End mill and method for machining workpiece with end mill

Abstract

The invention relates to an end mill (1) comprising a shank (2) which can be driven in rotation about a longitudinal axis (L) of the end mill (1) and is designed to be received in a rotating tool holder of a machine tool, and comprising a tool head (3) which is rigidly connected to the shank (2) and has a milling section (4), the tool head (3) has a milling section (5) having at least one geometrically defined cutting edge (7) on its circumference around the longitudinal axis (L), characterized in that the tool head (3) has a grinding section (5) with abrasive grains (17) made of abrasive material with geometrically undefined cutting edges, on the circumference of the grinding section around the longitudinal axis (L) and bonded in a bonding matrix (18).

Description

Technical Field

[0001] The present invention relates to an end mill having a shank that is rotatably driven about the longitudinal axis of the end mill and is designed to be received in a rotating tool holder (tool holder) of a machine tool. The end mill also includes a tool head rigidly connected to the shank, the tool head having at least one milling section with at least one geometrically defined cutting edge around its circumference about the longitudinal axis. Background Art

[0002] Such a tool is known from DE 103 18 948 A1, in which the tool is designed as a combined drilling, roughing, and finishing tool. The drilling tool is driven to rotate along an axis of rotation and has a cutting edge for removing material only at the distal end, i.e., on the front side in the direction of the longitudinal axis. The cutting edge at the distal end of the tool also extends along a cone, making drilling easier at the beginning of the drilling process, as only one tool distal end comes into contact with the workpiece to be machined. This cutting method also improves chip removal. The drilling tool has no cutting edge circumferentially around the longitudinal axis. Only a spiral groove is provided to remove chips from the drilled hole. Consequently, the drilling tool has a single machining direction in the direction of the longitudinal axis, which also serves as the axis of rotation.

[0003] In contrast to drilling tools, milling tools have one or more cutting edges around the 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 typically arranged in a plane perpendicular to the longitudinal axis, forming a flat surface parallel to the feed direction when the feed direction is transverse to the longitudinal axis. Thus, milling tools can process material in various directions. The primary working direction is transverse to the longitudinal axis.

[0004] The combined tool according to DE 103 18 948 A1 is a combination of a drilling tool and a milling tool. The tool has a cutting edge arranged along a conical surface at the end and a cutting edge arranged circumferentially around the longitudinal axis. The cutting edge extends helically around the circumference.

[0005] The tool's cutting edge can be provided with a wear protection layer along a longitudinal section. This wear protection layer can, for example, comprise nanocrystalline diamond or another hard material. This coating maintains the geometrically defined shape of the cutting edge while providing enhanced wear protection. This means that the tool can be used for different machining steps on the same workpiece made of the same material without having to change the tool between machining steps. For example, the first section can be designed as a roughing section, enabling the machining of large quantities 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, enabling the production of smooth surfaces at a low feed rate. The roughing section can have serrated cutting edges, which are also coated as described above, to extend the tool's service life. For machining, for example, a plate-like workpiece, the tool is initially positioned longitudinally, with the roughing section aligned transversely to the plate, thereby aligning the tool's longitudinal axis transversely to the plane of the plate. The tool is then moved at a high feed rate in the plane of the plate, removing material with the main cutting edge surrounding the circumference of the milling tool. For the finishing process, the tool is subsequently moved axially in such a way that the finishing section of the tool is aligned at right angles to the workpiece, so that the workpiece can be machined at a low feed rate in a subsequent machining step.

[0006] DE 10 2013 000 942 A1 discloses a milling tool having a rotating tool head, wherein at least one cutting edge is provided in the region of the circumferential surface of the tool head. An abrasive is arranged on the peripheral surface of the tool head, adjoining the at least one cutting edge in the direction of rotation. Consequently, the at least one cutting edge and the region provided with the abrasive completely overlap along their axial extent.

[0007] Conventional tools can present problems when working with plate-like workpieces made of different materials, with a ductile layer and a brittle, wear-resistant layer. In this case, tools with geometrically defined cutting edges wear more rapidly in the areas of the workpiece's brittle, more wear-resistant layer. Consequently, the tool must be replaced even if the cutting edge in the section machining the workpiece's ductile layer is less worn and can be used for machining. When using tools with geometrically undefined cutting edges, these edges quickly clog in the area of the workpiece's ductile layer, significantly reducing the tool's service life compared to grinding the brittle layer. Summary of the Invention

[0008] 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, the tool having improved wear resistance and thus a longer service life.

