PULSE GENERATOR FOR EDM MACHINE

• US 3,832,510 A
• Filed: 06/08/1973
• Issued: 08/27/1974
• Est. Priority Date: 06/16/1972
• Status: Expired due to Term

• Current Assignee: Charmilles Technologies SA (Georg Fischer AG)
• Original Assignee: Georges-Andre Marendaz, Heinz Rhyner, Jean Pfau
• Inventors: Pfau, Jean, Marendaz, Georges-Andre, Rhyner, Heinz
• Primary Examiner(s): Truhe, J. V.
• Assistant Examiner(s): Jaeger, Hugh D.
• Application Number:
  US05/368,220
• Time in Patent Office: 445 Days
• Field of Search: 219/69C,69V,69P
• US Class Current: 219/69.13
• CPC Class Codes: B23H 1/022 for shaping the discharge pulse train B23H1/024 takes precedence
• CPC Class Codes: B23H 2300/20 Relaxation circuit power supplies for supplying the machining current, e.g. capacitor or inductance energy storage circuits

Abstract

The present invention is a pulse generator for electro-erosion machining which is capable of providing controlled voltage pulses between an electrode tool and an electrode workpiece, such pulses having a sharp vertical leading edge throughout a wide frequency range and providing an optimum energy efficiency. The pulse generator of the invention, which is connected across the electrode tool-workpiece machining gap, comprises essentially a DC power supply, an electromagnetic energy storage element and a first circuit make and break element, such as a switch, connected between one of the DC power supply terminals and one of the terminals of the electromagnetic storage device. A first unidirectional element is connected between the first terminal of the electromagnetic storage element and the other terminal of the power supply, so as to provide a current path through a first auxiliary circuit when the first circuit make and break element is open. The circuit comprises a second unidirectional element connected between one of the power supply terminals and one of the electrodes, tool or workpiece, and a second circuit make and break element or switch connected so as to provide a current path, when the second circuit make and break element is open, through a second auxiliary circuit, or through a third auxiliary circuit when both circuit make and break elements are open. The first circuit make and break element is controlled in such manner as to cause the current flowing across the energy storage element to be maintained at a predetermined value and the second circuit make and break element is controlled so as to control in turn the duration of each voltage or current pulse and/or the time interval during two consecutive voltage pulses.

Claims

1. In an electrical discharge machining apparatus for electroerosion of material from an electrode workpiece by means of consecutive intermittent pulses being applied across a machining gap between said electrode workpiece and an electrode tool, a pulse generator comprising a DC power supply having a first and a second terminal, an electromagnetic energy accumulator, a first make and break element connected between the first of the terminals of said power supply and a first terminal of said accumulator, a first unidirectional element connected between the second terminal of said power supply and the first terminal of said accumulator, a second unidirectional element connected between the second terminal of said accumulator and the first terminal of said power supply, and a second make and break element connected such as to provide a current path in a main circuit when at least said first make and break element is closed, in a first auxiliary circuit when at least said first make and break element is open, in a second auxiliary circuit when at least said second make and break element is open, and in a third auxiliary circuit when both said make and break elements are open, means for controlling said first make and break element for maintaining the current flowing through said accumulator at a predetermined value, and means for controlling said second make and break element at a predetermined frequency for controlling the period of each current-voltage pulse across the machining gap.

2. The pulse generator of claim 1 wherein said main circuit comprises at least said power supply, said first make and break element and said accumulator, the first of said auxiliary circuits comprises said accumulator and said first unidirectional element, the second of said auxiliary circuits comprises said accumulator, and the third of said auxiliary circuits comprises said accumulator, said second unidirectional element, said power supply and said first unidirectional element.

3. The pulse generator of claim 2 wherein said main circuit further comprises said machining gap and said second make and break element, the first of said auxiliary circuits further comprises said machining gap and said second make and break element, and the second of said auxiliary circuits further comprises said first make and break element.

4. The pulse generator of claim 1 wherein said electromagnetic energy accumulator is a self-inductance coil, and the make and break elements consist each of at least the transistor and each unidirectional element consists of at least one diode.

5. The pulse generator circuit of claim 2 wherein the second make and break element is connected in series with said electrodes in the first of said auxiliary circuits.

