JPS6239118A - Electric discharge machining method by paired electrode - Google Patents

Abstract

PURPOSE:To remove the principal part from a workpiece by electric discharge energy, by placing electrodes, paired in one or more spacing a required distance, to be opposed to a workpiece, not connected to the earth, and giving mutually different polarity to the paired electrodes within a common time. CONSTITUTION:Paired electrodes 3a, 3b are held spacing a predetermined distance D by an insulating material 4. A machine, placing point ends 31, 31 of the electrodes to be opposed to the principal machined part 10 of a workpiece 1, applies high pressure alternating voltage to the electrodes 3a, 3b in machining fluid 5. The strong electric field is formed in the point end of the paired electrodes with mutually different polarity, and the principal part 10 is efficiently removed by an avalanche effect phenomenon. The machine enables the workpiece, moving in a high speed, to be efficiently electric discharge machined with no necessity for connecting an electric discharge power supply with the workpiece.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to electrical discharge machining, particularly electrical discharge machining using a counter electrode.

[Conventional technology and its problems]

Electric discharge machining is one of the electrochemical machining methods for various materials. This processing method can be processed regardless of the hardness or brittleness of the material, so it can be used for carving molds, drilling, cutting, grinding, slitting, etc. of stepped materials such as cemented carbide and ceramics. It is used as.

However, the conventional electrical discharge machining method generally uses a single electrode as a tool and a workpiece as bipolar poles.

Since this method applied intermittent voltage using an RC circuit, it was necessary to connect the discharge power source directly to the workpiece. Therefore, it was the national policy to connect the workpiece and electrodes in an electrically insulated state. There has been a problem in that rotating workpieces or objects moving at high speed cannot be easily machined.

In addition, in electrical discharge machining of high-speed rotating objects, it is necessary to ground the workpiece using brushes, etc., which makes it difficult to provide insulation for the machine itself, and furthermore, radio interference such as brush wear and noise occurs. Countermeasures against malfunctions such as these are also required, which has the problem of complicating work and reducing efficiency.

[Means for solving problems]

The present invention was devised after repeated research in view of the above-mentioned circumstances, and its purpose is to eliminate the need to connect a discharge power source directly to the workpiece, and to make it insulated from the main body of the processing machine. An object of the present invention is to provide an electric discharge machining method that can easily and efficiently remove a certain workpiece or a workpiece that rotates at high speed or moves at high speed.

In order to achieve this objective, the present invention employs a special electric discharge machining method that changes the conventional concept, namely, one or more pairs of electrodes separated by a required distance are The method is characterized by applying different polarities to the pair of electrodes within a shared time while facing the object, and removing the main part of the workpiece by electric discharge energy between the tips of the pair of electrodes and the workpiece. It is something to do.

In the present invention, in addition to a fixed type electrode, a movable type, that is, a type that automatically replenishes consumable electrodes, is used.

〔Example〕

Embodiments of the present invention will be described below based on the accompanying drawings.

FIG. 1 shows the principle of the counter-electrode electrical discharge machining method according to the present invention. Reference numeral 1 denotes a workpiece, which is grounded via an insulating layer 11.

2 is an electrical discharge machining mechanism that is a feature of the present invention.

A pair of electrodes 3a and 3b are held by an insulating material 4 with a predetermined spacing between them. The electric discharge machining mechanism 2 is attached to a processing machine, a robot arm, etc., and has counter electrodes 3a, 3b.
The tips 31.31 of the electrodes 3a, 31 are opposed to the main processing part 10 of the workpiece 1 at a required distance, and in this state, the electrodes 3a,
A liquid consisting of water, oil, or a mixture thereof is interposed between the tip 31.degree. 31 of 3b and the main processing part 10.

This solution may also contain particles such as abrasives.

In this state, a high voltage (
current). At this time, the pair of electrodes 3a and 3b have
It is necessary to provide mutually opposite polarities within the shared time, and this can be done by making one electrode always positive and the other always negative, or by alternately switching the polarity at a fixed cycle.

