JPS6336892B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electrode assembly for microhole electrical discharge machining, in which no deflection occurs even when the electrode is rotated, and commercially available thin wire (electrode core wire) is used as the electrode material. ) can be used, and when the electrode wears out, the wire that becomes the electrode can be pulled out, and the purpose is to provide an electrode structure for microhole electrical discharge machining that has a long life that can be used repeatedly, and that is easy to manufacture. do.

Conventional configuration and its problems In electrical discharge machining of micro holes with a diameter of 0.1 mm or less,
There are two machining methods: one with the machining electrode stationary and one with the machining electrode rotating. By rotating the electrode, it is possible to improve machining speed, roundness of the machined hole, and shape accuracy, but conventionally machining is mainly performed with the electrode stopped in consideration of electrode deflection and electrode forming time. It was hot.

The electrode structure for machining with the electrode stopped is as follows:
When using a small diameter wire that does not require electrode manufacturing by cutting, use a wire soldered directly to the holder,
Alternatively, there are thin wires coated with plating, reinforced and chucked, and wires protected and guided with glass, ruby, etc., and when using relatively thick wires, only the tip, which becomes the processing electrode, is used. There are electrodes made thinner by electrolytic polishing.

However, with any of the electrode structures, it is not possible to achieve a concentricity of several microns or less between the tip of the electrode on the processing side and the outer circumference of the electrode, and it is difficult to attach the electrode perpendicularly to the workpiece. It was impossible to perform machining by rotating it.

Furthermore, when performing electrical discharge machining with the electrode stopped,
Since the wire shape is transferred to the workpiece, it has been difficult to form a hole with good roundness when processing is performed using a commercially available small diameter wire that has not been finished with sufficient dimensional accuracy.

On the other hand, as for the electrode structure that can be machined by rotating the electrode, a chuckable method is used in which the electrode material is rotated from a round bar with a diameter of about 1 mm and formed into an electrode of the desired diameter by reverse discharge. Ta.
Such molded electrodes can be obtained with sufficient accuracy, but when molding an electrode for a microhole with a diameter of 30 μm from an electrode material with a diameter of 1 mm, it takes about the first hour, and it takes a considerable amount of time to manufacture. I need. In addition, the molded part (the part with a diameter of 30 μm) is short, so its lifespan is short, and once it is removed from the chuck, it warps, so it has to be used while being molded each time it is processed.

Purpose of the Invention The present invention has been made in view of the above-mentioned problems, and it is possible to prevent deflection even when the electrode is rotated by aligning the central axis of the support tube and the rotation center of the rotating support with high precision. If no electrical discharge occurs and the electrode is worn out due to electrical discharge, it can be fed out from the rotating support and used, and a commercially available small diameter core wire can be used as the electrode material, making it possible to machine micro holes with good roundness and shape accuracy. Rather, the purpose is to provide an electrode structure for microhole electrical discharge machining that has a long life and is easy to manufacture.

Structure of the Invention In order to achieve the above objects, the present invention supports the electrode core wire in a slidable manner by a support tube, and also makes the concentricity of the outer periphery of the support tube and the hole through which the electrode core wire is inserted sufficiently good. The support tube is press-fitted into a rotary support in which the concentricity between the support tube insertion hole and the outer periphery is sufficiently small so that the eccentricity of the hole in the support tube and the eccentricity of the hole in the rotary support cancel each other out.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an overall configuration diagram of an embodiment of an electrode assembly for microhole electrical discharge machining according to the present invention, FIG. 2 shows a side sectional view of the same, and FIG. 3 shows a front view of the same.

Thin diameter wire (electrode core wire) 1 that becomes the processing electrode
is guided by a wire guide (support tube) 2 made of ceramic and attached to a mandrel (rotary support) 3 made of hardened steel. The wire guide 2 is JISh6 as shown in Figure 2.
-It is press-fitted into the mandrel 3 with a fit of about p6. In this embodiment, the wire guide 2 is made of a ceramic pipe for optical fiber connectors in which the concentricity between the outer periphery and the hole is 1 μm or less, and the mandrel 3 is processed so that the concentricity between the outer periphery and the hole is 1 μm or less. . The above two pieces are combined and press-fitted at a position where the fringes of the electrode 1 are minimized. Furthermore, since the press-fitting allowance in the longitudinal direction is sufficiently long compared to the diameter of the wire guide, there is little inclination. For this reason, the wire has very little deflection.

Here, a method for manufacturing a wire guide 2 in which the concentricity between the outer periphery and the hole is sufficiently small as 1 μm or less will be explained using FIGS. 4a and 4b.

If the wire guide 2 is made of a sintered material, for example ceramics, it is possible to manufacture the guide by vacuum extrusion. FIG. 4a is a left side view of the vacuum extrusion mold, and FIG. 4b is a front sectional view. That is, the mold consists of a cap 6, a pin 7, and a pin holder 8 in which the pin 7 is embedded, and a ceramic material 9 is fed from the left side of FIG. 4b in the direction of the arrow through the gap 10 of the pin holder 8. The fed material 9 is formed into a pipe shape by the pin 7 and the die 6 and is pushed out of the mold. By increasing the accuracy of the combination of the pin 7 and the cap 6, the concentricity between the hole and the outer periphery of the extruded ceramic pipe can be less than 10 μm. After firing this material, a wire is passed through the hole and the outer periphery of the pipe is cylindrically ground using a centerless grinder using the wire as a guide to obtain a high-precision ceramic pipe with a concentricity of 3 μm or less.

