WO2023170985A1

WO2023170985A1 - Ball end mill

Info

Publication number: WO2023170985A1
Application number: PCT/JP2022/015055
Authority: WO
Inventors: 将弘清藤
Original assignee: オーエスジー株式会社
Priority date: 2022-03-07
Filing date: 2022-03-28
Publication date: 2023-09-14
Also published as: KR20240119309A; CN118829503A; JPWO2023170985A1

Abstract

This ball end mill comprises a ball blade part formed in a partially spherical shape, and when viewed from a rotational axis direction from the distal end, the ball blade part has at least one first groove in a first torsion form and a plurality of second grooves in a second torsion form, the first and second grooves extending from the distal end side of the ball blade part to the outer peripheral side. When, in one of the second grooves, an intersecting portion, located at a prescribed position from the distal end side, among intersecting portions intersecting the at least one first groove is defined as a first intersecting portion and, in another of the second grooves, an intersecting portion, located at the prescribed position from the distal end side, among the intersecting portions intersecting the at least one first groove is defined as a second intersecting portion, the length from the distal end to the first intersecting portion is different than the length from the distal end to the second intersecting portion.

Description

ball end mill

The present invention relates to a ball end mill.

Patent Documents 1 and 2 disclose ball end mills in which the surface roughness of the ball blade portion is reduced in order to give the machined surface of the workpiece a mirror finish.

Japanese Patent Application Publication No. 2018-122365 Japanese Patent Application Publication No. 2016-112678

In ball end mills such as those described in Patent Document 1 and Patent Document 2, the contact area between the ball blade and the surface of the workpiece is large, so the resistance during machining may become large. Therefore, by forming a plurality of grooves in the ball blade and reducing the contact area between the ball blade and the surface of the workpiece, the resistance during machining can be reduced.

Incidentally, an intersection where grooves intersect may be formed in the ball blade portion. When the ball blade rotates and processes a workpiece, machining may be insufficient in a region of the machined surface of the workpiece through which a large number of intersections pass.

Some embodiments of the present invention aim to improve the quality of the machined surface of a workpiece.

Some embodiments of the present invention include a ball blade portion formed in a partially spherical shape, and the ball blade portion extends from the tip side of the ball blade portion toward the outer circumferential side when viewed from the tip in the direction of the rotation axis. At least one first groove having a first twist pattern and a plurality of second grooves having a second twist pattern, and among the intersections that intersect with the at least one first groove in one of the second grooves, An intersection located at a predetermined point from the tip side is defined as a first intersection, and among intersections that intersect with the at least one first groove in another of the second grooves, the intersection is located at the predetermined point from the tip side. When the intersection is a second intersection, the ball end mill has a length from the tip to the first intersection that is different from a length from the tip to the second intersection.

Other features of the present invention will become clear from the description and drawings described below.

According to some embodiments of the present invention, the quality of the machined surface of the workpiece can be improved.

1A is a side view of the ball end mill 10, and FIG. 1B is a view seen from the tip 13 of the ball blade portion 12 in the rotation axis direction. FIG. 3 is a cross-sectional view of groove 20. FIG. 3B is an explanatory diagram of the aspect of the groove 20 formed in the ball blade part 12, FIG. 3A is a diagram of the ball blade part 12 in which only the groove 20A is formed, and FIG. 3B is a diagram in which the ball blade part 12 is shown in which only the groove 20B is formed. FIG. 3C is a diagram of the ball blade part 12 in which

grooves

20A and 20B are formed. FIG. 4A is an explanatory diagram of the intersections 21 of the grooves 20, FIG. 4A is an explanatory diagram of a plurality of intersections 21 in the ball blade part 12X of a comparative example, and FIG. 4B is an explanatory diagram of the intersections 21 in an enlarged manner. , FIG. 4C is an explanatory diagram of the plurality of intersections 21 in the ball blade part 12 of this embodiment. 5A is an explanatory diagram of an example in which the number of grooves 20 formed in the ball blade part 12 is changed, FIG. 5A is an explanatory diagram of an example in which the number of grooves 20A is 16 and the number of grooves 20B is 13, and FIG. 5B is It is an explanatory view of an example in which 16

grooves

20A and 11 grooves 20B are provided. 6A is an explanatory diagram of an example in which the number of grooves 20 formed in the ball blade part 12 is changed, FIG. 6A is an explanatory diagram of an example in which the number of grooves 20A is 17 and the number of grooves 20B is 15, and FIG. 6B is FIG. 6C is an explanatory diagram of an example in which the number of grooves 20A is nine and the number of grooves 20B is seven, and FIG. 6C is an explanatory diagram of an example in which the number of grooves 20A is seven and the number of grooves 20B is five. 7A is an explanatory diagram of an example in which the number of grooves 20 formed in the ball blade part 12 is changed, FIG. 7A is an explanatory diagram of an example in which the number of grooves 20A is 16 and the number of grooves 20B is 14, and FIG. 7B is It is an explanatory view of an example in which 15

grooves

20A and 10 grooves 20B are provided. FIG. 8A is an explanatory diagram of the aspect of the groove 20 formed in the ball blade part 32 of the first modification, FIG. 8A is a diagram of the ball blade part 32 in which only the groove 20C is formed, and FIG. 8B is a diagram showing only the groove 20B. FIG. 8C is a diagram of the ball blade portion 32 in which a groove 20C and a groove 20B are formed. FIG. 9A is an explanatory diagram of the aspect of the groove 20 formed in the ball blade part 42 of the second modification, FIG. 9A is a diagram of the ball blade part 42 in which only the groove 20A is formed, and FIG. 9B is a diagram showing only the groove 20D. FIG. 9C is a diagram of the ball blade part 42 in which a groove 20A and a groove 20D are formed. 10A is an illustration of a ball end mill 50 having a ball blade portion 52, and FIG. 10B is an illustration of a ball end mill 60 having a ball blade portion 62. FIG. FIG. 10C is a diagram of a ball end mill 10 having a ball blade part 12. It is an explanatory view explaining processing conditions in a processing test. 12A is a graph showing an example of a comparison result of machining torque under machining condition 1, FIG. 12A is a graph showing an average torque value, and FIG. 12B is a graph showing a maximum torque value. 13A is a graph showing an example of a comparison result of machining torque under machining condition 2, FIG. 13A is a graph showing an average torque value, and FIG. 13B is a graph showing a maximum torque value. 14A is a diagram illustrating machining errors under machining conditions 1 and 2; FIG. 14B is a table showing an example of comparison results of machining errors; FIG. 15A is a diagram of the

ball blade portions

72 and 82 of the second embodiment, FIG. 15A is a view of the ball blade portion 72 of the first example as seen from the tip 13 in the rotation axis direction, and FIG. 15B is a diagram of the second embodiment. FIG. 3 is a view seen from the tip 13 of the ball blade portion 82 in the direction of the rotation axis. FIG. 7 is a view seen from the tip 13 of the ball blade part 92 of the third embodiment in the direction of the rotation axis. 17A is a first example of the shape of the ball blade part 12, and FIG. 17B is a second example of the shape of the ball blade part 12. FIG. This is another example regarding the groove 20 of the ball blade part 12.

At least the following matters will become clear from the description of this specification and the attached drawings.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Identical or equivalent components, members, etc. shown in each drawing are designated by the same reference numerals, and redundant explanations will be omitted as appropriate.

