JPH022650B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention qualitatively or quantitatively detects the non-arc discharge time, arc discharge time, and short circuit time with respect to the electric discharge machining voltage application time, and
The present invention relates to an electric discharge machining state detection method that detects when an abnormally long arc discharge time occurs continuously compared to the electric discharge machining voltage application time.

The electrical discharge machining method, which actively utilizes the phenomenon of electrode wear caused by electrical discharge, is a process in which the workpiece (hereinafter simply referred to as the workpiece) and the machining electrode as a tool are separated into an extremely narrow gap in a machining fluid such as kerosene or transformer oil. It is well known that the workpiece is machined by periodically and repeatedly generating an impactful transient arc discharge through the gap while facing each other at a distance, but in order to perform electrical discharge machining in good condition During electrical discharge machining, the voltage across the discharge gap must be maintained at an appropriate waveform. For convenience, the discharge gap voltage with respect to the applied voltage during pulsed electrical discharge machining can be roughly divided into four types as shown in Figures 1a to d. Of these, the gap gap voltage Vga waveform shown in Figure 1 is for normal discharge. However, if the gap interval adjustment control is not appropriate, the result will be as shown in FIGS. 1b to 1d.

That is, Fig. 1b shows the gap voltage Vgb waveform when arc discharge continues during application of the machining voltage, and Fig. 1c shows the gap gap voltage Vgb waveform when the workpiece and the machining electrode are in contact and in a short-circuit state. Voltage Vgc waveform,
Furthermore, Figure 1d shows the voltage between the gaps when transient arc discharge does not occur because the gap distance is large.
Shows Vgd waveform. The voltage between these gaps Vgb~
Of the Vgd waveforms, Vgd does not have a particularly negative effect on the machining conditions, but the inter-gap voltage Vgb and Vgc waveforms worsen the roughness of the finished surface and increase electrode wear.On the other hand, the arc discharge time with the _Vga waveform Increasing the size means improving processing conditions. Therefore, for the above reasons, the gap voltage
It can be said that it is extremely important to control electrical discharge machining by detecting the Vgb and Vgc waveforms.

It is not unthinkable to control electrical discharge machining by detecting something like the conventional gap voltage Vgb waveform. For example, Showa 53
Patent Application No. 122425 of 2007 discloses that gap voltage waveforms are divided into four types as shown in Figures 1a to d, and the frequency of occurrence of these four types of waveforms is quantified and captured. Therefore, it is possible to understand whether the current machining condition is good or not, and if the machining condition is not good, the quantified values can be used to control the subsequent electric discharge machining with regard to machining fluid pressure, machining voltage application cycle, machining voltage value, etc. It's getting old. However, when the machining speed is changed, there is a slight discrepancy in the correspondence between the detected quantification value and the machining speed.
The drawback is that it is not possible to accurately determine whether the machining condition is good or bad at any machining speed, and it is also impossible to perform subsequent control accurately. Note that the control referred to here refers to control in a direction in which the machining condition is good and the machining speed is high.

The purpose of the present invention is to accurately grasp the electrical discharge machining state qualitatively or quantitatively at any machining speed, thereby accurately grasping the quality of the electrical discharge machining state at the present time, and also to accurately grasp the quality of the electrical discharge machining state at the present time. The purpose is to ensure that processing control is performed accurately.

For this purpose, the present invention aims to reduce the impact on the electrical discharge machining voltage application time (or its machining time) over a relatively long machining time while the electrical discharge machining voltage is repeatedly and periodically applied to the workpiece and the machining electrode. The purpose is to achieve the desired objective by qualitatively or quantitatively understanding the ratio of arc discharge time, arc discharge time, and short-circuit time in a unique manner.

The present invention will be explained below with reference to FIGS. 2 and 3.

FIG. 2 shows a circuit configuration according to an embodiment of the present invention.
Further, FIG. 3 shows an example of input/output signal waveforms at the main part of the circuit configuration.

