JPS62114829A - Manufacture of electrode wore for wire-cut electro-discharge machining - Google Patents

Abstract

PURPOSE:To make an electrolytic current go down and improve a removal rate, by letting a copper-based electrode wire pass through the inside of oxygen low temperature plasma, forming an oxide film on its surface, and oxidizing the surface without entailing any drop in the strength. CONSTITUTION:A Cu-30% Zn alloyed wire 9 extended to 0.2mm in diameter as an electrode wire is pickled prior to treatment and washed clean and dried up. On the other hand, it is deaerated by a vacuum pump 11, feeding it with 100% oxygen by a gas cylinder 6, and a gas flow rate is set to a range of 500cc/min., taking in a microwave of 24.5GHz and output 500W from an microwave generator 1. And, when the wire 9 is passed through the inside of a reaction pipe 3, temperature of the wire 9 is 180 deg. in the measured result by an infrared radiation thermometer, and its surface color is changed to black, thus formation of an oxide film is confirmed. In consequence, the surface of the electrode wire is smooth, and its tensile strength remains unchanged prior to treatment so that a removal rate can be improved as much as 33% over.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a machining electrode wire that can particularly improve machining speed in wire-cut electrical discharge machining. □ [Conventional technology and problems] Wire-cut electrical discharge machining involves placing electrode wires for electrical discharge machining facing the workpiece, causing pulsed discharge between them, and machining the workpiece using the heat and impact caused by the discharge. This is a method for manufacturing press molds with complex shapes with high precision. Various materials have been proposed for wire-cut electrical discharge machining electrode wires, but in general, the materials are easy to obtain and economical, and they can be easily processed into thin wires of 0.5 # or less. In many cases, certain copper or copper alloys such as brass are used.

In the above machining, water is generally used as the machining fluid, and an electrolytic current flows through the machining fluid. This electrolytic current reduces the machining energy due to electric discharge and becomes one of the major factors that reduce the machining speed. For this reason, several methods have been proposed to reduce such electrolytic current. One such proposal is, for example, as disclosed in Japanese Unexamined Patent Publication No. 58-4317, in which the surface of a conductor is coated with an insulating material to reduce electrolytic current during processing. However, with this method, the unevenness on the surface of the electrode wire becomes large, causing debris to clog the electrode wire guide of the wire cutting machine, causing wire breakage during processing, or even causing irregularities in the wire diameter. There is a risk that the uniformity will lead to a decrease in processing accuracy.

As a method to avoid the above-mentioned problems, a method has been proposed in which an electrode wire is heated in the atmosphere to form an oxide film on its surface, as disclosed in JP-A No. 56-91308. . This method takes into consideration the fact that the copper oxide film has semiconductivity, and attempts to reduce the electrolytic current without inhibiting the discharge phenomenon.
The heating temperature for forming the oxide film is as high as about 400'C, and the annealing effect reduces the strength of the electrode wire.
It is not possible to increase the wire tension during electric discharge machining, which not only results in a decrease in machining accuracy, but also has the disadvantage that wire breakage is likely to occur due to a decrease in strength.

[Object of the Invention] In view of the above-mentioned circumstances, the present invention provides an electric discharge that can prevent the electrolytic current that impairs the electric discharge machining conditions from decreasing without making the outer diameter of the electrode wire uneven or reducing the strength of the electrode wire. The purpose of this invention is to provide a method for manufacturing electrode wires for processing.

[Summary of the Invention] In other words, the gist of the present invention is to pass a copper-based electrode wire through a low-temperature oxygen plasma to form an oxide film on the surface. The present invention aims to obtain an electrode wire for electrical discharge machining that can oxidize the surface of the electrode wire and reduce the electrolytic current without reducing the strength of the electrode wire.

[Example] This will be explained below based on examples.

FIG. 1 is an explanatory diagram showing an embodiment in which electrode wires are manufactured by the manufacturing method according to the present invention, in which oxygen plasma is generated by so-called microwave discharge in the reaction tube 3 by introducing microwaves, and the An example is shown in which an oxide film is formed on the surface of the wire 9 by passing the wire 9 into plasma.

