Ball end mill

Abstract

When cutting a workpiece with a ball end mill, this design prevents the ball cutting edge at the tip of the shank from chipping or wearing down, enabling stable cutting over a long period of time. [Solution] In a ball end mill in which two or more ball blades 11 are provided at the tip of a shank body 10 that rotates around a rotation axis, a recessed mid-low cutting edge 12 is formed from the tip of each ball blade toward the rotation axis c, and the relief angle α of the relief surface 12a of the mid-low cutting edge is made smaller than the relief angle β of the relief surface 11a of the ball blade.

Description

Technical Field

[0001] The present invention relates to a ball end mill provided with two or more ball blades at the tip of a shank body that rotates about a rotation axis. In particular, it is characterized in that it suppresses the tip of each ball blade provided at the tip of the shank body from being chipped or worn, so that stable cutting can be performed over a long period of time.

Background Art

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

[0003] Here, as a conventional ball end mill, for example, one provided with two or more ball blades at the tip of a shank body that rotates about a rotation axis is used.

[0004] However, when the workpiece is cut using the above-described ball end mill, the cutting speed becomes 0 at the rotation axis of the ball blade, and the cutting speed of the ball blade near the rotation axis becomes extremely low and close to 0. Therefore, during cutting, the load applied to the rotation axis of the ball blade and its vicinity increases, and the wear of the ball blade near the rotation axis becomes faster. Furthermore, this causes problems such as chipping and loss of the ball blade.

[0005] And in order to suppress the occurrence of chipping and loss at the rotation axis portion of the ball blade in the above-described ball end mill, in Patent Document 1, a substantially V-shaped bottom blade is provided from the tip of each ball blade to the rotation axis, the rake angle of the ball blade is set as a negative angle in the normal direction, and a ball end mill with a rake angle of the bottom blade of 0° has been proposed.

[0006] Furthermore, Patent Document 2 proposes a ball end mill in which a medium-to-low gradient blade extends from the tip of each ball blade to the rotation axis near the rotation axis of the tip, the medium-to-low gradient blade is inclined at 0.5° to 3° toward the shank body with respect to a plane perpendicular to the rotation axis, and at least the portion of each medium-to-low gradient blade on the rotation axis side is curved and recessed toward the rear in the direction of rotation.

[0007] However, even when cutting a workpiece using the ball end mills described in Patent Documents 1 and 2, the load is applied to the approximately V-shaped bottom cutting edge and the medium-low gradient cutting edge, causing wear near the rotation axis to accelerate. As a result, chipping and breakage still occur at the tip of the ball cutting edge and the medium-low gradient cutting edge. Furthermore, the approximately V-shaped bottom cutting edge and the medium-low gradient cutting edge become larger, resulting in problems such as uncut or over-cutting of the workpiece. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 9-267211 [Patent Document 2] Patent No. 5846098 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0009] The present invention aims to solve the aforementioned problems when cutting a workpiece using a ball end mill, which has two or more ball cutting edges at the tip of a shank body that rotates around a rotation axis.

[0010] In other words, the present invention aims to prevent the ball cutting edge at the tip of the shank body from chipping or wearing down when cutting a workpiece using the ball end mill described above, thereby enabling stable cutting over a long period of time. [Means for solving the problem]

[0011] In the end mill of the present invention, in order to solve the above-mentioned problems, a ball end mill is provided with two or more ball cutting edges at the tip of a shank body that rotates around a rotation axis, and a recessed mid-low cutting edge is formed from the tip of each ball cutting edge toward the rotation axis, and the relief angle α of the relief surface of the mid-low cutting edge is made smaller than the relief angle β of the relief surface of the ball cutting edge.

[0012] Furthermore, in forming a medium-low cutting edge that is recessed toward the rotation axis from the tip of each ball cutting edge, as in the end mill of the present invention, if the relief angle α of the relief surface of the medium-low cutting edge is made smaller than the relief angle β of the relief surface of the ball cutting edge, the load applied to the tip of the ball cutting edge and the medium-low cutting edge during cutting is reduced, improving strength and preventing chipping or breakage from occurring at the tip of the ball cutting edge and the medium-low tapered edge.

