JPH09267211A - Ball end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve chip discharge performance and cutting accuracy by forming an almost V-shaped bottom edge having a specific width along a cutting edge and a specific gradient in a nose part of a ball edge in a ball end mill where a circular arc-shaped ball edge is continuously connected to the tip of twisted plural outer peripheral cutting edges. SOLUTION: A ball end mill to be used for three-dimensional curved surface work has twisted plural outer peripheral cutting edges 3 and an almost 1/4 circular arc-shaped ball edge 4 continuously connected to these, and an almost V-shaped bottom edge having at least a width not less than two times a land width lain along the cutting edges 3 and a medium and low gradient 6 not less than 4 deg., is arranged in a nose part of this ball edge 4. Preferably, a width 7 of a bottom edge is set to two to three times of a land width, and the medium and low gradient 6 is set to 5 deg. to 10 deg., and a rake angle of a ball edge 4 part is set to a negative angle in the normal direction, and a rake angle of the bottom edge is set to 0 deg. to a positive angle in the axial direction. Therefore, in the case of horizontal directional cutting, a cutting speed 0 area is eliminated, and high speed cutting excellent in chip discharge can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball end mill mainly used for a machine tool.

[0002]

2. Description of the Related Art A ball end mill is used for three-dimensional curved surface machining using a machine tool such as a machining center. Among them, a solid ball end mill having an outer peripheral edge and a cutting edge twisted on a ball edge is used. Is widely used because of its good cutting property and excellent ball blade accuracy. On the other hand, in recent years, in curved surface processing of dies and the like, it has been desired to form a three-dimensional shape with a minimum number of tools and in a short time, and the transition from manual finishing to mechanical finishing that enables high-speed finishing. Needs are increasing. For this purpose, for example, there is a ball end mill (hereinafter referred to as a conventional product) disclosed in JP-A-7-1218. This is to attach a curved blade tip to the tip of the tool body and separate the tip to prevent excessive cutting resistance at the center of rotation to obtain a good machined surface.

[0003]

Generally, a ball end mill has a cutting edge whose rotation locus is hemispherical, and also has a cutting edge at the center of rotation. In this part, the cutting speed is physically zero. Therefore, only the rubbing phenomenon due to the feed rate is emphasized and local wear becomes large, which becomes a cause of impeding the cutting property. In the case of a solid ball end mill, although the cutting performance is improved by making the outer peripheral blade and the ball blade into twisted cutting edges, the effect at the center of rotation cannot be expected. Some ball end mills that use chips for the cutting edge do not have a zero cutting speed region as shown in the conventional products, but in this case, the sharpness is poor because the helix angle is not added, and the rotation center There was a problem that it could not be fed vertically because there was no cutting edge.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is particularly suitable for use in a machine tool for high-speed cutting, which is used for three-dimensional curved surface machining of dies and the like, to perform curved surface forming processing. At the same time, the present invention provides a ball end mill suitable for finishing applications.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is a solid comprising a plurality of outer peripheral cutting edges having twists and a ball edge of approximately 1/4 arc shape connected to the outer peripheral cutting edges. In the ball end mill of No. 3, the nose portion of the ball blade has a substantially V-shaped shape along the cutting edge with a width of at least twice the land width and a medium or low gradient of 4 ° or more. It has a bottom blade. And preferably, the width of the substantially V-shaped bottom blade is set to 2 to 3 of the land width in the vicinity of the nose of the ball blade.
The double and middle and low gradients are 5 ° to 10 °. The rake angle of the ball blade portion is a negative angle in the normal direction, and the rake angle of the bottom blade is 0 ° or a positive angle in the axial direction.

[0006]

[Action] end mill cutting a three-dimensional curved surface, must be guaranteed machinability to any direction for the cutting feed direction is not constant. When cutting horizontally, the center of rotation of the tip of the cutting edge (hereinafter referred to as the nose)
Is mainly used, and the wear tends to occur on the nose. In the case of a steeply inclined surface, the outer peripheral portion of the ball blade is cut, and since this portion has a high cutting speed, if sufficient cutting properties are not maintained, thermal wear will be severe and the performance will be impaired. These are phenomena related to the cutting property of the cutting edge as well as the chip discharging property.

By applying the present invention, the nose along the cutting edge has a width of at least twice the width of the land of 4 °.
Since a substantially V-shaped bottom blade is provided with the above-mentioned medium-low gradient, in the case of horizontal cutting, there is no cutting speed 0 area, and excessive cutting due to nose is avoided and high-speed cutting with good chip discharge is possible. Becomes In the case of a steeply inclined surface, an appropriate helix angle and a rake angle for assisting chip discharge are provided, so that the effect of heat is mitigated and stable cutting can be performed. When the V-shaped bottom blade is inclined and cut in the vertical direction, it has an action of shortening the length of the cutting edge involved in cutting and reduces cutting resistance.
Further, since the bottom blade reaches the center of rotation, it is possible to perform cutting without any problem even if a cut is made in the direction perpendicular to the rotation axis.

