle material, such as silicon carbide or silicon.

[0039] To machine the workpiece 23, the end mill 1 is positioned so that the milling section 4 is axially disposed along the longitudinal axis L in the plane of the first layer 24 or overlaps it. In addition, the grinding section 5 is axially disposed in the plane of the second layer 25. The additional milling section 6 is at least partially axially disposed in the plane of the third layer 26. To machine the workpiece 23, the end mill 1 is driven in rotation about the longitudinal axis L while being moved transversely to the longitudinal axis L in the direction of the arrow P. Thus, the geometrically regular cutting edges 7, 8 are able to cut the ductile material. The geometrically irregular cutting edges of the grinding wheel of the grinding section 5 are used to machine the brittle material of the second layer 25. This means that the appropriate section of the end mill 1 is used for each material of the individual layers 24, 25, 26. [Explanation of symbols]

[0040] 1 end mill 2 Shaft 3 Tool Head 4 Milling divisions 5 Grinding Classification 6 additional milling sections 7 Geometrically shaped cutting edge 8 Geometrically shaped cutting edge 9 Tool Tip 10 Geometrically shaped cutting edge 11 Milling shaft 12 Grinding wheels 13 Additional milling shank 14 Cylindrical division 15 Outer surface 16 Peripheral groove 17 Abrasive grains 18 Bonding base material 19 Centering protrusion 20 Centering protrusion 21 Centering recess 22 Centering recess 23 Workpiece 24 1st layer 25 2nd layer 26 3rd layer 27 Abrasive grains 28 Bonding base material 29 Edge P arrow

Claims

1. a shaft (2) that can be driven to rotate about the longitudinal axis (L) of the end mill (1) and that is designed to be accommodated in a rotary tool holder of a machine tool; a tool head (3) rigidly connected to the shank (2) and comprising a milling section (4) having at least one geometrically regular cutting edge (7) around its periphery centered on the longitudinal axis (L); An end mill (1) comprising: the tool head (3) has a grinding section (5) arranged at a distance from the milling section (4) in the direction of the longitudinal axis (L), the grinding section (5) having abrasive grains (17) of an abrasive material with cutting edges of irregular geometry bonded to a bonding matrix (18) over an outer periphery centered on the longitudinal axis (L); An end mill (1) characterized by:

2. the milling section (4) having only geometrically defined cutting edges (7); 2. An end mill (1) according to claim 1, characterized in that:

3. the grinding section (5) has only cutting edges (7) of irregular geometry; An end mill (1) according to claim 1 or 2, characterized in that

4. the grinding section (5) is arranged axially between the shank (2) and the milling section (4) in the direction of the longitudinal axis (L); An end mill (1) according to one of claims 1 to 3, characterized in that

5. an additional milling section (6) is arranged axially between the grinding section (5) and the shank (2) in the direction of the longitudinal axis (L), the additional milling section having at least one cutting edge (8) of a geometrically regular shape over its periphery around the longitudinal axis (L); An end mill (1) according to one of claims 1 to 4, characterized in that

6. the grinding section (5) is formed by a grinding wheel (12) formed from the abrasive grains (17) bonded to the bonding matrix (18); the milling section (4) is formed by a milling shank (11); the grinding wheel (12) and the milling shank (11) are rigidly connected to each other by material or force fit; An end mill (1) according to one of claims 1 to 5, characterized in that

7. the grinding wheel (12) and the shank (2) are rigidly connected to each other by material or force fit; 7. An end mill (1) according to claim 6, characterized in that:

8. an additional milling shank (13) is arranged between the grinding wheel (12) and the shank (2); An end mill (1) according to claim 6 or 7, characterized in that

9. the additional milling shank (13) is rigidly connected to the grinding wheel (12) on the one hand and to the shank (2) on the other hand in a material or press-fit manner; 9. An end mill (1) according to claim 8, characterized in that

10. said grinding section (5) being formed by a cylindrical section (14) having an outer peripheral surface (15); The bonding matrix (18) containing the abrasive grains (17) is applied to the outer peripheral surface (15); An end mill (1) according to one of claims 1 to 5, characterized in that

11. a circumferential groove (16) defining said cylindrical section (14); An end mill (1) according to claim 10, characterized in that

12. A method for machining a workpiece (23) with an end mill (1) according to one of the preceding claims, wherein the workpiece (23) comprises a plurality of planar layers (24, 25, 26) of different materials, positioning the end mill (1) so that the longitudinal axis (L) of the end mill (1) is disposed transversely to the plane of the layers (24, 25, 26); positioning the end mill (1) so that the milling section (4) is axially disposed in the plane of a first layer (24) and the grinding section (5) is axially disposed in the plane of a second layer (25) of the workpiece (23); a step of removing material from the workpiece (23) with the end mill (1) driven in rotation in a feed direction (P) parallel to the plane of the layers (24, 25, 26); A method that encompasses

13. Axial alignment of the milling section (4) in the plane of the first layer (24) of ductile material (e.g., plastic, non-ferrous metal, aluminum, synthetic resin); Axial positioning of the grinding section (5) in the plane of the second layer (25) made of brittle material (e.g. silicon carbide, silicon, glass, ceramic); The method of claim 12, wherein:

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