SU948597A1 - Apparatus for registration of short circuits - Google Patents

Description

The invention relates to the field of electrophysical processing methods, in particular, relates to a device for detecting short circuits during EDM processing.

Protection devices against short circuits during EDM processing are known that have a relay element connected to the interelectrode gap — a short circuit sensor whose output is connected to one of the two inputs of the AND circuit, to the other input of which impulses come from the master oscillator 1.

The known device cannot be used to register short circuits that occur during the duration of a discharge current pulse. For some combinations of the materials being processed and processing modes (for example, when steel is treated with a copper electrode in direct polarity), the relative frequency of the closures that occur during the discharge pulse duration reaches 100%. Information on the intensity of such closures is important because they cannot be eliminated by adjusting the gap, and a change in the processing mode, the polarity of the electrode, the reduction of the pulse duration, and other special measures are necessary. In known devices, short circuits are registered in the same way, regardless of whether they occurred during the duration of the discharge current pulse or preceded it.

The purpose of the present invention is to enable the detection of short circuits occurring only during the duration of the discharge, i.e. more accurate processing information that can be used to

15 to increase the process stability, the quality of the regulation of the interelectrode gap and the performance of EDM processing.

20

The goal is achieved by the fact that a short-circuit protection device with a relay element, whose input is connected to the interelectrode gap, and the output to one

25 of the inputs is a coincidence circuit and, the other input of which is connected to the master oscillator, and the output is connected to the short circuit indication circuit, is entered. differentiating circuit whose input

30 is associated with the output of a relay element,

and the output with the second input of the matching circuit.

FIG. 1 shows a block diagram of the device proposed in FIG. 2, voltage graphs on circuit elements.

The following block diagram shows the master oscillator 1, the output of which is connected to the input of the circuit AND 2, connected to the interelectrode gap, the relay element 3, whose output through the differentiating circuit 4 is connected to the second input of the circuit AND 2 of the short boiling display circuit 5 associated with the output cxe№: i and 2. The display circuit 5 may, for example, consist of a series-connected input pulse forwarder b, an integrating circuit 7, a threshold device 8 and an indicator 9.

The relay element 3 changes its state during the closing-opening of the interelectrode gap. The moments of change in the state of the relay element (interelectrode gap closure) are fixed by differentiating circuit 4, and if they occur during the duration of master oscillator 1, the signals from the output of differentiating circuit 4 are transmitted to the input of the coincidence circuit 2 and then to the display circuit 5. Presented version of the display scheme works as follows.

The input pulses go to shaper b, where they are normalized in amplitude and duration, and then go to the input of the integrating circuit 74. The integrating circuit 7 is a capacitor with a resistor connected in parallel. The impulse of the imaging device charges the integrating capacitor, and in the absence of impulse, the capacitor discharges through a resistor and the input resistance of the next stage. When a certain level of charge of the integrating capacitor is reached, the threshold device 8 is triggered. the quality of which the Schmitt trigger can be used, and the indicator lamp is ignited, transmitting to the operator a signal 6 of an excessively high intensity of short circuits arising during the discharge. The triggering level of the display circuit is determined by the constant charging and discharging time of the integrating capacitor and the threshold response of the device 8.

Differentiation of the signal from the relay element provides the possibility of separating the signal of the occurrence of a short circuit during the operating impulse duration. The information on the relative frequency of such closures can be used to timely Reorganize the processing modes, i.e., can improve the stability, quality and processing performance.

Claims (1)

1. USSR author's certificate 622613, cl. B 23 P 1/02, 1977. 3 tp t