Method and device for controlling a wire cut electric discharging machine

• US 5,393,947 A
• Filed: 11/26/1993
• Issued: 02/28/1995
• Est. Priority Date: 11/26/1993
• Status: Expired due to Term

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Wang, Yu-Chin, Liang, Re-Fang, Chuang, Hsin-Jung
• Primary Examiner(s): Evans, Geoffrey S.
• Application Number:
  US08/157,997
• Time in Patent Office: 459 Days
• Field of Search: 219/69.13, 219/69.18, 219/69.12
• US Class Current: 219/69.18
• CPC Class Codes: B23H 1/022 for shaping the discharge pulse train B23H1/024 takes precedence
• CPC Class Codes: B23H 1/024 Detection of, and response to, abnormal gap conditions, e.g. short circuits preventing short circuits or other abnormal discharges by altering machining parameters using adaptive control B23H7/16

Abstract

A device for controlling a wire cut electric discharging machine is provided with a testing circuit to detect the condition between the wire electrode and the workpiece before every discharge process so as to regulate the discharge energy according to one of the detected conditions: normal discharge, arc discharge, or short circuit. The device includes two switching transistors controlled by a control unit according to the comparison result between a reference voltage and the voltage measured between the wire electrode and the workpiece being processed.

Claims

1. A control device for controlling an electric discharge of a wire cut electric discharging machine comprising:

(a) a first power source to provide a discharge energy between a wire electrode and a workpiece to be processed, said first power source having a negative terminal connected to said wire electrode of said wire cut EDM, and a positive terminal;

(b) a first switching means having a first end connected to the positive terminal of said first power source and a second end connected to said workpiece to be processed;

(c) a second power source to provide a testing voltage between said wire electrode and said workpiece, said second power source having a negative terminal connected to said wire electrode, and a positive terminal;

(d) a diode having a positive terminal connected to said positive terminal of said second power source, and a negative terminal;

(e) a resistor having a first end connected to the negative terminal of said diode, and a second end;

(f) a second switching means having a first end connected to said second end of said resistor and a second end connected to said workpiece; and

(g) a control unit connected between said first switch and said second switch to compare the voltage between said wire electrode and said workpiece with a reference voltage to obtain a comparison result, and to control an operation of said first switching means and said second switching means according to said comparison result;

(h) wherein said control unit comprises;

a first comparator connected to said first power source to compare said testing voltage between said wire electrode and said workpiece supplied by said second power source with said reference voltage;

said comparator causing said first power source to induce a normal discharge when said testing voltage is higher than said reference voltage, or an arc discharge when said testing voltage is lower than said reference voltage;

a logic gate to receive said comparison result from said first comparator, a first counter, and a frequency divider controlled by a computer to provide a timed pulse to said first counter, said logic gate being driven by said first counter to provide an output in accordance with said comparison result received from said first comparator when said first counter has reached a predetermined count value; and

a second counter, said second counter counting one each time said voltage supplied from said first power source induces an arc discharge between said wire electrode and said workpiece, said second counter providing an output to the logic gate for a determination of said normal discharge or said arc discharge, when a total count of said second counter reaches a preset value, said second counter being adapted to be reset to zero and start counting from zero when a normal discharge is detected during the counting.

2. The wire cut electric discharging machine control device of claim 1 wherein said control unit further comprises a low pass filter and a second comparator, said low pass filter being adapted to filtrate said testing voltage obtained between said wire electrode and said workpiece so as to provide an average voltage for comparison with said reference voltage for outputting to said logic gate by said second comparator for a determination of a short circuit between said wire electrode and said workpiece.