JPH10151511A - Multiblade ball end mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform precise shaping and proper direct curving of a narrow portion by a method wherein a linear end cutting edge connected to a ball blade and extending to a rotary center is arranged in the vicinity of the rotation center of a ball blade, and a plurality of a cutting edge at the nose part of which a bottom blade is notched are provided. SOLUTION: At a nose part, two end cutting edges having a middle low gradient of approximate 5 deg. and length of approximate 1mm are arranged. Other four cutting edges have a part corresponding to length being notched and a chip pocket is formed. The rake of the ball blade part is approximate -10 deg. and the rake of the end cutting edge is approximate 2 deg. and a Ti rigid covering is applied thereon by a PVD method. Since, as noted above, the number of blades is high as a diameter is fine, a blade groove is shallow as natural conclusion, namely, a web thickness is increased. By effecting high speed high feed cutting, through cutting is low, a cutting amount per unit time is rendered excellent.

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 machining a three-dimensional curved surface of a mold or the like.

[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. Recently, it has been desired to form a three-dimensional shape with a minimum number of tools and in a short time in curved surface processing such as a mold. In addition, there is a need to shift from manual finishing to mechanization capable of high-speed finishing. Are increasing. This is not limited to large products, and there is the same need for small products with complicated shapes, and direct carving is being used instead of rough machining. For this purpose, for example, a ball disclosed in JP-A-7-1218 is used.
There is a lure mill (hereinafter referred to as conventional product 1). 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. Further, as a similar solid product, there is, for example, a ball end mill (hereinafter referred to as conventional product 2) shown in Japanese Utility Model Laid-Open No. 4-122414.

[0003]

Problems to be Solved by the Invention Conventional Product 1, Conventional Product 2
Is provided with a notch near the center of rotation of the tip of the cutting edge, that is, in the nose portion so as not to have a cutting speed of 0 region. There was a problem that vertical feed was not possible because there was no cutting edge at the center. In the past, solid ball end mills have overwhelmingly used two blades, and multi-blade balls such as conventional product 2 have been limited to large diameter products. Therefore, when a small-diameter product is used in a recent high-speed machine tool, the performance is insufficient, and there is a problem that efficiency cannot be achieved.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is a ball end mill mainly used for machining a three-dimensional curved surface such as a mold. An object of the present invention is to provide a multi-blade ball end mill for high-speed cutting used for engraving.

[0005]

In order to achieve the above object, the present invention provides a plurality of twisted outer peripheral cutting edges,
In a solid multi-blade ball end mill comprising a substantially quarter-arc ball blade connected thereto, one or two ball blades continuously rotate near the rotation center of the ball blade. A substantially linear bottom blade reaching the center is provided, and three or more cutting blades lacking the bottom blade at the nose portion are provided.
In addition, the above-described substantially straight bottom blade has a feature that the slope of the midsole is 6 ° or less.

[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 in the horizontal direction, cutting is mainly performed at the nose portion, and the nose is easily rubbed and worn. 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.
Furthermore, in the case of engraving cutting, there is no use unless there is a cutting edge at the center of rotation. These are phenomena that are not only related to the cutting property of the cutting edge but also to the chip discharging property.

By applying the present invention, even if the diameter is small, the number of cutting edges is increased, so that high feed can be achieved in the case of horizontal or inclined surface cutting, and the cut surface roughness can be reduced. In the present invention, the cutting edge of the nose portion is not formed in an arc shape, but since the bottom edge is provided, there is no problem in performing engraving cutting. Here, one or two bottom blades
Since only one sheet is required, a large number of tip pockets can be provided without a large number of blades congesting in the nose portion. The substantially straight bottom blade of the nose portion may be in a direction perpendicular to the rotation axis.
High-speed cutting with good chip discharge can be avoided by avoiding unreasonable cutting due to chip size. Note that the same effect can be obtained even if the substantially straight bottom blade is slightly curved in a direction where a middle to low gradient is applied.

Here, the length of the bottom blade may be determined according to the purpose of use of the end mill. The length is short when emphasizing the finishing use, and may be large for high-speed forming. However, exceeding 1/2 of the arc radius of the ball blade impairs the function as a ball blade, which is not preferable.
Also, if the gradient is too large, the connecting position between the ball blade and the bottom blade becomes too sharp, and the progress of wear is accelerated locally. It is desirable to round or chamfer the surface. The material of the end mill is desirably a cemented carbide in order to achieve high-speed cutting, and the function can be further enhanced by adhering various tough hard coatings to the cemented carbide. Needless to say, a high-speed cutting tool material such as ceramics and CBN sintered body may be used. Hereinafter, examples will be described in detail.

[0009]

1 and 2 show one embodiment of the present invention.
In a ball end mill made of ultrafine cemented carbide with a diameter of 6 mm, a blade length of 12 mm, a total length of 90 mm, a number of blades of 6 and a helix angle of 30 °, two bottom blades are formed on the nose with a medium-low gradient. It is provided at 5 ° and 1 mm in length. The other four cutting edges have a portion corresponding to the length of the bottom blade missing, and a chip pocket is formed. 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. Since the number of blades is large while having such a small diameter, a natural result is that the blade grooves are shallow, that is, the core thickness is large. This means that the tool stiffness is improved while large infeeds cannot be made.However, high-speed high-feed cutting can achieve a cut per unit time greater than that of a normal end mill even if the infeed is small. You can.

This tool was subjected to three-dimensional cutting using a machining center. An S50C annealed material was selected as a work material, and a scanning curved cutting was performed on a convex curved surface at a rotation speed of 6000 rpm, a feed speed of 1000 mm / min, and a cut of 1 to 2 mm. Irrespective of the cutting direction, such as inclination and curved surface, chip discharge was extremely good 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. 3 and 4 show the same dimensions as above, but with four cutting edges and one bottom edge. High feed cannot be achieved due to the small number of blades, but the depth of cut can be increased. Another feature is that the cutting edge can be easily formed. Thus, the number of the bottom blades may be appropriately used depending on the purpose.

[0011]

As described above, according to the present invention, the ball end mill used for machining a three-dimensional curved surface such as a mold is improved mainly by increasing the number of blades and providing a bottom blade. A multi-blade ball end mill for high-speed cutting that has superior performance to conventional products when used for precise molding and direct engraving has been realized.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the product of the present invention.

FIG. 2 is a left side view of FIG. 1;

FIG. 3 is a front view showing another embodiment of the product of the present invention.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main body 2 Blade part 3 Outer peripheral blade 4 Ball blade 5 Bottom blade 6 Middle / low gradient 7 Bottom blade length

Claims (2)

[Claims] 1. A solid multi-flute ball end mill comprising a twisted outer peripheral cutting edge and an approximately 1/4 arc-shaped ball blade connected to the cutting edge. 1. One or two ball blades are provided with a substantially straight bottom blade continuously reaching the center of rotation, and three or more cutting blades lacking the bottom blade at the nose portion are provided. Multi-blade ball end mill. 2. The multi-blade ball end mill according to claim 1, wherein the substantially straight bottom blade continuously reaching one or two ball blades and reaching the center of rotation has a middle slope of 6 ° or less. A multi-blade ball end mill characterized in that: