Ball end mill

Abstract

To provide a technique capable of smoothly cutting a cutting object.SOLUTION: Flanks may include: a second flank extending rearward in a rotation direction of a ball end mill from an end cutting edge; a third flank extending rearward in the rotation direction from an end portion of the second flank on the rearward side in the rotation direction; and an additional flank extending obliquely outward in a radial direction of the ball end mill from the end portion of the second flank on the rearward side in the rotation direction on a central axis side of the ball end mill with respect to the third flank.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to a ball end mill.

Background Art

[0002] A ball end mill is disclosed in Patent Document 1. The ball end mill of Patent Document 1 includes a bottom edge, a rake face of the bottom edge, and a flank face of the bottom edge.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The ball end mill of Patent Document 1 aims to improve machining accuracy, but in some cases, it may not be able to cut the workpiece smoothly depending on the type of the workpiece to be cut. For example, when cutting urethane, the ball end mill of Patent Document 1 may not be able to cut it smoothly in some cases. This specification provides a technology that can cut the workpiece smoothly.

Means for Solving the Problems

[0005] In the first aspect of the present technology, the ball end mill has a right-hand cutting edge with left-hand helix or a left-hand cutting edge with right-hand helix. The ball end mill includes a bottom cutting edge, a rake face of the bottom cutting edge, and a flank face of the bottom cutting edge. The rake face may include a first rake face and a second rake face on the central axis side of the ball end mill with respect to the first rake face. The flank face may include a second flank face extending rearward in the rotational direction of the ball end mill from the bottom cutting edge, a third flank face extending rearward in the rotational direction from an end portion of the second flank face on the rear side in the rotational direction, and an additional flank face obliquely extending outward in the radial direction of the ball end mill from the end portion of the second flank face on the rear side in the rotational direction on the central axis side of the ball end mill with respect to the third flank face.

[0006] According to this configuration, in a ball end mill with a right-hand cutting edge with left-hand helix or a left-hand cutting edge with right-hand helix, by further providing an additional flank face in addition to the second flank face and the third flank face, the ball end mill can be rotated smoothly when cutting a workpiece to be cut, and the workpiece to be cut can be cut smoothly.

[0007] In the second aspect, in the first aspect, taking the intersection of the first rake face, the second rake face, and the second flank face as a first intersection point, and taking the intersection of the second flank face, the third flank face, and the additional flank face as a second intersection point, when the ball end mill is viewed axially from the tip side of the ball end mill, the angle formed by a first straight line connecting the central axis of the ball end mill and the first intersection point and a second straight line connecting the central axis of the ball end mill and the second intersection point may be from 5° to 35°. When the ball end mill is viewed radially from the side face side of the ball end mill, the inclination angle of the additional flank face with respect to the central axis of the ball end mill may be from 20° to 30°.

[0008] According to this configuration, by adjusting the angle related to the flank face, the workpiece to be cut can be cut smoothly.

[0009] In the third aspect, in the first or second aspect described above, the object to be cut may be urethane. According to this configuration, the urethane that is the object to be cut can be cut smoothly.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0011] The ball end mill of the embodiment will be described with reference to the drawings. As shown in FIGS. 1 and 2, the ball end mill 2 of the embodiment includes a body portion 4 and a shank portion 6. The body portion 4 and the shank portion 6 are arranged in the axial direction of the ball end mill 2. The body portion 4 is provided on the tip side in the axial direction of the ball end mill 2, and the shank portion 6 is provided on the base end side in the axial direction of the ball end mill 2. The shank portion 6 is attached to a machine that rotates the ball end mill 2. The ball end mill 2 is a tool for cutting an object to be cut by rotating. The object to be cut by the ball end mill 2 is, for example, a urethane product.

[0012] The ball end mill 2 of the embodiment has a right-edge left-twist configuration. This ball end mill 2 cuts the object to be cut by rotating clockwise. In a modified example, the ball end mill 2 may have a left-edge right-twist configuration. In this case, the ball end mill 2 cuts the object to be cut by rotating counterclockwise. The ball end mill 2 with a right-edge left-twist or left-edge right-twist discharges the cutting chips generated by cutting the object to be cut to the tip side in the axial direction of the ball end mill 2.