[0009] According to the invention, this problem is solved by an end mill having a shank and a tool head, the shank being rotatably driven about the longitudinal axis of the end mill and being designed to be received in a rotating tool holder of a machine tool, the tool head being rigidly connected to the shank and having at least one milling section having at least one geometrically defined cutting edge around its circumference about the longitudinal axis. The tool head having a grinding section having abrasive grains of an abrasive material with a geometrically undefined cutting edge, the abrasive grains being bonded in a bonding matrix around the circumference of the grinding section about the longitudinal axis and being arranged at a distance from the milling section in the direction of the longitudinal axis.

[0010] This makes the end mill suitable for machining the different material layers of workpieces consisting of multiple layers in a single machining step. It is an end mill with a grinding section and can therefore also be described as a combined milling and grinding tool. The geometrically defined cutting edges of the milling section are particularly suitable for machining ductile materials such as plastics, non-ferrous metals, aluminum, and even steel. The geometrically undefined cutting edges of the grinding section are particularly suitable for machining hard and brittle materials such as silicon carbide, silicon, glass, and ceramics. When machining hard and brittle materials, the geometrically defined cutting edges of the grinding section wear faster than the geometrically undefined cutting edges of the grinding section because the abrasive grains are stronger than the base material of the grinding section. On the other hand, when machining soft and ductile materials, the geometrically undefined cutting edges of the grinding section clog quickly, necessitating costly cleaning or replacement. Therefore, the combination of a milling section and a grinding section is ideally suited for machining plate-like workpieces consisting of different material layers in a single machining step.

[0011] To this end, the grinding section is spaced a certain distance from the milling section in the direction of the longitudinal axis. This also includes arranging the milling section and the grinding section directly adjacent to each other. The milling section and the grinding section are arranged so as not to overlap in the circumferential direction about the longitudinal axis. In the circumferential direction, only one of the two sections, the milling section or the grinding section, is in contact with the workpiece to be machined in any given section. This does not exclude the possibility of arranging another section between the milling section and the grinding section that combines the features of the milling section and the grinding section.

[0012] The milling section may have only geometrically defined cutting edges. In addition to geometrically undefined cutting edges, the grinding section may also have geometrically defined cutting edges or corresponding contours. However, the grinding section may also have only geometrically undefined cutting edges.

[0013] In one embodiment, the grinding section is arranged axially between the shank and the milling section.

[0014] A further milling section can be arranged between the grinding section and the shank, which has at least one geometrically defined cutting edge around its circumference about the longitudinal axis. The grinding section is thus arranged between two milling sections and is particularly suitable for plate-like workpieces, such as semiconductor chips, having two outer layers of ductile material and a middle layer of brittle material.

[0015] In one exemplary embodiment, a grinding wheel formed of abrasive bonded in a bonding matrix forms the grinding section, a milling shank made of a metallic material, such as hard metal, forms the milling section, and the grinding wheel and the milling shank are rigidly connected to each other in a materially or non-positive manner. Furthermore, the grinding wheel and the shank may also be rigidly connected to each other in a materially or non-positive manner.

[0016] A further milling shank, for example made of a metallic material such as hard metal, forming a further milling section can be arranged between the grinding wheel and the shank, whereby the further milling shank can be rigidly connected to the grinding wheel on the one hand and to the shank on the other hand in a materially or force-fitting manner.

[0017] The grinding wheel can be shaped such that its outer contour corresponds to the contour of the grinding segment, so that it continuously continues the cutting edge defined by the geometry of the grinding segment.

[0018] According to a further exemplary embodiment, the grinding segment is formed by a cylindrical segment having a peripheral surface, wherein a bonding matrix containing abrasive particles is applied to the peripheral surface.

[0019] The cylindrical section may be formed by a peripheral groove.

[0020] In all embodiments, the bonding matrix can be a metal, ceramic, or synthetic resin-based bonding matrix. The abrasive particles can be completely encapsulated in the bonding matrix. The abrasive particles can have an average particle size of at least 15 μm. For example, the abrasive material used to make the abrasive particles can be cubic boron nitride (CBN), diamond, corundum, zirconium corundum, ceramic corundum, or silicon carbide.

[0021] The problem is also solved by a method for machining a workpiece with an end mill as described above, wherein the workpiece comprises a plurality of planar layers of different materials. The method comprises the following steps:

[0022] - aligning the end mill so that the longitudinal axis of the end mill is transverse to the plane of the layers;

[0023] - aligning the end mill such that the milling section is arranged in the axial direction in the plane of the first layer of the workpiece and the grinding section is arranged in the axial direction in the plane of the second layer of the workpiece; and

[0024] - Material removal from the workpiece is performed using a rotary driven end mill in a feed direction parallel to the plane of the layers.