===First embodiment===
FIG. 1 is a diagram of a ball end mill 10 according to a first embodiment. Note that FIG. 1A is a side view of the ball end mill 10, and FIG. 1B is a view seen from the tip 13 of the ball blade portion 12 in the direction of the rotation axis. Further, FIG. 2 is a cross-sectional view of the groove 20.

<Definition of directions and terms>
First, with reference to FIG. 1, directions, terms, etc. in the ball end mill 10 will be defined.

As shown in FIG. 1A, the direction along the rotation axis A of the ball end mill 10 is referred to as the "rotation axis direction" or simply the "axial direction." The “rotation axis direction” is also the longitudinal direction of the ball end mill 10. Note that the direction of the rotation axis of the ball end mill 10 includes both the "distal direction" and the "proximal direction." As shown in FIG. 1A, the "distal direction" is the direction toward the distal end of the ball end mill 10, and the "proximal direction" is the direction toward the proximal end of the ball end mill 10. Each of the "distal direction" and the "proximal direction" is a direction with a fixed orientation.

Furthermore, as shown in FIG. 1B, the direction along the rotation direction of the ball end mill 10 is sometimes referred to as the "circumferential direction." The "circumferential direction" is also a direction along the outer periphery 14 of the ball blade part 12, which will be described later. Note that the circumferential direction of the ball end mill 10 includes both the "clockwise direction" and the "counterclockwise direction." Each of the "clockwise direction" and "counterclockwise direction" is a direction with a fixed orientation. Note that the "clockwise direction" may be referred to as a "clockwise direction," and the "counterclockwise direction" may be referred to as a "counterclockwise direction."

Here, the "rotating shaft" of the ball end mill 10 refers to the shaft around which the ball end mill 10 rotates. The "rotation axis" is sometimes called the "axis center." In this embodiment, the rotation axis A of the ball end mill 10 is the central axis of the ball end mill 10, as shown in FIG. 1A.

Further, the "tip" of the ball end mill 10 refers to the most tip part of the part of the ball end mill 10 that processes the workpiece (namely, the ball blade part 12). In this embodiment, the tip 13 of the ball end mill 10 is located on the surface of the ball blade portion 12 of the ball end mill 10. Note that, as shown in FIG. 1B, the tip 13 is located at the center of the ball blade portion 12 when viewed from the tip 13 in the direction of the rotation axis. Therefore, the tip 13 will be located on the rotation axis A.

Note that the above-mentioned directions and definitions of terms, etc. are also common to other embodiments of this specification, unless otherwise specified.

<Overview of ball end mill 10>
Next, an overview of the ball end mill 10 in this embodiment will be described with reference to FIGS. 1 and 2.

The ball end mill 10 is a tool that processes a workpiece using a partially spherical blade.

Here, "partially spherical" is the shape of a portion of a sphere. In the ball end mill 10 of this embodiment, the blade portion is formed in a hemispherical shape, as shown in FIG. 1A. However, the blade portion of the ball end mill 10 may be formed in a partially spherical shape other than a hemispherical shape, for example, it may be formed in the shape shown in FIG. 17A, which will be described later. Furthermore, the term "sphere" is not limited to a strict sphere, but also includes an elliptical sphere and the like. Therefore, the "partial spherical shape" includes, for example, not only a hemispherical shape but also a semielliptic spherical shape shown in FIG. 17B, which will be described later.

Further, in the "partially spherical shape", a part of the sphere may be deformed, that is, a part of the sphere may be provided with a notch (concave part) or a protrusion (convex part). Specifically, as will be described later, a groove 20 that is a recess with respect to the surface is formed in a partially spherical portion of the ball end mill 10 (that is, the ball blade portion 12).

In a typical ball end mill, a curved surface is formed on the workpiece by machining it with a partially spherical blade. The ball end mill 10 of this embodiment is used to perform at least burnishing on the surface of a workpiece. Here, "burnishing" is a process that forms a smooth finished surface while causing plastic deformation and work hardening on the surface of a workpiece. Therefore, the ball end mill 10 of this embodiment is sometimes referred to as a "vanishing end mill." Furthermore, the effect of forming a smooth finished surface on the surface of a workpiece by burnishing is sometimes referred to as a "burnishing effect." Further, "vanishing processing" and "vanishing effect" may also be referred to as "vanishing processing" and "vanishing effect", respectively.

The ball end mill 10 of this embodiment is attached to a machine tool or the like via a holder (not shown), and burnishing is performed on the curved surface of a workpiece by rotating the blade. By performing burnishing on the workpiece, the processed surface of the workpiece can be finished with a mirror finish.

The ball end mill 10 has a shank 11 and a ball blade part 12, as shown in FIG. 1A.

The shank 11 is a member that is supported by a holder (not shown) when the ball end mill 10 is attached to a machine tool or the like. The shank 11 is formed long in the direction of the rotation axis.

The ball blade part 12 is a blade member that performs at least burnishing of a workpiece. The ball blade portion 12 is formed into a partially spherical shape on the tip side of the ball end mill 10.

The ball blade part 12 is made of a sintered body formed with high hardness in order to burnish the work material. As the material of the ball blade part 12, for example, PCD (Poly Crystalline Diamond), CBN (Cubic Boron Nitride), ceramics, cemented carbide, etc. can be used. However, as long as the work material can be burnished, a material other than the sintered body formed with high hardness may be used as the material for the ball blade portion 12.

Furthermore, the surface of the ball blade portion 12 is formed smoothly by grinding, laser processing, or the like. Specifically, the surface of the ball blade portion 12 is formed to have a surface roughness Rz of 1.6 μm or less. This can enhance the burnishing effect on the machined surface of the workpiece. However, the ball blade portion 12 may be formed to have a surface roughness greater than Rz 1.6 μm as long as a burnishing effect can be obtained on the machined surface of the workpiece. Further, the surface of the ball blade portion 12 may be formed smoothly by coating with a smooth film.

Note that, as described later, a groove 20 (recess) is formed in the ball blade portion 12. Therefore, in the present embodiment, the "surface of the ball blade part 12" that is smoothly formed means a region of the ball blade part 12 in which the groove 20 is not formed.

By the way, in ball end mills where the surface of the ball blade is formed smoothly, the contact area between the surface of the ball blade and the surface of the workpiece is large, resulting in increased resistance during burnishing. There is. For this reason, in the ball end mill 10 of this embodiment, the groove 20 is formed in the ball blade portion 12. The groove 20 is a recess formed in the ball blade portion 12, as shown in FIG.

As a result, in the region of the ball blade part 12 where the groove 20 is formed, the surface of the workpiece 100 does not come into contact with the ball blade part 12, as shown in FIG. Therefore, in the ball end mill 10 of this embodiment in which the grooves 20 are formed, the contact area between the ball blade part 12 and the surface of the workpiece 100 is reduced compared to the ball blade part in which the grooves 20 are not formed. It turns out. That is, in the ball end mill 10 of this embodiment, the grooves 20 are formed in the ball blade portion 12, so that resistance during burnishing can be reduced. Note that the burnishing process is mainly performed on a portion of the ball blade portion 12 where the groove 20 is not formed, that is, a portion that contacts the surface of the workpiece 100.

