JPH0542410A - Ball end mill - Google Patents

Abstract

PURPOSE:To improve cutting efficiency, to enable preforming with a ball end mill and to enlarge its application range by improving the blade form of the ball end mill with a ball blade constituted of a single tool material so as to facilitate ejection of chips outside the cutting part. CONSTITUTION:The blade form of a ball end mill is made so that, when it is projected in the direction perpendicular to the line from the ball center of the ball blade part to a cutting edge located at 45 degrees relative to an end mill rotation axis on the plane including the end mill rotation axis, the rake angle at this position is more than 5 degrees and the radius (R) of the blade bottom radius of the end mill relative to the end mill diameter is in the relationship of R=(0.15-0.3)muD.

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 used for three-dimensional cutting of a soft metal material such as die cutting of an aluminum die, and more particularly to a ball end mill suitable for roughing.

[0002]

2. Description of the Related Art Aluminum alloys are lightweight and excellent in strength and are widely used for machine parts, but in recent years, they have been widely used as mold materials. The feature of die processing is that it requires a lot of heavy cutting to remove large-capacity chips, and it is indispensable to process a three-dimensional shape, and ball end mills are often used for aluminum alloys. Is coming.

For three-dimensional cutting of metal materials, a machine tool such as a machining center or a copy milling machine is usually used, and a ball end mill is used as a cutting tool. However, because the ball end mill needs to have a cutting edge at the center of rotation and the aim is to make the ball edge and the outer peripheral edge continue as smoothly as possible, the rake angle and chip pocket cannot be increased, and the degree of freedom in shape design is great. Are very limited. As a result, it is convenient for steel-based materials having relatively poor machinability, but it is not always possible to obtain the desired shape for aluminum alloys.

[0004]

Problems to be Solved by the Invention Aluminum alloys, copper alloys, etc. are among the metal materials having good machinability. With such a material, the cutting edge can be sharpened and the chip pocket can be enlarged to improve the cutting efficiency. However, it has been difficult to realize a ball end mill due to the above reasons. That is,
If you try to increase the efficiency by high speed rotation or large cutting, the phenomenon of clogging of chips immediately occurs, and there is a risk of damaging the work piece and the tool. Under these circumstances, conventional ball end mills alone are not sufficient, and an efficient ball end mill for aluminum alloys has been desired.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and is a ball capable of efficiently forming an aluminum alloy by high-speed rotation and large cutting without causing a chip clogging phenomenon. It is intended to provide an end mill.

[0006]

In order to achieve the above-mentioned object, the present invention is one in which the blade groove of the ball blade and the rake angle are increased. That is, the blade shape of the ball end mill having a ball blade made of a single tool material as the means,
When projected in a direction perpendicular to the line segment connecting the cutting edge located at 45 ° to the end mill rotation axis from the ball center of the ball blade in the plane including the end mill rotation axis, the rake angle at this position is 5 °. Above, and technically achieved by setting the radius (R) of the roundness of the edge of the end mill to the end mill diameter (D) in a relation of R = (0.15 to 0.3) × D. It is a thing. Further, the outer peripheral portion is provided with a blade groove or an outer peripheral blade which is twisted rightward on the rotary cylinder, so that technical means are taken to facilitate discharge of the chips to other than the cutting portion.

[0007]

[Operation] The ball end mill is used for forming curved surfaces, and the cutting edge is usually partially involved in cutting. The part involved changes over time depending on the shape to be molded. However, the cutting speed required for cutting action is different between the center of the ball blade and the vicinity of the outer circumference, and therefore, the cutting performance and chip removal tend to be discontinuous, but in order to cut this as evenly and evenly as possible, The chip pocket of the ball blade is smoothly continuous with the peripheral blade.

Therefore, in this shape, the blade shape of the ball blade portion is uniquely determined by the groove depth of the outer peripheral blade and the size of the rake angle. Although this shape has a small chip pocket especially near the nose and good finishing accuracy, it hinders cutting efficiency.