[0013] Further, the ball end mill 2 of the embodiment has a two-edge configuration. The ball end mill 2 includes a first edge 8a and a second edge 8b that are point-symmetrical with respect to the central axis C of the ball end mill 2. In the following description, the first edge 8a may be denoted by the symbol with "a", and the second edge 8b may be denoted by the symbol with "b". Also, there may be descriptions without attaching "a" and "b" to the symbols. In the following description, mainly the first edge 8a will be focused on for explanation, and the explanation of the second edge 8b may be omitted. In a modified example, the ball end mill 2 may have a configuration with three or more edges.

[0014] The body portion 4 of the ball end mill 2 includes a bottom edge 10 (10a, 10b) and an outer peripheral edge 12 (12a, 12b) continuous with the bottom edge 10. The body portion 4 also includes a bottom-edge rake face 14 (14a, 14b) and an outer-peripheral-edge rake face 15 (15a, 15b) continuous with the bottom-edge rake face 14. The body portion 4 further includes a bottom-edge flank face 16 (16a, 16b) and an outer-peripheral-edge flank face 17 (17a, 17b) continuous with the bottom-edge flank face 16.

[0015] The body portion 4 includes the bottom edge 10a and the outer peripheral edge 12a of the first edge 8a, and the bottom edge 10b and the outer peripheral edge 12b of the second edge 8b. The body portion 4 also includes the bottom-edge rake face 14a and the outer-peripheral-edge rake face 15a of the first edge 8a, and the bottom-edge rake face 14b and the outer-peripheral-edge rake face 15b of the second edge 8b. The body portion 4 further includes the bottom-edge flank face 16a and the outer-peripheral-edge flank face 17a of the first edge 8a, and the bottom-edge flank face 16b and the outer-peripheral-edge flank face 17b of the second edge 8b.

[0016] The bottom edge 10 and the outer peripheral edge 12 will be described. The bottom edge 10 is provided at the axial tip of the ball end mill 2. The bottom edge 10 cuts the object to be cut at the axial tip of the ball end mill 2. As shown in FIG. 3, when the ball end mill 2 is viewed axially from the tip side of the ball end mill 2, the bottom edge 10 extends radially outward from the central axis C of the ball end mill 2. The bottom edge 10 is configured in a curved shape.

[0017] The bottom edge 10 includes a first portion 101 and a second portion 102. The first portion 101 is provided on the radially outer side of the ball end mill 2, and the second portion 102 is provided on the radially inner side of the ball end mill 2 relative to the first portion 101. The second portion 102 is provided closer to the central axis C of the ball end mill 2 than the first portion 101.

[0018] When the ball end mill 2 is viewed axially from the tip side of the ball end mill 2, the second portion 102a of the bottom edge 10a of the first cutting edge 8a and the second portion 102b of the bottom edge 10b of the second cutting edge 8b are connected to each other via the central axis C of the ball end mill 2. A chisel edge 50 of the ball end mill 2 is formed at the portion where the second portion 102a of the bottom edge 10a of the first cutting edge 8a and the second portion 102b of the bottom edge 10b of the second cutting edge 8b are connected. The chisel edge 50 is formed at the tip of the ball end mill 2.

[0019] The outer peripheral edge 12 is provided on the proximal side of the bottom edge 10 in the axial direction of the ball end mill 2 (see FIGS. 1 and 2). The outer peripheral edge 12 extends spirally along the axial direction and the circumferential direction of the ball end mill 2. The helix angle of the ball end mill 2 (the inclination angle of the outer peripheral edge 12 with respect to the central axis C of the ball end mill 2) is set, for example, in the range of 30° to 70°. The outer peripheral edge 12 cuts the object to be cut at the outer peripheral portion of the ball end mill 2.