Here, the width of the V-shaped bottom blade is set to be at least twice the width of the land. If the width is smaller than this, it means that the rear portion of the land width is involved in cutting as illustrated in FIG. This is because it was avoided, and the reason why the gradient of middle and low is set to 4 ° or more is to prevent the entire bottom blade from hitting at the feed rate normally applied in the case of inclined cutting. In the present invention, the nose lacks an arcuate cutting edge, and the cutting bottom surface deviates from the perfect circle, but the error is considered to be slight,
In the grade cutting, the same accuracy as the conventional ball end mill can be obtained. However, if the width of the bottom blade becomes too wide, the influence on the shape error cannot be ignored, and it is preferably 2 to 3 times the width of the land near the nose. Further, if the gradient of middle and low is too large, the connecting position of the ball blade and the bottom blade becomes too sharp, and the progress of wear is locally accelerated, so that 5 ° to 10 ° is preferable. It is desirable to round or chamfer the position.

In high-speed cutting, by making the rake angle negative, chips can be quickly removed from the cutting site.
There is an effect. However, in the case of the boh end mill, the nose has a negative angle as in the case of the outer peripheral blade, which further deteriorates the machinability and cannot withstand particularly the axial cutting. By applying the present invention, it is possible to improve the machinability by setting the rake angle of the ball blade to a negative angle and the vicinity of the nose to 0 ° or a positive angle. Hereinafter, examples will be described in detail.

[0010]

2 and 3 show an embodiment of the present invention,
A ball end mill made of ultrafine cemented carbide with a diameter of 10 mm, a blade length of 15 mm, a total length of 100 mm, a blade count of 2 and a helix angle of 30 °.
It has a bottom blade of °. Since the land width near the nose of this end mill is 1.5 mm, the width of the bottom blade is twice the width of the land. The rake angle of the ball blade is -10
°, the rake angle of the bottom blade was 2 °, and a Ti-based hard coating was applied to this by the PVD method. This tool was subjected to three-dimensional cutting using a machining center. S50C for work material
Select the annealed material, rotation speed 4000rpm, feed rate 100
Scanning copying was performed on the convex curved surface at 0 mm / min and a cut of 2 to 3 mm. The chip discharge was excellent regardless of the cutting direction such as inclination or curved surface, and stable cutting was possible for a long time. Since the pitch feed was 0.5 mm, the cut surface was good despite the large amount of cut.

[0011]

As described above, according to the present invention, improvements have been made in a ball end mill suitable for a machine tool for high-speed cutting particularly used for three-dimensional curved surface machining of dies and the like. Machining with high efficiency and excellent cutting accuracy has become possible. In the horizontal feed, the machinability is improved, the feed speed can be increased, and it is also effective for tilt feed and vertical feed. In particular, the effect of a twisting blade can be obtained even near the nose, and a large cut can be made. Since it is a solid tool, a long-life tool can be economically realized simply by applying a hard coating.

[Brief description of drawings]

FIG. 1 is a front view showing an example of a conventional product.

FIG. 2 is a front view showing an embodiment of the present invention.

FIG. 3 is a partially enlarged view of FIG.

FIG. 4 is a side view of FIG. 3;

FIG. 5 is a partially enlarged view showing another embodiment of the present invention.

[Explanation of symbols]

 1 Main Body 2 Blade Part 3 Peripheral Blade 4 Ball Blade 5 Bottom Blade 6 Middle-Low Gradient 7 Bottom Blade Width

Claims (3)

[Claims] 1. A solid ball end mill comprising a plurality of outer peripheral cutting edges having a twist and a substantially circular arc-shaped ball edge connected to the outer edge cutting edges, wherein the nose of the ball edges is provided. A ball end mill characterized in that a substantially V-shaped bottom blade having a width of at least twice the width of the land and having a middle to low slope of 4 ° or more is provided along the cutting edge. 2. The ball end mill according to claim 1, wherein the width of the substantially V-shaped bottom blade is 2 to 3 times the width of the land in the vicinity of the nose of the ball blade, and a medium-low slope is provided. A ball end mill characterized by being set at 5 ° to 10 °. 3. The ball end mill according to claim 1, wherein the rake angle of the ball blade portion is a negative angle in the normal direction and the rake angle of the bottom blade is 0 ° or positive in the axial direction. A ball end mill characterized by being square.