JPH02185316A - Electric discharge machining device - Google Patents

Abstract

PURPOSE:To effectively perform electric discharge machining on not only metal but also a workpiece having high resistance by connecting a circuit to change discharge circuit characteristics from vibration into attenuation according to the resistance value of the work piece to the discharge circuit formed of a main electrode and the workpiece. CONSTITUTION:In machining a metallic workpiece 10 having resistance value 10<-5> - 10<-4>OMEGAcm, the switches S1, S2, S3 of a characteristics establishing circuit 14 are opened to minimize the resistance value of a variable resistance Re, and a discharge circuit therefore turns into a vibration circuit to make a d. c. voltage applied to the same circuit generate discharge. In machining the workpiece 10 having high resistance value of 10<-1> - 10<0>OMEGAcm, the switches S1, S2, S3 are closed to decrease a capacity component and to increase an inductance compo nent and further to minimize the variable resistance Re. A discharge circuit therefore keep vibration circuit characteristics even if connected with a high resistance, and the application of d. c. current generates the discharge. In the case where, even when the workpiece 10 is high in resistance, and the switches S1, S2, S3 have been closed, the discharge circuit does not change into vibration circuit characteristics to keep attenuation circuit characteristics, the switches S1, S2 are closed to decrease a apacity component for establishing the attenuation circuit characteristics in the discharge circuit. When the voltage of a d. c. source 12 is raised, the peak value of a discharge current becomes higher and the width of pulse narrower.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an electrical discharge machining apparatus that performs machining by generating electrical discharge between a workpiece and a main electrode.

(Prior Art) FIG. 4 is a configuration diagram of a wire electrical discharge machining apparatus, in which a wire electrode 2 is arranged with respect to a workpiece 1. and,
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 lo-5 to 10-'Ω. On the other hand, the discharge circuit in electrical discharge machining, that is, the equivalent circuit seen from the DC power supply 3, is a series circuit of inductance, resistance, and capacitor due to discharge gap resistance, discharge gap capacity, 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. In other words, the combined inductance in such a discharge circuit is LO.The combined resistance is Ro.
1 If the combined capacity is co, then the following formula holds.O Then, when calculating the discharge current l from this formula, iwpIA
, εD11+p, A, εp, t, where, and A 1 + A 2 are integral constants, which are determined by the initial conditions.

Depending on the sign of the radical of p++ pz above, 1) I
I p2 can be a real number or a complex number, and the radical sign is ``
0'', p1+1'2 become equal real numbers. The discharge current l will differ depending on these three cases.

However, as mentioned above, when performing electric discharge machining on the metal workpiece 1, the electric discharge circuit is a vibration circuit, so Rg < 2 Lo/C.

The circuit constants are set to . However, the discharge current i 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 l shown in FIG. 5 are cut off.

However, when using a discharge circuit with the above configuration, a high resistance value to-
When machining a workpiece, such as a ceramic, on the order of ~100Ω (up to), the resistance R0 in the discharge circuit increases and the discharge circuit changes from an oscillating circuit to a damping circuit Ro > 2JT:
τ]γ'7. Therefore, the peak value of the discharge current i decreases significantly as shown in Figure 6.As a result, an abnormal discharge occurs, or a short circuit occurs, causing the discharge to decrease. Processing was impossible.

(Problems to be Solved by the Invention) As described above, when electrical discharge machining is attempted on a workpiece with high resistance, abnormal electrical discharge occurs, which not only reduces the efficiency of electrical discharge machining, but also makes electrical discharge machining impossible. was.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electric discharge machining apparatus that can efficiently perform electric discharge machining not only on ordinary metals but also on high-resistance workpieces.

[Structure of the Invention] (Means for Solving the Problems) The present invention applies a voltage between the main electrode and the workpiece to generate an electric discharge between the main electrode and the workpiece to process the workpiece. In electrical discharge machining equipment for machining objects, a characteristic setting circuit is connected to a discharge circuit formed from a main electrode, a workpiece, etc., and sets the characteristics of the discharge circuit from vibration to damping according to the resistance value of the workpiece. This is an electric discharge machining device that aims to achieve its purpose.

(Function) By providing such a means, the characteristics of the discharge circuit are set to oscillation or damping by the characteristic setting circuit according to the resistance of the workpiece, and even when a high resistance workpiece is connected, for example. The discharge circuit is set from a damping circuit to an oscillating circuit.

However, electric discharge occurs between the workpiece and the wire electrode, and machining is performed.

(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.

In the figure, 10 is a workpiece. This workpiece 10
A wire electrode 11 is placed in the processing area. A DC power supply 12 is connected between the workpiece 10 and the wire electrode 11 via a lead wire 13, with the workpiece 10 serving as a positive terminal (+). Furthermore, the wire electrode 11
A characteristic setting circuit 14 is connected between the DC power supply 12 and the DC power supply 12 .

This characteristic setting circuit 14 connects the DC power supply 12 to the workpiece 1.
0. Wire electrode 11. It has a function of setting the characteristics of the discharge circuit that returns to the DC power supply 12 through the lead wire 13 to vibration or damping. Specifically, a variable resistor Re, a series circuit of a capacitor C1 and a switch S, a series circuit of a capacitor C2 and a switch S2, and a series circuit of a coil Le and a switch S3 are connected in parallel.

