Controller of wire electric discharge machine

• US 6,278,075 B1
• Filed: 02/05/1999
• Issued: 08/21/2001
• Est. Priority Date: 02/05/1998
• Status: Expired due to Term

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Hiraga, Kaoru, Kurihara, Masaki, Kamiguchi, Masao
• Primary Examiner(s): Evans, Geoffrey S.
• Application Number:
  US09/244,861
• Time in Patent Office: 928 Days
• Field of Search: 219/69.12, 219/69.13, 700/162
• US Class Current: 219/69.12
• CPC Class Codes: B23H 7/04 Apparatus for supplying current to working gap; Electric circuits specially adapted therefor

Abstract

A controller of a wire electric discharge machine monitoring a change in thickness of a workpiece and a current density in real time, promoting a machining speed by preventing occurrence of disconnection of a wire electrode even when the change in the thickness is caused in the workpiece and improving a dispersion in a machining enlargement amount. A machining distance calculating device outputs a signal at each progress of machining by a predetermined distance Δx. A main pulse number storing device counts a main pulse number for discharge machining outputted from a main pulse generator during a time period of the signal. A thickness calculating device calculates the thickness from a reference main pulse number in machining a reference thickness, the main pulse number stored to the main pulse number storing device and the reference thickness at each reception of the signal. The calculated thickness, further, a machining current, the machining speed and a machining current density are displayed. A discharge pause time control device changes a pause time period of voltage applied to the wire electrode and the workpiece in accordance with a thickness change rate and adjusts the machining current density such that no change is caused before and after the change in the thickness.

Claims

1. A controller of a wire electric discharge machine, comprising:

a thickness detecting device periodically detecting thickness of a workpiece during a machining operation;

a determining device periodically determining a change of the thickness of the workpiece based on a change of a discharge energy during the machining operation;

an altering device altering a machining condition in accordance with the change of the thickness of the workpiece; and

a display control device displaying a relationship between a movement distance or a machining time on a machining path and the thickness of the workpiece on a display device.

2. A controller of a wire electric discharge machine according to claim 1, further comprising a second detecting device detecting at least one of a machining current, a machining speed and a machining current density in respect of machining face of the workpiece during the machining operation, wherein said display control device displays a relationship between the movement distance of the machining time on the machining path and at least one of the detected machining current, the detected machining speed and the detected machining current density on said display device.

3. A controller of a wire electric discharge machine according to claim 1, wherein the relationship is displayed on a graph with the movement distance or the machining time on the machining path as an abscissa.

4. A controller of a wire electric discharge machine according to claim 1, wherein said thickness detecting device calculates a change rate of the thickness of the workpiece based on a ratio of an inputted energy when the workpiece is machined by a predetermined distance to a reference inputted energy when a reference workpiece having a predetermined thickness is machined by the predetermined distance and calculates the thickness of the workpiece based on the change rate the thickness of the reference workpiece.

5. A controller of a wire electric discharge machine according to claim 4, wherein the ratio between the inputted energies is calculated by a ratio between a number of main pulses for carrying out the discharge machining operation.

6. A controller of a wire electric discharge machine according to claim 4, wherein the ratio between the inputted energies is calculated by a ratio between summed values of discharge machining currents.

7. A controller of a wire electric discharge machine, comprising:

a current density detector detecting a machining current density on a machining face of a workpiece during a machining operation; and

a display controller displaying a relationship between a movement distance or a machining time on a machining path and the detected machining current density on a display device.

8. A controller of a wire electric discharge machine according to claim 7, wherein the relationship is displayed on a graph with the movement distance or the machining time on the machining path as an abscissa.

9. A controller of a wire electric discharge machine according to claim 7, wherein said current density detector calculates the machining current density based on thickness of the workpiece and a machining current during the machining operation.

10. A controller of a wire electric discharge machine according to claim 9, wherein said current density detector calculates a change rate of the thickness of the workpiece based on a ratio of an inputted energy when the workpiece is machined by a predetermined distance to a reference inputted energy when a reference workpiece having a predetermined thickness is machined by the predetermined distance and calculates the thickness of the workpiece based on the change rate and the thickness of the reference workpiece.

