JPS6365480B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrical discharge machining method, and more particularly to a method of electrical discharge machining while suppressing local wear of an electrical discharge machining electrode. Generally, in order to drill holes with a diamond die, as shown in Fig. 1, an electrode 1 for electrical discharge machining made of platinum group metal or a platinum group alloy and having a tip 1a polished to a sharp angle of 10 degrees is immersed in an electrolytic solution (potassium nitrate).
10%) Diamond 3 dipped approximately 4 mm in 2 and set below the electrode 1 for electrical discharge machining in the electrolyte 2
While rotating the diamond 3, a die hole 3a is drilled in the diamond 3 by electrical discharge from the electrical discharge machining electrode 1. By the way, during electrical discharge machining of this diamond die, due to the generation of oxygen and hydrogen (gas) bubbles, a slight gap is created between the electrolytic solution 2 and the electrical discharge machining electrode 1, and electrical discharge occurs below the liquid surface. In particular, the discharge is intense near the liquid surface, and as shown in Figure 2, the electrolyte boundary part 1b of the electric discharge machining electrode 1 is locally worn out, and as shown in Figure 3, the electrolyte boundary part 1b becomes thin and broken. It ends up. For this reason, although it is polished and reused as shown by the dotted line, the tip portion 1a is wasted, so the number of times the electric discharge machining electrode 1 is used is small, resulting in poor yield. The present invention has been made to solve these problems, and it is an object of the present invention to provide an electric discharge machining method that can suppress the consumption of the electrolyte boundary portion of the electric discharge machining electrode and increase the number of times of use. The electric discharge machining method of the present invention is used to drill holes in diamond by rotating the diamond using an electric discharge machining electrode made of platinum group metal or platinum group alloy and having a sharply polished tip. , the electrolytic solution is jetted down to form a water film at the electrolytic solution boundary part of the electrode for electrical discharge machining. The details of the electrical discharge machining method according to the present invention will be explained below with reference to the drawings. As shown in FIG. 4, an electrode 1 for electrical discharge machining is made of a platinum group metal or a platinum group alloy and has a tip portion 1a polished to a sharp point at an angle of 10 degrees. is inserted into the spout 5 of a funnel-shaped electrolyte receiver 6 which is supported by a support 4 fixed to the electrolyte tank and has a spout 5 with a diameter slightly larger than the diameter of the electrode 1. Electrode 1 is immersed in electrolyte solution (potassium nitrate 10%) 2, and electrolyte metering pump 7 is placed in electrolyte receiver 6.
is driven to inject the electrolytic solution, and the electrolytic solution is jetted down from the spout 5 onto the outer circumferential surface of the electrical discharge machining electrode 1 to form a water film 8 of the electrolytic solution at the electrolytic solution boundary portion 1b. In this state, while rotating the diamond 3 set below the electrode 1 for electric discharge machining immersed in the electrolytic solution 2, an electric discharge is generated from the electrode 1 for electric discharge machining to drill a die hole 3a in the diamond 3. On this occasion,
Oxygen and hydrogen (gas) bubbles are generated and rise along the outer circumferential surface of the electrical discharge machining electrode 1, but the electrolyte is ejected and flows out, forming a water film 8 on the outer circumferential surface of the electrical discharge machining electrode 1. Therefore, the bubbles are pushed out to the outside, and no gap is created between the electrolytic solution 2 and the electrode 1 for electrical discharge machining, and the electrode 1 for electrical discharge machining is inserted under the liquid surface.
It is possible to suppress electrical discharge from the outer peripheral surface of the Further, even if oxygen and hydrogen (gas) bubbles are generated between the outer circumferential surface of the electrode 1 for electrical discharge machining and the water film 8, the amount thereof is extremely small. Therefore, even if a discharge occurs, the electrolyte boundary portion 1b is not locally consumed, and the tip portion 1a is uniformly consumed as shown in FIG. 5, and eventually the tip portion 1a is consumed as shown in FIG. If it is thin, polish it and mold it as shown in the dotted line and reuse it. In order to form a water film 8 of electrolyte at the electrolyte boundary portion 1b of the electrode for electrical discharge machining 1, the means for jetting the electrolyte down onto the outer peripheral surface of the electrode for electrical discharge machining 1 is the above-mentioned funnel-shaped electrolyte. Receiver 6 and electrolyte metering pump 7
It is not limited to an electrolyte jetting device consisting of
As shown in FIG. 7, a ring pipe 10 having a large number of electrolyte injection ports 9 at equal intervals on the inner circumferential side, an electrolyte supply pump 11 connected thereto, and an electrolyte supply source (not shown) (which may be an electrolyte tank) ), or as shown in FIG. 8, an electrolytic solution jetting device consisting of a bifurcated electrolytic solution jetting pipe 12, an electrolytic solution supply pump 11 connected thereto, and an electrolytic solution supply source (not shown) (in the case of an electrolytic solution tank) An electrolyte ejecting device consisting of the following may also be used. In short, any electrolyte jetting device may be used as long as it can form a water film 8 on the electrolyte boundary portion 1b of the electrode 1 for electrical discharge machining. Next, in order to clarify the effects of the electrical discharge machining method according to the present invention, the degree of wear of the electrical discharge machining electrode in drilling with a diamond die according to a specific example and a conventional example will be described. [Example] As shown in Fig. 4, an electric discharge machining electrode 1 made of platinum-iridium 33 w/o and having a diameter of 0.5 mm and a length of 50 mm, the tip portion 1a of which was polished to a sharp point at an angle of 10 degrees, was prepared.
A funnel-shaped electrolyte receiver 6 with a height of 5 mm and an outer diameter of 10 mm has a spout 5 with a diameter of 0.6 mm and is supported by a support 4 fixed to the electrolyte tank and positioned at a height of 5 mm from the liquid level. The electric discharge machining electrode 1 is inserted into the spout 5 and placed in the electrolyte (potassium nitrate 10%) 2.
mm, and drive the electrolyte metering pump 7 to inject the electrolyte into the electrolyte receiver 6, and pour the electrolyte onto the outer peripheral surface of the electrical discharge machining electrode 1 from the spout 5.
The electrode 1 for electrical discharge machining is immersed in the electrolytic solution 2 in this state by ejecting and flowing down at a rate of 0.5 to 11 c.c./sec to form a water film 8 with a thickness of approximately 0.1 to 0.5 mm at the electrolytic solution boundary part 1b. While rotating the diamond 3 set in advance at the lower position of the diamond 3, an electric discharge is generated from the electrode 1 for electrical discharge machining to form the diamond 3 into the die hole 3a with a diameter of 0.03 mm and a depth of 0.3 mm.
Hole drilling process was carried out. [Conventional example] As shown in Fig. 1, an electric discharge machining electrode 1 made of platinum-iridium 33w/o and having a diameter of 0.5 mm and a length of 50 mm, the tip portion 1a of which is polished to a sharp point at an angle of 10 degrees, is made of platinum-iridium 33w/o.
A diamond 3 is immersed in electrolytic solution 2 by about 4 mm and set in advance below the immersed electrode 1 for electrical discharge machining. While rotating the diamond 3 is discharged from the electrode 1 for electrical discharge machining to form a diamond 3 with a diameter of 0.03 mm and a depth of 0.3 mm. mm
The die hole 3a was drilled. In both the example and conventional electrical discharge machining methods, the amount and time of use until the electrical discharge machining electrode 1 was worn out and re-grinded, and the number of times the electrical discharge machining electrode 1 was used by re-polishing until the length was 10 mm were measured. However, we obtained the results as shown in the table below.