[0020] Next, the bottom flute face 14 and the outer peripheral flute face 15 will be described. The bottom flute face 14 and the outer peripheral flute face 15 face the front side in the rotational direction of the ball end mill 2. The bottom flute face 14 extends from the bottom edge 10 on the front side in the rotational direction of the ball end mill 2. The outer peripheral flute face 15 extends from the outer peripheral edge 12 on the front side in the rotational direction of the ball end mill 2. The bottom flute face 14 is a face that scoops up the cutting chips generated when the bottom edge 10 cuts the object to be cut. The outer peripheral flute face 15 is a face that scoops up the cutting chips generated when the outer peripheral edge 12 cuts the object to be cut. The cutting chips scooped up by the bottom flute face 14 and the outer peripheral flute face 15 are discharged to the tip side in the axial direction of the ball end mill 2.

[0021] The bottom flute face 14 includes a first flute face 141 and a second flute face 142. The first flute face 141 is provided on the radially outer side of the ball end mill 2, and the second flute face 142 is provided on the radially inner side of the ball end mill 2 rather than the first flute face 141. The second flute face 142 is provided closer to the central axis C of the ball end mill 2 than the first flute face 141. The first flute face 141 extends from the first portion 101 of the bottom edge 10. The second flute face 142 extends from the second portion 102 of the bottom edge 10. The second flute face 142 is sometimes called thinning or gashing.

[0022] The outer peripheral flute face 15 is integrally formed with the first flute face 141 of the bottom flute face 14. The outer peripheral flute face 15 is continuous with the first flute face 141. The outer peripheral flute face 15 forms a groove 40 that extends spirally along the axial direction and the circumferential direction of the ball end mill 2.

[0023] Next, the bottom edge relief surface 16 will be described. The bottom edge relief surface 16 is provided along the bottom edge 10. The bottom edge relief surface 16 is provided on the rear side in the rotation direction of the ball end mill 2 with respect to the bottom edge 10. The bottom edge relief surface 16 extends from the bottom edge 10 to the rear side in the rotation direction of the ball end mill 2. The bottom edge relief surface 16 includes a second relief surface 20, a third relief surface 22 continuous with the second relief surface 20, and a fourth relief surface 24 continuous with the third relief surface 22. Further, the bottom edge relief surface 16 includes an additional relief surface 30 continuous with the second relief surface 20. In the technical field of ball end mills, it is common to call the first relief surface with respect to the cutting edge the second relief surface instead of the first relief surface.

[0024] The second relief surface 20 of the bottom edge 10 extends obliquely from the bottom edge 10 to the rear side in the rotation direction of the ball end mill 2. The third relief surface 22 of the bottom edge 10 is provided on the rear side in the rotation direction of the ball end mill 2 with respect to the second relief surface 20. The third relief surface 22 extends from the end portion on the rear side in the rotation direction of the second relief surface 20 to the rear side in the rotation direction. The relief angle of the third relief surface 22 is larger than the relief angle of the second relief surface 20.

[0025] The fourth relief surface 24 of the bottom edge 10 is provided on the rear side in the rotation direction of the ball end mill 2 with respect to the third relief surface 22. The fourth relief surface 24 extends from the end portion on the rear side in the rotation direction of the third relief surface 22 to the rear side in the rotation direction. The relief angle of the fourth relief surface 24 is larger than the relief angle of the third relief surface 22.

[0026] The additional relief surface 30 is provided on the rear side in the rotational direction of the ball end mill 2 with respect to the second relief surface 20. The additional relief surface 30 extends obliquely outward in the radial direction of the ball end mill 2 from the end on the rear side in the rotational direction of the second relief surface 20. The additional relief surface 30 is provided closer to the central axis C of the ball end mill 2 than the third relief surface 22 and the fourth relief surface 24. The additional relief surface 30 is provided so as to cross the third relief surface 22 and the fourth relief surface 24. The additional relief surface 30a of the first cutting edge 8a is provided between the second relief surface 20a of the first cutting edge 8a and the groove 40b that constitutes the peripheral cutting edge relief surface 15b of the second cutting edge 8b. The relief angle of the additional relief surface 30 is larger than the relief angle of the second relief surface 20. Also, the relief angle of the additional relief surface 30 is larger than the relief angle of the third relief surface 22. Also, the relief angle of the additional relief surface 30 is larger than the relief angle of the fourth relief surface 24.