In this embodiment, as shown in FIG. 1B, the groove 20 is composed of a groove 20A and a groove 20B. The groove 20A and the groove 20B have different twisting modes, as will be described later. Here, the term "twisting mode" refers to a mode of deformation in the shape of the groove 20 when viewed from the tip 13 of the ball blade part 12 in the direction of the rotation axis, as shown in FIG. 1B. For example, in the present embodiment, the groove 20A has a "right-handed" twist mode, which will be described later, and the groove 20B has a "left-handed twist", which will be described later. Note that the "twisting mode" is not limited to "right-handed twisting" or "left-handed twisting" and includes spirals and meandering.

In the following, when the groove 20A and the groove 20B are explained in common, or when one of the

grooves

20A and 20B is explained as a representative, a subscript may not be added. For example, all of the

grooves

20A and 20B may be simply referred to as "grooves 20." Either the groove 20A or the groove 20B may be simply referred to as a "groove 20".

In this embodiment, by forming the groove 20 in the ball blade part 12, the peripheral edge 22 of the groove 20 shown in FIG. 2 becomes a cutting edge, and it is possible to perform minute cutting of the work material. In other words, the ball blade portion 12 of this embodiment can perform not only burnishing but also minute cutting on a workpiece. Hereinafter, the minute cutting process may be simply referred to as "cutting process". In the ball end mill 10 of this embodiment, since the groove 20 is formed in the ball blade part 12, the curved surface of the workpiece 100 can be mirror-finished by both burnishing and cutting.

By the way, depending on the degree of the rake angle in the peripheral edge part 22, the peripheral edge part 22 may bite into the workpiece 100 (biting phenomenon) when the workpiece 100 is processed. Due to this biting phenomenon, the workpiece 100 may be overcut (excessively cut), resulting in problems such as deterioration of the machined dimensions of the workpiece 100 and reduction of the burnishing effect. Furthermore, the movement of the peripheral edge portion 22 biting into the workpiece 100 and the movement of trying to return from the biting occur periodically in a short period of time, which may result in chatter vibration.

Therefore, in the ball blade portion 12 of this embodiment, in order to suppress the problem caused by such a biting phenomenon, the groove 20 has a negative rake angle R, as shown in FIG. However, if it is possible to allow the peripheral portion 22 to dig into the workpiece 100 to some extent during machining of the workpiece 100, the groove 20 may be formed to have a positive rake angle.

Additionally, the groove 20 has an intersection 21, as shown in FIG. 1B. The intersection portion 21 is a portion where the groove 20A and the groove 20B intersect. The characteristics of the intersection 21 in this embodiment will be described later.

<Twisted mode of groove 20>
Hereinafter, the twisting mode of the groove 20 will be explained with reference to FIG. 3 as well as FIG. 1 described above.

FIG. 3 is an explanatory diagram of the form of the groove 20 formed in the ball blade part 12. Note that FIG. 3A is a diagram of the ball blade part 12 in which only the groove 20A is formed, FIG. 3B is a diagram of the ball blade part 12 in which only the groove 20B is formed, and FIG. 3C is a diagram of the ball blade part 12 in which only the groove 20A and the groove are formed. It is a figure of the ball blade part 12 in which 20B was formed. Note that FIGS. 3A and 3B are diagrams of the ball blade portion 12 with the

grooves

20A and 20B taken out, respectively, in order to explain the

grooves

20A and 20B individually. Furthermore, in FIGS. 3A to 3C, one groove 20A that is the subject of explanation among the plurality of grooves 20A is indicated by a thick line. Similarly, one groove 20B to be explained among the plurality of grooves 20B is indicated by a thick line.

As described above, the

grooves

20A and 20B have different twisting modes.

The groove 20A is a right-handed groove. The right-handed groove is a groove that twists clockwise from the tip 13 of the ball blade portion 12 to the outer periphery 14. In other words, the right-handed groove is a groove that curves convexly in the counterclockwise direction along the outer periphery 14 of the ball blade portion 12.

A plurality of grooves 20A are formed in the ball blade portion 12 of this embodiment. Specifically, as shown in FIG. 3A, the ball blade portion 12 has 16 grooves 20A formed therein. The plurality of grooves 20A are provided radially from the tip 13 to the outer periphery 14. As shown in FIG. 3A, a plurality of grooves 20A are formed in the ball blade portion 12 so that circumferentially adjacent grooves 20A are equally spaced. In other words, a plurality of grooves 20A are formed in the ball blade portion 12 so as to be equally divided. In other words, the plurality of grooves 20A are positioned rotationally symmetrically about the tip 13.

Here, "rotationally symmetrical" means that when n grooves are located radially around a certain center, when the certain grooves are rotated by (360/n) degrees around the center, they overlap. Here, 16 grooves 20A are formed in the ball blade part 12. Therefore, the plurality of grooves 20A are provided so as to overlap when rotated by 22.5 (360/16) degrees in the circumferential direction.

The groove 20B is a left-handed twisted groove. The left-handed twisted groove is a groove twisted in a counterclockwise direction from the tip 13 of the ball blade part 12 to the outer periphery 14. In other words, the left-handed groove is a groove that curves convexly in the clockwise direction along the outer periphery 14 of the ball blade portion 12.

A plurality of grooves 20B are formed in the ball blade portion 12 of this embodiment. Specifically, as shown in FIG. 3B, fifteen grooves 20B are formed in the ball blade portion 12. The plurality of grooves 20B are provided radially from the tip 13 to the outer periphery 14. As shown in FIG. 3B, a plurality of grooves 20B are formed in the ball blade portion 12 so that circumferentially adjacent grooves 20B are equally spaced. In other words, a plurality of grooves 20B are formed in the ball blade portion 12 so as to be equally divided. In other words, the plurality of grooves 20B are positioned rotationally symmetrically about the tip 13.

In the ball blade portion 12 of this embodiment, as shown in FIG. 3C, right-handed helical grooves 20A and left-handed helical grooves 20B are alternately arranged in the rotation direction of the ball end mill 10. As a result, when machining a workpiece by rotation of the ball end mill 10, the machining direction of the workpiece changes for each groove 20. In addition, when machining a workpiece by rotating the ball end mill 10, an unequal twisting effect is also produced. Therefore, it is possible to suppress the formation of burrs on the workpiece material after processing. Furthermore, the vibration damping effect during machining of the work material can be enhanced.

Furthermore, in the ball blade portion 12 of this embodiment, as shown in FIG. 3C, the plurality of grooves 20 composed of the

grooves

20A and 20B are not connected at the tip 13. As described above, the burnishing process is performed on the portion where the groove 20 is not formed. Therefore, by disabling the plurality of grooves 20 at the tip 13, the grooves 20 (recesses) are not formed in the tip 13, and a burnishing effect at the tip 13 can be obtained.

<Intersection 21>
Below, the characteristics of the intersection part 21 of the ball blade part 12 of this embodiment will be explained using a comparative example.

FIG. 4 is an explanatory diagram of the intersection portion 21 of the groove 20. Note that FIG. 4A is an explanatory diagram of a plurality of intersections 21 in the ball blade portion 12X of the comparative example, FIG. 4B is an explanatory diagram of the intersections 21 in an enlarged manner, and FIG. FIG. 3 is an explanatory diagram of a plurality of intersections 21 in the blade portion 12. FIG. Further, FIGS. 4A to 4C show views (side view) of the ball blade portion 12X or the ball blade portion 12 as viewed in a direction perpendicular to the rotation axis direction.

