JPH059212B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for manufacturing a machining electrode wire that can particularly improve machining speed in wire cut electric discharge machining. [Prior art and problems] Wire-cut electrical discharge machining involves placing an electrode wire for electrical discharge machining opposite the workpiece, causing a pulse discharge between them, and machining the workpiece using the heat and shock generated by the discharge. This is a method for manufacturing press molds with complex shapes with high precision. Various materials have been proposed for the wire cut electrode wire for electric discharge machining, but in general, the material is easy to obtain and economical, and it is easy to process into thin wires of 0.5 mm or less. In many cases, copper or a copper alloy such as brass is 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,
Several methods have been proposed to reduce such electrolytic current. As one of them, for example, JP-A-58
4317, there is a proposal to coat the surface of a conductor with an insulating material to reduce electrolytic current during processing. However, with this method, the irregularities on the surface of the electrode wire become large, causing debris to clog the electrode wire guide of the wire cutting machine and causing wire breakage during processing, and furthermore, the unevenness of the wire diameter This may lead to a decrease in 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 focuses on the fact that the copper oxide film has semiconductivity, and attempts to reduce the electrolytic current without inhibiting the discharge phenomenon, but the heating temperature for forming the oxide film is The temperature is high at around 400℃, and the annealing effect reduces the strength of the electrode wire, making it impossible to increase the wire tension during electrical discharge machining, which not only results in a decrease in machining accuracy, but also causes a decrease in strength. It has the disadvantage of easily inducing disconnection. [Object of the Invention] In view of the above-mentioned circumstances, the present invention provides an electric discharge that can reduce the electrolytic current that impairs the electric discharge machining conditions without making the outer diameter of the electrode wire uneven or reducing the strength. The present invention aims to provide a method for manufacturing an electrode wire for processing. [Summary of the Invention] That is, 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 electric 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] The following is a description based on an example. FIG. 1 is an explanatory diagram showing an embodiment in which an electrode wire is 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 explained in more detail. A Cu-35% Zn alloy wire 9 drawn to a final size of 0.2 mm in 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 was evacuated by a vacuum pump 11, and the internal pressure of 100% oxygen supplied from a gas cylinder 6 was adjusted to 100 torr using a vacuum gauge 5. The gas flow rate at this time was 500 c.c./min. From the microwave generator 1 to the reaction tube 3 above.
A 24.5GHz microwave with an output of 500W was introduced.
At this time, the temperature of the wire 9 in the reaction tube 3 was 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. This is No. 1 in Table 1. FIG. 2 shows another embodiment of the present invention, illustrating a case where oxygen plasma is generated by high frequency induction. The same symbols as in FIG. 1 indicate the same configurations, and instead of the microwave generator in FIG. 1, a high frequency generator 12 and a high frequency coil 1 are used.
The only difference is that 3 is used,
There are no substantial differences in other configurations. The specific test material was a Cu-35% Zn alloy wire with a diameter of 0.2 mm as in the case of Fig. 1, the supplied oxygen gas was 100%, the gas flow rate was 200 cc/min, and the pressure was 10 toor. The added high frequency had a frequency of 13.56MHz and an output of 750W. The temperature of the wire 9 in the reaction tube 3 is 250
℃, the surface of the treated wire turned black and an oxide film was observed to form. This is No. 2 in Table 1. In addition to the above, as comparative examples, the same test material as above was heated in the atmosphere at 400°C to form an oxide film on the surface (No. 3), and the material without any treatment (No. 4) was prepared. This was used as comparative data. Table 1 shows the results of electrical discharge machining experiments using the wires Nos. 1 to 4 described above and a 20 mm thick SKD11 steel plate as the workpiece. In addition, the processing speed is 100 for No. 4 without surface treatment.

[Table] 1...Kg/mm ²
2...Represented by relative speed with No. 4. As is clear from Table 1, No. 1 according to the present invention has almost no decrease in tensile strength compared to No. 4 without surface treatment, and moreover, at a processing speed of about 30%
It can be seen that there was no wire breakage during processing even though the percentage increased. Furthermore, in the case of No. 2 according to the present invention, although the tensile strength is slightly lower than that of No. 1, it can be seen that the processing speed increases on the contrary, and there is no wire breakage at all. However, compared to the above-mentioned wire according to the present invention, in the case of No. 3 in which an oxide film was formed by heating in the atmosphere, the tensile strength decreased significantly, and wire clogging in the guide and wire breakage during processing occurred frequently. , turned out to be problematic. [Effect of the invention] As described above, according to the manufacturing method according to the present invention,
Because it has high strength and a smooth surface, there is no occurrence of wire clogging in the guide, there is less breakage during electrical discharge machining, and it is possible to obtain electrode wires that can be processed quickly, improving the efficiency of wire cut electrical discharge machining. The significance of being able to significantly improve this is enormous.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory diagrams showing two embodiments of the present invention. 1...Microwave generator, 2...Waveguide, 3
...Reaction tube, 6...Oxygen gas cylinder, 9...Wire, 12...High frequency generator.

Claims (1)

[Claims] 1. A method for forming an oxide film on the surface of a wire for wire cutting using copper as a base material, in which low-temperature plasma of oxygen is generated and the wire is passed through the plasma to form an oxide film on the surface of the wire. A method for manufacturing a wire cut electrode wire for electric discharge machining, which is characterized by forming an oxide film. 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.