Micro Forming End Mill

Abstract

The present disclosure relates to a micro forming end mill (1) for the manufacture of forming tools, for example in the fabrication of tools and dies for the formation of fuel cell components. The disclosed micro forming end mill comprises a tool shank (2) designed to be received in a tool holder of a milling machine, and a cutting head (3) fixedly connected to the tool shank (2). The cutting head (3) has a plurality of cutting teeth (Z), each of the plurality of cutting teeth (Z) having a cutting edge (S). The maximum distance (A) from the longitudinal axis (L) to a cutting point (6, 7, 8, 9) on the cutting edge (S) is 1 / 2 the maximum distance (A) from the longitudinal axis (L) to the cutting point (6, 7, 8, 9) on the cutting edge (S). max ) is less than 0.5 mm. At least two cutting edges (S) are arranged at least locally radially offset from one another, the radial offset (V) corresponding to the difference in distance from the longitudinal axis (L) of the cutting point (6, 7, 8, 9) to the at least two cutting edges (S) lying in a common plane (E) perpendicular to the longitudinal axis (L).

Description

[Technical field]

[0001] The present invention relates to a forming end mill for milling workpieces in the micron range. [Background technology]

[0002] In recent years, innovative products such as bipolar plates for fuel cells have increased the need for ever smaller components, which place increasingly stringent requirements on the dimensional accuracy and surface roughness of these components.

[0003] At the same time, the need for smaller and smaller parts places stringent requirements on the tooling used to manufacture these parts. For this reason, the need for micro-end mills has arisen in the field of milling tools. End mills with a tool diameter of less than 1 mm are called micro-end mills. The machining conditions of micro-end mills cannot be compared with the machining conditions of larger end mills with tool diameters of, for example, 3 mm, 4 mm, or 6 mm. Therefore, the geometry of micro-end mills cannot be determined by simply reducing the geometry of larger end mills.

[0004] Chamfer end mills with tool diameters in the range of 0.4 mm to 3 mm are known from 6C Tools. For example, a 6C Tools chamfer end mill with part number CM-P-1045-030-020 has eight cutting teeth, each cutting edge. The cutting edges have a maximum diameter of 3.0 mm and a minimum diameter of 2.0 mm. The cutting edges extend at a constant angle of attack of 45°.

[0005] The technical problem underlying the present invention is to improve the dimensional accuracy and surface roughness in the manufacture of parts in the micron range compared to known end mills. Summary of the Invention

[0006] The technical problem underlying the present invention is solved by a micro forming end mill for the manufacture of forming tools, for example in the production of tools and dies for the formation of fuel cell components. The micro forming end mill comprises a tool shank designed to be received in a tool holder of a milling machine and a cutting head fixedly connected to the tool shank. The tool shank and the cutting head have a common longitudinal axis about which the micro forming end mill rotates during use. The cutting head has a plurality of cutting teeth, each of the plurality of cutting teeth having a cutting edge. The maximum distance from any cutting point on the cutting edge to the longitudinal axis is less than 0.5 mm. At least two cutting edges are arranged at least locally radially offset from one another. The radial offset corresponds to the difference in distance from the longitudinal axis of such cutting point to those at least two cutting edges that lie in a common plane perpendicular to the longitudinal axis.

[0007] The concept underlying the present invention is to adjust and tune the engagement conditions of the cutting edges of multiple cutting teeth of a micro-forming end mill so that uniform and optimal dimensional accuracy of the workpiece being machined using the micro-forming end mill can be achieved.

[0008] The engagement condition is adjusted by the radial offset of the cutting edges relative to one another. Thus, a pre-finishing effect can be achieved during machining of the workpiece. The cutting edges offset radially inwardly towards the longitudinal axis can pre-finish the final contour of the workpiece to be machined. The radially outermost cutting edges form the final contour on the workpiece.

[0009] The cutting edges may be offset over the entire cutting edge length or may only have an offset locally, so that the final profile may also be formed by the outermost regions of the different cutting edges.

[0010] Due to the offset of the cutting edges, not all cutting edges of the micro forming end mill are on the outer envelope, but rather are more or less set back depending on their position on the tool and their wrap around in the part. The envelope represents the enveloping surface of all paths of any cutting point rotating around the longitudinal axis during use of the micro forming end mill. The envelope is therefore formed by the points with the greatest radial distance from the longitudinal axis, and each point of a common plane perpendicular to the longitudinal axis is considered. This prevents chatter marks and ensures a better surface quality of the part. For example, the cutting edges of the front region of the cutting head can be arranged such that the cutting edges of all cutting teeth are on the outer envelope, while the cutting edges of the rear region of the cutting head can be arranged such that only the cutting edges of some of all cutting teeth are on the outer envelope.