[0013] In the end mill of the present invention, when forming a recessed mid-depth cutting edge that extends from the tip of each ball cutting edge toward the axis of rotation as described above, if the width of the mid-depth cutting edge becomes too narrow, the tip of each ball cutting edge approaches the axis of rotation, and, as in the case where there is no mid-depth cutting edge, the load applied to the tip of each ball cutting edge during cutting becomes large, causing wear at the tip of each ball cutting edge to accelerate and making chipping and breakage more likely. On the other hand, if the width of the mid-depth cutting edge becomes large, it becomes difficult to adjust the depth of cut into the workpiece during cutting, and problems arise such as uncut areas remaining in the workpiece that are not cut by the mid-depth cutting edge, or over-cutting.

[0014] Therefore, it is preferable to provide the aforementioned medium- and low cutting edges within a range of 1 to 10° from the rotation center of the ball blade with respect to the rotation axis. The rotation center of the ball blade refers to the center of the arc formed by the rotating ball blade when the shank body rotates around the rotation axis.

[0015] Furthermore, in the end mill of the present invention, when making the relief angle α of the flank surface of the medium-low cutting edge smaller than the relief angle β of the flank surface of the ball cutting edge, if the relief angle α of the flank surface of the medium-low cutting edge is made too small, there is a risk that the flank surface of the medium-low cutting edge may come into contact with the workpiece during cutting, potentially damaging the workpiece. On the other hand, if the relief angle α of the flank surface of the medium-low cutting edge is made too large, the strength of the medium-low cutting edge and the strength of the ball cutting edge, where the relief angle β of the flank surface is larger than the relief angle α of the flank surface of the medium-low cutting edge, will decrease, making it easier for chipping and breakage to occur at the tip of the medium-low taper cutting edge or ball cutting edge during cutting. For this reason, it is preferable to set the minimum angle of the relief angle α of the flank surface of the medium-low cutting edge in the range of 1 to 10°, and to make the relief angle α of the flank surface of the medium-low cutting edge increase toward the ball cutting edge. [Effects of the Invention]

[0016] In the end mill of the present invention, a medium-low cutting edge is formed by recessing the tip of each of the two or more ball blades provided at the tip of the shank body that rotates around the rotation axis, and by making the relief angle α of the relief surface of the medium-low cutting edge smaller than the relief angle β of the relief surface of the ball blade, the load applied to the tip of the ball blade and the medium-low cutting edge during cutting is reduced, their strength is improved, and chipping and breakage of the tip of the ball blade and the medium-low tapered cutting edge can be prevented. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic side view showing the state of the tip of the shank body in an end mill according to an embodiment of the present invention. [Figure 2] This is a schematic front view of the end mill in the same embodiment, as seen from the tip side of the shank body. [Figure 3] This is a schematic side view illustrating the relationship between the ball cutting edge at the tip of the shank body and the mid-to-low cutting edge formed from the tip of the ball cutting edge toward the axis of rotation in the end mill according to the same embodiment. [Figure 4]It is a schematic enlarged front view seen from the tip side of a shank body showing a state in which a middle-low cutting edge is formed from the tip of each ball blade toward the rotation axis center in the end mill in the same embodiment. [Figure 5] It is a cross-sectional explanatory view showing the relief angle of the relief surface in the middle-low cutting edge in the end mill in the same embodiment. [Figure 6] It is a cross-sectional explanatory view showing the relief angle of the relief surface in the ball blade in the end mill in the same embodiment.

Best Mode for Carrying Out the Invention

[0018] Hereinafter, the end mill according to the 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 changed and implemented within the range of not changing the gist thereof.

[0019] As shown in FIGS. 1, FIGS. 2, etc., the end mill in this embodiment is provided with three arc-shaped ball blades 11 extending in the radial direction and convex toward the center at the tip of a shank body 10, and a middle-low cutting edge 12 recessed from the tip of each ball blade 11 toward the rotation axis center is formed.

[0020] Here, when forming the middle-low cutting edge 12 recessed from the tip of each ball blade 11 toward the rotation axis center in this way, as shown in FIG. 3, the angle θ at which the middle-low cutting edge 12 is provided with respect to the rotation axis center c from the rotation center o of the ball blade 11 is in the range of 1 to 10°. And in this embodiment, the angle θ at which the middle-low cutting edge 12 is provided with respect to the rotation axis center c from the rotation center o of the ball blade 11 is set to about 5°.

