JPH04310310A - Ball end mill and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent a cutting edge from being worn and defective and to form a good finishing face by equipping plural cutting edges at the tip spherical face for cutting tone front face side and the outer peripheral part for cutting the side face of a shank main body end part and providing a V grooved recessed part having specific width and open angle in the area including the chisel part of the tip spherical face center. CONSTITUTION:A tip spherical face cutting edge 2 cutting a front face side and an outer peripheral part cutting edge 3 cutting a side face are provided at the end of a shank main body 1 and these cutting edges are composed of plural cutting edges. The cutting edge is not formed at the rotation center including a chisel part and a recessed part 4 in the V grooved shape viewed from a vertical face is formed on the rotation center shaft of a tool. The recessed part 4 in the V grooved shape is then limited because of being effected sensitively by the deterioration of the finishing face caused on the cutting performance especially the cutting edge defect by the shape and size. Namely an open angle theta is set in the range of 80-150 deg. and an open width lis set in <=0.05mm at its straddle l1, l2 errors from the center and the total width in about 1mm because of the work error being effected by the size of an open width thereon.

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 machining flat or curved surfaces of steel or cast iron, and a method for manufacturing the same.

0002

[Prior Art and Problems to be Solved by the Invention] In conventional ball end mills, the cutting speed near the rotation center axis of the arcuate cutting blade approaches zero, which causes friction between the cutting blade and the workpiece. As a result, the cutting edge wears quickly, and built-up edges are easily generated, resulting in problems such as excessive depth of cut and falling off of the built-up edges, resulting in damage to the cutting edges. As a countermeasure for these, a non-cutting area is created by shifting each cutting edge from the rotational center axis of the arcuate cutting edge, and this prevents the progress of wear and breakage of the cutting edge near the rotational center axis of the arcuate cutting edge. It is prevented (Jitsukai Showa 6)
1-141014, Jikkoi No. 1-12893). However, in these cases, by shifting each cutting edge from the rotational center axis of the arcuate cutting edge, the end of each cutting edge on the rotational center axis side leaves cutting marks on the finished cutting surface, which should be solved practically. have a problem

[0003] Another countermeasure is not to form a cutting edge at the center of rotation including the chisel portion, to eliminate the cutting edge portion where the cutting speed becomes zero, and to provide an appropriate radius at the boundary between the tip spherical surface and the cutting edge removed portion. There are some examples of using this method to improve the fracture resistance of that part, but this is extremely difficult in terms of production technology. Furthermore, for high-efficiency machining, it is necessary to increase the feed rate, but even if the feed rate is increased, there is a limit to the load per cutting edge, and as a countermeasure to this, it is necessary to increase the number of blades. The above-mentioned rounding cannot be applied to such a multi-blade ball end mill.

0004

[Means for Solving the Problems] As described above, the present invention solves the problem of wear and tear on the cutting edge that occurs due to the cutting speed near the rotation center axis of the spherical cutting edge of a ball end mill approaching zero. Furthermore, the present invention provides an improved ball end mill that prevents the deterioration of finished surface roughness caused by these factors, and a method for manufacturing the same.The first feature thereof is that the front side of the end of the shank body is cut. A plurality of cutting blades are provided on the outer periphery of the spherical tip and the side surface, and the total width is approximately 1 mm in the area including the chisel at the center of the spherical tip, 80 to 15 mm.
This ball end mill has a V-groove recess with an opening angle of 0°. The second feature of the present invention is that a diamond grindstone having a half-angle that is half the opening angle of the V-groove forming the recess is arranged so that the axis of the end mill and the axis of rotation of the grindstone are perpendicular to each other. The method of manufacturing a ball end mill includes grinding half of the V-groove by cutting into the ball end mill, and forming a V-groove-shaped recess at the center of the spherical end portion while sequentially rotating the end mill.

[0005]

[Example] Fig. 1 is a side view of an embodiment of the ball end mill of the present invention, Fig. 2 (a) is a front view of the spherical end portion of the ball end mill, and Fig. 2 (b) is a side view of an embodiment of the ball end mill of the present invention. FIG. 2 is an enlarged view of a V-groove-shaped recess. As shown in the drawing, the end of the shank body 1 is provided with a spherical tip cutting edge 2 for cutting the front side and an outer peripheral cutting edge 3 for cutting the side surface, and these cutting edges have a plurality of cutting edges. Consists of a blade. and,
No cutting edge is formed in the rotation center including the chisel portion, and a V-groove-shaped recess 4 is formed in the region including the chisel portion when viewed from the direction perpendicular to the rotation center axis of the tool.

The V-groove-shaped recess 4 is shown in detail in FIG. 2B, and its shape and size can have a sensitive effect on cutting performance, especially on the deterioration of the finished surface due to cutting edge damage. Therefore, it is necessary to limit Opening angle θ is 80-15
0°, preferably in the range of 100 to 140°, and the opening width l is determined by the size of the processing error, so the distribution l1 and l2 errors from the center are 0.05 mm or less, and the total width is approximately 1 mm. It is necessary to set it to . Here, V
The reason why we set the total width of the groove-shaped recess to approximately 1 mm is because if it becomes larger, the shape accuracy of the spherical tip of the ball end mill will deteriorate.
This is because it becomes difficult to maintain a predetermined accuracy after machining, and if the diameter is made smaller than this, it becomes difficult to form a V-groove-shaped concave portion of the end mill. The reason why the opening angle of the V-groove-shaped recess is set to 80 to 150 degrees is based on the experimental results described later.