[0027] The ball end mill 2 of the embodiment includes an intersection point P1 of the second relief surface 20, the first relief surface 141, and the second relief surface 142 of the bottom cutting edge 10. This intersection point P1 is designated as the first intersection point P1. Further, the ball end mill 2 includes an intersection point P2 of the second relief surface 20, the third relief surface 22, and the additional relief surface 30 of the bottom cutting edge 10. This intersection point P2 is designated as the second intersection point P2. As shown in FIG. 4, in the ball end mill 2 of the embodiment, when the ball end mill 2 is viewed axially from the tip side of the ball end mill 2, the angle θ1 formed between the first straight line L1 connecting the central axis C of the ball end mill 2 and the first intersection point P1 and the second straight line L2 connecting the central axis C of the ball end mill 2 and the second intersection point P2 is set in the range of, for example, 5° to 35°. The angle θ1 formed between the first straight line L1 and the second straight line L2 may be set in the range of 10° to 30°. Also, the angle θ1 formed between the first straight line L1 and the second straight line L2 may be set in the range of 15° to 25°.

[0028] Also, when a straight line along the chisel edge 50 on the central axis C of the ball end mill 2 is designated as the third straight line L3, the angle θ11 formed between the first straight line L1 and the third straight line L3 is set in the range of 0° to 5°, and the angle θ12 formed between the second straight line L2 and the third straight line L3 may be set in the range of 5° to 30°.

[0029] Further, as shown in FIG. 5, in the ball end mill 2 of the embodiment, when the ball end mill 2 is viewed in the radial direction from the side surface side of the ball end mill 2, the inclination angle θ2 of the additional relief surface 30 with respect to the central axis C of the ball end mill 2 is set in the range of, for example, 20° to 30°. The inclination angle θ2 of the additional relief surface 30 may be set in the range of 15° to 25°. It should be noted that the viewing angle of the side view in FIG. 5 is different from the viewing angle of the side view in FIG. 2. In FIG. 5, the second relief surface 20a of the bottom edge 10a of the first cutting edge 8a is visible, but in FIG. 2, the second relief surface 20a of the bottom edge 10a of the first cutting edge 8a is not visible.

[0030] Next, the peripheral cutting edge relief surface 17 will be described. The peripheral cutting edge relief surface 17 is provided along the peripheral cutting edge 12. The peripheral cutting edge relief surface 17 is provided on the rear side in the rotation direction of the ball end mill 2 with respect to the peripheral cutting edge 12. The peripheral cutting edge relief surface 17 extends from the peripheral cutting edge 12 to the rear side in the rotation direction of the ball end mill 2. The peripheral cutting edge relief surface 17 includes a second relief surface 60, a third relief surface 62 continuous with the second relief surface 60, and a fourth relief surface 64 continuous with the third relief surface 62. The second relief surface 60, the third relief surface 62, and the fourth relief surface 64 of the peripheral cutting edge 12 are respectively continuous with the second relief surface 20, the third relief surface 22, and the fourth relief surface 24 of the bottom edge 10.

[0031] The second relief surface 60 of the peripheral cutting edge 12 extends obliquely from the peripheral cutting edge 12 to the rear side in the rotation direction of the ball end mill 2. The third relief surface 62 of the peripheral cutting edge 12 is provided on the rear side in the rotation direction of the ball end mill 2 with respect to the second relief surface 60. The third relief surface 62 extends from the rear end in the rotation direction of the second relief surface 60 to the rear side in the rotation direction. The relief angle of the third relief surface 62 is larger than the relief angle of the second relief surface 60.

