JPS62264818A - Electric discharge machine - Google Patents

Abstract

PURPOSE:To keep off any nondesirous deformation in a main structural body and make the extent of machining accuracy improvable as well as to prevent a discharge waveform from dulling and make machining performance improvable, by forming the main structural body with ceramics of a nonmagnetic material. CONSTITUTION:A bed 1, a column 2, an upper arm 3 and a lower arm 4, constituting a main structural body, are all formed with ceramics. Thus, the main structural body is formed by the ceramics, whereby any deformation in it is preventable from occurring. That is to say, because of a nonmagnetic material, a vortex loss due to a discharge current can be brought to nothing. And, since a coefficient of thermal expansion is very small, various thermal effects such as a variation in room temperature, a temperature rise in a dielectric fluid generated heat in electric parts, etc., are preventable. In addition, there is no occurrence of secular distortion as in a casting or a weldment. Moreover, since the main structural body is constituted of the ceramics, any dullness in a discharge waveform is preventable, thus machining performance is improvable.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides an electric discharge machining apparatus, in particular, a support structure that supports at least an electrode holding part is formed of a non-magnetic structure, thereby preventing the support structure from changing due to temperature changes. The present invention relates to an electrical discharge machining device that prevents deformation of the body and blunting of the discharge waveform, thereby enabling precision machining.

[Conventional technology] The electric discharge machining apparatus is as shown in FIG.

2. A wire electrical discharge machining device using a wire electrode; 2. An electrical discharge machining device using an electrode formed into a shape corresponding to the shape to be machined of, for example, graphite (hereinafter referred to as a die-sinker electrical discharge machining device 9; illustrations are omitted); However, as is generally well known, the wire electric discharge machining apparatus and the die-sinking electric discharge machining apparatus are basically the same in terms of the machining principle and the configuration of the main structure.

FIG. 4 shows a basic schematic configuration diagram of a conventional wire electric discharge machining apparatus. In the figure, 1 is a bed, 2 is a column, 3 is an upper arm, 4 is a lower arm, 5 is a wire electrode, 6 is an electric reel, and 7 is a take-up reel.

8 is an upper guide, 9 is a lower guide, and 10 is a UV table which is driven by a control device (not shown) to control the upper guide 8.

11 is an XY table that is driven in two orthogonal directions by a control device (not shown); 12 is a workpiece;
13 represents a workpiece support tool.

The wire electrical discharge machining apparatus shown in FIG. 4 supplies electrical discharge energy from a power source (not shown) between the wire electrode 5, which travels by being wound around the take-up reel 7, and the workpiece 12. Generate electrical discharge, workpiece 1
This is to perform electric discharge machining on 2. It goes without saying that a machining fluid (for example, steamed water) is supplied to the machining portion by a machining fluid supply device (not shown).

In the electric discharge machining, the position of the workpiece 12 is controlled by the XY table 11, and the U
By controlling the position of the upper guide 8 using a control means such as NC control, processing into a desired shape is performed.

[Problems to be solved by the present invention]

The machining accuracy of the wire electrical discharge machining apparatus shown in FIG. 4 is as follows: upper guide 8. It is no exaggeration to say that it is determined by how the relative positional relationship between the lower guide 9 and the workpiece 12 is controlled. However, in the conventional electric discharge machining apparatus, for example, the bed 1 in the wire electric discharge machining apparatus shown in FIG. Column 2゜Upper arm 3. The main structures such as the lower arm 4 are as follows.

It was manufactured by casting or sheet metal welding. Therefore,
These main structures are susceptible to deformation (expansion, contraction) due to temperature changes. Therefore, no matter how accurately the above-mentioned U■Y table 0 and XY table 11 are controlled, the above-mentioned main structures.

Especially upper arm 3. When the lower arm 4 and the column 2 are deformed, a relative positional shift occurs between the upper guide 8 and the lower guide 9, making it impossible to obtain a high degree of processing accuracy. The following may be considered as sources of temperature changes that cause deformation of the main structure.

(i) Eddy current loss due to discharge current since the above main structure is a magnetic material.

(ii) Change in room temperature.

(iii) Temperature rise of machining fluid due to discharge energy.

(iv) Heat generated by the electrical components used.

Generally, electrical discharge machining equipment is often operated continuously for a long time (for example, several days). The inventor of the present application carried out electric discharge machining using a conventional wire electric discharge machining device for several days in a row, and the results were as follows.