[0021] Also, when forming the middle-low cutting edge 12 recessed from the tip of each ball blade 11 toward the rotation axis center as described above, the relief angle α of the relief surface 12a in the middle-low cutting edge 12 shown in FIG. 4 is made smaller than the relief angle β of the relief surface 11a in the ball blade 11 shown in FIG. 5.

[0022] In this embodiment, the minimum angle of the relief angle α of the relief surface 12a of the medium-low cutting edge 12 is in the range of 1 to 10°, and the relief angle α of the relief surface of the medium-low cutting edge increases toward the ball blade, with the relief angle β of the relief surface 11a of the ball blade 11 being about 14.5°, and the relief angle α of the relief surface 12a of the medium-low cutting edge 12 gradually increasing from 3°, so that at the position where it connects with the ball blade 11, the relief angle β of the relief surface 11a of the ball blade 11 becomes 14.5°.

[0023] Furthermore, in the end mill of this embodiment, the medium-low cutting edge 12 is provided at the tip of the shank body 10 as described above, so that the angle θ from the rotation center o of the ball blade 11 to the rotation axis c is about 5°, which is in the range of 1 to 10°. As a result, unlike when the medium-low cutting edge 12 is not provided, the load applied to the tip of each ball blade 11 during cutting becomes large, and wear on the tip of each ball blade 11 becomes faster, preventing chipping and breakage. In addition, the width of the medium-low cutting edge 12 is increased, which makes it difficult to adjust the depth of cut to the workpiece (not shown) during cutting, and prevents the creation of uncut material in the workpiece that is not cut by the medium-low cutting edge 12, or over-cutting of the workpiece.

[0024] Furthermore, in this embodiment of the end mill, the relief angle α of the flank surface 12a of the medium-low cutting edge 12 is made smaller than the relief angle β of the flank surface 11a of the ball cutting edge 11, the minimum angle of the relief angle α of the flank surface 12a of the medium-low cutting edge 12 is set to a range of 1 to 10°, the relief angle α of the flank surface 12a of the medium-low cutting edge 12 increases toward the ball cutting edge 11, and at the position where it connects with the ball cutting edge 11, it becomes the same as the relief angle β of the flank surface 11a of the ball cutting edge 11. As a result, during cutting, the flank surface 12a of the medium-low cutting edge 12 does not come into contact with the workpiece, preventing damage to the workpiece. At the same time, the relief angle α of the flank surface 12a of the medium-low cutting edge 12 is increased, reducing the strength of the medium-low cutting edge 12 and the strength of the ball cutting edge 11, whose relief angle β is larger than the relief angle α of the flank surface 12a of the medium-low cutting edge 12. This prevents chipping and breakage from occurring at the tip of the medium-low cutting edge 12 and the ball cutting edge 11 during cutting. [Explanation of Symbols]

[0025] 10: Shank body 11: Ball blade 11a: Relief surface of ball end blade 12: Medium-low cutting edge 12a: Flank surface of medium-low cutting edge c:Rotation axis center o: Center of rotation of the ball blade α: Relief angle of the flank face of the medium-low cutting edge β: Relief angle of the relief face of the ball cutting edge θ: Angle at which the medium-low cutting edge is positioned relative to the rotation axis of the ball end mill from the rotation center.

Claims

1. A ball end mill having two or more ball cutting edges at the tip of a shank body that rotates around a rotation axis, characterized in that a recessed mid-to-low cutting edge is formed from the tip of each ball cutting edge toward the rotation axis, and the relief angle α of the relief surface of the mid-to-low cutting edge is smaller than the relief angle β of the relief surface of the ball cutting edge.

2. A ball end mill according to claim 1, characterized in that the medium-low cutting edge is provided in a range of 1 to 10° from the rotation center of the ball cutting edge with respect to the rotation axis.

3. A ball end mill according to claim 1 or claim 2, characterized in that the minimum angle of the relief angle α of the relief surface at the medium-low cutting edge is in the range of 1 to 10°, and the relief angle α of the relief surface at the medium-low cutting edge increases toward the ball cutting edge.

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