A plurality of right-handed helical grooves 20A and a plurality of left-handed helical grooves 20B, the same number as the grooves 20A, are formed in the ball blade portion 12X of the comparative example shown in FIG. 4A. Specifically, 15

grooves

20A and 15 grooves 20B are formed in the ball blade portion 12X of the comparative example. Further, in the ball blade portion 12X of the comparative example, the plurality of grooves 20A and the plurality of grooves 20B are each positioned rotationally symmetrically about the tip 13. As a result, in a side view of the ball blade part 12X, the plurality of intersections 21 formed by the

grooves

20A and 20B are aligned on a line along the rotation direction, as shown by the area surrounded by lines in FIG. 4A. It will be located in a concentrated manner.

Here, when the ball end mill 10X of the comparative example processes a workpiece while rotating in the rotation direction shown in FIG. 4A, how does a certain point of the workpiece pass through the groove 20 and the intersection 21? This will be explained using FIG. 4B. FIG. 4B shows an enlarged portion of the ball blade portion 12X including an intersection 21 where a certain groove 20A and a certain groove 20B intersect. Further, in FIG. 4B, the area of the intersection 21 is shown by hatching using dots.

In FIG. 4B, the trajectory through which a certain point of the workpiece passes in the ball blade portion 12X is indicated by a broken line L1. Further, in the ball blade portion 12X, a locus along which another point of the workpiece passes is indicated by L2. As shown in FIG. 4B, the trajectory L1 does not pass through the intersection 21, and the trajectory L2 does pass through the intersection 21.

As described above, among the processes performed by the ball end mill 10, burnishing is mainly performed in the portion of the ball blade portion 12 where the groove 20 is not formed. Therefore, burnishing is not performed on the grooves 20 or the intersections 21 that the grooves 20 have.

The part of the ball blade part 12 where the burnishing process is performed will be explained with reference to the diagram shown in FIG. 4B. The burnishing process is performed in the part shown by the arrow between the locus L1 and the locus L2. Here, in the trajectory L1, the arrow portions where the burnishing process is performed appear regularly across the

grooves

20B or 20A. On the other hand, in the trajectory L2, the arrow portion where the burnishing process is performed does not appear from the time it starts passing through the groove 20B until it finishes passing through the groove 20A. That is, in the trajectory L2, there are more portions where burnishing is not performed than in the trajectory L1. Therefore, the trajectory L2 that passes through the intersection 21 is more disadvantageous in terms of burnishing than the trajectory L1 that does not pass through the intersection 21.

Furthermore, as described above, among the machining operations performed by the ball end mill 10, the cutting process is performed at a portion C of the peripheral edge portion 22 of the groove 20 on the side that becomes the cutting edge, as shown in FIG. 4B. Mainly done. Note that the peripheral edge portion 22 has two locations on the trajectory L1 and the trajectory L2, one on the side where the passage begins and the side on which the passage ends, and the portion C is the portion of the peripheral edge portion 22 on the side where the passage ends.

Here, in the trajectory L1, the portion C where cutting is performed appears twice. On the other hand, in the trajectory L2, the portion C where cutting is performed appears only once. That is, in the trajectory L2, the portion C where cutting is performed is smaller than in the trajectory L1. Therefore, the trajectory L2 that passes through the intersection 21 is more disadvantageous in terms of cutting than the trajectory L1 that does not pass through the intersection 21.

As described above, the trajectory L2 that passes through the intersection 21 is more disadvantageous in both burnishing and cutting than the trajectory L1 that does not pass through the intersection 21. Here, in the ball blade portion 12X of the comparative example, the intersection portions 21, which are disadvantageous for such burnishing and cutting, are concentrated and located on a line along the rotation direction. In a region of the machined surface of the workpiece through which such a large number of intersections 21 pass, machining may be insufficient and the quality of the machined surface of the workpiece may deteriorate.

In the ball blade part 12 of this embodiment, in order to improve the quality of the machined surface of the workpiece, the intersection parts 21 are suppressed from being concentrated on a line along the rotation direction. Thereby, it is possible to improve the quality of the machined surface of the work material and also to increase the precision. Below, the arrangement of the intersection portion 21 of the ball blade portion 12 of this embodiment will be explained using FIG. 3C described above.

When viewed from the tip 13 of the ball blade part 12 in the rotational axis direction shown in FIG. 3C, in a certain groove 20B, the intersection 21 located at a predetermined position (for example, the third) from the tip 13 side is called the first intersection 21A. do. In addition, in another circumferentially adjacent groove 20B, an intersection located at the same predetermined position (third) from the tip 13 side as described above is referred to as a second intersection 21B. At this time, in the ball blade portion 12 of this embodiment, the length from the tip 13 to the first intersection 21A is different from the length from the tip 13 to the second intersection 21B.

Therefore, in the ball blade portion 12 of the present embodiment, it is possible to prevent the intersection portions 21 from being located in a concentrated manner on a line along the rotation direction. That is, in the side view of the ball blade part 12 shown in FIG. 4C, the line where the plurality of intersections 21 are located (that is, the area surrounded by the line in FIG. 4C) is inclined with respect to the line along the rotation direction. There is. In the ball blade portion 12 of this embodiment, only one intersection portion 21 is located on each line along the rotation direction. When viewed from the tip 13 of the ball blade part 12 shown in FIG. 3C in the direction of the rotation axis, the plurality of intersections 21 are located on a spiral curve centered on the tip 13 (i.e., the broken line in FIG. 3C). There is.

In the ball blade part 12 of this embodiment, the number of grooves 20A and the number of grooves 20B that are different from the number of grooves 20A are formed. Specifically, as described above, 16

grooves

20A and 15 grooves 20B are formed. Further, in the ball blade portion 12 of this embodiment, the plurality of grooves 20A and the plurality of grooves 20B are each positioned rotationally symmetrically about the tip 13. Thereby, the length from the tip 13 of the ball blade part 12 to the first intersection part 21A can be made different from the length from the tip 13 of the ball blade part 12 to the second intersection part 21B.

<Example of changing the number of grooves 20>
Below, examples in which the number of grooves 20A and the number of grooves 20B are changed will be described using FIGS. 5 to 7.

- Example in which the number of grooves 20A and the number of grooves 20B are in a mutually prime relationship FIG. 5 is an explanatory diagram of an example in which the number of grooves 20 formed in the ball blade portion 12 is changed. Note that FIG. 5A is an explanatory diagram of an example in which the number of grooves 20A is 16 and the number of grooves 20B is 13. FIG. 5B is an explanatory diagram of an example in which the number of grooves 20A is 16 and the number of grooves 20B is 11.

Further, FIG. 6 is an explanatory diagram of an example in which the number of grooves 20 formed in the ball blade portion 12 is changed. Note that FIG. 6A is an explanatory diagram of an example in which 17

grooves

20A and 15 grooves 20B are provided, and FIG. 6B is an explanatory diagram of an example in which 9 grooves 20A and 7 grooves 20B are provided, FIG. 6C is an explanatory diagram of an example in which there are seven grooves 20A and five grooves 20B.

In the ball blade portion 12 shown in FIGS. 5A, 5B, and 6A to 6C, the number of grooves 20A and the number of grooves 20B are in a mutually prime relationship. At this time, as shown in FIGS. 5A, 5B, and 6A to 6C, when viewed from the tip 13 of the ball blade part 12 in the direction of the rotation axis, the length from the tip 13 to the intersection 21 is equal to The difference will be in section 21. At this time, the plurality of intersections 21 are located on a spiral curve centered on the tip 13 (ie, the broken lines in FIGS. 5A, 5B, and 6A to 6C).

