JPS605412B2 - Electric discharge machining equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of an electrical discharge machining apparatus that utilizes charging and discharging of a capacitor.

Conventional electric discharge machining apparatuses have the disadvantage that the impedance of the discharge circuit is high and the efficiency is poor, and that the peak value lp of the discharge flow cannot be set high.

The present invention was proposed in view of this drawback, and a capacitor is provided at a processing surface near a processing gap, and a high-frequency voltage pulse is generated by switching on and off a DC power source as a power source for charging the capacitor. A pulse power source that outputs is provided, a cable is connected between the pulse power source and the capacitor, and the voltage is set to a high voltage that allows the capacitor to be charged to a discharge voltage by multiple pulses of high-frequency voltage pulses supplied from the pulse power source. It is characterized by what it did.

The present invention will be explained below with reference to one embodiment. In FIG. 1, 1 is an input terminal of a commercial AC power source, and 2 is a rectifier, which directly rectifies the AC to obtain a DC power.

3 and 4 are switches (transistors) that control the on/off switching of the DC output, and 5 is an on/off switch for the switches 3 and 4.
A transformer that transforms the high frequency alternating current generated by turning off, 6
, 7 is a rectifier that full-wave rectifies the output of the transformer to produce a DC pulse. 8 is a high frequency oscillator, and the oscillated high frequency is applied to the switches 3 and 4 through the transformer 9 for control.

Usually, the oscillation frequency used is IKHZ to 8MH2. 1
0 and 11 are interrupt control switches (thyristors) inserted into the control circuits of switches 3 and 4, and are controlled on/off by an oscillator 12 that oscillates interrupt control pulses.

14 is an electrode (wire electrode in case of wire cut), 1
Reference numeral 5 denotes a workpiece, which faces each other on a processing table within the processing tank 15 to form a processing gap.

A capacitor 17 is connected in parallel to the machining gap in the machining tank, and machining is performed by this electric discharge.

A cable 18 connects the power source and the machine part, and connects the output end of the high frequency voltage pulse power source and the machining gap. As the cable, coaxial cables, feeder wires, etc. with low high frequency loss are suitable, but others can also be used. In addition to using the electrode 14 as the positive electrode and the workpiece 15 as the negative electrode as shown in the figure, the troughs that are energized may be connected in the opposite manner depending on the combination of materials, processing conditions, etc. The high frequency voltage pulse is rectified by a rectifier 2,
It is supplied from an AC-DC-HF-Pulse inverter consisting of switches 3, 4, transformer 5, rectifiers 6, 7, etc.

The switch 34 outputs the inverter from IKH2 to the oscillator 8.
The desired high-frequency pulse can be easily generated by turning on and off at a high frequency similar to that of insect MH2, and the responsiveness is high at high frequencies. Interruption control by the oscillator 12 can be easily controlled at any frequency and interval. Even when oscillation is stopped, output pulses can be blocked with high density. The high frequency is transformed to an appropriate voltage by the transformer 5, but the output voltage is normally about twice the discharge voltage or more, for example, so that the discharge capacitor 17 is charged to the discharge voltage with multiple pulses. 50~
It is controlled to output 5000y. In electrical discharge machining, the capacitor 17 is charged by pulses from the power source, and is charged to a discharge voltage with multiple pulses, and the electrode 14 and the workpiece 1 are
Machining is performed while the capacitor is repeatedly charged and discharged by the pulses. When charging a capacitor, the supply pulse is of high voltage and frequency, so it can be charged rapidly and the number of repetitions of discharge can be increased. The discharge capacitor 17 is disposed near the machining gap, connected with a connecting lead wire of the shortest length, and discharges, so that the peak value of the discharge stream can be increased and discharge machining can be performed with high energy efficiency. The capacitor 17 has the function of integrating and accumulating pulse power from a pulse power source installed far away in the processing part through a cable 18, and collects a predetermined pulse to generate a discharge.Since the discharge is performed through a short lead wire, efficiency is improved. High discharge is possible, and even if the pulse power source is installed far away and energy is supplied via a long cable 18, processing can be performed without affecting the discharge. By selecting a capacitor with a capacity that corresponds to the desired machining, the peak value of the discharge can be made arbitrarily high, and there is no power loss, waveform distortion is reduced, and machining can be performed at high speed. The pulses supplied from the pulse power supply via the cable 18 are generated by an oscillator 8 that oscillates at IKHZ to QMHZ by turning switches 3 and 4 on and off, and the high frequency alternating current is generated by a transformer 5 and a rectifier 7.
It is a high frequency pulse rectified by 7 in the pulse.