[0025] In one embodiment of the method, the milling segments can be aligned axially in the plane of a first layer made of a ductile material, such as plastic, non-ferrous metal, aluminum, or synthetic resin. Furthermore, the grinding segments can be aligned axially in the plane of a second layer made of a brittle material, such as silicon carbide, silicon, glass, or ceramic. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The exemplary embodiments are explained in more detail below with reference to the accompanying drawings, in which:

[0027] Figure 1 It is a three-dimensional diagram of the end mill;

[0028] Figure 2 is an enlarged perspective view of a tool tip of a first embodiment of an end mill;

[0029] Figure 3 is an enlarged perspective view of a tool tip of a second embodiment of an end mill;

[0030] Figure 4 is a partial longitudinal sectional view of the end mill according to the first embodiment or the second embodiment;

[0031] Figure 5 yes Figure 4 An enlarged longitudinal section of the end mill shown in the tool end region;

[0032] Figure 6 yes Figure 5 A partial enlarged cross-sectional view of the grinding wheel of the end mill shown;

[0033] Figure 7 is a partial longitudinal sectional view of a third embodiment of an end mill;

[0034] Figure 8 yes Figure 7 An enlarged longitudinal section of the end mill shown in the grinding section area; and

[0035] Figure 9 is based on Figure 1 A view of arranging an end mill onto a plate-like workpiece for machining thereof. DETAILED DESCRIPTION

[0036] Figure 1 A perspective view of an end mill 1 is shown. The end mill 1 has a shank 2 and a tool head 3. The end mill 1 or the shank 2 can be driven rotatably about the longitudinal axis L of the end mill 1. For this purpose, the shank 2 is designed to be held in a rotating 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 made in one piece from a common tool blank. Alternatively, the shank 2 and the tool head 3 can be made from different tool blanks that are subsequently rigidly connected to each other.

[0037] The tool head 3 comprises a milling section 4, a grinding section 5 adjoining it in the longitudinal direction, and a further milling section 6 adjoining the grinding section 5 in the longitudinal direction. The milling section 4, the grinding section 5, and the further milling section 6 are arranged axially 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 further milling section 6, so that the further 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 one grinding section 5. It is also conceivable for several milling sections and several grinding sections to be arranged alternately adjacent to one another along the longitudinal axis L.

[0038] In the design example shown, the milling section 4 is arranged on the tool head 9 facing away from the shank 2. The grinding section 5 can also be arranged on the tool tip 9.

[0039] The two milling sections 4, 6 each have several geometrically defined cutting edges 7, 8 over the entire circumference, which extend in a spiral pattern. Geometrically defined cutting edges are characterized by the number of cutting edges, their travel and the geometry of the cutting edges in cross section (cutting wedge) being predetermined and well defined.

[0040] The grinding section 5 has abrasive grains bonded around its entire circumference about the longitudinal axis L in a bonded matrix consisting of abrasive material with geometrically undefined cutting edges. Geometrically undefined cutting edges are characterized by the fact that the number of cutting edges, their travel, and the geometry of the cutting edges in cross section (cutting wedge) are not predetermined or clearly defined. The abrasive grains consist, in particular, of cubic boron nitride (CBN), diamond, corundum, zirconium corundum, ceramic corundum, or silicon carbide.

[0041] Figure 2 Shown according to Figure 1 An enlarged view of the tool head 3 of a first embodiment of an end mill 1 in the area of the tool end 9 , corresponding components being designated by the same reference numerals. The first embodiment of the end mill 1 comprises a grinding section 5 having only geometrically undefined cutting edges, i.e., essentially forming a cylindrical outer circumferential surface. The grinding section 5 is formed by a grinding wheel 12 consisting of abrasive grains bonded in a bonding matrix. The milling section 4 and the further milling section 6 form only geometrically defined cutting edges 7 , 8 . In the illustrated design example, the grinding section 5 is located between the milling section 4 and the further milling section 6 . The milling section 4 is arranged at the tool end 9 .