- Example where the number of grooves 20A and the number of grooves 20B are not in a mutually prime relationship FIG. 7 is an explanatory diagram of an example in which the number of grooves 20 formed in the ball blade portion 12 is changed. Note that FIG. 7A is an explanatory diagram of an example in which 16

grooves

20A and 14 grooves 20B are provided, and FIG. 7B is an explanatory diagram in an example in which 15

grooves

20A and 10 grooves 20B are provided.

In the ball blade portion 12 shown in FIGS. 7A and 7B, the number of grooves 20A and the number of grooves 20B are not in a mutually prime relationship. At this time, for example, in the ball blade portion 12 shown in FIG. 7A, two intersection portions 21 appear at symmetrical positions in a plane including the rotation axis. In other words, in the case of the ball blade part 12 shown in FIG. 7A, the two intersections 21 are located on the line along the rotation direction (that is, the broken line in FIG. 7A). Similarly, in the case of the ball blade part 12 shown in FIG. 7B, the five intersections 21 are located on the line along the rotation direction (that is, the broken line in FIG. 7B). Therefore, in the case of the ball blade part 12 shown in FIGS. 7A and 7B, when viewed from the tip 13 in the rotation axis direction, two or more intersections 21 having the same length from the tip 13 to the intersection 21 appear. Become.

Therefore, in the ball blade part 12 of this embodiment, it is more preferable that the number of grooves 20A and the number of grooves 20B are different and have a mutually prime relationship.

In the above description, the number of grooves 20A and the number of grooves 20B are different, so that the length from the tip 13 of the ball blade part 12 to the first intersection part 21A and the length from the tip 13 of the ball blade part 12 to the second intersection part 21B are different. I explained that the lengths are different. However, the aspect in which the length from the tip 13 of the ball blade part 12 to the first intersection part 21A is different from the length from the tip 13 of the ball blade part 12 to the second intersection part 21B is not limited to the above case. . Also in the case of the modified examples (first modified example and second modified example) shown below, the length from the tip 13 of the ball blade part 12 to the first intersection 21A and the length from the tip 13 of the ball blade part 12 to the second intersection The length up to part 21B is different.

<First modification example>
FIG. 8 is an explanatory diagram of an aspect of the groove 20 formed in the ball blade part 32 of the first modification. Note that FIG. 8A is a diagram of the ball blade part 32 in which only the groove 20C is formed, FIG. 8B is a diagram of the ball blade part 32 in which only the groove 20B is formed, and FIG. 8C is a diagram of the ball blade part 32 in which only the groove 20C and the groove are formed. It is a figure of the ball blade part 32 in which 20B was formed.

In the ball blade portion 12 shown in FIG. 3C described above, the plurality of grooves 20A and the plurality of grooves 20B are both positioned rotationally symmetrically about the tip 13. However, in the ball blade part 32 of the first modification, at least one of the plurality of grooves 20A and the plurality of grooves 20B does not have to be positioned rotationally symmetrically about the tip 13.

In the ball blade portion 32 of the first modification, as shown in FIG. 8A, the dividing angle between the grooves 20C adjacent to each other in the circumferential direction is provided so as to gradually increase. In other words, regarding the dividing angle between circumferentially adjacent grooves 20C, when comparing the dividing angle α between a certain groove 20C and the dividing angle β between another groove 20C, the dividing angle β is larger than the dividing angle α. (β>α).

On the other hand, in the ball blade part 32 of the first modification, the groove 20B having a twisting pattern different from the groove 20C is rotationally symmetrical about the tip 13, as in the ball blade part 12 described above, as shown in FIG. 8B. It is located so that

Also in the ball blade portion 32 of the first modification, it is possible to prevent the intersection portions 21 from being concentrated on the line along the rotation direction. That is, even in the ball blade part 32 of the first modification, only one intersection part 21 is located on each line along the rotation direction. When viewed in the direction of the rotation axis from the tip 13 of the ball blade 32 shown in FIG. (dashed line). Therefore, also in the ball blade part 32 of the first modification, the quality of the machined surface of the workpiece can be improved.

In the ball blade portion 32 of the first modified example described above, the right-handed helical groove 20C is provided so that the angle of the grooves 20 adjacent to each other in the circumferential direction gradually increases. However, instead of the right-handed helical groove 20C, the left-handed helical groove 20B may be provided such that the angle between circumferentially adjacent grooves 20B gradually increases. Further, both the right-handed helical groove 20C and the left-handed helical groove 20B may be provided so that the angles between the circumferentially adjacent grooves 20C and the circumferentially adjacent grooves 20B gradually increase.

Furthermore, the grooves 20 adjacent to each other in the circumferential direction may be provided so that the angle thereof gradually becomes smaller. Not limited to these, if it is possible to prevent the intersections 21 from being concentrated on a line along the rotational direction, the angle between the grooves 20 adjacent to each other in a certain circumferential direction will be the angle between the grooves 20 adjacent to each other in another circumferential direction. It's good just to be different. Moreover, in the ball blade part 32 of the first modification, the number of grooves 20C and the number of grooves 20B may be the same.

<Second modification example>
FIG. 9 is an explanatory diagram of an aspect of the groove 20 formed in the ball blade part 42 of the second modification. Note that FIG. 9A is a diagram of the ball blade part 42 in which only the groove 20A is formed, FIG. 9B is a diagram of the ball blade part 42 in which only the groove 20D is formed, and FIG. 9C is a diagram of the ball blade part 42 in which only the groove 20A and the groove are formed. It is a figure of the ball blade part 42 in which 20D was formed.

In the ball blade portion 12 shown in FIG. 3C described above, a plurality of grooves 20A and a plurality of grooves 20B were formed. However, in the ball blade part 42 of the second modification, only one of the

grooves

20A and 20B may be formed. The twist mode of only one groove formed may be other than the right-handed twist and left-handed twist shown in FIG. 3C.

In the ball blade part 42 of the second modification, a plurality of grooves 20A are formed. As shown in FIG. 9A, the plurality of grooves 20A are positioned so as to be rotationally symmetrical about the tip 13, similar to the above-described ball blade portion 12.

On the other hand, in the ball blade part 42 of the second modification, one groove 20D is formed, as shown in FIG. 9B. The groove 20D is a groove formed in a spiral curve centered on the tip 13.

Also in the ball blade portion 42 of the second modification, it is possible to prevent the intersection portions 21 from being concentrated on the line along the rotation direction. That is, even in the ball blade part 42 of the second modification, only one intersection part 21 is located on each line along the rotation direction. When viewed in the rotational axis direction from the tip 13 of the ball blade 42 shown in FIG. groove 20D). Therefore, also in the ball blade part 42 of the second modification, the quality of the machined surface of the workpiece can be improved.

<Processing test>
Three types of ball end mills were prepared and machining tests were conducted on workpieces with regard to the presence or absence of grooves on the ball cutting edge and the shape of the grooves. First, an overview of three types of ball end mills will be explained below.

FIG. 10 is an explanatory diagram of a ball cutting edge used in a machining test using a ball end mill. 10A is a diagram of the ball end mill 50 having the ball blade part 52, FIG. 10B is a diagram of the ball end mill 60 having the ball blade part 62, and FIG. 10C is a diagram of the ball end mill 50 having the ball blade part 12. FIG.

