JPS62271632A - Wire electrode for wire cut electric discharge machining - Google Patents

Abstract

PURPOSE:To increase the modulus of elasticity of an electrode wire, to increase tensile strength, and to enable change of physical properties of the discharge surface of a wire, by a method wherein a wire electrode is formed by a core, formed such that a number of carbon fibres, with which a metal is covered, are bundles to apply heating compression thereon, and a conductive member, the surface of which is covered with a conductive material. CONSTITUTION:Since carbon fibre 2 having high elasticity and high yield strength is used in a central part as a conductive strength member for a core 4, the core 4 is capable of providing tension further higher than that of a conductive member 3 with which the surface of the core is covered. Through the conductive member 3 on the surface of the core bears the subject of electrical conduction, since a short pulselike current is caused to flow through an electrode wire, most of the current flows over the surfaces of the electrode wire. Thereby, the intensity of apparent electric resistance of the wire is neglected, and in phenomenon of adhesion to an object to be machined due to the electric discharge machining, an adhesion amount can be decreased because an alloy of tin and the like is usuable as a conductive material. Further, since the carbon fibre is covered with a metal 1, drape with a conductive member is excellent.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a wire electrode for wire-cut electrical discharge machining, specifically, a core material formed by bundling a large number of carbon fibers and coated with a conductive material. The present invention relates to a wire electrode for wire-cut electrical discharge machining.

[Prior Art] A wire electrode for wire-cut electrical discharge machining is naturally given a large amount of tension because it is necessary to hold the wire electrode straight in order to perform high-precision machining.

Furthermore, in order to perform machining at the highest possible speed, it is necessary to supply a large amount of power. Since such high tension and power induce wire breakage, wire electrodes for wire-cut electric discharge machining are desired to have high tensile strength at high temperatures and the ability to maintain stable discharge.

Generally, the electrode material of the wire electrode used in wire-cut electrical discharge machining has a diameter of about 0.03 to 0.3 thc. In this electric discharge machining method, the quality of the electrode wire used has a direct and significant effect on the machining speed, machining accuracy, and surface texture of the workpiece surface, so there is a strong demand for the creation of suitable materials suitable for this method. There is.

Conventionally, wire electrodes for wire-cut electrical discharge machining include hard copper wire, brass wire, tungsten wire, zinc or aluminum coated copper wire, 0.1-4% Al-20-38%
Zn-Cu alloy wire is used, but since it is based on copper except for tungsten wire, large tensile strength is not required.Furthermore, in order to have high rigidity against external stress, the material The elastic modulus of the copper alloy has a large influence, but a high elastic modulus cannot be obtained for copper alloys.

Conventionally, due to these drawbacks, thin wires (for example, diameter 0.05
mm), tungsten wire is used since it can have a high tension, but tungsten wire has the disadvantage that not only can the processing speed be very high, but it is also expensive. In addition, recently, composite wires in which ceramics or carbon are attached to the surface of copper or brass have been proposed, but they do not meet the conventional requirement of increasing the tension of the electrode wires.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems of wire electrodes for wire-cut electrical discharge machining. An object of the present invention is to provide a wire electrode for wire-cut electric discharge machining, which allows the physical properties of the discharge surface to be varied in various ways.

[Means for Solving the Problems 1] The wire electrode for wire-cut electric discharge machining of the present invention includes a core material made of a bundle of carbon fibers coated with metal, and a conductive material coated on the surface of the core material. The gist is that it consists of a conductive member.

[Function] The wire electrode for wire-cut electrical discharge machining of the present invention uses carbon fiber in the center as a conductive strength member, which exhibits high elastic modulus and high yield strength, so that the rupture of the composite material due to ordinary long fibers is avoided. The stress is σcom=Vfσfiber+(1-Vf)σmatr
Indicated by +x. Here, σcow: Breaking stress of composite material, σfiber: Breaking stress of carbon fiber, σcow atrix
; breaking stress of matrix, Vf; volume fraction of carbon fiber.

Therefore, the core material can apply a much larger tension than the conductive material covering the surface.Also, in the present invention, the conductive material on the surface is responsible for the main electrical conduction, but in wire cut electrical discharge machining, Since a short pulse current is passed through the electrode wire, most of the current flows on the surface of the electrode wire, so the apparent high electrical resistance of the wire is not a problem, and it is not a problem during electric discharge machining. The adhesion phenomenon of workpieces is also
Since the conductive material covering the surface can be made of an alloy such as tin, the amount of adhesion can also be reduced. Furthermore, since the carbon fibers are not left bare but are coated with metal, they blend well with the conductive material forming the surface, making them ideal as composite wires.

[Example] A preferred example of the present invention will be described based on the drawings.

FIG. 1 shows a cross section of an embodiment of a wire electrode for wire-cut electrical discharge machining according to the present invention, in which carbon fiber 2 has a single fiber diameter of 7.
The surface was coated with a nickel film 1 having a thickness of 0.5μ. The carbon fibers 2 were bundled in the number necessary to form an electrode wire, and heated and compressed to form a core material 4.

When the tensile strength and Young's modulus of the obtained core material 4 were measured, the results shown in Table 1 were obtained.

Table 1 The tensile strength and Young's modulus of the core material 4 are both 2 to 4 compared to conventional wires.
It was double the value. The surface of the obtained core material 4 contains copper, zinc,
The conductive member 3 made of a conductive material such as tin or an alloy thereof was covered to form a wire electrode. When wire-cut electric discharge machining was performed using this wire electrode, the table feed speed was significantly increased compared to conventional ones, and a high machining speed was obtained. Furthermore, the processed surface properties were comparable to those of conventional products. In this example, the metal coated on the carbon fibers was nickel, but it was confirmed that similar effects could be obtained by coating copper or brass in addition to nickel.

[Effects of the Invention] As explained above, the present invention includes a core material formed by bundling a large number of metal-coated carbon fibers and heating and compressing them, and a conductive member made of a conductive material and coated on the surface of the core material. This is a wire electrode for wire-cut electric discharge machining, which uses carbon fiber in the center as a conductive strength member that exhibits high elastic modulus and high yield strength, so a large tension can be applied to the wire electrode. Machining accuracy improves. Furthermore, as the wire electrode becomes stronger, high power can be supplied to the wire electrode, resulting in a high processing speed. Furthermore, since the carbon fiber that serves as the core material is coated with metal, it is compatible with the conductive material coated on the surface. It has a number of excellent effects such as good surface quality of the processed material and no adhesion of the processed material to the wire electrode.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a wire electrode for wire-cut electric discharge machining according to an embodiment of the present invention. 1... Nickel film, 2... Carbon fiber, 3... Conductive member, 4... Core material

Claims (1)

[Claims] (1) A wire electrode for wire-cut electrical discharge machining, comprising a core material made of a bundle of carbon fibers coated with metal, and a conductive member made of a conductive material and coated on the surface of the core material.