JPH02185314A - Electric discharge machining - Google Patents

Abstract

PURPOSE:To effectively perform electric discharge machining on even a workpiece having high resistance by, in the case of the workpiece having high resistance, making an electric circuit which starts from a d. c. source and returns to the same source through a workpiece and a main discharge electrode function as an attenuation circuit. CONSTITUTION:A d. c. source 12 is connected through a lead wire 13 between a work piece 10 and a wire electrode 11 with the workpiece 10 set as a positive pole (+). An equivalent circuit of a discharge circuit is composed of resistance R of the lead wire 13, an inductance L, a contact resistance r1 between the lead wire 13 and the wire electrode 11, a gap resistance r2 between the workpiece 10 and the wire electrode 11, discharge gap capacity Cg and a resistance Ra of the workpiece 10, which are mutually connected in series, with the d, c source 12 used as a capacitor Ca, and a discharge current i is expressed by the equation of V=Lodi/dt+Roi+1/Cintegral idt, where Lo, Ro, Co and V denote combined inductance, combined resistance, combined capacity and applied voltage respectively. When the workpiece 10 is changed for one having high resistance, the circuit becomes an attenuation circuit, but when the capacity of the capacitor C0 is reduced and the applied d. c. voltage is raised, the peak value of the discharge current i becomes higher and the width of pulse shorter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an electric discharge machining method in which machining is performed by generating electric discharge between a workpiece and a main electrode.

(Prior art) FIG. 4 is a diagram showing wire electrical discharge machining, in which a workpiece 1
A wire electrode 2 is arranged against. A DC power source 3 is connected between the workpiece 1 and the wire electrode 2, with the workpiece 1 as the positive electrode (+). As a result, when the wire electrode 2 reaches a predetermined distance from the workpiece 1, electric discharge occurs between the workpiece 1 and the wire electrode 2, and the workpiece 1 is machined.

By the way, in such electrical discharge machining, metal is processed as the workpiece 1. The resistance value of this metal is on the order of 10-5 to 10-4 ohms. On the other hand, a discharge circuit in electrical discharge machining, that is, both circuits as seen from the DC power supply 3, is a series circuit of an inductance, a resistor, and a capacitor due to discharge gap resistance, discharge gap capacitance, and the like. This discharge circuit is formed into a vibrating circuit so that the metal workpiece 1 having the above-mentioned resistance value can be machined with the highest efficiency. However, the discharge current oscillates over time as shown in FIG. Note that in actual electrical discharge machining, the second half wave and subsequent waves of the discharge current shown in FIG. 5 are cut off.

However, using the discharge circuit with the above configuration, a high resistance value of 10-
When processing the workpiece 1, for example, ceramic, on the order of '-100Ω■, the resistance in the discharge circuit becomes large and the discharge circuit changes from an oscillating circuit to a damping circuit. Therefore, the peak value of the discharge current is greatly reduced as shown in FIG.

For this reason, abnormal electrical discharge occurs or short circuit occurs, making electrical discharge machining impossible.

(Problem WJ to be solved by the invention) As described above, when attempting to perform electric discharge machining on a workpiece with high resistance, abnormal electric discharge occurs, which not only reduces the efficiency of electric discharge machining, but also makes electric discharge machining impossible. It had become.

Therefore, an object of the present invention is to provide an electric discharge machining method that can efficiently perform electric discharge machining even on a workpiece having a high resistance.

[Structure of the invention] (Means and effects for solving the problem) The present invention applies a voltage from a DC power source between the main electrode and the workpiece to generate an electric discharge between the main electrode and the workpiece. In the electric discharge machining method that processes the workpiece by generating electrical discharge, when the workpiece has high resistance, the electric circuit from the DC power source, through the workpiece and main discharge electrode, and returning to the DC power source is set as an attenuation circuit. This is an electric discharge machining method.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of a wire electrical discharge machining apparatus to which the method of the present invention is applied. In the figure, numeral 10 indicates a workpiece having a high resistance of 10 -3 Ω■ or more, and is made of, for example, ceramic. A wire electrode 11 is arranged in the processing portion of the workpiece 10. A DC power supply 12 is connected between the workpiece 10 and the wire electrode 11 to connect the workpiece 10 to the positive electrode (
+) is connected via a lead wire 13. By the way, the equivalent circuit of such a device is as shown in FIG.

