JPH08141816A - Graphite machining ball end mill - Google Patents

Abstract

PURPOSE: To accommodate powdery chips sufficiently and discharge them smoothly by deepening a gash part continuous from the cutting face of a ball cutting edge part so as to recess the chip pocket of the ball cutting edge part large. CONSTITUTION: Tool dimensions are about 6mm in diameter, about 30mm in blade length and about 100mm in the whole length, and diamond abrasive grain is electrodeposited on the surface of a high-speed steel ball end mill. In this case, a thick wall part on the back face is made small, and the cross-sectional area of a chip pocket part is made large. In order to make the chip pocket part large, a gash part 7 is formed smooth with a fillet radius and grinding wheel angle made large. Powdery chips in a ball cutting edge part 2 can thereby discharged smoothly even in the case of cutting to three-dimensionally form graphite material containing hard grain in raw material.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a graphite material containing hard particles in a material such as an electrode material used for electric discharge machining.
TECHNICAL FIELD The present invention relates to a ball end mill for three-dimensional forming and cutting of graphite.

[0002]

2. Description of the Related Art As a conventional ball end mill for graphite processing, there is an end mill made of cemented carbide, which is characterized by using a hard material having excellent wear resistance among cemented carbides. It was suitable for graphite processing. In addition, an improved version of this is disclosed in Japanese Patent Laid-Open No.
The milling tool shown in 1-265207 (hereinafter,
Conventional product 1. This is a method in which a hard abrasive such as diamond or cubic boron nitride, which is harder than cemented carbide and has excellent wear resistance, is fixed to the blade surface of the end mill by the electrodeposition method.

[0003]

However, in the end mill made of cemented carbide, the cutting edge becomes chips when a graphite material containing hard particles is cut into the material like an electrode material for electric discharge machining. Rubbing powdery hard particles,
There was a problem that the wear of the cutting edge due to the friction generated here was large.

Further, in the conventional product 1, there is no description about the shape of the tool as the base material, and it is proper to consider it as an end mill for general-purpose metal or steel material cutting. Therefore, in consideration of the characteristics of the work material, the tool shape of the base material is a shape that emphasizes the tool rigidity including the ball blade portion. That is, the thickness of the part of the ball blade portion that follows the No. 2 and No. 3 surfaces of the cutting edge is increased, and the chip pocket is kept within the range where metal or steel chips can be accommodated to give tool rigidity and strength. . However, when cutting a graphite material containing hard particles in the material, since the chip pocket is small in the above blade shape, there are many scratches when the powdery chips described above are discharged from the narrow chip pocket. However, at this time, there is a problem that the relatively soft electrodeposition layer is worn and the hard abrasive material comes off.

The present invention has been made based on the background as described above, and even if a graphite material containing hard particles is cut by enlarging the chip pocket of the ball blade portion, a powdery cutting is performed. The present invention provides a ball end mill for graphite processing, which has a blade shape capable of sufficiently containing waste and discharging it smoothly so as to reduce friction between the cutting edge and the scrap and improve wear of the cutting edge.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is a graphite having a ball blade in which a hard abrasive such as diamond and / or cubic boron nitride is fixed to a blade by an electrodeposition method. In the processing ball end mill, the wall thickness of the back surface portion following the cutting blade third surface of the ball blade portion is made thin, and the blade groove portion following the rake surface of the ball blade portion is deepened to make the tip of the ball blade portion. It has a large recessed pocket. In addition, specifically, the cross-sectional shape perpendicular to the tool axis at the boundary position between the ball blade portion and the outer peripheral blade portion,
Blade thickness is 55-65% of blade diameter, core thickness is 40-50% of blade diameter
The roundness of the blade bottom is set to 10% or more of the blade diameter. In addition, a measure is taken to appropriately insert a nick into the outer peripheral spiral blade and the cutting edge of the ball blade portion.

[0007]

In a graphite processing end mill, as a means for avoiding wear of a cutting edge, particularly a ball blade having a small chip pocket, which occurs when cutting a graphite material containing hard particles in the material, a ball blade portion By reducing the wall thickness of the back surface portion following the third surface of the cutting edge, and deepening the groove groove portion following the rake surface of the ball blade portion, the chip pocket of the ball blade portion is largely recessed, Not only in three-dimensional forming cutting but also in groove cutting, which is the most heavy cutting in graphite material cutting, the discharge of powdery chips becomes smooth, and the hard abrasive material of the tool cutting edge works effectively,
Cutting edge wear is small and long-term processing is possible.