[0011] Micro forming end mills are suitable for precision milling of very small workpieces, such as forming tools in the manufacture of tools and dies for forming fuel cell components, corresponding to the very small distance from the longitudinal axis of any cutting point on the cutting edge.

[0012] Preferably, the cutting teeth are integrally formed with the cutting head. Preferably, the manufacturing is carried out from a polycrystalline diamond (PCD) blank using laser technology. Material can be removed by laser ablation until the desired geometric shape of the cutting edge of each cutting tooth remains on the cutting tooth.

[0013] According to a preferred embodiment, at least one cutting edge extends from a minimum distance at the cutting edge start point facing the exposed end of the cutting head to a maximum distance at the cutting edge end point facing the tool shank in an S-shaped segment. The S-shaped segment preferably includes, when viewed in a direction from the cutting edge start point towards the cutting edge end point, a first curved region in which the attack angle of the cutting edge changes so that the cutting edge extends in an arc-shaped curved shape with a first radius, an intermediate region in which the cutting edge extends at a constant attack angle, and a second curved region in which the attack angle of the cutting edge changes so that the cutting edge extends in an arc-shaped curved shape with a second radius. The attack angle of a cutting point is the angle between a tangent to the cutting edge at this cutting point and a line parallel to the longitudinal axis extending through this cutting point.

[0014] At least one cutting edge having an S-shaped segment can be used to establish a radial offset of the cutting edge to improve adjustment of the engagement condition. The S-shaped segments of the cutting edge allow for the spacing of the cutting points along the cutting edge to be tailored depending on the requirements of the workpiece being machined. Compared to a straight cutting edge, the S-shape allows different cutting points along the cutting edge to have different angles of attack.

[0015] The S-shape of the cutting edges allows multiple cutting edges to be positioned relative to one another such that they extend offset from one another only locally. The cutting edge may be formed by only an S-shaped segment. Alternatively, additional segments may be connected to the cutting edge in front of the S-shaped segment and / or behind the S-shaped segment. For example, both in front and behind the S-shaped segment may be provided with segments having a constant angle of attack that connect the S-shaped segment to the cutting edge start and cutting edge end, respectively.

[0016] In another exemplary embodiment of the invention, a first curved portion of the S-shaped segments is curved away from the common longitudinal axis and a second curved portion is curved toward the common longitudinal axis.

[0017] Alternatively, a first curved region of the S-shaped segment may be curved toward the common longitudinal axis and a second curved region may be curved away from the common longitudinal axis, thereby allowing the engagement conditions of the cutting points along the cutting edge to be better tailored to the workpiece being machined.

[0018] In another exemplary embodiment of the present invention, the cutting edge is in the same plane as the longitudinal axis, which may affect the engagement conditions of the micro forming end mill. In another exemplary embodiment of the invention, the cutting edge lies in a plane that intersects the longitudinal axis, which may affect the engagement conditions of the micro-molding end mill.

[0019] In another exemplary embodiment of the invention, the wedge angle and / or clearance angle and / or rake angle of the cutting point vary at least locally along the cutting edge. The wedge angle can be variably adjusted according to the distance of the cutting point along the cutting edge and / or the attack angle. Therefore, uniform ablation can be obtained along the cutting edge, and the best possible tool life can be achieved. The dimensional accuracy and surface accuracy of the workpiece can be more accurately met.

[0020] Additionally, the rake and clearance angles can be adjusted along the cutting edge based on the altered engagement conditions for different milling operations. p , cutting width a e , Feed per tooth f z , cutting speed v c , and the distance from the cutting point on the cutting edge to the longitudinal axis.

[0021] As a result, for example, a large rake angle may be favored in areas where the cutting point is less distant from the longitudinal axis and for the outer radii of the cutting edge, i.e., the radii curved away from the longitudinal axis, while a small or negative rake angle is favored for the inner radii of the cutting edge, i.e., the radii curved toward the longitudinal axis, and in areas where the cutting point is more distant from the longitudinal axis.

