Ball end mill

Abstract

When cutting a workpiece with a ball end mill, the cutting edge strength of the ball blade is increased, and chip evacuation is improved to prevent chip clogging. [Solution] In a ball end mill in which a ball cutting edge 11 and a chip discharge groove 13 are provided at the tip of a shank body 10 that rotates around a rotation axis, a first rake face 14 is formed by a first gash g1 on the downstream side of the ball cutting edge in the direction of rotation, and a second rake face 15 is formed by a second gash g2 on the downstream side of the first rake face in the direction of rotation without contacting the ball cutting edge, the first rake angle γ of the first rake face with respect to the ball cutting edge is made negative, while the second rake angle δ of the second rake face with respect to the first rake face is made positive, and the width d of the first rake face with respect to the ball cutting edge is kept constant and used as a chamfered surface.

Description

Technical Field

[0001] The present invention relates to a ball end mill in which a ball blade and a chip discharge groove portion are provided on the downstream side in the rotation direction from the ball blade at the tip of a shank body that rotates about a rotation axis. In particular, in a ball end mill in which a first rake face by a first gash is formed on the downstream side in the rotation direction of the ball blade and a second rake face by a second gash is formed on the downstream side in the rotation direction from the first gash, the tip strength of the ball blade is increased, and the chip discharge property is improved to prevent chip clogging.

Background Art

[0002] In recent years, in order to quickly perform cutting on a three-dimensional curved surface or the like with respect to a mold, a ball end mill is often used.

[0003] Here, as a ball end mill, for example, a ball blade and a chip discharge groove portion are provided on the downstream side in the rotation direction from the ball blade at the tip of a shank body that rotates about a rotation axis.

[0004] When cutting a workpiece using the ball end mill as described above, in order to improve the cutting performance of the ball blade, if the rake angle of the ball blade is increased, the strength of the ball blade decreases. In particular, the load applied to the ball blade near the rotation axis and its vicinity increases, and the wear of the ball blade near the rotation axis becomes faster, resulting in problems such as chipping and loss occurring on the ball blade.

[0005] Also, conventionally, as shown in Patent Documents 1 and 2, a first gash is provided on the downstream side in the rotation direction of the ball blade, and a second gash is provided on the downstream side in the rotation direction from the first gash.

[0006] In the ball end mills shown in the aforementioned Patent Documents 1 and 2, the first gash provides a first wall surface, bottom surface, groove bottom, second wall surface, and chamfer surface, and the second gash is provided downstream of the first gash in the rotational direction.

[0007] Furthermore, Patent Document 1 shows that the first and second gashes have different torsions, and Patent Document 2 shows that the width of the chamfer surface provided by the first gash is made larger on the tip side of the ball blade than on the outer circumference side of the ball blade.

[0008] However, the process of providing the first and second gashes as shown in the aforementioned Patent Documents 1 and 2 is extremely cumbersome, and it is also difficult to enlarge the chip discharge groove to improve chip discharge efficiency and adequately prevent chip clogging. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Patent No. 7409244 [Patent Document 2] Patent No. 7491105 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0010] The present invention aims to solve the aforementioned problems in a ball end mill in which a ball cutting edge and a chip evacuation groove are provided at the tip of the shank body that rotates around a rotation axis, and the ball cutting edge is located downstream of the ball cutting edge in the rotational direction.

[0011] In other words, the present invention aims to improve the cutting edge strength of the ball end mill and enhance chip evacuation to prevent chip clogging, in a ball end mill in which a first rake face is formed by a first gash on the downstream side in the rotational direction of the ball end mill, and a second rake face is formed by a second gash on the downstream side of the first gash in the rotational direction. [Means for solving the problem]

[0012] In the end mill of the present invention, in order to solve the above-mentioned problems, a ball end mill is provided at the tip of the shank body which rotates around a rotation axis, and a ball cutting edge and a chip discharge groove located downstream of the ball cutting edge in the rotational direction, wherein a first rake face is formed by a first gash downstream of the ball cutting edge in the rotational direction, and a second rake face is formed by a second gash downstream of the first rake face in the rotational direction without contacting the ball cutting edge, the first rake angle of the first rake face with respect to the ball cutting edge is made negative, while the second rake angle of the second rake face with respect to the first rake face is made positive, and the width of the first rake face with respect to the ball cutting edge is made constant by the second gash and used as a chamfered surface.

