JP2009291856A - Electrode wire for electrical discharge machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode wire for electrical discharge machining can perform micro-discharge machining and manufacturable at low cost. <P>SOLUTION: This electrode wire includes a cross section surrounded by a first flat surface 3 and a second flat surface which are opposed to each other, a first projecting curved surface 5 connected to one of the first flat surface 3 and the second flat surface 4 and projecting outward, and a second projecting curved surface 6 connected to the other of the first flat surface 3 and the second flat surface 4 and projecting outward. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electrode wire used as a tool electrode for wire electric discharge machining, and particularly to an electrode wire for electric discharge machining excellent in performance at a low cost.

  Wire electrical discharge machining uses a thin wire as an electrode wire, supplies machining fluid (high-purity water or light oil) to the discharge site, applies voltage to the electrode wire and workpiece, and applies tension to the electrode wire. While continuously running, a pulsed discharge is repeatedly generated between the workpiece and the electrode wire in the machining liquid, and the workpiece is machined by this discharge energy.

  The electric discharge is composed of melting, explosion, scattering, cooling, and sludge removal processes. When the electrode wire and the workpiece are continuously approached, the electric discharge machining is repeatedly executed, and the workpiece is predetermined. It is processed into the shape.

  In recent years, precision equipment has been in the trend of downsizing, and the need for further miniaturization and refinement of the size and shape of workpieces has increased. Along with this, it is required to further improve the electrical discharge machining accuracy (surface roughness and dimensional accuracy).

  In order to perform processing of a workpiece having a minute size and shape, slit processing, or the like, it is necessary to make the wire diameter of the electrode wire as small as possible. Moreover, since the vibration generated by the explosion during electric discharge machining has a great influence on the electric discharge machining accuracy, it is necessary to apply a high tension to the electrode wire. Therefore, when electric discharge machining is performed on a minute workpiece with high machining accuracy, an electrode wire that is thinner (for example, about 50 μm in diameter) and has a high tensile strength is required.

  As an electrode wire for electric discharge machining that meets such a demand, for example, an electrode wire for electric discharge machining using tungsten as a material described in Patent Document 1 is known. The electrode wire for electric discharge machining described in Patent Document 1 has high tensile strength, so that electric discharge machining can be performed under high tension, but the magnitude of explosion on the wire surface during electric discharge machining is controlled. Therefore, since the explosion has a characteristic that the size of the explosion is extremely uneven, a relatively large explosion and a small explosion are mixed, and high processing accuracy cannot be obtained. In addition, since tungsten is used as the material, there is a problem that the cost of the product is high because the material cost and the manufacturing cost are high.

  Patent Document 2 discloses a brass-coated electrode for electric discharge machining in which a piano wire is used as a core material, a copper lower layer and a zinc upper layer are sequentially coated on the surface of the core material, and the final cross-sectional diameter is 0.10 mm or less. Lines are listed. The manufacturing cost of this brass-coated electrode wire for electric discharge machining is about 1/5 to 1/8 of the electrode wire for electric discharge machining made of tungsten described in Patent Document 1, and is extremely inexpensive, and on the wire surface during electric discharge machining. Because it is easier to control the magnitude of the explosion than the electrode wire for electrical discharge machining made of tungsten, it is possible to prevent the mixing of relatively large explosions and minute explosions, but the tensile strength is low Therefore, electric discharge machining must be performed under a low tension, and as a result, there are disadvantages that the machining speed is low and the variation of the machined surface roughness is large. Therefore, this brass-coated electrode wire for electric discharge machining cannot be used for fine machining.

 Further, Patent Document 3 describes an electric discharge machine wire 11 having a rectangular cross section as shown in FIG. This document describes that the wire 11 shown in FIG. 4 can have a relatively large cutting depth and a large area close to the workpiece, so that a wide width can be discharged simultaneously at the same time. However, in the case of a wire having a rectangular cross section as shown in FIG. 4, as shown in FIG. 5, since the discharge 13 concentrates on the sharp corners of the wire 12, uniform distributed discharge cannot be performed, and the workpiece 14 is It is difficult to process finely.

Moreover, as shown in FIG. 6, in the wire 15 having an elliptical cross section, the discharge 16 is generated not only at the apex on the long diameter side but also at the apex on the short diameter side, so that the machining allowance (portion removed by the electric discharge) is large. In this case, it is difficult to finely process the workpiece 17.
Japanese Patent No. 2669436 JP 2000-107943 A Utility Model Registration No. 3002783

  The present invention has been made in view of such problems of the prior art, and an object thereof is to provide a low-cost electric discharge machining electrode wire capable of fine electric discharge machining.

  In order to execute fine electric discharge machining, the electrode wire for electric discharge machining needs to satisfy the conditions described below.

  Since the electrode wire is run in a tensioned state so as not to be affected as much as possible by the vibration generated by the explosion during the electric discharge machining, it is necessary to have a high tensile strength. As a matter of course, it is preferable that the diameter of the electrode wire is as small as possible for fine processing. With respect to these high tensile strength and thinning conditions, the wire 11 having a rectangular cross section shown in FIG. 4 has a higher tensile strength because the cross-sectional area is larger than a general spherical cross section line, and the width W on the short diameter side is increased. The diameter can be reduced by reducing the diameter. However, as described above, the wire having a rectangular cross section has a drawback that the discharge is concentrated at sharp corners, so that uniform distributed discharge cannot be performed.

