JPH02303707A - Ball end mill - Google Patents

Abstract

PURPOSE:To eliminate a residual cutting in the vicinity of the end face center where the cutting edge peripheral speed is small by projecting the cutting edge of the end face center vicinity by a curve on the plane orthogonal with a rotating center shaft, and simultaneously making the cutting edge not coincident with the moving direction of a ball end mill. CONSTITUTION:A ball end mill 1 is formed with a cutting edge spirally on the side face, cutting edges 4a, 4b are formed at the extension part from the cutting edge of the side face and at the vicinity of a rotating center 2 semi-circular recessed cutting edges 3a, 3b in the radius R of curvature to the degree of the feeding of while the ball end mill 1 is rotated half are formed. The cutting edges 3, 4a, 4b are also arranged on the virtual sphere generated with the ball and mill 1 being rotated from the nature of the ball end mill 1. Consequently the phase of the cutting edge differs against the rotation of the ball end mill 1, the coincidence of the moving direction of the ball end mill 1 and the direction of the cutting edge 3 simultaneously in all is eliminated, residual cuttings are reduced and the surface roughness is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application> The present invention relates to a ball end mill that can improve the finish of machined surfaces.

<Conventional technology> A ball end mill has cutting edges on the outer peripheral surface and end surface, and the third
As shown in the figure, it is attached to the main shaft 52 of the machine tool, and the main shaft 5
Machining is carried out by being fed in the X-axis, X-axis, or two-axis direction while being rotated by the ball end mill 2. An end plan view of a conventional ball end mill 1 is shown in FIG.

In particular, this ball end mill 1 is often used for machining that requires three-dimensional machining, such as molding. Further, the ball end mill 1 has a cylindrical shape as a whole, and the end face, which is the tip thereof, is formed into a hemispherical shape, and the cutting edge 56 is provided in a spiral or linear shape from the outer peripheral surface to the vicinity of the tip. , continuous with the cutting edge 5 on the end face. This ball end mill 1 moves while rotating, and the cutting blades 5, 5G come into contact with the processing surface of the workpiece 58, thereby processing the workpiece into an arbitrary shape.

<Problems to be Solved by the Invention> Conventionally, in machining using a ball end mill, cutting defects may occur due to the advancing directions of the cutting blade 5 and the ball end mill 1 coinciding during machining. This is the 6th
This is because, as shown in the figure, the end face of the ball end mill 1 has one straight cutting blade, or two straight cutting blades are provided, and the cutting blade 5 provided in this way does not advance. This problem occurs because the moment the direction A coincides with direction A, the surface to be cut moves along the direction AI2, leaving uncut surfaces on the machined surface. For example, in the case of a single-flute tool, this uncut portion will be removed when Ball En 1 Mill 1 makes one more revolution, but during this time the tool moves by the feed rate per revolution. Because of this, the cutting edge 5 is arranged on a spherical surface.
The material will be cut closer to the edge of the outer blade.

As a result, since the cutting blade 5 only cuts the high edge of the uncut portion, the height after machining of 1 becomes higher compared to the surrounding area, creating a step, which worsens the surface roughness of the crab surface, resulting in a finished finish. It was a bad t.

The present invention attempts to solve two problems mentioned above.

<Means for solving am> The ball end mill according to the present invention is characterized in that at least the cutting edge near the center of the end face is projected as a curve on a plane perpendicular to the rotation center axis.

When the ball end mill rotates and moves, machining is performed by the cutting blades on the outer peripheral surface and end surface of the ball end mill.

At this time, since the cutting edge near the center of the end face is formed in a curved shape projected onto a plane perpendicular to the rotation center axis, the phase of the cutting edge will be different when the ball end mill rotates.

As a result, the cutting edges at all positions do not coincide with the moving direction of the bogol end mill at the same time, so machining is possible without uncut material even near the center of the end face where the cutting edge passes through the rotational center axis where the circumferential speed of the cutting edge is low. It will be carried out.