[0032] The fourth relief surface 64 of the peripheral cutting edge 12 is provided on the rear side in the rotation direction of the ball end mill 2 with respect to the third relief surface 62. The fourth relief surface 64 extends from the rear end in the rotation direction of the third relief surface 62 to the rear side in the rotation direction. The relief angle of the fourth relief surface 64 is larger than the relief angle of the third relief surface 62.

[0033] (Effect) The ball end mill 2 of the embodiment has been described above. As is clear from the above description, the ball end mill 2 has a configuration of a right blade left twist or a left blade right twist. Further, the bottom blade relief surface 16 of the ball end mill 2 includes a second relief surface 20 extending rearward in the rotational direction of the ball end mill 2 from the bottom blade 10, and a third relief surface 22 extending rearward in the rotational direction from the end portion on the rearward side in the rotational direction of the second relief surface 20. Further, the bottom blade relief surface 16 includes an additional relief surface 30 that obliquely extends outward in the radial direction of the ball end mill 2 from the end portion on the rearward side in the rotational direction of the second relief surface 20 on the side of the central axis C of the ball end mill 2 rather than the third relief surface 22.

[0034] According to this configuration, in the ball end mill 2 of a right blade left twist or a left blade right twist, by further providing the additional relief surface 30 in addition to the second relief surface 20 and the third relief surface 22, the ball end mill 2 can be rotated smoothly when cutting the object to be cut, and the object to be cut can be cut smoothly.

[0035] Further, in the ball end mill 2, the angle θ1 formed by a first straight line L1 connecting the central axis C of the ball end mill 2 and a first intersection point P1 and a second straight line L2 connecting the central axis C of the ball end mill 2 and a second intersection point P2 is from 5° to 35°. Further, the inclination angle θ2 of the additional relief surface 30 with respect to the central axis C of the ball end mill 2 is from 20° to 30°. According to this configuration, by adjusting the angle related to the bottom blade relief surface 16, the object to be cut can be cut smoothly. The ball end mill 2 of the embodiment is particularly effective when the object to be cut is urethane.

[0036] (Test Example) A comparative test was conducted with a test example and a comparative example. The ball end mill 2 of the test example was the ball end mill 2 described in the above embodiment. Therefore, the ball end mill 2 of the test example has a configuration of a right blade left twist (or a left blade right twist). Further, the ball end mill 2 of the test example includes an additional relief surface 30.

[0037] On the one hand, the ball end mill of the comparative example has a right blade right twist (or left blade left twist) configuration. Also, the ball end mill of the comparative example does not have an additional relief surface.

[0038] Also, in the ball end mill 2 of the test example, the angle θ1 formed by the first straight line L1 connecting the central axis C of the ball end mill 2 and the first intersection point P1 and the second straight line L2 connecting the central axis C of the ball end mill 2 and the second intersection point P2 is set in the range of 5° to 35° (see Fig. 4). Also, in the ball end mill 2 of the test example, the inclination angle θ2 of the additional relief surface 30 with respect to the central axis C of the ball end mill 2 is set in the range of 20° to 30° (see Fig. 5).

[0039] As the ball end mills of the comparative examples, two types of ball end mills were used. One was a ball end mill with the same twist angle as that of the ball end mill 2 of the test example (Comparative Example 1). The other was a ball end mill with a twist angle of 0° (i.e., a straight blade) (Comparative Example 2).

[0040] The urethane plates were cut with the ball end mill 2 of the test example and the ball end mills of the comparative examples respectively. As the test urethane plates, a plate with a urethane hardness of 70 (unit: Shore A) and a plate with a urethane hardness of 90 (unit: Shore A) were used. Then, for the urethane plates, the surface roughness of the cut surfaces after cutting was compared between the test example and the comparative examples. The surface roughness to be compared is the arithmetic mean roughness defined in JIS B 0601.

[0041] (Test Results) As shown in Fig. 6, in the case of the ball end mill 2 of the test example, for the urethane plate with a hardness of 70 Shore A, the surface roughness of the cut surface was 2.82, and for the urethane plate with a hardness of 90 Shore A, the surface roughness of the cut surface was 0.67.