This will be further explained with specific examples.

A Cu-35% Zn alloy wire 9 drawn to a final size of 0.2 # wire diameter was used as a test material as an electrode wire for electrical discharge machining. The test materials were pickled, washed and dried before treatment.

The reaction tube 3 is evacuated by the vacuum pump 11, and the internal pressure of 100% oxygen supplied from the gas cylinder 6 is 100 torr.
Adjustment was made using the vacuum gauge 5 so that the value was r. The gas flow rate at this time was 500 cc/min. A microwave of 24.5 GH7 and an output of 500 W was introduced into the reaction tube 3 from the microwave generator 1. Reaction tube 3 at this time
The temperature of the wire 9 inside was determined to be 180°C as measured by an infrared radiation thermometer. The surface of the alloy wire passed through the reaction tube 3 turned black, and the formation of an oxide film was confirmed. That is Nα1 shown in Table 1.

FIG. 2 shows another embodiment according to the present invention,
The case of oxygen plasma generation by high frequency induction is exemplified. The same reference numerals as in Fig. 1 indicate the same configuration;
The only difference is that a high frequency generator 12 and a high frequency coil 13 are used in place of the microwave generator shown in the figure, and there is no substantial difference in other configurations.

The specific test material is Cu with a diameter of 0.2 m, which is the same as in the case of Fig. 1.
-35% Zn alloy wire, oxygen gas supplied was 100%, gas flow was 1200 cc/min, and pressure was 10 toor.

The added high frequency has a frequency of 13.56MHz and an output of 5
It was 0W. The temperature of the wire 9 in the reaction tube 3 is 2
At 50'C, the surface of the treated wire turned black and formation of an oxide film was observed. This is No. 2 in Table 1.

In addition to the above, as a comparative example, the same test material was
Those with an oxide film formed on the surface by heating at 0'C (Nα3) and those without any treatment (Nα
4) was used as comparative data.

Table 1 shows the thickness of 20 mm using the above Nα1 to 4 wires.
The results of an electrical discharge machining experiment using #SKD'l 1 steel plate as the workpiece side are shown below. Note that the machining speed was expressed as a relative speed with No. 4, which was not subjected to surface treatment, as 100, and the relative speed with KVmA 2...Nα4.

As is clear from Table 1, Nα1 according to the present invention has almost no decrease in tensile strength compared to Nα4 without surface treatment, and even though the processing speed has increased by about 30%, It can be seen that there were no wire breaks during processing.

It can also be seen that in the case of Nα2 according to the present invention, the tensile strength is slightly lower than that of NQI, but the processing speed increases, and there is no wire breakage at all.

However, compared to the above-mentioned wire according to the present invention, in the case of Nα3, which has an oxide film formed by heating in the atmosphere, the tensile strength decreases significantly, and wire clogging in the guide causes frequent wire breakage during processing, causing problems. It turns out that there are many.

[Effects of the Invention] As described above, according to the manufacturing method of the present invention, the strength is high and the surface is smooth, so there is no occurrence of wire clogging in the guide, and there are fewer wire breaks during electrical discharge machining. Moreover, it is possible to obtain an electrode wire with a high machining speed, and the efficiency of wire-cut electric discharge machining can be greatly improved, which is of great significance.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams showing two embodiments of the present invention. DESCRIPTION OF SYMBOLS 1...Microwave generator, 2...Waveguide, 3...Reaction tube, 6...Oxygen gas cylinder, 9...Wire, 12...High frequency generator, Agent Patent attorney Sa Fujio Fujio Ward 1

Claims (3)

[Claims] (1) A method for producing an electrode wire for wire-cut electric discharge machining, which uses low-temperature oxygen plasma to form an oxide film on the surface of a wire for wire-cutting made of copper as a base material. (2) The method for manufacturing an electrode wire according to claim 1, wherein oxygen plasma is generated by introducing microwaves. (3) The method for manufacturing an electrode wire according to claim 1, wherein oxygen plasma is generated by induction using high frequency waves.