[0042] Figure 3 Shown according to Figure 1An enlarged view of the tool head 3 in the area of the tool tip 9 of a second embodiment of an end mill 1, corresponding components being provided with the same reference numerals. The second embodiment of the end mill 1 has a grinding section 5 that forms a geometrically undefined cutting edge and is additionally shaped to form a geometrically defined cutting edge 10. The grinding section 5 is formed by a grinding wheel 12 composed of abrasive grains bonded in a bonding matrix. As in the first embodiment, the grinding section 5 is located between the milling section 4 and a further milling section 6. The geometrically defined cutting edges 7, 8, 10 can be aligned with one another in the axial direction.

[0043] Figure 4 and Figure 5 Different views of partial longitudinal sections of the first and second embodiments are shown. It can be seen that the milling section 4 is formed by the milling shank 11. The other milling section 6 is formed by another milling shank 13. The two milling shafts 11, 13 are designed as separate components. In the design example shown, the additional milling shank 13 is integrally connected, i.e., in one piece, to the shank 2. Alternatively, the additional milling shank 13 can be designed as a separate component from the shank 2, with the milling shank 13 being rigidly connected to the shank 2 by a material-fitting or form-fitting connection, for example, by welding. 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 located between the milling shank 11 and the other milling shank 13 and is rigidly connected to them by a material-fitting or form-fitting connection. For example, the grinding wheel 12 can be adhesively bonded or welded to both milling shanks 11, 13. In order to enable the milling shanks 11, 13 and the grinding wheel 12 to be connected to each other in a centered manner relative to each other and the longitudinal axis L, the milling shanks 11, 13 each have a central centering projection 19, 20 pointing towards the grinding wheel 12, each projection cutting into a centering recess 21, 22 of the grinding wheel 12. In principle, it is also conceivable that the milling shanks 11, 13 have no centering projection and the grinding wheel 12 correspondingly have no centering recess.

[0044] For production, a continuous tool blank with a geometrically defined cutting edge 8 can first be formed. The tool head 9 is then cut off. The grinding wheel 12 can then be rigidly connected between the milling shank 11 formed by the cut-off and another milling shank 13.

[0045] Alternatively, initial production can be performed using a tool blank that has not yet been formed into a geometrically defined cutting edge. The tool head 9 is then cut off or provided as a separate component. The grinding wheel 12 is then positioned between the two milling shanks 11, 13 and rigidly connected to them. The geometrically defined cutting edge can then be ground continuously via the two milling sections 4, 6 and the grinding section 5.

[0046] like Figure 6As shown schematically, the grinding wheel 12 has a metal, ceramic or synthetic resin based bonding matrix 18 in which abrasive particles 17 are bonded. The abrasive particles 17 comprise abrasive materials with cutting edges of undefined geometry.

[0047] Figure 7 and Figure 8 Shown according to Figure 1 1 , in which corresponding parts bear the same reference numerals. The grinding section 5 is formed by a cylindrical section 14 having a peripheral surface 15. The peripheral surface 15 is coated with abrasive grains 27 held in a bonding matrix 28. Here, the peripheral surface 15 is formed by a peripheral groove 16 located between the milling section 4 and the further 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.

[0048] The abrasive particles 27 are housed in a bonding matrix 28 and protrude outward from the bonding matrix 28 or may be encapsulated by the bonding matrix 28. The bonding matrix 28 is an electrochemical (e.g., electroplated) bonding matrix made of nickel. The abrasive particles 27 can be made of the same materials as in the previous two embodiments. For cutting removal, the abrasive particles 17 have a geometrically undefined cutting edge in the form of an edge 29.

[0049] Figure 9 The figure shows the alignment of the end mill 1 during machining of a workpiece 23. The workpiece 23 is a plate-like component, such as a semiconductor chip. The workpiece 23 includes a first layer 24, a second layer 25, and a third layer 26, with the second layer 26 disposed between the first and third layers 24 and 26. The first and third layers 24 and 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.

[0050] To machine the workpiece 23, the end mill 1 is aligned in such a way that the milling section 4 is arranged in the axial direction along the longitudinal axis L in the plane of the first layer 24 or overlaps with it. In addition, the grinding section 5 is arranged in the axial direction in the plane of the second layer 25. Another milling section 6 is arranged at least partially in the axial direction in the plane of the third layer 26. To machine the workpiece 23, the end mill 1 is moved transversely to the longitudinal axis L in the direction of the arrow P while rotating around the longitudinal axis L. As a result, the geometrically defined cutting edges 7, 8 can cut ductile materials. The geometrically undefined 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 a suitable section of the end mill 1 is used for each material of the respective layer 24, 25, 26.