[0022] In another exemplary embodiment of the present invention, the cutting head comprises at least 4, and more particularly 8 to 12, cutting teeth, preferably uniformly distributed around the circumference of the cutting head.

[0023] The cutting edges are the wear parts of the micro-formed end mill. The more cutting edges a micro-formed end mill has, the more cutting edges share the wear and the longer the tool life. Furthermore, a micro-formed end mill with multiple cutting edges will run "smoother" than one with only one cutting edge. Multiple cutting edges can achieve a smoother surface on the workpiece being machined.

[0024] Furthermore, by utilizing multiple cutting edges, the engagement time of the cutting edges is significantly reduced, thereby allowing steel based polycrystalline diamond (PCD) tools to be used for finishing without issue.

[0025] In another exemplary embodiment of the invention, the cutting head has a group of at least two consecutive cutting teeth, the cutting edges of which are at least locally arranged radially offset from one another, the group of at least two consecutive cutting teeth being repeated at least once in the circumferential direction of the cutting head.

[0026] The partial offset of the cutting edges and the circumferentially repeating sequence of groups of cutting teeth with multiple cutting edges offset relative to one another can have a positive effect on the smooth operation of the tool and the surface quality during milling.

[0027] Furthermore, it is possible to design the geometry of the cutting head such that there is a radial offset of the cutting edge in a rear region of the cutting edge where the cutting point on the cutting edge is at a greater distance from the longitudinal axis, while there is no radial offset of the cutting edge in a front region of the cutting edge where the cutting point on the cutting edge is at a smaller distance from the longitudinal axis.

[0028] In an embodiment having a total of 12 cutting edges, each having an S-shaped segment, the cutting edges can be arranged such that, for example, there is no cutting edge offset in the front region of the cutting edge that is closer to the longitudinal axis of the cutting point, but there are only four cutting edges on the outer envelope in the rear region of the cutting edge that is closer to the longitudinal axis of the cutting point. Thus, the number of teeth with cutting edges on the outer envelope is reduced from 12 in the region of the cutting edge start to four cutting edges in the region of the cutting edge end.

[0029] Preferably, the cutting edge on the cutting teeth is formed such that the ratio of the feed per tooth to the effective diameter of the cutting edge along the cutting edge is in the range of 0.8% to 1.5%. As a result, the load on the cutting edge is as constant as possible along the cutting edge from the beginning to the end of the cutting edge. The effective diameter of a cutting point corresponds to twice the distance of this cutting point from the longitudinal axis. The effective diameter of the cutting point along the cutting edge increases from the front to the rear along the longitudinal axis.

[0030] In another exemplary embodiment of the present invention, the minimum distance of the cutting edges in the region of the first curved region (I) is in the range of 0.1-0.3 mm, and the maximum distance of the cutting edges in the region of the second curved region (III) is in the range of 0.3-0.5 mm. Furthermore, the first radius of the first curved region is in the range of 0.005 mm-0.25 mm, and the constant angle of attack in the middle region of the S-shaped segment is in the range of 0°-45°. Furthermore, the second radius of the second curved region is in the range of 0.1 mm-0.25 mm, and the cutting edges are radially offset from each other such that the maximum cutting edge offset (Vmax) is in the range of 0.001 mm-0.08 mm.

[0031] The design of the cutting edges according to the dimensions of this exemplary embodiment allows for an optimal layout of the individual cutting edges and optimal tuning of multiple cutting edges relative to each other, with the local offset of the cutting edges leading to pre-finishing effects as well as high dimensional accuracy and surface roughness of the workpiece to be machined.

[0032] According to another aspect of the invention, the technical problem is solved by a micro forming end mill for the manufacture of forming tools, for example in the production of tools and dies for forming fuel cell components. The micro forming end mill comprises at least one cutting edge, which extends with an S-shaped segment from a minimum distance at the cutting edge start point facing the exposed end of the cutter head to a maximum distance at the cutting edge end point facing the tool shank. The S-shaped segment preferably includes a first curved region in which the attack angle of the cutting edge changes so that the cutting edge extends in an arc-shaped curved shape with a first radius, an intermediate region in which the cutting edge extends with a constant attack angle, and a second curved region in which the attack angle of the cutting edge changes so that the cutting edge extends in an arc-shaped curved shape with a second radius, when viewed in a direction from the cutting edge start point towards the cutting edge end point. The attack angle of a cutting point is the angle between a tangent to the cutting edge at the cutting point and a line parallel to the longitudinal axis extending through the cutting point.