FIG. 2 shows an example of a power supply circuit used in carrying out the present invention. In the figure, E is a capacitor, R is a non-inductive resistor for setting a current value, T is a switching transistor, and S is a polarity switch. By using this circuit, the opposite electrode 3a
, 3b are alternately switched, each electrode 3a, 3b is switched alternately.
The discharge of b is averaged, and the same degree of discharge can be stably obtained from each electrode. Although not shown, it is also recommended to use software to correct the engraving depth or electrode path.

The voltage applied to the electrodes 3a and 3b may be an alternating voltage, such as an alternating current, a biased alternating current, or a pulsating current. The power waveform may be appropriately selected from a pulse wave, a rectangular wave, a sawtooth wave, a sine wave, a biased wave thereof, and the like.

By the above operation, the pair of electrodes 3a, 3 having mutually different polarities
A strong electric field is formed at the tip of the electrode b using the conductive workpiece 1 as a medium, and due to the so-called electron avalanche phenomenon, the gap between the tips 31, 31 of the pair of electrodes 3a, 3b and the main part 10 of the workpiece 1 is generated. The discharge is excited and the main part 10 is efficiently removed.

In the above method, a desired motion may be applied to the paired electrodes 3a, 3b and/or the workpiece 1 in order to stabilize the processing.

FIG. 3 shows an embodiment in which the present invention is applied to removal processing (for example, shaping) when the workpiece 1 is a conductive high-speed rotating body. The main body 6 rotates the main body 6 at high speed. Counter electrode 3a.

3b is opposed to the workpiece 1 at a suitable position, and is moved in the radial direction as appropriate, while voltages are applied so as to give mutually different polarities as described above. Then, the electrode tip 31
．． A liquid 5 is injected between the main part 31 and the main part. This results in
A discharge is excited between the pair of electrodes 3a and 3b using the moving conductive main part 1o as a medium, and processing is performed for each electrode tip.

FIG. 4 shows an embodiment in which the present invention is applied to removal processing of a non-conductive workpiece 1. In this case, the tips 31 and 31 of the pair of electrodes 3a and 3b in the electric discharge machine 2 are close to each other. The pair of electrodes 3a is held obliquely by the insulating material 4 so as to be close to or in contact with the main part 10 of the workpiece 1 within a shared time.

A voltage is applied from a circuit as shown in FIG. 2 so that the polarities of the terminals 3b are opposite to each other.

As a result, a discharge occurs between the electrode tips 31 and 31 approaching each other, and this impulsive discharge energy hits and removes a small amount of the non-conductive essential part immediately below via the medium 5. Alternatively, foreign matter (for example, chips, fine powder) attached to or deposited on the non-conductive main portion is removed. It goes without saying that even when the non-conductive workpiece 1 is a rotating body, the same method as shown in FIG. 3 can be adopted.

Figures 5 through 8 illustrate several examples of electrical discharge machining mechanisms that may be used in the practice of the present invention. First, in FIGS. 5 and 6, plate-shaped electrodes 3a, 3b are placed on an insulating material 4 made of synthetic resin or the like.
are fixed with screws 15 via an insulating bush 14.

Figures 7 and 8 are for carrying out the present invention with higher precision. When performing electric discharge machining, it is possible to adopt low electrode wear conditions or to detect the wear state of the electrode and provide feedback. Although it is possible, it would be effective to automatically replenish the consumed amount at the same time. The one shown is
Guide grooves 41 and 41 corresponding to the electrodes are formed from the side to the bottom of the block-shaped insulating material 4 such as ceramics,
Wire electrodes 3a and 3b of different polarities are connected to the guide groove 41.
．． 41, and the wire electrode is fed and moved by a roller or the like.

According to this method, new electrodes are always supplied, so
High-precision machining is possible.

Note that although a pair of electrodes is shown in the drawing, the present invention is not limited to this, and there is no limitation to the shape of the electrodes.

Next, specific examples of the present invention will be shown.

Example I ① A fully automatic NC electrical discharge machine was used to perform electrical discharge machining of a flat member.

The specifications of the electrical discharge machine are as follows.

Table movement amount (left and right) 300+n+table movement I! (front and back) 200nnDistance on both sides 500
~250 m The electrode was a 110×25×2 copper plate and had a two-pole structure (spacing 3IIn) shown in FIGS. 5 and 6, and the circuit shown in FIG. 2 was used.