The temperatures of the column, processing fluid, and room temperature were measured (as shown in Figure 5), and processing errors during this time were also measured. In addition, in Fig. 5, 9 illustrated arrow a (△-△) indicates the upper arm;
b(・-・) is the lower arm.

C (rollo) is a column, and d (xx-x) is a processing fluid.

e (0-→) indicates each temperature change in room temperature.

The machining error is +15 to -20μ in the X direction.
Measured values of +5 to -10 μm were obtained in the m and Y directions, and the processing error occurred irregularly over time.

According to the above measurement results, the temperature changes in each part of the device are irregular, and it is therefore thought that the deformation of the upper arm, lower arm, column, etc. that occurs based on the temperature change also occurs irregularly. .

In addition, since the main structure of conventional electric discharge machining apparatuses is made of cast iron or welded sheet metal, there is an undesirable problem that distortion occurs over many years, resulting in deformation over time.

Yet again. The problem with conventional electrical discharge machining equipment is not only the deformation of the main structure, but also the fact that the main structure is made of magnetic material, which causes the discharge waveform to become dull, resulting in a decrease in machining performance. There was a desired problem.

[Means for solving problems]

The present invention aims to solve the above-mentioned problems, and therefore, the electric discharge machining apparatus of the present invention includes an electrode holding part that holds an electrode, a support structure that supports the electrode holding part,
and a machining table on which the workpiece is placed. 2. Electric discharge machining in which the workpiece is machined by feeding the electrode to the workpiece and generating electric discharge between the electrode and the workpiece. The device is characterized in that the support structure is formed of a non-magnetic structure.

This will be explained below with reference to one drawing.

〔Example〕

FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a sectional view of the arrow (A) shown in FIG. 1, and FIG. 3 is a block diagram of another embodiment of the present invention.

FIG. 1 shows an embodiment of a wire electrical discharge machining apparatus to which the present invention is applied. In FIG. 1, reference numeral 14 represents a shielding cover, 15 represents a bellows body, 16 represents a conductive air, 0.17 represents a bold character, and other symbols represent a shielding cover. corresponds to Fig. 4.

In the embodiment shown in FIG. 1, a head 1.
Column 2. Upper arm 3. and the lower arm 4 is made of ceramics.

The other mechanisms are the same as the conventional example shown in FIG. 4 described at the beginning of this specification.

Ceramics are ceramic products that are non-magnetic and have a characteristic that their coefficient of thermal expansion is significantly smaller than that of iron.

Therefore, since the main structure is made of ceramic, it is possible to prevent the deformation described in the first part of the specification of the present application. That is.

(i) Since it is a non-magnetic material, eddy current loss due to discharge current (
This makes it possible to completely eliminate heat generation due to eddy currents.

(ii) Because the coefficient of thermal expansion is extremely small, changes in room temperature,
It is possible to prevent thermal effects such as temperature rise of machining fluid and heat generated by electrical parts.

(iii) Deformation over time does not occur as with cast products or sheet metal welded products.

Furthermore, since the main structure is made of ceramic, which is a non-magnetic material, it is possible to prevent the discharge waveform from becoming blunt, and it is possible to improve machining performance.

In the embodiment shown in FIG. 1, the groove 1 is also made of ceramics, but the reduction in machining accuracy due to deformation of the main structure is due to misalignment of the upper guide 8 and lower guide 9. The elements that have a large influence on the occurrence of the positional deviation are the upper arm 3. which holds the upper guide 8 via the child table 0. Lower arm 4 holding the lower guide 9. and a column 2 to which the upper arm 3 and lower arm 4 are fixed.
This is a variation of Therefore, at least the upper arm 3.
The lower arm 4 and column 2 may be made of ceramics.

In FIG. 1, the shielding cover 14 forms a predetermined space that is substantially sealed with respect to at least the main structure. Incidentally, a bellows body 15 is provided on a part of the shielding cover 14 for the moving U/X child table 0 and the XY table 11, and air guide ports 16 are provided at multiple locations.
Also, an exhaust port (not shown) is provided. Then, the temperature inside the space formed by the shielding cover 14 is constant.

In order to maintain constant humidity, gas is introduced through the air inlet 16. Note that the temperature and humidity of the gas introduced from the air guide port 16 are adjusted in accordance with the temperature and humidity within the space.