[0033] Exemplary embodiments of the invention are described and explained in more detail below with reference to the accompanying drawings. [Brief description of the drawings]

[0034] [Figure 1] FIG. 2 is a side view of a micro forming end mill according to the present invention. [Diagram 2] FIG. 2 is a front view of the cutting head of the micro forming end mill shown in FIG. 1. [Diagram 3] FIG. 3 is a cross-sectional view along section BB of the cutting tooth Z1 of the cutting head shown in FIG. 2, the cross-sectional plane being configured to include the longitudinal axis of the cutting head and the cutting edge S1 of the illustrated cutting tooth Z1. [Figure 4] 3A-3C are cross-sectional views of cutting teeth Z1-Z12 of the cutting head shown in FIG. 2, each of which is shown in superimposed form, with the cross-sectional planes configured to include the longitudinal axis of the cutting head and the cutting edges S1-S12 of each of the illustrated cutting teeth Z1-Z12. [Diagram 5] FIG. 2 is a cross-sectional view of twelve cutting teeth Z1-Z12 of another cutting head according to the present invention, the cross-sectional views being shown in superimposed form, the cross-sectional planes being configured to include the longitudinal axis of the cutting head and the cutting edges S1-S12 of each of the illustrated cutting teeth Z1-Z12. [Figure 6] FIG. 2 is a side view of a cutting head according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] Hereinafter, the direction along the longitudinal axis is referred to as the front-rear direction and / or the longitudinal direction. The side of the micro forming end mill where the cutting head is located is referred to as the front side of the micro forming end mill. The side where the tool shank is located is referred to as the rear side of the micro forming device. The direction perpendicular to the longitudinal axis is referred to as the radial direction.

[0036] FIG. 1 shows a side view of a micro forming end mill 1 according to the invention. The micro forming end mill 1 comprises a tool shank 2 and a cutting head 3. The cutting head 3 is fixedly connected to the tool shank 2. For example, the tool shank 2 and the cutting head 3 can be fixedly connected to each other by a solder joint. A plurality of cutting teeth Z are located in the front region of the cutting head 3. The tool shank 2 and the cutting head 3 have a common longitudinal axis L. In use, the micro forming end mill 1 rotates around this common longitudinal axis L. When using the micro forming end mill shown in FIG. 1, the feed is perpendicular to the longitudinal axis L.

[0037] Preferably, the tool shank 2 is made of solid carbide (SC). Preferably, the cutting head 3 is made of polycrystalline diamond (PCD) or cubic boron nitride (CBN).

[0038] FIG. 2 shows a front view of the micro forming end mill 1 shown in FIG. The cutting head 3 comprises a total of 12 cutting teeth Z1-Z12. Each of these cutting teeth Z1-Z12 includes a cutting edge S1-S12. These cutting edges S1-S12 engage with a workpiece during use of the micro forming end mill 1. The illustrated micro forming end mill 1 rotates counterclockwise during use. In the illustrated embodiment of the micro forming end mill 1, the cutting edges S1-S12 extend in a straight line from front to rear, i.e. in the direction of the longitudinal axis. The cutting edges S1-S12 are arranged such that the cutting edge start ends of the cutting edges are located at a common point on the longitudinal axis L.

[0039] According to further embodiments, the cutting edge may extend obliquely or helically from front to rear. The rake face 11 may extend radially outwardly from the longitudinal axis L in a straight, oblique or curved manner. The surface where the cutting is performed during machining of the cutting teeth Z is called the rake face 11.

[0040] 3 shows a cross-sectional view along the section BB of the cutting tooth Z1 of the cutting head shown in FIG. 2, the cross-sectional plane being configured to include the longitudinal axis of the cutting head and the cutting edge S1 of the illustrated cutting tooth Z1. The cutting edge S extends from the cutting edge start point 4 to the cutting edge end point 5. The cutting edge start point 4 is located in front of the cutting edge end point 5. The distance A from any cutting point 6, 7, 8, 9 on the cutting edge S increases from front to rear along the cutting edge S. The distance of the cutting edge S is maximum at the cutting edge end point 5. The distance of the cutting edge S is minimum at the cutting edge start point 4. In this case, the cutting edge S starts from the longitudinal axis L, so the minimum distance is 0.