As shown in FIG. 10A, the ball blade portion 52 of the ball end mill 50 does not have the groove 20 formed therein. That is, the entire surface of the ball blade portion 52 comes into contact with the surface of the workpiece, and burnishing of the workpiece is performed. Note that since no groove is formed in the ball blade portion 52, the above-mentioned cutting process is not performed.

Furthermore, a groove 20 is formed in the ball blade portion 62 of the ball end mill 60, as shown in FIG. 10B. The groove 20 is composed of only 16 right-handed grooves 20A. Note that a cross-sectional view of the groove 20 is shown on the right side of FIG. 10B. Groove 20 has a negative rake angle, similar to the groove 20 shown in FIG. 2 described above.

Further, the ball blade portion 12 of the ball end mill 10 has a groove 20 formed therein, as shown in FIG. 10C. The grooves 20 are composed of 16 grooves 20A with a right-handed twist and 15 grooves 20B with a left-handed twist. That is, the ball blade part 12 is similar to the ball blade part 12 of the ball end mill 10 of this embodiment shown in FIG. 3C etc. mentioned above. Note that a cross-sectional view of the groove 20 is shown on the right side of FIG. 10C. Groove 20 has a negative rake angle, similar to the groove 20 shown in FIG. 2 described above.

Next, two types of processing conditions (processing condition 1 and processing condition 2) in this processing test will be explained.

FIG. 11 is an explanatory diagram illustrating the processing conditions in the processing test. In addition, in FIG. 11, the machining conditions are representatively shown for the ball blade part 12 (ball end mill 10), but the machining conditions for the ball blade part 52 (ball end mill 50) and the ball blade part 62 (ball end mill 60) are shown as a representative example. The same applies to the case.

As shown in FIG. 11, the ball end mill 10 processes the workpiece 100 by up-cutting by moving in the direction of the arrow shown in FIG. 11 while rotating the ball blade part 12. Here, in the region of the workpiece 100 to be machined, as shown in FIG. 11, a concave portion having a curved surface has already been cut. The ball blade portion 12 of the ball end mill 10 is planned to cut in a direction perpendicular to the axial direction by machining.

Here, in machining conditions 1, the rotation speed of the ball blade part 12 is 800 min ^-1 (cutting speed: 20 m/min), the table feed speed is 320 mm/min, the axial depth of cut is 4 mm, and the planned depth of cut is 0.005 mm. is set to In addition, under machining conditions 2, the rotation speed of the ball blade part 12 is 800 min ^-1 (cutting speed: 20 m/min), the table feed rate is 32 mm/min, the axial depth of cut is 4 mm, and the planned depth of cut is 0.010 mm. Set.

<Comparison results of machining torque>
FIG. 12 is a graph showing an example of a comparison result of machining torque under machining condition 1. Note that FIG. 12A is a graph showing the average torque value, and FIG. 12B is a graph showing the maximum torque value. FIG. 13 is a graph showing an example of a comparison result of machining torque under machining condition 2. Note that FIG. 13A is a graph showing the average torque value, and FIG. 13B is a graph showing the maximum torque value.

Under machining condition 1, both the average torque value shown in FIG. 12A and the maximum torque value shown in FIG. 12B, the machining torque in the ball blade portion 52 where the groove 20 is not formed is the highest. The machining torque at the ball blade portion 62, which is formed only by the right-handed helical groove 20A, is the second highest after the machining torque at the ball blade portion 52. Furthermore, the machining torque in the ball blade portion 12 composed of the right-handed helical groove 20A and the left-handed helical groove 20B is the lowest.

Also, under machining condition 2, both the average torque value shown in FIG. 13A and the maximum torque value shown in FIG. 13B, the machining torque in the ball blade portion 52 where the groove 20 is not formed is the highest. The machining torque at the ball blade portion 62, which is formed only by the right-handed helical groove 20A, is the second highest after the machining torque at the ball blade portion 52. Furthermore, the machining torque in the ball blade portion 12 composed of the right-handed helical groove 20A and the left-handed helical groove 20B is the lowest.

From the comparative results of this machining test, it is clear that there is a significant difference due to the formation of the groove 20 on the ball cutting edge. As described above, in the ball end mill 10 of this embodiment, the grooves 20 are formed in the ball blade portion, so that resistance during burnishing can be reduced. However, the formation of the groove 20 in the ball cutting edge may generate resistance to the workpiece due to cutting. In other words, this machining test showed that even if resistance was generated due to the cutting process, the effect of reducing the resistance due to the burnishing process was greater than that.

<Comparison results of processing errors>
Next, we will verify machining errors for three types of ball end mills.

FIG. 14 is a chart regarding machining errors under machining conditions 1 and 2. Note that FIG. 14A is an explanatory diagram of machining errors, and FIG. 14B is a table showing an example of comparison results of machining errors. Moreover, FIG. 14A shows a cross-sectional view of the workpiece seen in the moving direction of the ball end mill.

Here, as shown in FIG. 14A, the machining error is defined as the actual machining position (i.e., the solid line shown in FIG. 14A) with respect to the planned cutting position of the workpiece (i.e., the position of the broken line shown in FIG. It is expressed as the difference between Then, the side opposite to the ball blade side is set as a positive value, and the side of the ball blade side is set as a negative value. In other words, when the machining error is a positive value, it means that the cut is actually made too far with respect to the planned cut position. Moreover, when the processing error is a negative value, it means that the depth of cut is actually insufficient with respect to the planned cut position.

Under machining condition 1, as shown in FIG. 14B, the machining error in the ball blade portion 52 where the groove 20 is not formed is the largest. The machining error in the ball blade portion 62, which is composed of only the right-handed groove 20A, is the second highest after the machining error in the ball blade portion 52. Further, the machining error in the ball blade portion 12, which is composed of the right-handed helical groove 20A and the left-handed helical groove 20B, is the smallest.

Also, under machining condition 2, as shown in FIG. 14B, the machining error is the largest in the ball blade portion 52 where the groove 20 is not formed. The machining error in the ball blade portion 62, which is composed of only the right-handed groove 20A, is the second highest after the machining error in the ball blade portion 52. Further, the machining error in the ball blade portion 12, which is composed of the right-handed helical groove 20A and the left-handed helical groove 20B, is the smallest.

From the above, it is clear from the verification results of machining errors that there is a significant difference due to the formation of the groove 20 on the ball cutting edge. Furthermore, the ball blade part 12 composed of the right-handed helical groove 20A and the left-handed helical groove 20B is more advantageous in terms of machining errors than the ball blade part 62 composed only of the right-handed helical groove 20A. I found out something.

===Second embodiment===
In the ball end mill 10 of the first embodiment described above, the plurality of grooves 20 formed in the ball blade part 12 are not connected at the tip 13. Thereby, the groove 20 (recess) is not formed in the tip 13, and a burnishing effect at the tip 13 can be obtained.

Further, the plurality of grooves 20 are provided radially from the tip 13 to the outer periphery 14. Therefore, in the ball blade portion 12 of the first embodiment, the plurality of grooves 20 become more concentrated as they get closer to the tip 13. As described above, since the burnishing process is not performed on the portion of the ball blade portion 12 where the groove 20 is formed, the burnishing effect may be weakened around the tip 13.

Therefore, a ball end mill that improves the burnishing effect around the tip of the ball blade will be described below.

FIG. 15 is a diagram of the

ball blade parts

72, 82 of the second embodiment. Note that FIG. 15A is a view seen from the tip 13 of the ball blade part 72 of the first embodiment in the direction of the rotation axis, and FIG. 15B is a view seen from the tip 13 of the ball blade part 82 of the second example in the direction of the rotation axis. It is a diagram. FIG. 16 is a view of the ball blade portion 92 of the third embodiment as viewed from the tip 13 in the direction of the rotation axis.