Embodiment One embodiment of the ball end mill of the present invention will be described. Figure 1 shows the end face of the ball end mill 1.
The cutting blade 4a and the cutting blade 4b face the flank 7 from two sides toward the center.
It is provided at the end of the As shown in FIG. 3, the ball end mill 1 has a cylindrical shape with a hemispherical tip, and a spiral cutting edge 56 is formed on the side surface.

The cutting edges 4g and 4b shown in FIG. 1 are extensions from the side cutting edge 56. These cutting blades 4a.

4b are each formed in a straight line near the outer peripheral end of the pole end mill as shown in the figure, but the ball end mill 1 is half-shaped in the vicinity of the rotation center 2, which is located on the surface of the ball end mill 1 through which the rotation center axis passes. Semicircular concave cutting edges 3a and 3b having a radius of curvature R equal to or less than the amount of feed during rotation are formed continuously to the cutting edges 4a and 4b, respectively, and the cutting edges 3a and 3b is the center of rotation 2
are connected.

Therefore, the first part is a plan view of the end face of the ball end mill 1.
At the top, a cutting blade 3 consisting of cutting blades 3a and 3b is formed in an S-shape, and due to the properties of the ball end mill 1, the cutting blades 3, 4m, and 4b are on a virtual sphere created by the rotation of the ball end mill 1. It is located in

The behavior of the cutting edge 3 during machining with the ball end mill 1 will be explained below based on FIG. 2.

The ball end mill 1 rotates in the B direction and is fed in the A direction.With the conventional cutting blade 5, the circumferential speed near the rotation center 2 is small compared to the feed amount of the ball end mill 1. An uncut portion 6 is generated on the left side in FIG. 2 of the position where the cutting edge 5 is parallel. On the other hand, if the cutting edge is S-shaped instead of a straight line as in this embodiment, the circumferential position of the cutting edge 30 is formed by a curved line that differs depending on the distance from the rotation center 2 to the cutting edge 3. . As a result, the phase of the cutting blade 3 differs with respect to the rotation of the ball end mill 1, and the moving direction A of the ball end mill 1 and the direction of the cutting blade 3 do not all coincide at the same time. Therefore, when machining with this ball end mill 1, the cutting blade 3 passes over the uncut part 6, and the cutting blade 3 near the most protruding rotation center 2 of the ball end mill 1 cuts the part with the uncut part 6. The height of the surface becomes lower and the surface roughness improves.

Further, as another embodiment of the present invention, as shown in FIG. 4, the cutting blades 3a and 3b are formed in a convex semicircular shape, or as shown in FIG. Even in the case of an asymmetrical or non-circular shape, the uncut portion 6 is removed in the same way as in the above embodiment, the surface roughness is improved, and a good finished surface can be obtained.

<Effects of the Invention> According to the ball end mill of the present invention, since the cutting edge near the center of the end face of the ball end mill is projected as a curve on a plane perpendicular to the rotation center axis, the phase of the cutting edge with respect to the rotation of the tool is This will cause a slight deviation.

Therefore, due to the low circumferential speed of the cutting edge, it was difficult to perform machining without leaving any uncut parts, but the cutting edge near the apex of the hemispherical shape located near the center of the end face can perform sufficient cutting, resulting in no uncut parts. It is possible to prevent this, improve surface roughness, and improve finish.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the end face of an embodiment of a ball end mill according to the present invention, FIG. 2 is an explanatory diagram of the movement of the cutting blade, and FIG.
The figure is a side view showing the outline of machining with a ball end mill.
4 and 5 are plan views showing the end surface of another embodiment of the ball end mill according to the present invention, and FIG. 6 is a plan view showing the end surface of the ball end mill according to the prior art. In the drawings, 1 is a ball end mill, 2 is a rotation center, 3.3m, 3b, 4m, 4b, 5.56 are cutting blades, 6 is an uncut material, 52 is a main shaft, and 58 is a workpiece material. Patent applicant Mitsubishi Heavy Industries, Ltd. Agent

Claims (1)

[Claims] A ball end mill characterized in that a cutting edge at least near the center of the end face is projected as a curve on a plane perpendicular to the rotation center axis.