6. The pulse generator circuit of claim 2 wherein the second make and break element is connected in parallel with said electrodes whereby when said second make and break element is closed during the time interval between two consecutive pulses and the first make and break element is open current flows through a fourth auxiliary circuit comprising said accumulator and said first unidirectional element.

7. The pulse generator of claim 6 wherein said main circuit further coMprises said machining gap, the first of said auxiliary circuits further comprises said machining gap, and the second of said auxiliary circuits further comprises said first make and break element.

8. The pulse generator circuit of claim 2 wherein the second make and break element is connected in series with a third unidirectional element providing a current path when the first make and break element is open and the second make and break element is closed during a time interval between two consecutive pulses through a fourth auxiliary circuit comprising said accumulator and said third unidirectional element.

9. The pulse generator of claim 8 wherein said main circuit further comprises said machining gap, the first of said auxiliary circuits further comprises said machining gap, and the second of said auxiliary circuits further comprises said first make and break element.

10. The pulse generator circuit of claim 2 wherein each of the terminals of the power supply is connected to a corresponding terminal of the accumulator by means of a make and break element, and a third unidirectional element is connected in series with said electrodes for providing a current path when both said make and break elements are open during a current pulse through a an auxiliary circuit comprising said accumulator and said third unidirectional element and said electrodes.

11. The pulse generator of claim 10 wherein said main circuit further comprises said second make and break element, the first of said auxiliary circuits further comprises said first make and break element and the second of said auxiliary circuits further comprises said second make and break element.

12. The pulse generator of claim 1 comprising at least two electrical energy accumulators each having a terminal connected to a terminal of at least one power supply through said first make and break element, the other of the terminals of each of said accumulators being connected to one of said electrodes through said second make and break element, at least a pair of unidirectional elements each connected between said other terminal of each accumulator and the other terminal of said power supply such as to provide a current path in said first auxiliary circuit when the first of said make and break elements is open, and at least two additional unidirectional elements each connected between said first terminal of said power supply and the other terminal of said accumulator such as to provide a current path through said second auxiliary circuit when the first make and break element is closed and the second is open, and through said third auxiliary circuit when both first and second make and break elements are open.

13. The pulse generator of claim 1 wherein at least one of the auxiliary circuits comprises an auxiliary DC power supply connected in series with said accumulator.

14. The pulse generator of claim 1 wherein said means for controlling said first make and break element opens said make and break element when the value of the current circulating through said accumulator reaches a first predetermined level and closes said make and break element when the value of said current reaches a second predetermined level, said second level being less than said first level.

15. The pulse generator circuit of claim 1 wherein said means for controlling said first make and break element opens said element for a predetermined time interval when the current flowing through said accumulator reaches a predetermined level.

16. The pulse generator circuit of claim 1 wherein said means for controlling said first make and break element opens said element for a predetermined time interval when the current flowing through the first make and break element reaches a predetermined level.

17. The pulse generator circuit of claim 1 wherein said means for controlling said first make and break element opens said element for a predetermined time interval when the current flowing through the machining gap reaches a predetermined level.

18. The pulse generator circuit of claim 1 wherein said means for controlling said first make and break element opens and closes said element as a function of the difference between the average current value flowing through said accumulator and a predetermined reference value.

19. The pulse generator circuit of claim 1 wherein said means for controlling said first and make break element controls the period of time during which said make and break element is open such as to decrease said period of time as a function of the voltage across said accumulator.

20. The pulse generator circuit of claim 15 wherein said means for controlling said first make and break element controls the period of time during which said make and break element is open such as to decrease said period of time as a function of the voltage across said accumulator.

21. The pulse generator circuit of claim 16 wherein said means for controlling said first make and break element controls the period of time during which said make and break element is open such as to decrease said period of time as a function of the voltage across said accumulator.

22. The pulse generator circuit of claim 17 wherein said means for controlling said first make and break element controls the period of time during which said make and break element is open such as to decrease said period of time as a function of the voltage across said accumulator.

23. The pulse generator circuit of claim 1 wherein means are provided for synchronizing the operation of the make and break elements such that the opening or closing of one of said elements correspond to the closing of the other of said elements.

24. The pulse generator circuit of claim 1 wherein the accumulator is a self-inductance coil having an inductance decreasing as a function of the current flow therethrough.