[0013] Furthermore, as in the end mill of the present invention, a first rake face is formed by a first gash on the downstream side of the ball cutting edge in the rotational direction, and a second rake face is formed by a second gash on the downstream side of the first gash in the rotational direction without contacting the ball cutting edge. By making the first rake angle of the first rake face relative to the ball cutting edge negative, the cutting edge strength of the ball cutting edge can be increased. Also, by making the second rake angle of the second rake face relative to the first rake face positive, the chip evacuation groove on the downstream side of the ball cutting edge in the rotational direction can be enlarged, thereby improving chip evacuation. Additionally, by using the second gash to keep the width of the first rake face relative to the ball cutting edge constant and using it as a chamfered surface, the overall cutting edge strength of the ball cutting edge can be stably increased.

[0014] In the end mill of the present invention, it is preferable that the width of the first rake face used as the chamfer surface be in the range of 0.2 to 10% of the rotation radius of the ball cutting edge. By doing so, the first rake angle of the first rake face is made negative, the cutting edge strength of the ball cutting edge is increased, and a large chip evacuation groove can be easily formed by the second gash.

[0015] Furthermore, in the end mill of the present invention, it is preferable to set the first rake angle of the first rake face in the range of -10° to -60°, and the second rake angle of the second rake face in the range of +10° to +80° relative to the first rake face. This makes it possible to sufficiently increase the cutting edge strength of the ball cutting edge and to easily form a large chip evacuation groove with the second gash. [Effects of the Invention]

[0016] In the end mill of the present invention, as described above, a first rake face is formed by a first gash on the downstream side of the ball cutting edge in the direction of rotation, and a second rake face is formed by a second gash downstream of the first rake face in the direction of rotation without contacting the ball cutting edge. The second gash makes the width of the first rake face relative to the ball cutting edge constant and uses it as a chamfered surface. The first rake angle of the first rake face is made negative, while the second rake angle of the second rake face is made positive with respect to the first rake face. As a result, the cutting edge strength of the ball cutting edge can be sufficiently increased, and the chip evacuation groove downstream of the ball cutting edge in the direction of rotation can be enlarged to improve chip evacuation.

[0017] As a result, in the end mill of the present invention, the cutting edge strength of the ball blade can be increased, chip clogging can be prevented, and damage to the ball blade can be suppressed. [Brief explanation of the drawing]

[0018] [Figure 1]In the end mill according to an embodiment of the present invention, it is a schematic side view showing the state of the tip of the shank body. [Figure 2] In the end mill according to this embodiment, it is a schematic front view of the tip of the shank body as viewed from the tip side of the shank body. [Figure 3] In the end mill according to this embodiment, it is an enlarged side view of the tip of the shank body. [Figure 4] In the end mill according to this embodiment, it is an enlarged front view of the tip of the shank body as viewed from the tip side of the shank body. [Figure 5] In the end mill according to this embodiment, a first rake face is formed on the downstream side in the rotational direction of the ball cutter, and a second rake face by a second gullet is formed on the downstream side in the rotational direction from the first gullet so as not to contact the ball cutter, and a state in which the first rake angle of the first rake face is negative and the second rake angle of the second rake face with respect to the first rake face is positive is shown in a cross-sectional explanatory view.

Best Mode for Carrying Out the Invention

[0019] Hereinafter, the end mill according to an embodiment of the present invention will be specifically described based on the attached drawings. Note that the end mill in the present invention is not particularly limited to that shown in the following embodiments, and can be appropriately modified and implemented within the scope of not changing the gist.