Here, since the DC power supply 12 actually applies a DC voltage to the capacitor Ca and uses the charging voltage V, the second
In the figure, the DC power supply 12 is shown as a capacitor Ca. Therefore, the equivalent circuit of the discharge circuit is: the lead wire resistance R1 of the lead wire 13, the inductance L1 of the lead wire 13, the contact resistance rl between the lead wire 13 and the wire electrode 11, and the distance between the workpiece 10 and the wire electrode 11. Resistance in the gap of “
2. The discharge gap capacitance Cg in the same gap and the resistor Ra of the resistor 10 are connected in series. Now, in the discharge circuit as described above, the capacitance component, for example, the capacitance of the capacitor Ca, is set to be small, and the DC voltage applied to this capacitor Ca is set to be high.

Here, the discharge current l flowing through the above equivalent circuit is determined. Therefore, if the combined inductance in the equivalent circuit is L01, the combined resistance is R, and the % combined capacitance is C, the following equation holds true.

Then, when calculating the discharge current i from this formula, i = p,
Atε#1'+psAtεp,twhere, A I + A 2 is an integration constant, which is determined by the initial conditions.

Depending on the sign of the radical in 1)++i)2 above, p1+
p2 can be a real number or a complex number, and the radical inside is "0"
Then ul+92 becomes equal real numbers. The discharge current i will differ depending on these three cases. However, as mentioned above, when electrical discharge machining is performed on a metal workpiece, the electrical discharge circuit is connected to a vibration circuit, so the circuit constant is set to Ru<2F[77]. However, the workpiece 10
If the discharge circuit is changed to a high resistance, the discharge circuit becomes an attenuation circuit, but in this circuit, by reducing the capacitance component co, L□/
Co is increasing.

That is, when processing a high-resistance workpiece 10, the capacitance component co is made small as described above, and the DC voltage V applied to the capacitor Ca is set high. As a result, the discharge current i has a higher peak value and a shorter pulse width, as shown in FIG. Specifically, the peak value of the discharge current i is about 10 times that of the discharge ff1ffi flow shown in FIG. 6, and the pulse width is about 1/15. However, with such a discharge current i, a discharge occurs between the workpiece 10 and the wire electrode 11, and the workpiece 10 is machined. In other words, the discharge current i is sufficient for electrical discharge machining the workpiece 10 having high resistance.

In this way, in the above embodiment, when the workpiece 10 has a high resistance, the capacitance component C is made small and the DC voltage V applied between the workpiece 10 and the wire electrode 11 is increased. It is possible to obtain a discharge current i with a high peak value and a short pulse width, so that the workpiece 10
Even if the resistance is high, on the order of 0-1 to 100 ohms, it is possible to process it by generating electric discharge.

Note that the present invention is not limited to the above-mentioned embodiment, and may be modified without departing from the spirit thereof. For example, in the above-mentioned embodiment, a case where the present invention is applied to wire electrical discharge machining has been described, but the present invention is not limited to wire electrical discharge machining, but can also be applied to electrolytic electrical discharge machining and electrical discharge machining using flat plate electrodes.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to provide an electric discharge machining method that can efficiently perform electric discharge machining even on a workpiece having a high resistance.

[Brief explanation of the drawing]

1 to 3 are diagrams for explaining the electrical discharge machining method according to the present invention, in which FIG. 1 is a configuration diagram of a wire electrical discharge machining device to which the method is applied, and FIG. 2 is an equivalent diagram of the same device. The circuit diagram, FIG. 3, is a diagram showing the discharge current in the same device, and FIGS. 4 to 6 are diagrams for explaining the prior art. 10... Workpiece, 11... Wire electrode, 12...
・DC power supply, 13... Lead wire, Ca... Capacitor, R... Lead wire resistance, L... Lead wire inductance, "1... Contact resistance of electrode, "2... Discharge gap Resistance, Cg...discharge gap capacity, Ra...
Workpiece resistance. Applicant's Representative Patent Attorney Takehiko Suzue No. 1 Fig. Fig. Karima () Is) Fig.

Claims (1)

[Claims] In the electric discharge machining method, the workpiece is machined by applying a voltage from a DC power source between the main electrode and the workpiece to generate an electric discharge between the main electrode and the workpiece. An electrical discharge machining method characterized in that when an object has a high resistance, an electric circuit that returns from the DC power source to the DC power source via the workpiece and the main discharge electrode is set as an attenuation circuit.