In pipe manufacturing by extrusion molding, no problems arise in manufacturing even if the outer diameter of the pipe becomes thicker than the hole diameter, or even if the hole becomes deep.
If the outer diameter of the pipe is approximately 2.5 mm or more, the tool will have sufficient rigidity even if the hole is drilled on the mandrel using the usual method, such as reaming after drilling, so the diameter of the pipe will be several μm from the mandrel outer circumference. A hole with a concentricity of is obtained.

Next, a method of press-fitting the wire guide 2 and the mandrel 3 together at a position where the deflection of the electrode 1 is minimized will be described.

FIG. 5a shows the positional relationship between the wire guide hole and the outer periphery, and FIG. 5b shows the positional relationship between the mandrel hole and the outer periphery. In the figure a, the hole center 0' is shifted by r ₁ at an angle θ ₁ from the center 0 of the outer periphery of the wire guide 2. In addition, in FIG. 1B, the hole center 0 of the mandrel 3 is shifted by r ₂ at an angle θ ₂ with respect to the center 0'' of the outer periphery.

When this wire guide 2 and _{mandrel 3 are combined, the mandrel is rotated clockwise by θ 2 in} FIG. The positional relationship will be as shown in the figure. In other words, the concentricity R between the hole of the wire guide 2 and the mandrel 3 in the assembled state is shown by the formula (1), R = r ₂ - _{r 1} ...... (1) The concentricity R after assembly is the concentricity in the single unit better than.

Therefore, by combining the wire guide 2 and the mandrel 3, each having a concentricity of several μm, an electrode structure for microhole electric discharge machining with almost no deflection can be obtained.

In actual work, concentricity is measured using a tool microscope with a high magnification (x800), θ ₁ and θ ₂ are determined, the position of the combination is determined, and press fitting is performed.

Now, the wire guide 2 and the mandrel 3 are assembled as described above, but in order to maintain the very thin wire 1 that will serve as the processing electrode with good straightness in the mandrel, and to ensure electrical continuity with the mandrel 3. In order to obtain a Fixed.
The outer diameter of wire guide 2 and the hole diameter of mandrel 3 are
The fit is approximately JIS h6-H7.

In actual electrical discharge machining, the mandrel 3 is chucked with a scroll chuck 11 as shown in FIG.
The mandrel 3 is supported by a pulley 13 and rotated directly by a belt 14. If the wire 1 becomes worn out after processing, it can be processed again by loosening the screw 5 shown in FIG. 2 and pulling the wire 1 out by gravity or by using tweezers.

The wire 1 can be guided by using a guide 15 with a sufficiently long guide part as shown in Fig. 10, or by using two guides 16 with short guide parts as shown in Fig. 11. There is a way. 1st
The case shown in FIG. 1 is suitable when a guide portion of sufficient length cannot be obtained depending on the hole diameter. In addition to ceramic, the material of the wire guide can also be ruby, sintered metal, hard metal, etc. The material of the pipe 5 may be any material as long as it is conductive.

In this embodiment, the clearance between the wire 1 and the wire guide 2 is about 1 μm and can be almost ignored.

Further, in the above description, the case where the power source is rotated is used, but it is also possible to perform processing without rotating the power source.

Effects of the Invention As explained above, according to the present invention, the support tube is press-fitted into the rotation support tube so that there is almost no misalignment between the center of rotation of the rotation support and the center of the hole in the support tube.
Since the electrode core wire is slidably supported by the support tube, there is almost no deflection even when the electrode is rotated.
Microholes with high roundness and shape accuracy can be obtained, and when the electrode wears out, it can be drawn out from the rotating support, and commercially available thin core wires can be used as electrodes, so it can withstand long-term use. An electrode for micro electrical discharge machining that is easy to manufacture can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing one embodiment of the electrode assembly for microhole electrical discharge machining of the present invention, Fig. 2 is a side sectional view of the same, Fig. 3 is a front view of the same, and Fig. 4 a and b are wire guides. 5a, b and 6 are diagrams for explaining the method of assembling the wire guide and mandrel, and FIG. 7 is a main part configuration of the above embodiment. 8 and 9 are diagrams for explaining how to use the same embodiment, and FIGS. 10 and 11 are sectional views showing respective structural examples of the support tube. 1... Wire (electrode core wire), 2, 15, 16
...Wire guide (support pipe), 3...Mandrel (rotating support), 4...Pipe fixing screw, 5...
...pipe, 6...cap, 7...pin, 8...pin holder, 11...scroll chuck, 12...
...Bearing, 13...Pulley.

Claims (1)

[Claims] 1. A support tube through which the electrode core wire is inserted and slidably supported therein, the hole through which the electrode core wire is inserted and the outer periphery thereof are sufficiently concentric, and the support tube through which the electrode core wire is inserted and supported; A rotating support having a sufficiently good concentricity between the hole through which the support tube is inserted and the outer periphery;
An electrode assembly for microhole electrical discharge machining, wherein the support tube is press-fitted into the rotary support so that the eccentricity of the hole in the support tube and the eccentricity of the hole in the rotary support cancel each other out.