Here, regarding the thickness of the back surface portion,
This can be achieved by setting the blade thickness to 55 to 65% of the blade diameter when the sectional shape perpendicular to the tool axis is expressed at the boundary position between the blade edge portion and the outer peripheral blade portion. This value is smaller than 80 to 85% that is generally adopted including the conventional product 1 and 55
% Or less causes a problem in strength even for a graphite material. The blade groove portion following the rake face is achieved by setting the core thickness to 40 to 50% of the blade diameter and the roundness of the blade bottom to 10% or more of the blade diameter. The core thickness is small compared to the standard of around 55% of the blade diameter, and the roundness of the blade bottom is limited to a large value even though it is a ball blade portion.

Further, for the purpose of smoothing out the discharge of the powdery chips, providing a nick on the outer peripheral blade, the ball blade, or both enhances the effect. Here, in the cutting of graphite material, since it is essentially powdery chips, it is not the purpose of chip crushing, but the purpose of controlling the generation of chips and providing clearance for discharging chips. There is. It should be noted that the tip pockets are made larger only for the ball blades that are mainly used for cutting, and the outer peripheral spiral blades other than the ball blades have the same blade shape as the conventional end mill for metal or steel cutting. By so doing, the tool rigidity and strength of the entire end mill can be maintained. The end mill of the present invention exerts its effect not only when it is used as a graphite material but also when it is used as a ceramic material containing hard particles in the material, a synthetic resin material, or the like.

[0010]

EXAMPLE FIG. 1 shows an example of the present invention in which the tool dimensions are 6 mm in diameter, the blade length is 30 mm, the total length is 100 mm, and diamond abrasive grains are electrodeposited on the surface of a high-speed ball end mill. Here, the back wall thickness portion is reduced by 30% and the chip pocket portion cross-sectional area is increased by 20% as compared with the conventional ball end mill for cutting metal or steel. In order to increase the size of the chip pocket, the gassh is formed smoothly by increasing the roundness of the blade bottom and the grindstone angle. FIG. 2 shows a conventional diamond electrodeposited high-speed ball end mill, which has the same diameter, blade length and overall length as the product of the present invention shown in FIG.

Both end mills were tested for graphite electrode material with the following cutting specifications. Graphite electrode material ED3 (Ibiden, Shore hardness 65) Rotational speed 15000 / min Feed rate 1200mm / min Depth of cut 3mm Groove dry air As a result, the ball end mill of the present invention has a life extension of 80% compared to conventional products. It was confirmed.

[0012]

As described above, according to the present invention, even when the graphite material containing hard particles in the material is three-dimensionally molded and cut, the powdery chips are discharged from the ball blade. It was done smoothly, and the wear of the cutting edge of the tool was greatly reduced, enabling long-term use.

[Brief description of drawings]

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

2 is a cross-sectional view at a boundary position between the ball blade portion and the outer peripheral blade portion in FIG.

FIG. 3 is a side view showing an example of a conventional product.

FIG. 4 shows a front view of FIG.

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

[Explanation of symbols]

 1 Main Body 2 Ball Blade 3 Peripheral Blade 4 Ball Blade 2nd Surface 5 Ball Blade 3rd Surface 6 Surface Following Ball Blade 3rd Surface 7 Gassie 8 Blade Thickness 9 Core Thickness 10 Blade Bottom Roundness 11 Nick

Claims (3)

[Claims] 1. A ball end mill for graphite machining having a ball blade, wherein a hard abrasive material such as diamond and / or cubic boron nitride is fixed to the blade portion by an electrodeposition method. For graphite processing, characterized in that the wall thickness of the back surface portion following the surface is thinned and the blade groove portion following the rake face of the ball blade portion is deepened so that the chip pocket of the ball blade portion is largely recessed. Ball end mill. 2. The ball end mill for graphite processing according to claim 1, wherein a cross-sectional shape of a boundary position between the ball blade portion and the outer peripheral blade portion perpendicular to the tool axis has a blade thickness of 55.
Ball end mill for graphite processing, characterized in that the core thickness is up to 65%, the core thickness is 40 to 50% of the blade diameter, and the roundness of the blade bottom is 10% or more of the blade diameter. 3. The ball end mill for graphite processing according to claim 1, wherein the outer peripheral helical blade and the cutting edge of the ball blade portion are provided with nicks.