As shown in Fig. 2, a rectangular electric discharge machining voltage is periodically applied to the tool electrode 2 and the workpiece 3 from the pulse power source 1, and electric discharge machining is performed thereby. The waveform of the gap voltage signal A is as shown in FIG. 3, for example. This gap voltage signal A is sent to a comparator 6, which receives threshold voltages E ₁ and E ₂ from setters 4 and 5.
7. threshold voltage
Since E ₁ and E ₂ are set as shown in FIG. 3, the comparators 6 and 7 each output a high level signal while the signal A is in the arc discharge state. On the other hand, the pulse power supply 1 outputs a signal synchronized with the electrical discharge machining voltage, and therefore, if this signal and the output signals of the comparators 6 and 7 are logically processed, the electrical discharge machining cycle or the electrical discharge machining voltage application time can be determined. The ratio of non-arc discharge time, arc discharge time, and short circuit time to the total time is known. That is, the AND gate 8 to which the output signals of the comparators 6 and 7 are input, outputs a high level signal as its output signal B in accordance with the arc discharge time.
Further, the NOR gate 17 to which the output signal of the comparator 6 and the signal are inputted outputs a high level signal according to the non-arc discharge time as its output signal G, and the NOR gate 18 to which the output signal and the signal from the comparator 7 are inputted. outputs a high level signal as its output signal H in accordance with the short circuit time. Then, the time during which the output signals B, G, and H are each in a high level state over a plurality of appropriate electrical discharge machining cycles is integrated using a counter or an integrating circuit, and each integrated value is calculated for each of the plurality of electrical discharge machining cycles. If you divide it by the time equivalent to the voltage application time, the arc discharge in one electric discharge machining,
The time ratios of non-arc discharge and short circuit are determined. These time ratios are displayed in analog or digital form and are used to understand the current state of electrical discharge machining and to control later electrical discharge machining. Note that the integral value of the electric discharge machining voltage application time is obtained by integrating the inverted signal of the signal.

By the way, electric discharge machining in which arc discharge starts at the same time as voltage is applied is not desirable, so if such electric discharge machining occurs continuously, it is necessary to detect this fact and change the electric discharge machining control settings. be. The present invention takes this detection into consideration. As shown in FIG. 2, the flip-flop 10 receives signals B,
It is reset by the fall of the output signal D of the NOR gate 9 to which C is input, and is set when the signal changes from high level to low level, thus causing arc discharge as described above. If occurs continuously, flip-flop 1
0 is set during that time, and the set output signal is integrated by the integrating circuit 11. When the time T for which the integral value exceeds the threshold voltage _E3 from the setting device 12 has elapsed, the comparator 13 outputs a high level signal as its output signal F, and this output signal F This is to detect abnormal arc discharge machining conditions. Incidentally, in this example, if the detection occurs twice in a row, it is immediately detected, but the number of consecutive detections depends on the time constant of the integrating circuit 11. In addition, in this example, an abnormality is detected using the integrating circuit 11, the comparator 13, etc., but the signal B is counted by a counter that is kept in a countable state while the flip-flop 10 is set. Of course, it is also possible to do so. Furthermore, and gate 1
4. The NOR gate 15 outputs the signal B while the signal F is at high level and low level, respectively, and the inverter 16 is for inverting the signal B.

As explained above, the present invention is capable of detecting the time ratio of no-arc discharge, arc discharge, and short-circuit to the voltage application time by logically processing the inter-gap voltage after threshold processing, and detecting abnormal arc discharge. If these are continuous, this is detected, so not only can you immediately know whether the current electrical discharge machining condition is good or bad, regardless of the machining speed, but you can also use these detected values to properly control subsequent electrical discharge machining. It has the effect of gaining.

[Brief explanation of drawings]

Figures 1 a to d are diagrams showing four typical gap voltage waveforms, Figure 2 is a circuit configuration diagram according to an embodiment of the present invention, and Figure 3 is an example of the main part thereof. FIG. 2 is an input/output signal waveform diagram of FIG. 1... Pulse power supply, 2... Machining electrode, 3... Workpiece,
4, 5, 12... (threshold voltage) setter, 6,
7, 13...Comparator, 8...And gate,
9, 17, 18...Nor gate, 10...flip-flop, 11...integrator circuit.

Claims (1)

[Claims] 1 In electrical discharge machining, in which a workpiece is machined by a machining electrode using a voltage that is repeatedly and periodically applied across the gap, the gap-to-gap voltage signal applied to the gap that exists between the workpiece and the machining electrode during electrical discharge machining. By processing the output signal using two types of threshold values and logically processing the output signal related to the processing and the signal synchronized with the applied voltage, arc-free discharge, arc discharge, and In addition to detecting the average time ratio of each state of short circuit, if the arc discharge state is continuously detected for a predetermined number of voltage applications immediately after voltage application, no arc discharge state is present. A method for detecting electrical discharge machining status, characterized by detecting that electrical discharge machining is being performed.