Diamond-dispersed cast iron with external dimensions of 30 x 5 tons and x 30 mm was used for the flat plate member. The concentration level is 75.

■The electrical discharge machining conditions were a low discharge gap, a constant no-load discharge voltage of 5OV, a discharge voltage of 20 to 25V, and a discharge current (
Current peak value) Ip was varied in the range of 8 to 30A.

To simplify the experiment, the discharge time (discharge pulse width) τp and rest time τr were made equal and varied within a range of 2 to 128 μsec. The processing was carried out while feeding in a direction perpendicular to the electrode axis at a feed rate F = 10 mm/win, in combination with polarity switching (2 times/second). The cleaning fluid was a water-soluble grinding fluid, and the injection pressure was 0.3 kg/aJ.

■As a result, a stable electric discharge was generated between both electrodes and the grinding wheel within the range shown below, and the engraving depth was 5.
The engraving was carried out without any problem at 10 μm and 20 μm.
Good results were obtained even when the diameter was more than μm, and protrusion of diamond grains from the matrix was observed.

Discharge current (current peak value) Ip = 8A, discharge time (discharge pulse width) τp = 4 to 32 μsec range, I
p=1OA, tp=4 to 128 μsec range,
At Ip=15A, τp=range of 8 to 128 μsec+at Ip=2OA, τp=range of 8 to 128.

This result shows that the present invention is an effective electric discharge machining method.

Example 2 10 Next, the present invention was applied to a rotating body with a shaft to perform electrical discharge machining.

The workpiece is a bronze plate with a diameter of 30 mmφ and a thickness of 3III11 integrated with an insulating layer interposed therebetween. The width of the electrode is 20
mm, and the same configuration as in Example 1, and the workpiece is l.
While rotating at rpm, the twin electrodes mounted on the table were fed and moved in the radial direction at 100 mm/min to carry out electrical discharge machining.

■The electrical discharge machining conditions are Example 1 except that the discharge time (discharge pulse width) τp and the two-rest period τr are 2 to 512μsecC.
The same is true.

II, as a result, τP=8~32 at IP=10A even though the bronze layer and the rotating shaft are not electrically connected.
p in the range of μsecC, I p = 1.5 A
At Ip=8 to 32 μsec, p=8 to 128 μsec at Ip=2OA, and perfectly stable discharge from both poles at p=30A and τp=8 to 32 μsec.

Machining was carried out without any problem up to the engraving depth of 20 μm.

〔Effect of the invention〕

According to the present invention as described above, there is no need to directly connect a discharge power source to the workpiece, and workpieces that are insulated from the basic machining body, etc., or workpieces that rotate or move at high speed can be easily and efficiently processed. It can perform electric discharge machining well, and has good workability because there is no need to take measures such as wiring work, brush wear, noise, etc., and it also has the advantage of being able to perform machining while the workpiece is being driven or in operation. You can get the same effect.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the principle of the electrical discharge machining method using a counter electrode according to the present invention, FIG. 2 is a circuit diagram showing an example of a discharge circuit applied to the present invention, and FIGS. An explanatory diagram showing an example of application, FIG. 5 is a front view showing an example of a counter electrode used in the implementation of the present invention, FIG. 6 is a longitudinal sectional view thereof, and FIG. 7 is an example in which the electrode is automatically refilled. The perspective view shown in FIG. 8 is also a side view thereof.

Claims (3)

[Claims] (1) One or more pairs of electrodes separated by a required distance are faced to an ungrounded workpiece, and the pairs of electrodes are given different polarities within a shared time, so that the tip of the pair of electrodes and the workpiece are An electric discharge machining method using a counter electrode, which is characterized by removing the main part of the workpiece by electrical discharge between the workpiece and the workpiece. (2) The electric discharge machining method using a counter electrode according to claim 1, wherein the workpiece includes a rotating body. (3) The electrical discharge machining method using a counter electrode according to claim 1, which includes a method in which the counter electrode is fed and moved during electrical discharge machining, and consumed parts are successively replenished.