  Accordingly, the present inventor has conceived an electric discharge machining electrode wire having the following characteristics as an electrode wire for electric discharge machining that satisfies the three conditions of high tensile strength, thinning, and uniform dispersed discharge.

  That is, the electrode wire for electric discharge machining according to the present invention includes a first flat surface (number 3 in FIG. 1 to be described later) and a second flat surface (number 4 in FIG. 1 to be described later), a first flat surface and a second flat surface. A first convex curved surface (number 5 in FIG. 1 to be described later) connecting one of the flat surfaces and projecting outward is connected to the other of the first flat surface and the second flat surface and projecting outward. It is characterized by having a cross section surrounded by a second convex curved surface (number 6 in FIG. 1 to be described later).

  The front end surface in the processing direction is the first convex curved surface, the rear end surface in the processing direction is the second convex curved surface, the connection point between the first flat surface and the first convex curved surface, the second flat surface and the first convex curved surface A straight line connecting the connection points of the first flat surface and the first convex curved surface and a straight line connecting the maximum convex point of the first convex curved surface as E, and the straight lines A and E Is defined as α, and a straight line connecting the connection point between the second flat surface and the first convex curved surface and the maximum convex point of the first convex curved surface is defined as F, and the angle formed between the straight line A and the straight line F is defined as F. In the case of β, it is preferable that 3 ° ≦ α and β ≦ 51 °.

  The distance between the first flat surface and the second flat surface is preferably equal or narrower from the front end surface side to the rear end surface side in the processing direction.

  Since the electrode wire for electric discharge machining of the present invention has a first convex curved surface and a second convex curved surface, if electric discharge machining is performed using the first convex curved surface or the second convex curved surface as a machining tip, the convex curved surface Since the discharge in the machining direction is dispersed and does not have sharp corners, no discharge occurs in any part other than the machining part. As a result, since the electric discharge concentrates in the machining direction, the machining allowance (portion removed by the electric discharge) is small, and fine machining becomes possible.

  In order to maximize such effects, it is necessary that the convex curved surface has a predetermined curved surface shape. The front end surface in the processing direction is the first convex curved surface, the rear end surface in the processing direction is the second convex curved surface, the angle formed by the straight line A and the straight line E defined as above is α, and When the angle formed by the straight line A and the straight line F defined as β is β, α and β can be 3 ° or more to obtain a curved surface effect, and α and β can be 51 ° or less. The discharge does not concentrate on the maximum convex portion of the first convex curved surface.

  As described above, the electrode wire for electric discharge machining according to the present invention can be finely processed and has a higher tensile strength because the cross-sectional area is larger than a general spherical cross-sectional line, and the first flat surface and the second flat surface. The diameter can be reduced by making them equal or narrower from the front end surface side to the rear end surface side in the processing direction.

  FIG. 1 is a diagram schematically showing an example of a cross section of an electrode wire for electric discharge machining according to the present invention. In FIG. 1, 1 is a core material made of piano wire, and 2 is a brass plating layer. The deformed wire was obtained by rolling a spherical wire having a brass plating layer on the surface of a core made of piano wire with a pair of upper and lower or two pairs of upper and lower and left and right rollers. The electrode wire for electric discharge machining has a first convex shape projecting outward by connecting one of the first flat surface 3 and the second flat surface 4 facing each other and the first flat surface 3 and the second flat surface 4. It has a cross section surrounded by a curved surface 5 and a second convex curved surface 6 that connects the other of the first flat surface 3 and the second flat surface 4 and protrudes outward.

  As shown in FIG. 2, a straight line connecting the connection point between the first flat surface 3 and the first convex curved surface 5 and the connection point between the second flat surface 4 and the first convex curved surface 5 is A, and the first flat surface 3 and the straight line connecting the connecting point of the first convex curved surface 5 and the maximum convex point 5a of the first convex curved surface 5 is E, and the angle between the straight line A and the straight line E is α, and the second flat surface 4 and the first convex curved surface 5 and the maximum convex point 5a of the first convex curved surface 5 are F, and the angle formed by the straight line A and the straight line F is β, and the first flat surface A straight line connecting the connection point between the third and second convex curved surfaces 6 and the connection point between the second flat surface 4 and the second convex curved surface 6 is C, and the connection point between the first flat surface 3 and the second convex curved surface 6 And G is the straight line connecting the maximum convex point 6a of the second convex curved surface 6 and the angle between the straight line C and the straight line G is γ, and the connection point between the second flat surface 4 and the second convex curved surface 6 And second The straight line connecting the maximum convex point 6a of Jo curved 6 H, angle between the straight line C and the straight line H is [delta].

