Wire electric discharge machine having function of moving from arbitrary retreat position in electric discharge state and returning to halt position

Abstract

Electric discharge machining is halted during machining program operation, and a position of the machining halt point is stored. A wire electrode is retreated from the machining halt point to an arbitrary position in which a short-circuit with a workpiece is removed (retreat position), by interrupt operation in which axis movement is performed manually. Then, a return is made from the retreat position to the machining halt point while electric discharge machining is performed, machining program operation is started from the machining halt point, and electric discharge machining is restarted.

Claims

1. A wire electric discharge machine having a function of restarting machining at a machining halt point, said wire electric discharge machine comprising: a table configured to support a workpiece; a wire electrode configured to machine the workpiece; and a numerical controller configured to start machining by a program operation; and store a halt position when the program operation is halted after the start of machining by the program operation; wherein when the wire electrode is retreated from the halt position to a retreat position away from the workpiece by a manual interrupt, the numerical controller is configured to cause the wire electrode in an electric discharge state to return from the retreat position to the halt position; and restart machining after the wire electrode is returned to the halt position.

2. The wire electric discharge machine according to claim 1, wherein the numerical controller is configured to control a feedrate under the same machining conditions as machining conditions for automatic machining by a program when the wire electrode in an electric discharge state is caused by the numerical controller to return from the retreat position to the halt position.

3. A wire electric discharge machine having a function of restarting machining at a machining halt point, said wire electric discharge machine comprising: a table configured to support a workpiece; a wire electrode configured to machine the workpiece; and a numerical controller configured to start machining by a program operation; trace back a programmed path of a movement block of a rapid traverse positioning instruction to a position in which a short-circuit is removed if the wire electrode and the workpiece are in a short-circuit state in a position in which the rapid traverse positioning instruction block is switched to a machining instruction block after the start of machining by the program operation, and start electric discharging and cause the wire electrode to return to a halt position while electric discharge machining is performed by reading the rapid traverse positioning instruction block as the machining instruction block after the short-circuit is removed.

4. A wire electric discharge machine having a function of restarting machining at a machining halt point, said wire electric discharge machine comprising: a table configured to support a workpiece; a wire electrode configured to machine the workpiece; and a numerical controller configured to start machining the workpiece by a program operation; make positioning for a return to a programmed start point of a movement block of a rapid traverse positioning instruction if the wire electrode and the workpiece are in a short-circuit state in a position in which the rapid traverse positioning instruction block is switched to a machining instruction block after the start of machining by the program operation, and cause the wire electrode to return to a halt position while electric discharge machining is performed by reading the rapid traverse positioning instruction block as the machining instruction block.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above and other objects and features of the present invention will be apparent from the following description of embodiments with reference to the appended drawings, in which:

(2) FIG. 1 is a schematic configuration diagram of an embodiment of a wire electric discharge machine according to the present invention;

(3) FIG. 2 illustrates an axis movement configuration of the wire electric discharge machine in FIG. 1;

(4) FIGS. 3A and 3B illustrate a first example of a machining restart function of the electric discharge machine according to the present invention in which a return to a machining halt position is made in an electric discharge state by movement from a retreat position;

(5) FIGS. 4A and 4B illustrate a modification of the first example of the machining restart function of the electric discharge machine according to the present invention in which a return to a machining halt position is made in an electric discharge state by movement from a retreat position;

(6) FIG. 5 is a flowchart illustrating the first example of the machining restart function of the electric discharge machine according to the present invention;

(7) FIGS. 6A and 6B illustrate a second example of the machining restart function of the electric discharge machine according to the present invention in which a return to a machining halt position is made in an electric discharge state by movement from a retreat position;

(8) FIG. 7 is a flowchart illustrating the second example of the machining restart function of the electric discharge machine according to the present invention;

(9) FIGS. 8A and 8B illustrate a third example of the machining restart function of the electric discharge machine according to the present invention in which a return to a machining halt position is made in an electric discharge state by movement from a retreat position;

(10) FIG. 9 is a flowchart illustrating the third example of the machining restart function of the electric discharge machine according to the present invention; and

(11) FIG. 10 is a flowchart illustrating a flow of return processing by a wire electric discharge machine according to a prior art technique.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(12) An embodiment of a wire electric discharge machine according to the present invention will be described with reference to FIG. 1.

(13) In a wire electric discharge machine 30, a wire bobbin 12 around which a wire electrode 4 is wound is attached to the top of a column 3. Predetermined low torque is given to the wire bobbin 12 by a feed unit torque motor 11 in a direction opposite to a direction in which the wire electrode 4 is pulled. The wire electrode 4 unreeled from the wire bobbin 12 passes through a brake shoe 14 driven by a brake motor 13, an upper guide 5a, a lower guide 5b, and a lower guide roller 15, and is wound around a feed roller 16. A tension between the brake shoe 14 driven by the brake motor 13 and the feed roller 16 driven by a wire electrode feed motor (not shown) is adjusted. The wire electrode 4 is put between a pinch roller 17 and the feed roller 16 driven by the wire electrode feed motor (not shown) and collected to a wire electrode collection box 18. A table on which a workpiece is to be placed is attached to the inside of a work tank 2 on a machine base 1. A workpiece (not shown) to be subjected to electric discharge machining is placed on the table (not shown) in an electric discharge machining region between the upper guide 5a and the lower guide 5b, high-frequency voltage is applied from a machining power supply to the wire electrode 4, and electric discharge machining is performed.