The present invention focuses on increasing the chip pocket of the ball blade portion. According to this structure, a large chip pocket sufficient to eliminate large chips generated by cutting a soft material is obtained, and The rake angle of the ball blade can be increased, which shows the effect of improving the machinability. Although the web of the ball blade is small and the connection between the ball blade and the outer peripheral blade is not smooth, it has a different structure from the conventional product, but when cutting soft materials, there is no concern about strength. In addition, there is no problem with connection in the molding process using the ball blade as the main cutting edge.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 is an external view of the ball end mill according to the present invention, and FIG. 2 shows a main part thereof. Here, the case where it is applied to a two-blade ball end mill made of φ25 mm high hardness tool steel is illustrated. As can be seen in FIG. 2, the radius of the blade bottom is 6 mm and the rake angle on the 45 ° plane is 10 °. Here, since the blade groove is formed by reciprocating the all-shaped grindstone having substantially this cross section, the roundness of the blade bottom in the ball blade portion is uniform. Comparing the area occupied by the conventional ball end mill and the blade groove, that is, the chip pocket in this cross section, the product of the present invention is about twice as wide as the conventional product.

A cutting test using this is a three-dimensional cutting using an aluminum mold material as a work material, a rotation speed of 3000 rpm, a feed rate of 500 to 1500 mm / min, a cutting depth of 12.5 mm, and a feed direction changed. Was done. As a result, the conventional product has reached the limit due to the machine overloading due to chip clogging near the feed of 1000 mm / min, rotation stopped, and the product of the present invention has good rejection of the cut chips and feed 1500 mm. It was possible to perform smooth cutting up / down or left / right up to / min.

As described above, it has been found that increasing the roundness of the blade bottom is effective in improving the machinability, but it is known that the usual ball end mill has the roundness of the blade bottom of 0.1 × D or less. Therefore, in order to exhibit the effect as a soft material, it is necessary that it is at least 0.15 × D or more. In addition, the upper limit of the roundness of the blade bottom exceeds 0.3 × D in consideration of the end mill strength, and the body becomes too thin, which is no longer practical.

Unlike the square blade, the rake angle is normally about 0 to 5 ° for a ball blade. However, considering aluminum alloy cutting, at least 5 ° is ideally 10 ° to 15 °. When grinding the rake face of the ball blade portion, the shape of the rake face or the blade groove differs depending on the size of the grindstone and the feeding direction. However, the change is not extreme, and the purpose can be almost achieved by defining the shape of the 45 ° cross section.

[0014]

As described above, according to the present invention, the blade shape of a ball end mill having a ball blade made of a single tool material is changed from the ball center of the ball blade portion to the end mill within a plane including the end mill rotating shaft. When projected in a direction perpendicular to the line segment connecting the cutting edges located at 45 ° to the rotation axis, the rake angle at this position is 5 ° or more, and the radius (R) of the rounded bottom of the end mill is , R = (0.15 to 0.3) × D with respect to the end mill diameter (D), and further, in the outer peripheral portion, there is a blade groove or outer peripheral blade twisted rightward on the rotating cylinder. In addition, not only the cutting efficiency is doubled by facilitating the discharge of the chips to the outside of the cutting area, but also the rough forming can be performed directly with the ball end mill, so the NC program for finish cutting can be used for rough forming. Can be applied.

[Brief description of drawings]

FIG. 1 is an external view of a conventional ball end mill.

FIG. 2 is an external view of a ball end mill according to the present invention.

FIG. 3 shows a main part of FIG.

Claims (2)

[Claims] 1. A ball end mill having a ball blade made of a single tool material, the blade shape of which is located at 45 ° with respect to the end mill rotation axis from the ball center of the ball blade portion in a plane including the end mill rotation axis. When projected in the direction perpendicular to the line connecting the cutting edges, the rake angle at this position is 5 ° or more, and the radius of the rounded bottom of the end mill (R) is R relative to the end mill diameter (D). = (0.
A ball end mill characterized by having a relationship of 15 to 0.3) × D. 2. The end mill according to claim 1, wherein the outer peripheral portion is provided with a blade groove or an outer peripheral blade which is twisted rightward on the rotary cylinder.