[0041] The cutting edge S has an S-shaped segment along its progression from the cutting edge start 4 to the cutting edge end 5. The S-shaped segment includes a first curved region I, in which the angle of attack α of the cutting edge S changes so that the cutting edge S extends in an arc-shaped curved shape with a first radius R1. The arc-shaped curved shape is curved outward, i.e., away from the longitudinal axis L. The cutting points 6 and 7 are located at the beginning and end of the first curved segment I, respectively. The S-shaped segment further includes an intermediate region II, in which the cutting edge S extends at a constant angle of attack α. The cutting points 7 and 8 are located at the beginning and end of the intermediate region II, respectively. The S-shaped segment further includes a second curved region III, in which the angle of attack α of the cutting edge S changes so that the cutting edge S extends in an arc-shaped curved shape with a second radius R2. The arcuate curved shape is curved inwardly, i.e., towards the longitudinal axis L. Cutting points 8 and 9 are located at the start and end points, respectively, of the second curved region III.

[0042] Both in front of the S-shaped segment of the cutting edge S and behind the S-shaped segment there is a region having a constant angle of attack that connects the S-shaped segment to the cutting edge start end 4 and the cutting edge end end 5, respectively.

[0043] The angle of attack α is the angle between a tangent to the cutting edge S at the cutting point 6 and a line parallel to the longitudinal axis L extending through the cutting point 6. E denotes a plane perpendicular to the longitudinal axis L and extending through the cutting point 8 on the cutting edge S.

[0044] FIG. 4 is a cross-sectional view of the cutting teeth Z1-Z12 of the cutting head shown in FIG. 2, with three cross-sectional views each shown in superimposed form, with the cross-sectional planes configured to include the longitudinal axis of the cutting head and the cutting edges S1-S12 of each of the illustrated cutting teeth Z1-Z12.

[0045] The cutting edges S1, S5 and S9 of the cutting teeth Z1, Z5 and Z9 are identical. The S-shaped segments of the cutting edges S1, S5 and S9 are characterized by the same radii R1, R2 of the first and second curved regions and the same angle of attack α of the intermediate region.

[0046] The cutting edges S2, S6, S10 of the cutting teeth Z2, Z6, and Z10 are identical. The S-shaped segments of the cutting edges S2, S6, and S10 are characterized by the same radii R1', R2' of the first and second curved regions and the same angle of attack α' of the intermediate region, with at least one of the radius R1', radius R2', and angle of attack α' differing from the corresponding sizes of the cutting edges S1, S5, and S9.

[0047] The cutting edges S3, S7, S11 of the cutting teeth Z3, Z7, and Z11 are identical. The S-shaped segments of the cutting edges S3, S7, and S11 are characterized by identical radii R1'', R2'' of the first and second curved regions and identical angles of attack α'' of the intermediate regions, with at least one of the radius R1'', radius R2'', and angle of attack α'' differing from the corresponding sizes of the cutting edges S1, S5, and S9.

[0048] The cutting edges S4, S8, S12 of the cutting teeth Z4, Z8, and Z12 are identical. The S-shaped segments of the cutting edges S4, S8, and S12 are characterized by identical radii R1''', R2''' of the first and second curved regions and identical angles of attack α'''' of the intermediate regions, with at least one of the radius R1''', radius R2'''', and angle of attack α'''' differing from the corresponding sizes of the cutting edges S1, S5, and S9.

[0049] Due to differences in their respective radii and respective angles of attack, any cutting points 6, 6', 6'', and 6''', all lying in a common plane perpendicular to the longitudinal axis L, may be spaced a different distance from the longitudinal axis. The cutting edge beginnings 4, 4', 4'', and 4''', and cutting edge endings 5, 5', 5'', and 5''', may be located at different points along the longitudinal axis L or may be spaced a different distance from the longitudinal axis.

[0050] FIG. 5 shows cross-sectional views of twelve cutting teeth Z1-Z12 of another cutting head according to the present invention, the cross-sectional views being shown in superimposed form, with the cross-sectional planes being configured to include the longitudinal axis of the cutting head and the cutting edges S1-S12 of each of the illustrated cutting teeth Z1-Z12.

[0051] Cutting edges S1, S5 and S9 are identical to each other. Cutting edges S2, S6 and S10 are identical to each other. Cutting edges S3, S7 and S11 are identical to each other. Cutting edges S4, S8 and S12 are identical to each other. However, the four groups of identical cutting edges are different from each other, e.g., cutting edges S1, S2, S3 and S4 are not identical to each other.