(14) FIG. 2 illustrates an axis movement configuration of the wire electric discharge machine 30 in FIG. 1.

(15) The entire wire electric discharge machine 30 is controlled by a numerical controller 20. The numerical controller 20 controls drives of motors 22X, 22Y, 22Z, 22U, and 22V for X, Y, Z, U, and V axes via a servo amplifier 21.

(16) To the machine base 1, the motors 22X and 22Y are attached that drive, in an X axis direction and a Y axis direction, the table (not shown) on which a workpiece is to be placed. Ball screws 23X and 23Y are coupled to the motors 22X and 22Y. Driving force of the motors 22X and 22Y is transferred to the ball screws 23X and 23Y, and thereby the table is moved in the X axis direction and the Y axis direction.

(17) The motors 22Z, 22U, and 22V are attached to the top of the column 3. Ball screws 23Z, 23U, and 23V are coupled to the motors 22Z, 22U, and 22V. Driving force of the motors 22Z, 22U, and 22V is transferred to the ball screws 23Z, 23U, and 23V, and thereby the upper guide 5a can be moved in a Z axis direction, a U axis direction, and a V axis direction.

(18) A first example of a machining restart function of the electric discharge machine according to the present invention in which a return to a machining halt position is made in an electric discharge state by movement from a retreat position will first be described with FIGS. 3A and 3B.

(19) FIG. 3A illustrate a problem that may occur in a prior art technique with a program in which, to perform electric discharge machining of a PCD tip 25 fixed to a tool body 24, an advance is made from an outer region of a workpiece by the rapid traverse positioning instruction G00 and machining is performed by the machining instruction G01. If the workpiece is fixed in a position short of an assumed position and a wire electrode advances to the workpiece by the rapid traverse positioning instruction G00, the wire electrode may come into contact with the workpiece, causing a short-circuit. In this case, there is a difficulty in removing the short-circuit between the wire electrode and the workpiece and restarting machining.

(20) FIG. 3B illustrates means for solving the aforementioned problem by the present invention, in which, after movement (retreat) by jog feed, a return to a halt point is made by speed control in proportion to average machining voltage set in machining conditions (hereinafter referred to as electric discharge servo control) while electric discharging is turned on. Because machining cannot be performed from the halt point at which a retraction alarm has occurred, the wire electrode is temporarily moved to the outside of the workpiece (retreated to a retreat position) in manual mode, a short-circuit is removed, and then the wire electrode is returned again to the halt point (from the retreat position) by electric discharge servo control based on the set machining conditions while electric discharging is turned on. Thus, machining can be easily restarted.

(21) A modification of the first example of the machining restart function of the electric discharge machine according to the present invention in which a return to a machining halt position is made in an electric discharge state by movement from a retreat position will next be described with FIGS. 4A and 4B.

(22) FIG. 4A illustrate a problem in a prior art technique which will occur in a case where a tool body is larger than expected and a short-circuit with a wire electrode arises during the positioning instruction (G00) immediately after the start of the positioning instruction. In the machining instruction (G01) in the next block, electric discharge machining cannot be performed due to the short-circuit and the wire electrode stops. There is a constraint that the short-circuit removal function (retraction control) that is started by short-circuit during machining is applied only to a machining instruction block such as G01, G02, or G03 and is not applied to the GOO positioning instruction.

(23) FIG. 4B illustrates means for solving the aforementioned problem by the present invention, in which, after movement (retreat) by jog feed, a return to a halt point is made by servo feed set in machining conditions while electric discharging is turned on. Because machining cannot be performed from the halt point at which a retraction alarm has occurred, the wire electrode is temporarily moved to the outside of the workpiece (retreated to a retreat position) in manual mode, a short-circuit is removed, and then the wire electrode is returned again to the halt point (from the retreat position) by electric discharge servo control based on the set machining conditions while electric discharging is turned on. Thus, machining can be easily restarted.

(24) The first example (and the modification of the first example) of the machining restart function of the electric discharge machine according to the present invention will be described with reference to a flowchart in FIG. 5.

(25) At the beginning of a program, a wire electrode and a workpiece are moved relatively by the rapid traverse positioning instruction (G00) (step sa01). Machining is started by the machining instruction (G01) (step sa02). Whether a short-circuit between the wire electrode and the workpiece has occurred or not is determined (step sa03). If a short-circuit has occurred (YES), the flow shifts to step sa04. If a short-circuit has not occurred (NO), the flow shifts to step sa05.

(26) In step sa05, machining is performed by the machining instruction (G01). Whether the program has ended or not is determined (step sa06). If the program has not yet ended, the flow returns to step sa02 and the processing continued.