[Table] As is clear from the table above, according to the electrical discharge machining method of the example, the usage time until re-polishing due to wear of the electrical discharge machining electrode is the same as the conventional electrical discharge machining method, but the amount used is small, It can be seen that the number of times the electric discharge machining electrode is used by re-polishing is much greater than that by the conventional electric discharge machining method. As detailed above, the electric discharge machining method according to the present invention forms a water film at the electrolyte boundary portion of the electric discharge machining electrode during electric discharge machining, so that electric discharge from this portion is suppressed and local wear does not occur. Therefore, the electrolyte boundary part of the electrode for electrical discharge machining does not break, so the tip of the electrode can be used effectively, there is no waste of metal, and the number of times it can be used for re-polishing is greatly increased, making the electrode for electrical discharge machining easier to use. It has the excellent effect of significantly extending lifespan.

[Brief explanation of drawings]

Figure 1 is a diagram showing the state of diamond die drilling using the conventional electrical discharge machining method;
Fig. 3 is a diagram showing the wear process of the electrode for electrical discharge machining in the electrical discharge machining method, Fig. 4 is a diagram showing the state of drilling a diamond die by the electrical discharge machining method according to the present invention, Fig. 5, Figure 6 is a diagram showing the wear process of the electric discharge machining electrode in the electric discharge machining method, and Figures 7 and 8 are diagrams showing the consumption process of the electric discharge machining electrode in the electric discharge machining method of the present invention. FIG. 3 is a schematic diagram showing another means for forming a water film of DESCRIPTION OF SYMBOLS 1...Electrode for electric discharge machining, 1b... Electrolyte boundary part, 8... Water film.

Claims (1)

[Claims] 1. When drilling a diamond by using an electrical discharge machining electrode made of platinum group metal or platinum group alloy with a sharply polished tip, the electrolytic discharge of the electrical discharge machining electrode is performed while rotating the diamond. An electric discharge machining method characterized in that a water film is formed by jetting an electrolytic solution down at a liquid boundary.