JPS61279432A - Electric discharge machine - Google Patents

Abstract

PURPOSE:To prevent even shapes of a work and an electrode having bad face engagement from a short-circuit phenomenon so as to provide stable electric discharge machining by constituting an auxiliary electrode juxtaposed near an original working electrode and provided additionally with a lift means separate from one for the working electrode. CONSTITUTION:Before electric discharge machining is started by a reversed conical working electrode 13 having a lower pointed end, an auxiliary electrode lift drive mechanism 33 is operated such that the heights of an auxiliary electrode 23 bearing against an auxiliary workpiece 37 and the working electrode 13 bearing against a workpiece 17 coincide with each other. In the beginning of the electric discharge, the working electrode 13 and the auxiliary electrode 23 begin to discharge simultaneously. Thus, working current is divided into both electrodes so that the working electrode 13 side do not have conventional excessive current concentration to produce short-circuit phenomenon, and thus stable electric discharge machining can be carried out from the beginning. And when the main working by the working electrode 13 reaches approximately a stationary condition, the lift drive mechanism 33 is operated to pull up the auxiliary electrode 23.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an improvement of an electric discharge machining apparatus, particularly a die-sinking electric discharge machining apparatus.

[Technical background and problem 1 Die-sinking electrical discharge machines have been widely used and are used in large numbers, and the machining shapes range from wide-area holes to small-diameter holes of about 0.5 mm. However, among these machining shapes, shapes that have a sharp tip but quickly become thicker, such as recess machining with a pointed inverted cone or inverted pyramid, are difficult to contact with the so-called surface of the electrode on the workpiece. At worst, there were problems. In other words, the electrode naturally has the same shape for such an inverted conical recess, and at the beginning of electrical discharge machining, the current density is often excessive, which can cause a short circuit between the electrode and the workpiece. This occurs frequently, causing a hunting operation on the electrode's vertical axis, which severely impairs the stability of machining, resulting in a state in which machining hardly progresses. As a countermeasure, the power supply device attached to this electrical discharge machine was operated to greatly extend the pulse pause time of the supplied pulsed power, thereby reducing the current density of electrical discharge machining at that point and stabilizing the machining state. However, since the machining is performed near the pointed tip of the inverted conical shape, the process progresses quickly and the changes are large, so adjustment and readjustment operations must be performed within a very short period of time, which is complicated and delicate, and requires a lot of skill. It required attention.

[Purpose of the Invention] This invention was devised in view of the above-mentioned problems, and it prevents the short-circuit phenomenon even in machining shapes and electrode shapes with poor surface contact conditions, enables stable electrical discharge machining, and is superior to conventional electrical discharge machining. The purpose of the present invention is to provide a die-sinking electrical discharge machine that does not require such complicated and delicate adjustment operations.

[Structure of the Invention] In order to achieve the above object, the present invention provides a discharge discharge having a structure in which an auxiliary electrode is provided in parallel with the original processing electrode and is provided with a lifting means separate from that for the processing electrode. It was used as a processing device.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 is a front view of the vicinity of the upper surface of a work table of a die sinking electric discharge machine to which the present invention is applied.

Near the bottom of the machining head (not shown) of the die-sinking electrical discharge machine (not shown) 1
There is a spindle 3 inside, and the lower end thereof is an electrode mounting unit 5. The electrode mounting unit 5 includes an indexing device 7, an electrode paralleling device M9, an electrode holder 11, and the like. The electrode holder 11 is equipped with a machining electrode 13 in the shape of an inverted cone with a sharp tip and a poor surface contact.
I am trying to form and process a recess with the following shapes.

Further, an auxiliary electrode unit 19 is provided adjacent to the electrode mounting unit 5. The auxiliary electrode unit 19 includes a base plate 21, an auxiliary electrode 23, and an auxiliary electrode 23 as shown in the figure.
As means for supporting and lifting the lifting spindle 25 and the auxiliary electrode 23, the lifting mechanism 33 includes a guide roller 27 for the spindle 25, a rubber roller 29 for lifting and lowering the spindle 25, a geared motor 31 for driving the rubber roller 29, etc. , a base plate 21 is attached to the lower part of the electrode mounting unit. A limit switch 35 is mounted on the lower surface of the base plate 21 near the spindle 25 to regulate the upper limit when the auxiliary electrode 23 is raised. The auxiliary electrode 23 has a disk shape with a flat lower end surface, and is prepared to generate electric discharge between it and an auxiliary workpiece 37 placed and fixed on the work table 15 below.

A machining tank 39 that can be raised and lowered is provided around the work table 15 and is filled with machining fluid, and the workpiece 17 is immersed in the machining fluid to a predetermined depth by raising the machining tank 39. There is.

Next, the operation of the above embodiment will be described.

Before starting electric discharge machining using the inverted conical machining electrode 13 with a pointed lower end, the auxiliary electrode 2 of the auxiliary electrode unit 19 is
3 is in contact with the auxiliary workpiece 37 surface and the machining electrode 13
The height is determined by operating the auxiliary electrode lifting/lowering drive mechanism 33 so that the height at which the electrode contacts the workpiece 17 matches the height. The machining tank 39 is raised and the machining liquid level is determined so that the workpiece 17 is immersed at a predetermined depth. This marks the start of electrical discharge machining, and electrical discharge begins simultaneously with the machining electrode 13 and the adjacent auxiliary electrode 23. Therefore, the machining current is divided between the two, and stable electric discharge machining can be carried out from the beginning without the excessive current density on the machining electrode 13 side that would cause a short-circuit phenomenon as in the prior art. Then, when the main machining using the machining electrode 13 reaches a substantially steady state, the lifting drive mechanism 33 is operated to lift up the auxiliary electrode 23 of the auxiliary electrode unit 19.

When the auxiliary electrode 23 is completely raised, the limit switch 35 is activated, the elevating drive mechanism 33 is stopped, and the auxiliary electrode 23 remains at that position.

In this way, stable machining can be performed from the beginning of electrical discharge machining using the machining electrode 13, and the delicate adjustment of the pulse power supply on the power supply device side, which is complicated and requires skill as in the past, is no longer necessary, making the machining work extremely easy and reliable. was realized, and machining efficiency was dramatically improved compared to conventional electrical discharge machining of such shapes using only machining electrodes.

This invention is not limited to the one embodiment described above, and various modifications are possible. For example, the auxiliary electrode lifting mechanism 33
It is also possible to simplify the operation by using a cylinder device or the like, or conversely, to make it more sophisticated so that it can be operated fully automatically. Further, the shape, material, etc. of the auxiliary electrode 23 can be changed as appropriate depending on the situation of the processing electrode, and the changing mechanism may also be a turret type.

Furthermore, the auxiliary electrode unit 1 is also used in conventional electrical discharge machines.
By preparing 9, it can be easily retrofitted and has a wide range of applications.

[Effects of the Invention] As is clear from the above, according to the apparatus of the present invention, even in electrical discharge machining of machined shapes and electrode shapes under so-called poor surface contact conditions, the current density becomes excessive and a short circuit phenomenon occurs. The result was an electrical discharge machining device that was able to perform extremely easy, reliable and stable machining from the beginning without any trouble, and did not require the complicated and delicate adjustment operations that were required in the past, with much higher work efficiency. .

[Brief explanation of the drawing]

FIG. 1 is a front view including a partial cross section of a main part of an electric discharge machine according to an embodiment of the present invention. Explanation of main drawing symbols

Claims (1)

[Claims] An electric discharge machining apparatus characterized in that an auxiliary electrode is provided in parallel in the vicinity of the original machining electrode, and is provided with a lifting means separate from that for the machining electrode.