[0052] Due to the different design of each cutting edge S1-S12, not all cutting points of the multiple cutting edges S1-S12 are the same distance from the longitudinal axis L when located in the same plane E perpendicular to the longitudinal axis L. Rather, due to the different design of each cutting edge S1-S12, a radial offset V occurs between the cutting edges S1-S12. The cutting offset V corresponds to the difference in radial distance to the longitudinal axis L of the cutting points on the different cutting edges S1-S12. Thus, the considered cutting points 6, 6' are in a common plane E perpendicular to the longitudinal axis L.

[0053] Referring to the points in Figure 5, the envelope (Hullkurve) is formed by points (4,4') through (6') through (5',7'), i.e., the points in plane E with the greatest radial distance from the longitudinal axis.

[0054] Cutting point 6 is on one of the cutting edges of group S3, S7, S11 or group S4, S8, S12. Cutting point 6' is on one of the cutting edges of group S1, S5, S9 or group S2, S6, S10. Cutting point 6' is farther away from the longitudinal axis L than cutting point 6. The difference is the radial offset V.

[0055] Cutting point 7 is on one of the cutting edges of group S3, S7, S11, group S4, S8, S12, or group S2, S6, S10. Cutting point 7' is on one of the cutting edges of group S1, S5, S9. It coincides with cutting edge end 5'. Cutting point 7' is further away from longitudinal axis L than cutting point 7. The difference is the radial offset V, which in this case is the maximum radial offset V max It is.

[0056] The cutting edges S1, S5 and S9 are, over their entire length, farther away from the longitudinal axis L than the remaining cutting edges or equally farther away from them, and therefore determine the final contour on the workpiece to be machined.

[0057] According to a preferred embodiment, the cutting teeth Z1-Z12 with their cutting edges S1-S12 are arranged on the cutting head 3 such that the different cutting edges S1-S4 follow one another in the circumferential direction of the cutting head 3 and this sequence of different cutting edges S1-S4 repeats in the circumferential direction. Thus, a sequence of different cutting teeth S5-S8 follows cutting tooth S4 in this order, which correspond to the cutting teeth S1-S4 in this order. Furthermore, a sequence of different cutting teeth S9-S12 follows cutting tooth S8 in this order, which correspond to the cutting teeth S1-S4 and to the cutting teeth S5-S8, respectively, in this order.

[0058] 6 shows a side view of a cutting head according to another embodiment of the present invention. In comparison with the other embodiments, the cutting edge includes two additional segments at the cutting edge end, each of which has a constant angle of attack α. These regions are non-cutting extensions associated with the production of the cutting edge. [Industrial Applicability]

[0059] The use of the micro-forming end mill according to the invention allows workpieces to be machined in the micro range and makes it possible to meet the most stringent requirements for dimensional accuracy and surface roughness.

[0060] For example, the micro forming end mill according to the invention can be used to manufacture forming tools in the production of tools and dies used to manufacture fuel cell components. In particular, the micro forming end mill according to the invention is used for contour finishing during the finishing of such forming tools. The height of the parts of such forming tools is generally less than 0.5 mm and the surface between the lateral contours is at most 0.6 mm. The requirements imposed on the parts in terms of dimensional accuracy and surface roughness Ra are very high. The dimensional accuracy is preferably in the range of less than 0.003 mm and the surface roughness Ra is preferably in the range of less than 0.2 μm. [Explanation of symbols]

[0061] 1 Micro Forming End Mill 2 Tool shank 3 Cutting head 4, 4', 4', 4''' Cutting edge start 5, 5', 5'', 5''' Cutting Edge Ends 6, 6', 7, 7', 8, 9 cutting points 10 Workpieces 11. Scooping surface 12 Main relief face α, α', α'', α''' Angle of attack β Wedge angle δ Clearance angle γ Rake angle Z, Z1~Z12 cutting teeth S, S1~S12 Cutting edge A Distance A min minimum distance A max maximum distance V Radial offset V max Maximum Radial Offset L Longitudinal axis E Plane perpendicular to the longitudinal axis L R 1 , R 1 ', R 1 '', R 1 ''' Radius of the first circular curve R 2 , R 2 ', R 2 '', R 2 ''' Radius of the second circular curve I First curved region II Intermediate area III Second curved region