In this way, the space formed by the shielding cover 14 is maintained at a constant temperature and humidity, which further helps prevent deformation of the main structure and also prevents metal parts present in the space. It is also possible to achieve a rust effect. In addition, ceramics have the property of being weak against impact forces,
In the electric discharge machining apparatus, no impact force is generated due to machining, so there is no problem in forming the main structure with ceramics. but.

Since it is weak against σi impact force, the shielding cover 14 is effective in preventing external impact.

The shielding cover 14 is preferably made of a non-magnetic material such as synthetic resin in order to prevent the discharge waveform from becoming blunt.

In addition, in the embodiment shown in FIG.
As a means for fixing to, a general fixing means using bolts is used. However, ceramics
Compared to iron, etc., it has low mechanical strength and is brittle. For this purpose, fixing means as shown in FIG. 2 are used. A metal bush 18 in which a screw hole corresponding to the bolt 17 is formed is installed in the punched bend 1 through a cement filling material 19 (such as an insulator or the like used for this purpose). The column 2 is fixed to the bed 1 by the bolt 17 via a spring washer 20. In addition, the above spring washer 20
In addition to softening the impact force caused by tightening,
This is to absorb the difference in expansion and contraction caused by the difference in expansion coefficient between the bold 17 and the ceramic.

The same applies to the means for fixing the upper arm 3 and lower arm 4° to the column 2.

The embodiment shown in FIG. 3 is a die-sinking electric discharge machining apparatus to which the present invention is applied, and is basically the same as the embodiment shown in FIG. That is, the main structure is the bed 1. Column 2. The arm 22 is made of ceramics. In Figure 1, reference numeral 21 is a processing head, 22 is an arm that supports the processing rod 21, 23 is a processing electrode, 24 is a spindle for processing and feeding the processing electrode 23, and 25 is a processing tank.

26 represents a machining fluid, and other symbols correspond to those in FIG.

In the embodiment shown in FIG. 3, the bed 1° column 2 is
The arm 22 is made of a non-magnetic material and is made of ceramic having a small coefficient of thermal expansion, as in the embodiment shown in FIG.
The present invention has the same effect as the embodiment shown in FIG. 1 in that it is possible to prevent undesired deformation of the column 2 and arm 22 and to prevent the discharge waveform from becoming blunt, thereby improving machining performance. It is something that can be demonstrated. Further, the effect of installing the shielding cover 14 is similar to that of the embodiment shown in FIG. 1 described above.

The ceramics used in the present invention include so-called old ceramics, which have been known for a long time, and new ceramics (also called fine ceramics), which are new materials that have been developed relatively recently. Nini Ceramics.

1 mechanical strength compared to the above old ceramics,
It is theoretically preferable because it has excellent properties such as heat resistance, thermal expansion property, and chemical resistance. However, since it is expensive, even if the above-mentioned old ceramics are used in order to expect the effects of the present invention, the result will be practically the same.

Although it has been explained that ceramics are used as the material for the main structure of the present invention, the present invention is not limited to this. You may also use

〔Effect of the invention〕

As explained above, according to the present invention, the main structure of the electrical discharge machining apparatus is formed of ceramic, which is a non-magnetic material, and therefore, undesired deformation of the main structure is prevented, thereby improving machining accuracy. It becomes possible to improve the machining performance by preventing the discharge waveform from becoming blunt.

[Brief explanation of drawings]

Fig. 1 is a block diagram of one embodiment of the present invention, Fig. 2 is a sectional view of the arrow (A) shown in Fig. 1, Fig. 3 is a block diagram of another embodiment of the present invention, and Fig. 4 is a conventional FIG. 5 is a schematic configuration diagram for explaining the conventional electric discharge machining apparatus, and FIG. 5 shows an actual measurement diagram of temperature changes in the conventional wire electric discharge machining apparatus. In the figure, 1 is a bed, 2 is a column, 3 is an upper arm, 4 is a lower arm, 5 is a wire electrode, 8 is an upper guide, 9 is a lower guide, 14 is a shielding cover, and 22 is an arm. Patent applicant: Discharge Precision Machining Institute Co., Ltd. Representative Patent Attorney Mori 1) Hiroshi (2 others) Sanku 1 Figure 1 Day 1d

Claims (1)

[Claims] An electrode holding part that holds an electrode, a support structure that supports the electrode holding part, and a processing table on which a workpiece is placed are provided, the electrode is fed to the workpiece, and the electrode is connected to the workpiece. An electric discharge machining apparatus that performs machining by generating electric discharge between the workpiece and the workpiece, wherein the support structure is formed of a non-magnetic structure.