[0051] Reference Signs List

[0052] 1 End mill

[0053] 2 handle

[0054] 3 Tool head

[0055] 4 Milling sections

[0056] 5 Grinding section

[0057] 6 Another milling section

[0058] 7 Geometrically defined cutting edges

[0059] 8 Geometrically defined cutting edges

[0060] 9 Tool end

[0061] 10 Geometrically defined cutting edges

[0062] 11 Milling shank

[0063] 12 Grinding Wheel

[0064] 13 Another milling shank

[0065] 14 cylindrical segments

[0066] 15 Peripheral surface

[0067] 16 Peripheral groove

[0068] 17 Abrasive

[0069] 18 Bonding matrix

[0070] 19 Centering protrusion

[0071] 20 Centering protrusion

[0072] 21 Centering the recess

[0073] 22 Centering the recess

[0074] 23 Workpiece

[0075] 24 First Floor

[0076] 25 Second Floor

[0077] 26 Third Floor

[0078] 27 Abrasive

[0079] 28 bonding matrix

[0080] 29 Edge

[0081] P arrow

Claims

1. An end mill (1), comprising: a shank (2) rotatably drivable about the longitudinal axis (L) of the end mill (1) and designed to be received in a rotary tool holder of a machine tool; as well as a tool head (3) rigidly connected to the shank (2) via a milling section (4) having at least one geometrically defined cutting edge (7) around its circumference about the longitudinal axis (L), It is characterized by: The tool head (3) has a grinding section (5) having abrasive grains (17) of an abrasive material with a geometrically undefined cutting edge, the abrasive grains being bonded in a bonding matrix (18) surrounding the grinding section around the longitudinal axis (L) and being arranged at a distance from the milling section (4) in the direction of the longitudinal axis (L).

2. The end mill (1) according to claim 1, It is characterized by: The milling section (4) has only geometrically defined cutting edges (7).

3. The end mill (1) according to claim 1 or 2, It is characterized by: The grinding section (5) has only a geometrically undefined cutting edge (7).

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

5. The end mill (1) according to any one of claims 1 to 4, It is characterized by: A further milling section (6) is arranged axially between the grinding section (5) and the shank (2) in the direction of the longitudinal axis (L), and has at least one geometrically defined cutting edge (8) on its circumference around the longitudinal axis (L).

6. An end mill (1) according to any one of claims 1 to 5, It is characterized by: The grinding section (5) is formed by a grinding wheel (12) formed by abrasive grains (17) bonded in the bonding matrix (18), The milling section (4) is formed by a milling shank (11), and The grinding wheel (12) and the milling shank (11) are rigidly connected to each other in a materially or force-fitting manner.

7. The end mill (6) according to claim 6, It is characterized by: The grinding wheel (12) and the shank (2) are rigidly connected to each other in a materially or force-fitting manner.

8. The end mill (6) according to claim 6 or 7, It is characterized by: A further milling shank (13) is arranged between the grinding wheel (12) and the shank (2).

9. The end mill (8) according to claim 8, It is characterized by: The further milling shank (13) is rigidly connected to the grinding wheel (12) on the one hand and is rigidly connected to the shank (2) on the other hand in a materially or force-fitting manner.

10. An end mill (1) according to any one of claims 1 to 5, It is characterized by: The grinding section (5) is formed by a cylindrical section (14) having an outer peripheral surface (15), and A bonding matrix (18) having abrasive particles (17) contained therein is applied to the peripheral surface (15).

11. The end mill (10) according to claim 10, It is characterized by: The cylindrical section (14) is formed by a peripheral groove (16).

12. Method for machining a workpiece (23) using an end mill (1) according to any one of the preceding claims, wherein: The workpiece (24) comprises a plurality of planar layers (24, 25, 26) of different materials, and the method comprises the following steps: aligning the end mill (1) so that the longitudinal axis (L) of the end mill is transverse to the plane of the layers (24, 25, 26); aligning the end mill (1) so that the milling section (4) is arranged in an axial direction in the plane of a first layer (24) of the workpiece (23), and the grinding section (5) is arranged in an axial direction in the plane of a second layer (25) of the workpiece (23); and The workpiece (23) is subjected to a material removal process by means of a rotationally driven end mill (1) along a feed direction (P) parallel to the plane of the layers (24, 25, 26).

13. The method according to claim 12, It is characterized by: aligning the milled section (4) in the axial direction in the plane of the first layer (24) of ductile material, such as plastic, non-ferrous metal, aluminum, synthetic resin; as well as The grinding segment (5) is aligned in the axial direction in the plane of the second layer (25) made of a brittle material, such as silicon carbide, silicon, glass, ceramic.

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