n. S=1 to 100 peaks, interval T. ff. s=0.5~
A pulse train of about 50 peaks is supplied. Of course, especially in rough machining etc., even larger pulse depth m. A pulse with s may also be provided. The discharge capacitor 7 is charged and discharged by a plurality of these pulse train pulses, and this charging and discharging is repeated.Since the discharge capacitor 7 is charged by the pulses, the discharge is caused by an arc.
It is stable with fewer occurrences of short circuits, and since a high-frequency voltage pulse power source is used, the impedance of the capacitor is reduced, so the charging time of the capacitor is shortened, and efficient high-speed electrical discharge machining can be performed. Further, the pulse train includes the output pulses of the pulse generator 12, the pulse center plate, and the interval.
The rectifier switches 10 and 11 are turned on by the pulse of ff.
Since it is turned off, it is controlled intermittently, 7 as shown in Figure 3. nG and 7off. The pulse train with s is on pulse 7. An interrupted pulse train is generated that lasts n times and occurs again after a pause of off-pulse 7M. The middle part of the pulse generated by the pulse oscillator 12. n, the interval ↑off is about 1~S~lows, and is set and controlled according to the machining conditions and machining state,
↑ when the processing condition is poor. Make n small and 7M large. 7.

n determines the number of pulse trains, and 7M determines the interruption control time. The machining gas, gas, etc. in the machining gap, which is generated and increases in concentration due to electric discharge, is removed and purified during the interruption control of this machine, and the electric discharge by the next pulse train is stabilized, so that stable machining can be repeated. Of course, this interruption control may not be necessary in some cases, such as when performing reciprocating control in which the electrode 14 is raised when machining debris accumulates to widen the gap for cleaning. When a short circuit occurs in the machining gap, the gap voltage decreases, and this is caused by the Schmidt-like discrimination circuit 1.
3, and in this case, the oscillation of the oscillator 8 is stopped and the supply of pulses from the power supply is stopped.

However, even if such a discrimination circuit is not provided, each voltage pulse does not have enough power to perform machining, so there is no need to worry about unnecessarily damaging the surface to be machined due to a short circuit. In addition, the power supply voltage is set to a value higher than the normal machining voltage, and if for some reason the gap widens and discharge does not occur, the capacitor 17 will be charged to a high voltage.
Although this must be prevented, even if the machining gap rises above a predetermined voltage, it will be determined by the discrimination circuit 13,
Control is performed to stop the oscillator 8 and stop the supply of machining pulses. Therefore, even if the supply pulse voltage is set to a high voltage for rapid charging of the capacitor 17, the charging pressure of the capacitor is prevented from increasing abnormally, and the machined surface roughness and machining accuracy deteriorate due to high voltage discharge. can be prevented. It should be noted that this power pulse stop control is also controlled by the high frequency oscillator 8, so it can be controlled with high response and stable control can be achieved.
Of course, the control to stop the pulse output of the pulse power source is the same whether the oscillator 12 is controlled or a switch is inserted on the power output side and controlled. Figure 2 shows another embodiment of the pulse power supply circuit, in which the L DC power supply 19 is turned on and off by a switch 20, the pulse is transformed by a transformer 21, the output AC is rectified by a half-wave rectifier 22, and a DC pulse is output. It was designed to do so.

The same symbols as in FIG. 1 indicate the same parts. 23 is a high-frequency pulse oscillator, 24 is an interruption control pulse oscillator, and by combining both signal pulses with an AND gate 25 and controlling a switch 20, a pulse train pulse as shown in FIG. 3 is generated. be.

Processing control and processing effects are the same as in the case of FIG. By using a step-up transformer for the transformer 21, the power supply 1
9 can be set to a low voltage, and the switch 20 circuit can be controlled at a low voltage. This also results in high efficiency, a high current peak value, and high performance machining with low machined surface roughness.