By the way, the equivalent circuit of such a device is as shown in FIG. Here, the DC power supply 12 is actually a capacitor Ca.
2, the DC power source 12 is shown as a capacitor Ca. Therefore, the equivalent circuit of the discharge circuit is the lead wire 13.
The lead wire resistance R1 is the inductance L of the lead wire 13.
1. Contact resistance between lead wire 13 and wire electrode 11Resistance in the gap between workpiece 10 and wire electrode 11 2.Discharge gear capacity in the same gap 11cg
, the resistor Ra of the workpiece 10 and the characteristic setting circuit 14 are connected in series.

Next, the operation of the apparatus configured as described above will be explained.

First, when electrical discharge machining is performed on a metal workpiece 10 having a resistance value on the order of 10-5 to 10-4 ΩC, each switch S, , S2+S3 of the characteristic setting circuit 14 is opened, and the resistance value of the variable resistor Re is set to the minimum value. Set to .

In this state, the discharge circuit becomes an oscillating circuit with RLI<2%/"mouth portion η3. However, due to the application of DC voltage and the movement of the wire electrode 11, the workpiece 10 and the wire electrode 11 are When the gap becomes a predetermined distance, the workpiece 10
Electric discharge occurs between the wire electrode 11 and the workpiece 1
o is processed.

Next, when the workpiece 10 has a high resistance on the order of 10-1 to 100 Ω, for example, is made of ceramic, each switch S1 of the characteristic setting circuit 14. S2. S3 is closed.

As a result, the capacitance component co in the discharge circuit becomes smaller, and the inductance component Lo is set larger. Note that the variable resistor Re has a minimum resistance value. However, even though a high resistance is connected, the discharge circuit does not become a damping circuit but is set to have the characteristics of an oscillating circuit. In this way, a discharge is generated between the workpiece 10 and the wire electrode 11 due to the application of the DC voltage, and the high resistance workpiece 10
is processed.

Further, when the workpiece 10 has a high resistance, even if the switches s, l, s21, and s3 are closed as described above, the discharge circuit does not change to the characteristics of the oscillating circuit, but remains the characteristic of the damping circuit, and each switch S1. By closing S2, the capacitance component co is reduced and set as an attenuation circuit. And capacitor C
Set the DC voltage (■) applied to a high. This results in
As shown in FIG. 3, the discharge current i has a higher peak value and a shorter pulse width. Specifically, the discharge current l
Compared to the discharge current shown in FIG. 6, the peak value is about 10 times larger and the pulse width is about 1/15th of that of the discharge current shown in FIG.

However, with such a discharge current l, the workpiece 1
Electric discharge occurs between the wire electrode 11 and the wire electrode 11, and the workpiece 10 is machined. In other words, the discharge current 1 is sufficient for electrical discharge machining the high-resistance liquid-filled object 10.

In this way, in the above embodiment, the characteristic setting circuit 14 sets the characteristic of the discharge circuit to vibration or damping according to the resistance of the workpiece 10, so that the resistance value is lo-
High resistance 10- as well as metals on the order of 5-100Ω
A workpiece 10 made of ceramic or the like with a mark of 1 to 100 Ω can also be processed. In addition, in the case of high resistance, it is possible to obtain a discharge current l with a high peak value and a short pulse width by applying a high voltage even without changing the oscillating circuit. Even if the resistance is as high as -+00Ω low order, discharge can be generated and machining can be performed.

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, the characteristic setting circuit 14 does not have the configuration of the above embodiment, but may have any other configuration as long as it is a circuit that changes the inductance component, resistance component, and capacitance component of the discharge circuit. Further, in the above 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 die-sinking electrical discharge machining.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide an electrical discharge machining apparatus that can efficiently perform electrical discharge machining not only for ordinary electrical discharge machining but also for high-resistance workpieces.

[Brief explanation of the drawing]

1 to 3 are diagrams for explaining one embodiment of the electrical discharge machining apparatus according to the present invention, in which FIG. 1 is a configuration diagram, FIG. 2 is an equivalent circuit diagram, and FIG. 3 is a discharge current FIGS. 4 to 6 are diagrams for explaining the prior art. 10... Workpiece, 11... Wire electrode, 12...
・DC power supply, 13... Lead wire, 14... Characteristic setting circuit, Rc-RJ variable resistance cl, c2-: r capacitor,
S1+S2. S3...switch, Lo...coil,
Ca...Capacitor, R...Lead wire resistance, L...
・Lead wire inductance, "l... Contact resistance of electrode, r2... Discharge gap resistance, Cg... Discharge gap capacity, Ra... Resistance of workpiece. Applicant's representative Patent attorney Takehiko Suzue Diagram Monument (2S) Figure

Claims (1)

[Claims] In an electric discharge machining apparatus that applies a voltage between a main electrode and a workpiece to generate a discharge between the main electrode and the workpiece to machine the workpiece, the main electrode and the workpiece are An electric discharge machining apparatus characterized in that a characteristic setting circuit is connected to a discharge circuit formed from a workpiece or the like for setting the characteristic of the discharge circuit from vibration to damping according to the resistance value of the workpiece.