JPS6351814B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrode for electric discharge machining for obtaining a deep hole by an electric discharge machining method, and more particularly to an improvement in an electrode for electric discharge machining for obtaining a narrow and deep hole in a blind hole.

Conventionally, when drilling holes, the drilling method has been widely used due to its workability and operability.
When drilling a hole in stainless steel, which is a difficult-to-cut material, using this drilling method, the drill diameter D and the hole depth L
Looking at the relationship, it can be seen that when L becomes three times or more than D, the discharge of chips, the supply of lubricating oil, etc. begin to be adversely affected, the wear and tear of the cutting edge become significant, and machining becomes difficult. This phenomenon becomes more pronounced as the drill diameter D becomes smaller.

Drilling holes in spinnerets that require such fine and deep holes, i.e., holes for polymer introduction with a hole diameter of 0.5 mm and a hole depth of 10 mm, cannot be made using the above-mentioned drill machining method, but can be done using the electrical discharge machining method. must be done.

However, even with the electric discharge machining method, there is a limit to the ability to drill small and deep holes, just like the drill machining method, and the electrode diameter D′,
Looking at the relationship between the depth L of the hole, when L becomes five times or more than D', the progress of machining stops. This is because when entering the deep machining region, the discharge of machining debris becomes poor, secondary discharge between the machining debris and the inner surface of the hole of the workpiece increases, and short-circuit phenomena occur frequently. In order to reduce this short-circuit phenomenon, an attempt was made to rotate the electrical discharge machining electrode to agitate the machining oil in the hole and discharge the machining debris, but the expected effect was not obtained. In addition, in order to promote the discharge of machining waste, a through hole 2 for spouting machining oil is provided in the center of the electric discharge machining electrode 1 as shown in Fig. 1, and machining oil is forced onto the machining surface of the workpiece. The hole diameter is 0.5mm and the hole depth is electrical discharge machined by oiling and rotating agitation.
Although we were able to drill an 8.0 mm deep hole in the workpiece, a short circuit phenomenon still occurred during machining. Furthermore, electric discharge machining was performed on the spinneret material with a thickness of 10 mm to obtain a blind hole with a hole diameter of 0.5 mm and a hole depth of 9.5 mm, as shown in Figure 2. A convex portion 4 was generated on the bottom of the central portion of 3, and secondary processing was required to remove the convex portion 4.

In order to develop an electrode for electric discharge machining that can prevent the occurrence of the convex portions, the present invention has conducted research and experiments, and as a result, a satisfactory electrode for electric discharge machining has been discovered.

The electric discharge machining electrode of the present invention has at least two thin rods inserted into the electrode material of the hollow pipe and caulked by die drawing to form a plurality of thin machining oil supply holes. This is a characteristic feature.

Since the electric discharge machining electrode of the present invention has a plurality of thin machining oil supply holes, machining oil can be forcibly supplied to the machining surface of a workpiece with strong pressure during electric discharge machining of a narrow deep hole. Furthermore, by rotating the electric discharge machining electrode, the supplied machining oil can be sufficiently stirred without foaming, and machining debris can be smoothly discharged to the outside. Therefore, the secondary discharge between the inner surface of the hole of the workpiece and the machining debris is greatly reduced, the occurrence of short circuit phenomenon is eliminated, and the depth of the hole is about 20 times the diameter of the hole and there is a convexity at the bottom of the hole. This enables easy electrical discharge machining of a narrow, deep hole that has no part.

Next, in order to clarify the effects of the electrode for electric discharge machining of the present invention, electric discharge machining of a narrow deep hole according to a specific example will be described.

As shown in Figure 3a, inside the hollow pipe electrode material 5 made of copper with an outer diameter of 0.8 mm and an inner diameter of 0.7 mm, a diameter
Insert two thin rods 6 made of 0.3 mm copper-chromium alloy, finish the outer diameter of the electrode material 5 to 0.46 mm by die drawing as shown in Figure 3b, and remove the two inner thin rods 6. Caulk these two thin rods 6 and electrode material 5
Using a 30 mm long electric discharge machining electrode 8 with two thin machining oil supply holes 7 formed between the spinneret material 9 made of stainless steel and 10 mm thick as shown in FIG. In order to perform electric discharge machining of a narrow and deep hole for the introduction hole, machining oil is forcibly supplied to the machining surface of the spinneret material 9 with strong pressure from the two machining oil supply holes 7, and the electric discharge machining electrode 8 is also heated at 300 rpm. The electric discharge machining process is performed while the machine rotates and the machining oil is thoroughly agitated. As shown in the figure, a blind narrow deep hole 10 with a hole diameter of 0.5 mm and a hole depth of 9.5 mm is obtained without a protrusion in the center of the bottom of the hole. I was able to do that. Thereafter, a thin polymer discharge hole 11 is penetrated through the bottom of this deep hole 10 as shown by a chain line to form a spinning hole, and a spinneret is obtained.

The electric discharge machining electrode 8 of the above embodiment is constructed by inserting two thin rods 6 into the electrode material 5 of the hollow pipe and caulking them by die drawing to form the two machining oil supply holes 7.
However, the present invention is not limited to this, and for example, as shown in FIGS. It is also possible to form eight machining oil supply holes 7 by arranging and inserting the machining oil around the machining oil supply holes 7 and caulking them by die drawing.

As can be seen from the above explanation, according to the electrode for electric discharge machining of the present invention, a narrow and deep hole with a depth of about 20 times the hole diameter can be easily drilled without forming a convex part at the bottom of the hole. Therefore, it can be said to be the best electrode for electrical discharge machining, especially for drilling small and deep holes for polymer introduction holes in spinneret materials.

[Brief explanation of the drawing]

Fig. 1 is a front view showing a conventional electrode for electrical discharge machining of a hollow pipe, Fig. 2 is a vertical cross-sectional view of a narrow deep hole drilled by the conventional electrode for electrical discharge machining, and Fig. 3 a and b are the invention of the present invention. FIG. 4 is a cross-sectional view showing the manufacturing process of an embodiment of the electrode for electrical discharge machining according to the present invention, and FIG. The top view and FIGS. 5a and 5b are cross-sectional views showing the manufacturing process of another embodiment of the electrode for electrical discharge machining according to the present invention. 5... Hollow pipe electrode material, 6... Thin rod, 6'
...Extremely thin rod, 7... Machining oil supply hole, 8... Electrode for electric discharge machining.

Claims (1)

[Claims] 1. An electrode for electric discharge machining, characterized in that at least two or more thin rods are inserted into an electrode material of a hollow pipe and caulked by die drawing to form a plurality of thin machining oil supply holes.