As shown in FIG. 15A, the ball blade portion 72 of the first example of this embodiment includes a tip 13 and has a region 15 wider than the tip 13. The end of each of the plurality of grooves 20 on the tip 13 side is located outside the region 15. In other words, the groove 20 is not formed inside the region 15 in the ball blade portion 72 . Thereby, the burnishing effect can be enhanced around the tip 13 of the ball blade portion where the grooves 20 are concentrated.

However, all the ends of the grooves 20 on the tip 13 side do not have to be located outside the region 15. As shown in FIG. 15B, among the plurality of grooves 20 formed in the ball blade part, the end of each of the grooves on the tip 13 side may be located inside the region 15.

As shown in FIG. 15B, the ball blade part 82 of the second example of this embodiment has a groove 20A whose end on the tip 13 side extends to the tip 13, and a groove 20A whose end on the tip 13 side is outside the area 15. It has a groove 20E and a groove 20F located at . In other words, the plurality of grooves 20 of the ball blade part 82 include grooves 20 whose ends on the tip 13 side are located outside the region 15 (i.e., grooves 20E and grooves 20F), and grooves 20 whose ends on the tip 13 side are located outside the region 15. It has a groove 20 (namely, groove 20A) located inside. Thereby, around the tip 13 of the ball blade portion where the grooves 20 are concentrated, it is possible to enhance the burnishing effect and also enhance the cutting effect.

Note that the position of the end of the groove 20 on the tip 13 side may be stepped. As shown in FIG. 16, the ball blade portion 92 of the third example of the present embodiment includes a tip 13 and has a region 16 narrower than the region 15. As shown in FIG. 16, the groove 20 has an end on the distal end 13 side located inside the region 15, a groove 20G located on the outside of the region 16, and an end on the distal end 13 side in the region 16. It may also be configured with a groove 20A located on the inside. Thereby, around the tip 13 of the ball blade portion where the grooves 20 are concentrated, it is possible to enhance the burnishing effect and also enhance the cutting effect.

===Other embodiments===
<Another example regarding the shape of the ball blade part 12>
17 is another example of the shape of the ball blade part 12, FIG. 17A is a first example of the shape of the ball blade part 12, and FIG. 17B is a second example of the shape of the ball blade part 12. .

The shape of the ball blade portion 12 is not limited to the hemispherical shape shown in FIG. 1A described above. For example, like the ball blade part 12 shown in FIG. 17A, the shape may be closer to a sphere than a hemisphere. Moreover, it may have an elliptical spherical shape like the ball blade part 12 shown in FIG. 17B.

<Another example regarding the groove 20 of the ball blade part 12>
FIG. 18 is another example regarding the groove 20 of the ball blade part 12.

The grooves 20 formed in the ball blade portion 12 described above were formed with the same width. However, as in the ball blade portion 12 shown in FIG. 18, in each of the plurality of grooves 20, the width of the groove 20 on the outer circumference 14 side may be larger than the width of the groove 20 on the tip 13 side. This makes it possible to suppress resistance during burnishing on the outer periphery 14 side.

===Summary===
The ball end mill that is an embodiment of the present invention has been described above.

The ball end mill 10 of the first embodiment includes, for example, a ball blade portion 12 formed into a partially spherical shape, as shown in FIGS. 1 to 3. Moreover, when the ball blade part 12 is viewed from the tip 13 in the direction of the rotation axis, the ball blade part 12 has at least one right-handed groove 20A extending from the tip 13 side to the outer periphery 14 side, and a plurality of left-handed grooves 20B. and has. In addition, in one groove 20B, among the intersections 21 that intersect with at least one groove 20A, the intersection 21 located at a predetermined point from the tip 13 side is defined as the first intersection 21A, and in another groove 20B, at least one Among the intersections 21 that intersect with the grooves 20A, when the intersection 21 located at a predetermined distance from the tip 13 side is defined as the second intersection 21B, the length from the tip 13 to the first intersection 21A and the length from the tip 13 to the second The length to the intersection 21B is different. Thereby, the quality of the machined surface of the workpiece can be improved.

Here, the groove 20A corresponds to a "first groove", and the groove 20B corresponds to a "second groove". Further, the right-handed twist corresponds to a "first twist mode" and the left-handed twist corresponds to a "second twist mode."

The ball end mill 30 of the first modification of the first embodiment includes, for example, a ball blade portion 32 formed in a partially spherical shape, as shown in FIG. Moreover, when the ball blade part 32 is viewed from the tip 13 in the direction of the rotation axis, the ball blade part 32 has at least one right-handed groove 20C extending from the tip 13 side to the outer periphery 14 side, and a plurality of left-handed grooves 20B. and has. In addition, in one groove 20B, among the intersections 21 that intersect with at least one groove 20C, the intersection 21 located at a predetermined distance from the tip 13 side is defined as the first intersection 21A, and in another groove 20B, at least one Among the intersections 21 that intersect with the grooves 20C, when the intersection 21 located at a predetermined point from the tip 13 side is defined as the second intersection 21B, the length from the tip 13 to the first intersection 21A, and the length from the tip 13 to the second intersection 21B. The length to the intersection 21B is different. Thereby, the quality of the machined surface of the workpiece can be improved.

Here, the groove 20C corresponds to a "first groove", and the groove 20B corresponds to a "second groove". Further, the right-handed twist corresponds to a "first twist mode" and the left-handed twist corresponds to a "second twist mode."

A ball end mill 40 according to a second modification of the first embodiment includes, for example, a ball blade portion 42 formed into a partially spherical shape, as shown in FIG. Moreover, when the ball blade part 42 is viewed from the tip 13 in the direction of the rotation axis, the ball blade part 42 has one spirally twisted groove 20D extending from the tip 13 side to the outer periphery 14 side of the ball blade part 42, and a plurality of right-handed screw grooves. 20A. Also, in one groove 20A, among the intersection parts 21 that intersect with one groove 20D, the intersection part 21 located at a predetermined point from the tip 13 side is defined as the first intersection part 21A, and in another groove 20A, one groove 20D When the intersection 21 located at a predetermined point from the tip 13 side is defined as the second intersection 21B, the length from the tip 13 to the first intersection 21A and the length from the tip 13 to the second intersection The length is different up to 21B. Thereby, the quality of the machined surface of the workpiece can be improved.

Here, the groove 20D corresponds to a "first groove", and the groove 20A corresponds to a "second groove". Further, the spiral twist corresponds to the "first twist mode", and the right twist corresponds to the "second twist mode".

Further, as shown in FIG. 3, the ball blade part 12 has a plurality of grooves 20A, and when viewed from the tip 13 of the ball blade part 12 in the direction of the rotation axis, the first twisting mode of the ball blade part 12 is It is a right-handed twist curved so as to be convex in the counterclockwise direction along the outer periphery 14, and the second twist mode is a right-handed twist that is curved in a clockwise direction opposite to the counterclockwise direction along the outer periphery 14 of the ball blade part 12. It is curved and twisted to the left. Thereby, it is possible to suppress the formation of burrs on the workpiece material after processing. Furthermore, the vibration damping effect during machining of the work material can be enhanced.

Here, the counterclockwise direction corresponds to a "first direction" and the clockwise direction corresponds to a "second direction."