[0020] As shown in FIGS. 1 to 4, the end mill in the present embodiment is provided with three arc-shaped ball cutters 11 that are convex toward the center and an outer peripheral cutter 12 continuous with the ball cutter 11 at the tip of the shank body 10 so as to be twisted with respect to the axial direction of the shank body 10, and a twisted chip discharge groove portion 13 is provided on the downstream side in the rotational direction of each ball cutter 11 and the outer peripheral cutter 12.

[0021] And in the end mill of the present embodiment, when forming each ball cutter 11 at the tip of the shank body 10, a first rake face 14 with a first relief gash g1 is formed on the downstream side in the rotation direction of each ball cutter 11, and a second rake face 15 with a second relief gash g2 is formed on the downstream side in the rotation direction from the first relief gash g1 so as not to contact the ball cutter 11.

[0022] Here, when forming the first rake face 14 with the first relief gash g1 as described above, the first rake angle γ of the first rake face 14 with respect to the ball cutter 11 is made negative. In the present embodiment, the first rake angle γ is set to about -25° within the range of -10° to -60°.

[0023] Also, when forming the second rake face 15 with the second relief gash g2, the second rake angle δ of the second rake face 15 with respect to the first rake face 14 is made positive. In the present embodiment, the second rake angle δ is set to about +20° within the range of +10° to +80°.

[0024] Further, with the second relief gash g2, the width d of the first rake face 14 with respect to the ball cutter 11 is made constant, and the first rake face 14 is used as a chamfer face. Here, in the present embodiment, the width d of the first rake face 14 is set to about 1.6% within the range of 0.2% to 10% with respect to the rotation radius R of the ball cutter 11.

[0025] In this embodiment of the end mill, a first rake face 14 is formed by a first gash g1 on the downstream side of the ball blade 11 in the rotational direction, and a second rake face 15 is formed by a second gash g2 on the downstream side of the first rake face 14 in the rotational direction without contacting the ball blade 11. The second gash g2 keeps the width d of the first rake face 14 constant relative to the ball blade 11, allowing it to be used as a chamfered surface. The first rake angle γ of the first rake face 14 is made negative with respect to the ball blade 11, while the second rake angle δ of the second rake face 15 is made positive with respect to the first rake face 14. As a result, the cutting edge strength of the ball blade 11 can be sufficiently increased, and the chip evacuation groove 13 on the downstream side of the ball blade 11 in the rotational direction can be enlarged to improve chip evacuation.

[0026] As a result, in the end mill of this embodiment, the cutting edge strength of the ball blade 11 can be increased, and chip clogging can be prevented, thereby suppressing damage to the ball blade 11. [Explanation of Symbols]

[0027] 10: Shank body 11: Ball blade 12: Peripheral blade 13: Chip discharge groove 14: First scoop face 15: Second scoop face d: Width of the first rake face g1: First gash g2: Second gash R: Radius of rotation γ: First rake angle of the first rake face relative to the ball end. δ: Second rake angle of the second rake face relative to the first rake face.

Claims

1. A ball end mill is characterized in that a ball cutting edge and a chip discharge groove are provided at the tip of the shank body which rotates around a rotation axis, a first rake face is formed by a first gash on the downstream side of the ball cutting edge in the direction of rotation, and a second rake face is formed by a second gash on the downstream side of the first gash in the direction of rotation without contacting the ball cutting edge, the first rake angle of the first rake face with respect to the ball cutting edge is made negative, while the second rake angle of the second rake face with respect to the first rake face is made positive, and the width of the first rake face with respect to the ball cutting edge is made constant by the second gash and used as a chamfered face.

2. A ball end mill according to claim 1, characterized in that the width of the first rake face used as the chamfer face is in the range of 0.2 to 10% of the rotation radius of the ball cutting edge.

3. A ball end mill according to claim 1, characterized in that the first rake angle of the first rake face is in the range of -10° to -60°, and the second rake angle of the second rake face relative to the first rake face is in the range of +10° to +80°.

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