When forming a V-groove-shaped recess at the end of the shank body 1 provided with the cutting edge 2 and the outer peripheral cutting edge 3 as described above, a grindstone 11 as shown in FIG. 3(A) is used. When the V-groove-shaped recess 4 is machined in one shot, eccentricity C as shown in FIG. 4 tends to occur, and as a result, both edges P
1. The heights of P2 are no longer aligned, creating a step D, which significantly impairs the cutting performance of the tool. In the present invention, in order to prevent this, a method as shown in FIG. 3(B) is used. That is, it has a straight shape with half the opening angle θ of the V groove, that is, a half angle of 40 to 75 degrees, or it has an r part to form an r shape at the opening end of the V groove as shown in FIG. 3(c). For example, place the diamond grindstone 12 or 13 at right angles to the axis of the end mill and the axis of rotation of the grinding wheel, rotate it toward the axis of the end mill and cut, thereby grinding half of the V-groove, and then rotate the end mill one by one to form a spherical tip. This is a method in which a V-groove-shaped recess is formed at the center of the part. When such a method is used, the height difference between both edges P1 and P2 can be managed with high accuracy of 0.02 mm or less.

[0008]

[Prototype example] Total length 100mm, outer diameter 20mm, number of cutting blades 4
Ball end mills of the present invention were experimentally manufactured in which the opening angles of the V-groove-shaped concave portion at the center were 80°, 120°, and 140°. The forming materials are TiC 38% and TiN for the head part by weight ratio.
Cermet whose main components are 14% TaN and 12% TaN, and the shank body has a composition of 94.5% WC and 5.5% Co, transverse rupture strength 205 kg/mm2, Young's modulus 63 x 103 kg/m
m2 cemented carbide. In addition, as a comparison product, a ball end mill with the same shape and material as the present invention product, the opening angle of the V-groove-shaped concave part in the center is 60 degrees, and the R0 We prototyped three types of ball end mills with .5 and an opening angle of 160°. Plane processing was performed using these five types of ball end mills, and the roughness of the finished surfaces was compared. The results are shown in Table 1.

The machines and cutting conditions used in the test are as follows. Machine: Vertical machining center 5.5kw Cutting conditions: N 4000rpm V (outer periphery) 70m/min F 2400mm/min Depth of cut 0.4mm Pick feed 0.5 Dry cutting

0010

[Table 1]

[0011] As can be seen from Table 1, the product of the present invention has no R, but when looking at the situation after cutting, R is naturally formed on the top of the ball end mill, probably due to wear. . Also, looking at the change in the roughness of the cut surface, it is not so good at the beginning, but as the cutting area increases, the roughness gradually improves, but this is because the progress of wear mentioned above contributes to the R shape. It can be considered that On the other hand, in the case of the V-groove-shaped recess with an opening angle of 60° and no radius, the cutting edge was severely chipped at the first measurement, and the experiment could not be continued. In addition, although those with radii have good surface roughness, they are very difficult in terms of tool production technology. Furthermore, the cutting edge of the 160° cutter clogged, making it impossible to continue the experiment.

0012

[Effects of the Invention] As explained above, according to the present invention,
It is possible to prevent wear and breakage of the cutting edge caused by the cutting speed near the rotation center axis of the tool approaching zero, and to obtain a good finished surface. Therefore, it is particularly effective when used for machining molds, etc., which have strict finishing surface accuracy.

[Brief explanation of drawings]

FIG. 1 is a side view of an embodiment of a ball end mill of the present invention.

2(A) is a front view of the spherical tip of the ball end mill shown in FIG. 1, and FIG. 2(B) is an enlarged view of a V-groove-shaped recess formed in the spherical tip.

FIG. 3 is an explanatory diagram of a method of forming a V-groove-shaped recess, in which (a) is a conventional example and (b) is a method of the present invention.

FIG. 4 is an explanatory diagram of problems in the method of forming a V-groove-shaped recess according to (A) of FIG. 3;

[Explanation of symbols]

1 Shank body 2 Spherical tip cutting edge 3 Outer cutting edge 4 V-groove shaped recess

Claims (2)

[Claims] Claim 1: The end of the shank body is provided with a spherical tip for cutting the front side and a plurality of cutting blades on the outer periphery for cutting the side. A ball end mill characterized in that a V-groove-shaped recess is formed with a diameter of 1 mm and an opening angle of 80 to 150 degrees. [Claim 2] 1/2 of the opening angle of the V groove forming the recess
Grind half of the V-groove by placing a diamond grindstone with a half-angle at right angles to the axis of the end mill and the rotation axis of the grinding wheel toward the axis of the end mill, and grind the center of the spherical tip while rotating the end mill sequentially. A method for manufacturing a ball end mill, comprising forming a V-groove-shaped recess in the ball end mill.