11. A controller of a wire electric discharge machine according to claim 10, wherein the ratio between the inputted energies is calculated by a ratio between a number of main pulses for carrying out the discharge machining.

12. A controller of a wire electric discharge machine according to claim 10, wherein the ratio between the inputted energies is calculated by a ratio between summed values of the discharge machining currents.

13. A controller of a wire electric discharge machine, comprising:

a discharge current generator for supplying a pulsating current to a discharge gap between a wire electrode and a workpiece;

a machining distance calculator calculating a machining distance;

a thickness change detector calculating a thickness change rate of the workpiece based on an energy amount inputted from said discharge current generator during machining by the predetermined distance; and

a machining condition adjustor adjusting the energy amount inputted from the discharge current generator based on the calculated thickness change rate so that a machining current density is substantially maintained.

14. A wire electric discharge machine according to claim 13, wherein said thickness change detector calculates the thickness change rate based on a set reference energy amount and the energy amount inputted from said discharge current generator during machining by the predetermined distance in the machining operation.

15. A wire electric discharge machine according to claim 13, wherein said thickness change detecting means comprises:

a summing unit summing and storing the energy amount inputted from the discharge current generator during machining of the predetermined distance; and

a storing unit storing the summed energy amount in machining the predetermined distance at a preceding time,

wherein the thickness change rate of the workpiece is calculated by the summed energy amounts at the preceding time and at a current time at each progress of the machining by the predetermined distance.

16. A wire electric discharge machine according to claim 13, wherein said thickness change detector calculates the thickness change rate with a pulse number inputted from said discharge current generator as the energy amount.

17. A controller of a wire electric discharge machine according to claim 13, wherein said thickness change detector calculates the thickness change rate with an integrated value of a pulsating current inputted from said discharge current generator as the energy amount.

18. A controller of a wire electric discharge machine according to claim 13, wherein said machining condition adjuster adjusts the energy amount inputted from said discharge current generator by adjusting a length of a machining pause time in which application of a voltage to the gap between the wire electrode and the workpiece pauses based on the thickness change rate.

19. A controller of a wire electric discharge machine according to claim 13, wherein said machining condition adjustor adjusts the energy amount inputted from said discharge current generator by adjusting a peak value of the pulsating current based on the thickness change rate.

20. A controller of a wire electric discharge machine according to claim 13, wherein said machining condition adjustor adjusts the energy amount inputted from said discharge current generator by adjusting a pulse width of the pulsating current based on the thickness change rate.

21. A controller of a wire electric discharge machine according to claim 13, wherein said machining condition adjustor adjusts the energy amount inputted form said discharge current generator by adjusting a set voltage in a servo feed control for carrying out a feedback control such that an average machining voltage at the gap between the wire electrode and the workpiece coincides with the set voltage, based on the thickness change rate.

22. A controller of a wire electric discharge machine according to claim 13, wherein said machining condition adjustor adjusts the energy amount inputted from said discharge current generator by adjusting a feedback gain in a servo feed control for carrying out a feedback control such that an average machining voltage at the gap between the wire electrode and the workpiece coincides with the set voltage, based on the thickness change rate.

23. A controller of a wire electric discharge machine according to claim 13, wherein said machining condition adjustor adjusts the energy amount inputted form said discharge current generator by adjusting a relative feed speed of the wire electrode with respect to the workpiece based on the thickness change rate.

24. A controller of a wire electric machine, comprising:

a reference determining device determining a number of reference discharge pulses required for machining a workpiece of a predetermined thickness by a predetermined distance;

a discharge pulse number determining device determining the number of discharge pulses generated in machining the workpiece by the predetermined distance during a machining operation;

a ratio determining device periodically determining a ratio between the number of reference discharge pulses and the number of discharge pulses, and a change of the thickness of the workpiece based on said ratio during the machining operation;

an altering device altering a machining condition in accordance with the change of the thickness of the workpiece during the machining operation; and

a display control device displaying a relationship between a movement distance or a machining time on a machining path and the thickness of the workpiece on a display device.