For example, when processing S5 material with a subordinate capacitor type processing machine, the processing speed is 0.0 when the processing surface roughness is 5 degrees Rmax.
2ta'mjn was the highest, but when the present invention was used, a processing speed of about 0.12 min/min was obtained with the same surface roughness. Also, if the surface roughness is 10 French Rmax, conventionally it is 0.1~
0.15 ta'mjn is about 1 ta'min in the present invention.
was obtained, and a processing speed of approximately 1 ping was obtained. The power supply that supplies pulse energy is a high-frequency AC obtained by rectifying commercial AC as described above, generating high-frequency AC or pulses by controlling the on/off of a switch, and transforming it to a predetermined voltage with a transformer. Since it is an AC-DC inverter that rectifies DC pulses to create DC pulses, the transformer in particular can be miniaturized, the entire power supply can be configured extremely compact, and the response at high frequencies has improved. can be easily obtained, but the pulse power source is not limited to this embodiment; for example, pulses can be generated in the same way by turning a DC voltage source on and off with a switch and controlling this switch with a high-frequency pulser. .

In this case, in order to prevent high voltage from being applied to the machining gap when the switch is damaged,
Voltage-resistance changeable bodies such as diodes and varistors,
It is necessary to connect an inductance circuit and other voltage rise prevention circuits. As for the generated pulses, by controlling the interruption of the high-frequency pulse train as described above, it is possible to give a pause to the repetitive discharge, thereby allowing removal and cleaning of machining shoulders, stopping arcs and short circuits, and achieving stable machining. During machining, a discharge capacitor is installed near the machining gap, and pulse energy is supplied to the capacitor to charge and discharge, so the peak value of the discharge current can be high and machining can be performed with high energy efficiency. The charging pulses are high voltage and high frequency so that the capacitor can be rapidly charged to a predetermined voltage in multiple pulses, so the impedance of the capacitor is lowered, the charging speed is increased, the number of discharge repetitions is increased, and the machining speed is increased. Even with rapid charging, the supply of energy is pulsed, so the occurrence of arcs, etc. can be reduced and stabilized, and by increasing the number of repeated discharges, the machining speed is 10 to 2 times faster than the conventional one. “It can also increase noise. It is especially effective in finishing.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of one embodiment of the present invention, FIG. 2 is a circuit diagram of another embodiment, and FIG. 3 is a pulse waveform diagram of a pulse power source. 1 is an AC power supply terminal, 2 is a rectifier, 3 and 4 are switches, 5 is a transformer, 6 and 7 are rectifiers, 8 is an oscillator, 9 is a transformer, 10 and 11 are switches, 12 is an oscillator, i3 is a discrimination circuit, and 14 is An electrode, 15 a workpiece, 16 a processing tank,
17 is a capacitor, 18 is a cable, 19 is a DC power supply,
2 river switches, 21 is a transformer, 22 is a rectifier, 23
, 24 is an oscillator, and 25 is a gate gate. Oh Geno 2Ja Oh Carp

Claims (1)

[Scope of Claims] 1. In an electric discharge machining device that performs machining by charging and discharging a capacitor connected in parallel to a machining gap between an electrode and a workpiece, the capacitor is provided in a part of the processing machine near the machining gap, and the capacitor is A pulse power source that outputs high-frequency voltage pulses by turning on and off a DC power source is provided as a charging power source, and a cable is connected between the pulse power source and the capacitor, and the pulse power source is supplied from the pulse power source. An electric discharge machining apparatus characterized in that the voltage value is set to such a value that the capacitor can be charged to a discharge voltage with a plurality of high-frequency voltage pulses. 2. The electric discharge machining apparatus according to claim 1, wherein the output voltage pulse of the pulse power source is set to a voltage value that is at least twice the discharge voltage of the capacitor. 3. The electric discharge machining apparatus according to claim 1, wherein the pulse power source outputs a high frequency voltage pulse having a frequency of 1 KHz to 5 MHz. 4. The electric discharge machining apparatus according to claim 1, wherein the pulse power source outputs high-frequency voltage pulses having a frequency of 1 KHz to 5 MHz, with interruptions controlled at predetermined intervals. 5. The electric discharge machining apparatus according to claim 1, wherein the frequency or interruption control interval of the pulse power source is controlled to change depending on machining conditions or the state of a machining gap. 6 The pulse power supply converts the DC obtained by rectifying the commercial AC into a high frequency pulse or high frequency AC HF by controlling the high frequency on/off of the switch, and further transforms it with a transformer and outputs the rectified pulse pulse. The electric discharge machining apparatus according to claim 1, characterized in that it is comprised of an AC-DC-HF-Pulse inverter.