JPS5827054B2 - Electric discharge machining equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrical discharge machining (including electrolytic erosion machining) in which a machining pulse is repeatedly applied to a machining gap between an electrode and a workpiece to produce a machining process. The purpose of this is to accurately detect and determine whether the machining gap is good or bad, that is, whether the change in the state of the machining gap is good or bad.

In electrical discharge machining, machining pulses are controlled according to the gap state (discharge state), flow rate of machining fluid, electrical conductivity are controlled,
When machining debris accumulates, it is necessary to optimally perform electrode vibration, cleaning by pulling up the electrode, servo control to make the gap length follow machining, etc.

Conventionally, in order to detect the state of the machining gap, the discharge state, the quality of the discharge, etc., changes in the voltage, current, impedance, etc. of the gap to which the machining pulse is applied are detected and determined.

Signal detection includes methods for detecting average voltage and current, and methods for detecting repeatedly supplied pulses and changes in voltage and current caused by these pulses in a pulse-like manner.

The former method of detecting average signals does not allow for quick state determination and quick response control.

In the latter case, since pulses are digitally detected and discriminated, it is possible to respond quickly to changes, thereby increasing the machining effect, but the machining pulses are usually controlled to change the pulse width etc. in response to changes in the gap condition. In addition, the machining pulses are set and controlled to the optimal conditions according to the target machining, and detection using these machining pulses, the state of the machining gap when the machining pulse is applied, and the waveform state are detected as voltage and current changes as signals. death,
Even if it is determined, it cannot be determined accurately.

In other words, accurate discrimination cannot actually be made unless changes in the applied machining pulse are also added to the signal.

Therefore, the present invention aims to increase the peak value (Ip) for easy detection and discrimination.
The inspection pulse with the selected and set pulse width (τOn) is incorporated into the machining pulse train and supplied to the machining gap, and the gap condition is inspected and detected by the constant set inspection pulse. It is characterized by the fact that

An embodiment of the present invention will be explained below with reference to the drawings.

Reference numerals 1 and 2 denote an electrode and a workpiece, which face each other and form a machining gap.

Reference numeral 3 denotes a voltage source for supplying machining power, and 4 a switching element such as a transistor, which is connected in series with the voltage source 3 and connected to the machining gap, and generates and supplies machining pulses by switching it on and off.

5 is a pulser that generates and applies switch control pulses to the switch 4. Although an independent oscillator may be used in some cases, it is also a vertical oscillator whose pulse width, rest period, frequency, etc. change in response to detection signals such as voltage and current in the machining gap. Oscillators may also be used.

Further, a conversion circuit that converts the gap detection signal into a pulse may be used.

6 is a voltage source for testing, and 7 is a switch, which is turned on and off under the control of a pulser 8 to generate testing pulses.

The peak value and pulse width of the test pulse are set so that the test for detection and discrimination is easy, that is, the peak value (Ip) is
by the voltage and also by the pulse width (τ.

n) is selectively set by the pulser 8.

The peak value (Ip) is set to 20OA or less, preferably about IOA, and the pulse width (τon) is set to about 5 to 20 μs.

Reference numeral 9 denotes an AND gate circuit that incorporates the inspection pulse into the processing pulse train.
By inverting and combining the output pulses at the knot gate 10, the inspection pulse can be incorporated into the machining pulse train when there is no machining pulse, that is, when the machining pulse is at rest, or when the machining pulse is interrupted and the machining pulse is at rest. An inspection pulse is incorporated so as to be applied to the machining gap, and the state of the machining gap is determined while the machining pulse is not applied.

11 is a resistor that detects the voltage signal in the gap, and 12 is a detection signal discrimination device, which is controlled by the pulser 8 and performs accurate inspection by synchronously discriminating the detection signal when the inspection pulse is applied to the gap. It operates to do this.

The state of the machining gap is inspected by applying a test pulse of a predetermined size, detecting the gap voltage, and determining the detection signal, so the applied test pulse is always constant; , detects and discriminates signals that change in response to changes in the gap state, so the accuracy of detection and discrimination is extremely high.Moreover, the peak value (Ip) and pulse width (τon) of the detection pulse can be inspected. It is easy to carry out and is set to the optimum value for the inspection, which also facilitates the inspection and improves the accuracy of the inspection.

The inspection pulses are generated at predetermined time intervals or at time intervals depending on the machining status of the gap, but the number of generated pulses is not limited to one pulse, and multiple pulses may be generated and supplied in succession. Often, the generation interval, pulses, etc. of this test pulse can be arbitrarily generated by selecting and setting the pulser 8, and the settings are controlled so that optimal testing can be performed at all times.

Further, the signal detected from the machining gap by applying this inspection pulse may be a current, impedance, high frequency, etc., and not only during the continuation of the inspection pulse, but also the signal immediately after the inspection pulse has stopped, such as voltage, current, resistance, etc. It is also possible to detect the impedance, their vibration state, or their change state, and the detection circuit can be configured and used as appropriate.

The detection signal is determined based on its magnitude, smallness, level, presence or absence, and composite determination to determine whether the discharge state and machining state are good or bad.

By detecting and determining the state of the machining gap using inspection pulses as described above, it is possible to more accurately detect and inspect changes in the state of the machining gap and whether the gap is good or bad, compared to conventional detection and discrimination using machining pulses.

Then, using this detection discrimination output as a signal, if you use this signal to control, for example, gap servo, follow-up control, gap cleaning by reciprocating control, processing pulse width, pause, duty factor, etc., these controls will always be performed. If the process is carried out optimally, stable machining can be performed under the optimal conditions, and machining effects such as machining speed, machining efficiency, and machining accuracy can be significantly improved.

[Brief explanation of the drawing]

The drawing is a circuit configuration diagram of an embodiment of the present invention. 1 is an electrode, 2 is a workpiece, 3 is a processing power source, 4 is a switch, 5 is a pulser, 6 is an inspection power source, 7 is a switch, 8 is a pulser, 9 is an AND gate, 10 is a not gate, 11 is a voltage The detection resistor 12 is a discrimination device.

Claims (1)

[Scope of Claims] 1. In electric discharge machining in which machining is performed by repeatedly performing pulse discharge using machining pulses supplied from a machining pulse power source into the gap between an electrode and a workpiece facing each other, a peak value set separately from the machining pulse power source. a pulse generator for generating an inspection pulse having a pulse width of , and a circuit for incorporating the output inspection pulse into the processing pulse train and supplying the processing pulse to the processing gap; 1. An electric discharge machining apparatus characterized in that a discriminating device is provided, which operates in synchronization with the generation of an inspection pulse, and detects and discriminates a change in the state of a machining gap, whether it is good or bad, using the inspection pulse. 2. Electrical discharge machining according to claim 1, which is equipped with an inspection pulse generator that generates a pulse with a peak value (Ip) of 200 A or less, preferably about IOA, and a pulse width of 5 to 20 μs as an inspection pulse. Device.