[0042] On the other hand, in the case of the ball end mill of Comparative Example 1, when machining a urethane plate with a Shore A hardness of 70, the surface roughness of the machined surface was 9.29, and when machining a urethane plate with a Shore A hardness of 90, the surface roughness of the machined surface was 5.83. In the case of the ball end mill of Comparative Example 2, when machining a urethane plate with a Shore A hardness of 70, the surface roughness of the machined surface was 8.64, and when machining a urethane plate with a Shore A hardness of 90, the surface roughness of the machined surface was 4.94.

[0043] As shown in the test results, according to the ball end mill 2 of the test example, the surface roughness of the machined surface could be made smaller than that of the ball end mills of the comparative examples. From the above, it was confirmed that according to the ball end mill 2 of the test example, the object to be machined could be machined smoothly. The configuration of the ball end mill 2 capable of machining urethane smoothly was found through experiments.

[0044] (Modification example) A part of the additional relief surface 30 may be curved. Also, the additional relief surface 30 may include a plurality of surfaces. For example, the additional relief surface 30 may include a first surface extending from the end of the second relief surface 20 and a second surface extending from the end of the first surface (not shown). The first surface of the additional relief surface 30 may be provided on the side of the second relief surface 20, and the second surface of the additional relief surface 30 may be provided on the side opposite to the second relief surface 20.

[0045] As described above, specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Also, the technology illustrated in this specification or the drawings can achieve a plurality of purposes simultaneously, and achieving one of those purposes itself has technical utility.

Description of reference numerals

[0046] 2: Ball end mill, 4: Body part, 6: Shank part, 8a: First cutting edge, 8b: Second cutting edge, 10: Bottom cutting edge, 12: Outer peripheral cutting edge, 14: Bottom cutting edge rake face, 15: Outer peripheral cutting edge rake face, 16: Bottom cutting edge relief face, 17: Outer peripheral cutting edge relief face, 20: Second relief face of bottom cutting edge, 22: Third relief face of bottom cutting edge, 24: Fourth relief face of bottom cutting edge, 30: Additional relief face, 40: Groove, 50: Chisel edge, 60: Second relief face of outer peripheral cutting edge, 62: Third relief face of outer peripheral cutting edge, 64: Fourth relief face of outer peripheral cutting edge, 101: First part, 102: Second part, 141: First rake face, 142: Second rake face, C: Central axis, L1: First straight line, L2: Second straight line, L3: Third straight line, P1: First intersection point, P2: Second intersection point

Claims

1. A ball end mill with a right-hand cutting edge and left-hand twist or a left-hand cutting edge and right-hand twist, comprising: a bottom cutting edge, a rake face of the bottom cutting edge, and a flank face of the bottom cutting edge; the rake face includes a first rake face and a second rake face on the central axis side of the ball end mill with respect to the first rake face; the flank face includes: a second flank face extending rearward in the rotational direction of the ball end mill from the bottom cutting edge; a third flank face extending rearward in the rotational direction from the rear end of the second flank face in the rotational direction; an additional flank face obliquely extending radially outward from the rear end of the second flank face in the rotational direction on the central axis side of the ball end mill with respect to the third flank face.

2. Taking the intersection of the first rake face, the second rake face, and the second flank face as the first intersection point, and the intersection of the second flank face, the third flank face, and the additional flank face as the second intersection point, when the ball end mill is viewed axially from the tip side of the ball end mill, the angle formed by a first straight line connecting the central axis of the ball end mill and the first intersection point and a second straight line connecting the central axis of the ball end mill and the second intersection point is from 5° to 35°; When the ball end mill is viewed radially from the side face side of the ball end mill, the inclination angle of the additional flank face with respect to the central axis of the ball end mill is from 20° to 30°. The ball end mill according to Claim 1.

3. The ball end mill according to Claim 1 or 2, wherein the cutting object is urethane.

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