(27) In step sa04, a program stop position is stored and the program is stopped. Then, an operator intervenes manually (step sa07). The wire electrode or the workpiece is manually moved to an arbitrary retreat position in which the short-circuit between the wire electrode and the workpiece is removed (step sa08). Then, movement from the retreat position to the program stop position is made while machining is performed in an electric discharge state (step sa09). Machining is performed again from the program stop position (step sa10).

(28) A second example of the machining restart function of the electric discharge machine according to the present invention in which a return to a machining halt position is made in an electric discharge state by movement from a retreat position will next be described with FIGS. 6A and 6B.

(29) FIG. 6A illustrates a problem with a program in which an advance is made from an outer region of a workpiece by the rapid traverse positioning instruction GOO and machining is performed by the machining instruction G01. If the workpiece is fixed in a position before an assumed position and a wire electrode advances to the workpiece by the rapid traverse positioning instruction G00, the wire electrode may come into contact with the workpiece, causing a short-circuit. In this case, there is a difficulty in removing the short-circuit between the wire electrode and the workpiece and restarting machining.

(30) FIG. 6B illustrates means for solving the aforementioned problem by the present invention, in which the G00 positioning instruction is read as the G01 machining instruction, retraction control is performed, and automatic recovery is made. After a short-circuit between a wire electrode and a workpiece has occurred and the wire electrode is stopped, the rapid traverse positioning instruction (G00) is read as the machining instruction (G01), retraction control is performed, and the wire electrode is made to trace back a path to a position in which the short-circuit is removed (to a retreat position). Then, after the short-circuit is removed, an automatic return to the machining halt point is made (from the retreat position) while electric discharging is turned on and machining is performed, and then machining is restarted.

(31) The second example of the machining restart function of the electric discharge machine according to the present invention will be described with reference to a flowchart in FIG. 7.

(32) At the beginning of a program, a wire electrode and a workpiece are moved relatively by the rapid traverse positioning instruction (G00) (step sb01). Machining is started by the machining instruction (G01) (step sb02). Whether a short-circuit between the wire electrode and the workpiece has occurred or not is determined (step sb03). If a short-circuit has occurred (YES), the flow shifts to step sb04. If a short-circuit has not occurred (NO), the flow shifts to step sb07.

(33) In step sb04, the G00 positioning instruction is read as the G01 machining movement instruction, and retraction control is performed. Whether a short-circuit between the wire electrode and the workpiece has occurred or not is detected (step sb05). Movement by G01 is made until the short circuit is removed. When the short-circuit state is removed, electric discharge machining is restarted (step sb06). Then, the flow returns to step sb03.

(34) In step sb07, machining is performed by the machining instruction (G01). Whether the program has ended or not is determined (step sb08). If the program has not yet ended, the flow returns to step sb02 and the processing is continued.

(35) A third example of the machining restart function of the electric discharge machine according to the present invention in which a return to a machining halt position is made in an electric discharge state by movement from a retreat position will next be described with FIGS. 8A and 8B.

(36) FIG. 8A illustrates a problem with a program in which an advance is made from an outer region of a workpiece by the rapid traverse positioning instruction G00 and machining is performed by the machining instruction G01. If the workpiece is fixed in a position before an assumed position and a wire electrode advances to the workpiece by the rapid traverse positioning instruction G00, the wire electrode may come into contact with the workpiece, causing a short-circuit. In this case, there is a difficulty in removing the short-circuit between the wire electrode and the workpiece and restarting machining.

(37) FIG. 8B illustrates means for solving the aforementioned problem by the present invention, in which the G00 positioning instruction is read as the G01 machining instruction, a return to a start point of the G00 positioning instruction is made, and automatic recovery is made. After a short-circuit between a wire electrode and a workpiece has occurred and the wire electrode is stopped, positioning movement for a return to the start position of the rapid traverse positioning instruction (G00) is made by rapid traverse, the rapid traverse positioning instruction (G00) is read as the machining instruction (G01), an automatic return to the machining halt point is made while machining is performed again, and then machining is continued.

(38) The third example of the machining restart function of the electric discharge machine according to the present invention will be described with reference to a flowchart in FIG. 9.

(39) At the beginning of a program, a wire electrode and a workpiece are moved relatively by the rapid traverse positioning instruction (G00) (step sc01). Machining is started by the machining instruction (G01) (step sc02). Whether a short-circuit between the wire electrode and the workpiece has occurred or not is determined (step sc03). If a short-circuit has occurred (YES), the flow shifts to step sc04. If a short-circuit has not occurred (NO), the flow shifts to step sc06.

(40) In step sc04, the wire electrode is automatically moved to the start position of the G00 positioning (step sc04). The G00 positioning instruction is read as the G01 machining movement instruction and machining is performed (step sc05). Then, the flow returns to step sc03.

(41) In step sc06, machining movement is performed by the machining movement instruction (G01). Whether the program has ended or not is determined (step sc07). If the program has not yet ended, the flow returns to step sc02 and the processing is continued.