Claims

1. A micro forming end mill (1) for the manufacture of forming tools, e.g. in the production of tools and moulds for the forming of fuel cell components, comprising: a tool shank (2) designed to be received in a tool holder of a milling machine; a cutting head (3) fixedly connected to the tool shank (2), the tool shank (2) and the cutting head (3) having a common longitudinal axis (L) about which the micro forming end mill (1) rotates in use; a) the cutting head (3) has a plurality of cutting teeth (Z), each of the plurality of cutting teeth (Z) having a cutting edge (S); b) the maximum distance (A) from any cutting point (6, 7, 8, 9) on said cutting edge (S) to said longitudinal axis (L); ｍａｘ ) is less than 0.5 mm; c) at least two cutting edges (S) are arranged radially offset from one another only locally, the radial offset (V) corresponding to the difference in distance from said longitudinal axis (L) of said cutting points (6, 7, 8, 9) on said at least two cutting edges (S) lying in a common plane (E) perpendicular to said longitudinal axis (L), d) a micro-forming end mill (1), wherein at least one cutting edge (S) extends with an S-shaped segment from a minimum distance (A min ) at a cutting edge start (4) facing the exposed end of the cutting head (3) to a maximum distance (A max ) at a cutting edge end (5) facing the tool shank (2).

2. When the S-shaped segment is viewed in a direction from the cutting edge starting end (4) toward the cutting edge terminal end (5), a first curved region (I) in which the angle of attack (α) of the cutting edge (S) varies such that the cutting edge (S) extends in an arcuate curved shape having a first radius (R1); an intermediate region (II) in which the cutting edge (S) extends at a constant angle of attack (α); a second curved region (III) in which the angle of attack (α) of the cutting edge (S) varies such that the cutting edge (S) extends in an arcuate curved shape having a second radius (R2); 2. The microforming end mill (1) according to claim 1, wherein the angle of attack (α) of a cutting point (6, 7, 8, 9) is the angle between a tangent to the cutting edge (S) at said cutting point (6, 7, 8, 9) and a line extending through said cutting point (6, 7, 8, 9) that is parallel to the longitudinal axis (L).

3. 3. The microforming end mill (1) according to claim 2, wherein the first curved region (I) of the S-shaped segment is curved away from the common longitudinal axis (L) and the second curved region (III) is curved towards the common longitudinal axis (L).

4. The microforming end mill (1) according to any one of claims 1 to 3, wherein the cutting edge (S) lies in the same plane as the longitudinal axis (L).

5. The microforming end mill (1) according to any one of claims 1 to 3, wherein the cutting edge (S) lies in a plane intersecting the longitudinal axis (L).

6. The microforming end mill (1) according to any one of claims 1 to 5, wherein at least one of the wedge angle (β), clearance angle (δ) and rake angle (γ) of the cutting points (6, 7, 8, 9) varies at least locally along the cutting edge (S).

7. A micro forming end mill (1) as described in any one of claims 1 to 6, wherein the cutting head (3) has at least four, more specifically 8 to 12 cutting teeth (Z).

8. A micro forming end mill (1) as described in claim 7, wherein the cutting teeth (Z) are uniformly distributed around the cutting head (3).

9. The cutting head (3) a group of at least two consecutive cutting teeth (Z1, Z2), the cutting edges (S1, S2) of which are arranged radially offset from one another only locally, A microforming end mill (1) according to any one of the preceding claims, wherein this group of at least two consecutive cutting teeth (Z1, Z2) is repeated at least once in the circumferential direction of the cutting head (3).

10. the minimum distance (Amin) of the cutting edge in the region of the first curved region (I) is in the range of 0.1 to 0.3 mm, and the maximum distance (Amax) of the cutting edge in the region of the second curved region (III) is in the range of 0.3 to 0.5 mm, The radius (R1) of the first curved region is within the range of 0.005 mm to 0.25 mm; the constant angle of attack (α) at ​​the intermediate region of the S-shaped segment is in the range of 0° to 45°; The radius (R2) of the second curved region is in the range of 0.1 mm to 0.25 mm; The microforming end mill (1) according to claim 2, claim 3 or any one of claims 4 to 9 which cite claim 2, wherein the cutting edges are radially offset from one another such that the maximum cutting edge offset (Vmax) is in the range of 0.001 mm to 0.08 mm.

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