  During the rolling, electrode wires having different angles of α, β, γ, and δ were obtained by variously changing the rolling reduction. In the case of the same electrode line, the angles of α, β, γ, and δ are all equal, and the lengths of the straight portions A and C of all the electrode lines having the convex curved surface portions are different except that the angles are different. Both are 0.030 mm, a straight line B connecting the connection point of the first flat surface 3 and the first convex curved surface 5 and the connection point of the first flat surface 3 and the second convex curved surface 6, and the second flat surface 4. The length of the straight line D connecting the connection point of the first convex curved surface 5 and the connection point of the second flat surface 4 and the second convex curved surface 6 is 0.100 mm.

  For comparison, a spherical cross-section electrode wire (0.030 mm in diameter) in which a brass plating layer was provided on the surface of a core made of piano wire was also prepared.

  Then, these electrode wires 7 are set in an electric discharge machine (not shown) manufactured by Mitsubishi Electric Corporation. In FIG. 3, the tip surface in the machining direction of the electrode wire 7 is the first convex curved surface 5, and the machining direction The rear end face was made into the 2nd convex curved surface 6, and the steel material 8 made from SKD11 steel whose thickness t is 10 mm with the electrode wire 7 was cut to the L direction. The wire feed speed of the electrode wire 7 at the time of cutting was 10 mm / min, and the cutting time required to cut 5 mm in the L direction and the maximum height roughness of the cut surface 9 after cutting were measured. The cutting time is directly related to the cutting speed. In order to compare the cutting speed, the relative cutting obtained by dividing the cutting time of the electrode wire having a spherical cross section by the cutting time of the electrode wire having a convex curved surface portion. Divide the numerical value of the velocity and the maximum height roughness of the cutting surface 9 after cutting by the electrode wire having the convex curved portion by the maximum height roughness of the cutting surface 9 after cutting by the electrode wire having a spherical cross section. The numerical values of the relative surface accuracy obtained by this are shown in Table 1 below.

  A larger value of the relative cutting speed means that the cutting speed is faster, and a smaller value of the relative surface accuracy means that the smoothness of the cutting surface is excellent. As is apparent from Table 1, it is understood that by adopting 3 ° to 51 ° as α, the cutting speed is increased and the smoothness of the cutting surface is improved.

  In FIG. 2, the surface formed by the straight line A, the straight line B, the straight line C, and the straight line D is rectangular, the straight lines A and C are equal in length, and the straight lines B and D are equal in length. It is preferable that the straight line B and the straight line D are at least twice as long as the straight line A and the straight line C. This is because finer processing becomes possible.

  In the embodiment shown in FIGS. 1 and 2, not only the first convex curved surface 5 on the front end surface side in the processing direction but also the second convex curved surface 6 on the rear end surface side in the processing direction has a predetermined curved surface shape. The angles α, β, γ and δ are defined so as to be provided, but γ and δ of the second convex curved surface 6 which is the rear end surface side in the processing direction are not necessarily between 3 ° and 51 °, The second convex curved surface 6 may be a curved surface. In order to reduce the diameter, the distance between the first flat surface 3 and the second flat surface 4 is changed from the front end surface side (first convex curved surface 5) to the rear end surface side (second convex shape). Towards the curved surface 6), it is preferably equal or narrower as shown in FIG.

It is a figure which shows typically one Example of the cross section of the electrode wire for electrical discharge machining of this invention. It is a figure explaining the angle of (alpha), (beta), (gamma), and (delta) showing the bending degree of the convex curved surface of the electrode wire for electrical discharge machining of this invention. It is a figure explaining the cutting method by electrical discharge machining. It is a figure which shows the cross section of the conventional wire for electric discharge machines. It is a figure explaining the processing condition by the conventional electrode wire for electrical discharge machining. It is another figure explaining the processing condition by the conventional electrode wire for electrical discharge machining.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Core material 2 Brass plating layer 3 1st flat surface 4 2nd flat surface 5 1st convex curved surface 5a Maximum convex-shaped point 6 2nd convex curved surface 6a Maximum convex-shaped point 7 Electrode wire 8 Steel material 9 Cutting surface

Claims (3)

  The first flat surface and the second flat surface facing each other, the first convex curved surface projecting outward by connecting one of the first flat surface and the second flat surface, and the first flat surface and the second flat surface An electrode wire for electric discharge machining having a cross section surrounded by a second convex curved surface connecting the other of the two and projecting outward. The front end surface in the processing direction is a first convex curved surface, the rear end surface in the processing direction is a second convex curved surface,
A straight line connecting the connection point of the first flat surface and the first convex curved surface and the connection point of the second flat surface and the first convex curved surface is A, and the connection point of the first flat surface and the first convex curved surface and the first Let E be the straight line connecting the maximum convex points of the single convex curved surface, and let α be the angle between the straight line A and the straight line E,
When the straight line connecting the connection point of the second flat surface and the first convex curved surface and the maximum convex point of the first convex curved surface is F, and the angle formed by the straight line A and the straight line F is β,
The electrode wire for electric discharge machining according to claim 1, wherein 3 ° ≦ α and β ≦ 51 °.   3. The electrode line for electric discharge machining according to claim 2, wherein the distance between the first flat surface and the second flat surface is equal or narrower from the front end surface side to the rear end surface side in the processing direction. .

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