Further, as shown in FIG. 3, when viewed from the tip 13 of the ball blade portion 12 in the direction of the rotation axis, the intersection 21 where the plurality of grooves 20A and the plurality of grooves 20B intersect is a spiral spiral centered on the tip 13. It is located on the curve of . Thereby, the quality of the machined surface of the workpiece can be improved.

Further, as shown in FIG. 3, when viewed from the tip 13 of the ball blade part 12 in the direction of the rotation axis, the plurality of grooves 20A are positioned rotationally symmetrically around the tip 13, and the plurality of grooves 20B are , are positioned rotationally symmetrically about the tip 13, and the number of the plurality of grooves 20A is different from the number of the plurality of grooves 20B. Thereby, the length from the tip 13 to the first intersection 21A and the length from the tip 13 to the second intersection 21B can be provided to be different.

Further, as shown in FIG. 3, the number of the plurality of grooves 20A and the number of the plurality of grooves 20B have a relatively prime relationship. Thereby, the length from the tip 13 to the first intersection 21A and the length from the tip 13 to the second intersection 21B can be provided to be different.

Further, as shown in FIG. 3, the difference between the number of multiple grooves 20A and the number of multiple grooves 20B is 1. Thereby, the length from the tip 13 to the first intersection 21A and the length from the tip 13 to the second intersection 21B can be provided to be different.

Although not shown, the number of the plurality of grooves 20C is the same as the number of the plurality of grooves 20B, and when viewed from the tip 13 of the ball blade part 32 in the rotation axis direction, the plurality of grooves 20C are adjacent to each other. The intervals between the matching grooves 20C are positioned so as to gradually increase in the circumferential direction along the outer periphery 14 of the ball blade portion 32, and the plurality of grooves 20B are positioned so as to be rotationally symmetrical about the tip 13. Thereby, the quality of the machined surface of the workpiece can be improved.

Here, the groove 20C corresponds to a "first groove", and the groove 20B corresponds to a "second groove". Further, the circumferential direction corresponds to a "predetermined direction".

Further, as shown in FIG. 9, the ball blade part 42 has one groove 20D, and when viewed from the tip 13 of the ball blade part 42 in the rotation axis direction, the first twisting mode is centered around the tip 13. The plurality of grooves 20A are positioned rotationally symmetrically around the tip 13, and the second twisting mode is a spiral curve in a counterclockwise direction along the outer periphery 14 of the ball blade part 42. It is a right-handed twist with a convex curve. Thereby, the quality of the machined surface of the workpiece can be improved.

Here, the groove 20D corresponds to a "first groove", and the groove 20A corresponds to a "second groove". Further, the counterclockwise direction corresponds to a "predetermined direction."

Further, as shown in FIG. 2, the rake angle at the peripheral edge portion 22 of each of the

grooves

20A and 20B is a negative rake angle. Thereby, it is possible to suppress the peripheral edge portion 22 from digging into the workpiece during machining of the workpiece.

Further, as shown in FIG. 18, the width of each of the

grooves

20A and 20B increases as the distance from the tip 13 of the ball blade portion 12 increases. Thereby, on the outer periphery 14 side of the ball blade part 12, resistance due to burnishing can be suppressed.

Although not shown, at least one groove 20A and a plurality of grooves 20B are formed on the surface of the ball blade portion 12 with a surface roughness of Rz 1.6 μm or less. can enhance the vanishing effect of

Further, as shown in FIG. 3, at least one groove 20A and a plurality of grooves 20B are not connected at the tip 13 of the ball blade part 12. Thereby, a burnishing effect can be obtained at the tip 13.

===Others===
The above-described embodiments are provided to facilitate understanding of the present invention, and are not intended to be interpreted as limiting the present invention. It goes without saying that the present invention may be modified and improved without departing from its spirit, and that equivalents thereof are included in the present invention.

10, 10X, 30, 40, 50, 60, 70, 80, 90 Ball end mill 11

Shank

12, 12X, 32, 42, 52, 62, 72, 82, 92 Ball blade part 13 Tip 14

Outer periphery

15, 16

Area

20 , 20A to

20G Grooves

21, 21A, 21B Intersection 22 Peripheral 100 Work material

Claims

Equipped with a ball blade part formed in a partially spherical shape,
When the ball blade portion is viewed from the tip in the direction of the rotation axis,
The ball blade portion has at least one first groove having a first twisting pattern and a plurality of second grooves having a second twisting pattern extending from the tip side to the outer peripheral side,
In one of the second grooves, among the intersections that intersect with the at least one first groove, an intersection located at a predetermined distance from the tip side is defined as a first intersection,
In another of the second grooves, among the intersections that intersect with the at least one first groove, when the intersection located at the predetermined point from the tip side is defined as the second intersection,
The length from the tip to the first intersection is different from the length from the tip to the second intersection,
ball end mill.
The ball blade portion has a plurality of the first grooves,
When viewed from the tip of the ball blade in the direction of the rotation axis,
The first twisting mode is a mode in which the ball blade portion is curved so as to be convex in a first direction along the outer periphery,
The second twisted mode is a curved mode along the outer periphery of the ball blade part so as to be convex in a second direction opposite to the first direction.
The ball end mill according to claim 1.
When viewed from the tip of the ball blade in the direction of the rotation axis,
The intersection where the plurality of first grooves and the plurality of second grooves intersect is located on a spiral curve centered on the tip,
The ball end mill according to claim 2.
When viewed from the tip of the ball blade in the direction of the rotation axis,
The plurality of first grooves are positioned rotationally symmetrically about the tip,
The plurality of second grooves are positioned rotationally symmetrically about the tip,
The number of the plurality of first grooves is different from the number of the plurality of second grooves,
The ball end mill according to claim 2 or 3.
The number of the plurality of first grooves and the number of the plurality of second grooves are in a mutually prime relationship;
The ball end mill according to claim 4.
The difference between the number of the plurality of first grooves and the number of the plurality of second grooves is 1,
The ball end mill according to claim 5.
The number of the plurality of first grooves and the number of the plurality of second grooves are the same,
When viewed from the tip of the ball blade in the direction of the rotation axis,
The plurality of first grooves are located such that the distance between adjacent first grooves gradually increases in a predetermined direction along the outer periphery of the ball blade portion,
The plurality of second grooves are positioned rotationally symmetrically about the tip,
The ball end mill according to claim 2 or 3.
The ball blade portion has one first groove,
When viewed from the tip of the ball blade in the direction of the rotation axis,
The first twisting mode is a mode forming a spiral curve centered on the tip,
The plurality of second grooves are positioned so as to be rotationally symmetrical about the tip, and the second twisting mode is a mode in which the plurality of second grooves are curved so as to be convex in a predetermined direction along the outer periphery of the ball blade part. ,
The ball end mill according to claim 1.
The rake angle at the peripheral edge of each of the first groove and the second groove is a negative rake angle,
The ball end mill according to any one of claims 1 to 8.
The width of each of the first groove and the second groove increases as the distance from the tip of the ball blade portion increases;
The ball end mill according to any one of claims 1 to 9.
The at least one first groove and the plurality of second grooves are formed on the surface of the ball blade portion having a surface roughness of Rz 1.6 μm or less,
The ball end mill according to any one of claims 1 to 10.
the at least one first groove and the plurality of second grooves are unconnected at the tip of the ball blade portion;
The ball end mill according to any one of claims 1 to 11.