JPH07253B2 - Wire cut electrical discharge machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a wire-cut electric discharge machining apparatus for repairing a wire electrode and continuing the machining when the wire electrode is broken during wire electric discharge machining, particularly The present invention relates to control that allows the machining to be restarted smoothly even if the machining groove is deformed due to release of internal stress of the workpiece.

[Prior Art] It is well known that, in general, a wire-cut electric discharge machine can easily and accurately machine a conductive work piece even in a complicated shape regardless of hardness. However, the wire electrode is usually a metal with a diameter of about 0.03 mm to 0.3 mm, and even if a new wire electrode is constantly supplied during EDM, the wire electrode itself wears out and is damaged. The wire may break without being able to withstand the tension, and the processing may be interrupted. As a measure against such a case, there has been an automatic wire feeder.

FIG. 6 shows a state of a repairing operation when a wire is broken in a conventional wire cut electric discharge machine. The wire electrode (1)
When the wire breaks, the X-axis driving device (2) and the Y-axis driving device (3) are automatically driven to move the workpiece (12) through the XY table (not shown), and the wire electrode (1)
Is moved from the wire electrode disconnection position (4) to the machining start position (5), and the wire electrode (1) is restored to a new one at the machining start position (5).

Next, the wire electrode (1) is returned to the wire electrode disconnection position (4) while passing the wire electrode (1) through the machining groove (7) of the already processed locus (6), and then the machining power source (8) is turned on to discharge electric energy. It is generated and it continues processing.

If the wire electrode (1) is broken during machining, the output of the rotary encoder (10) connected to the guide pulley (9) will not be sent to the control device (11), and the encoder (1
The count number of the output pulse train of 0) does not reach a certain number even after a certain period of time elapses, whereby a wire breakage is detected and the automatic wire feeder is activated. The repair operation at the time of wire breakage can be repeated indefinitely by setting the control device (11), but normally, a certain specified number of times is set, and within this specified number of times, the wire breakage Even if it occurs once, it can be repaired repeatedly.

[Problems to be Solved by the Invention] However, in the wire-cut electric discharge machine as described above, the repair operation at the time of wire breakage often reaches a prescribed number of times. The wire electrode (1) usually passes through the machining groove (7) with a very narrow gap of about 0.02 mm to 0.08 mm plus the diameter of the wire electrode, but due to the release of internal stress of the workpiece (12) generated during machining. As shown in FIG. 7, the machining groove width g is equal to the wire electrode diameter d in the middle of the already-processed locus (6) due to the distortion or the mismatch of the machining contour and the desired contour shape in the corner portion peculiar to the wire electric discharge machining. In some cases, the wire electrode (1) cannot pass through the processed groove (7) due to a smaller deformation. In such a case, since the wire electrode (1) is sheared again before reaching the wire disconnection position (4), the wire disconnection is detected at the same time when the machining is restarted, and thereafter, the same is performed until the specified number of times is reached. The repair operation will be repeated. When the repair operation reaches the specified number of times, the repair operation thereafter is not normally performed, and the machining is temporarily terminated while the unmachined portion remains. Alternatively, when the wire cut electric discharge machine is operated according to a program for machining a plurality of shapes and the next shape is reserved, the machining of the next shape is performed.

When an unprocessed portion is generated in this way, the operator must manually move the workpiece to the position where the processing was interrupted and restart the processing, which is extremely troublesome and requires a long time. There was a problem that the processing of could not be completed unattended and smoothly. Further, as described above, if the machining groove is deformed such that the wire electrode cannot pass through the already-processed locus, the machining cannot be restarted no matter how many times the repairing operation is repeated, so that the unmanned operation can be smoothly completed. It was an obstacle.

The present invention has been made to solve the conventional problems, and even when the machining groove is deformed such that the wire electrode cannot pass through the already-processed locus during the repair operation when the wire electrode is broken, the invention can be performed smoothly. An object of the present invention is to obtain a wire-cut electric discharge machining device that can continue machining and can complete machining unattended.

[Means for Solving Problems] A wire-cut electric discharge machining apparatus according to the present invention includes a wire-breakage detecting means for detecting wire-breakage during movement of a wire electrode from a machining start position to a wire-electrode wire-breakage position, and wire-breakage detection. When the detection signal from the means is input, the control means returns to the machining start position again, and from that position, the wire electrode is moved in the direction opposite to the forward direction of the machining trajectory to continue the machining.

[Operation] In the present invention, when the wire electrode is broken during wire electric discharge machining, when it is detected that the wire electrode has broken while passing through the machining groove when the wire electrode is repaired, the wire electrode is moved to the machining start position. After a new restoration, the machining start position is moved in the direction opposite to the forward direction of the machining trajectory to continue the machining.

[Embodiment] Next, an embodiment of the present invention will be described with reference to FIGS. It should be noted that the same or corresponding parts as those in the conventional example of FIG.

FIG. 1 is a block diagram of a wire-cut electric discharge machining apparatus according to an embodiment of the present invention, showing a state where a workpiece (12) is distorted and the wire electrode (1) cannot pass through a preprocessed locus. ing. In the figure, (11a) is a control device, and its user memory (13) stores a machining program of a machining trajectory in the forward direction and a machining program of a machining trajectory in the opposite direction by NC tapes (14) and (15). ing. A control device (16) detects whether or not the wire electrode (1) is broken when the wire electrode (1) is repaired.

FIG. 2 is a block diagram showing a hardware configuration of the control device (11a) of FIG. 1, in which (21) is a tape reader,
(22) is a CRT, (23) is a CRT controller, (24) is a keyboard, and (25) is a keyboard interface.
(26) is an input interface to which the output of the control device (16) is input. (27) is the CPU, (28) is the ROM that stores the program that regulates the arithmetic operation of the CPU (27), and (29) is the
It is a servo controller that controls the X and Y axis drive units (2) and (3), respectively. (30) is an output interface, the control output of which is sent to the machining power supply (8). (13
A) and (13B) are RAMs of the user memory, which store the machining programs of the machining trajectory in the forward direction and the machining trajectory in the reverse direction, respectively. For example, as shown in FIG. 3, a machining trajectory (A1) in the forward direction and a machining trajectory (A2) in the reverse direction are stored together with machining information. Here, the machining locus is a path that starts from the machining start point (5) and returns to the machining machining start point (5) again. Only differ from each other in the direction of their processing.

FIG. 4 is a block diagram of the control device (16). In the figure, (31) is an input gate to which the output of the rotary encoder (10) is input. (32) is a counter circuit, which is a rotary encoder (10) sent through an input gate (31).
The pulse train of is counted. (33) is a register for temporarily storing the count value of the counter circuit (32). (34) is a comparator, which compares the count value from the counter circuit (32) with a predetermined value set to determine the wire electrode disconnection,
The result is sent to the control device (11a). (35) is a control circuit, which sends a gate signal to the input gate (31) to open the gate, sends a reset signal to the counter circuit (32) at a constant cycle to set the initial state, and latches to the register (33). Send a signal to temporarily store data.

The wire cut electric discharge machine configured as described above will be described with reference to the flow chart of FIG. If the wire electrode (1) is broken during the machining by reading the machining program of the machining trajectory in the forward direction from the user memory (13A), the X-axis drive unit (2) and the Y-axis drive unit (3) will move the X-axis. The workpiece (12) is moved by moving a Y table (not shown), which moves the wire electrode (1) from the wire disconnection position (4) to the machining start position (5) (S1). After repairing the wire electrode (1) (S
2) In the same manner as in the conventional case, the processed groove (7) is moved through the processed groove (6) (S3). At that time, the presence or absence of disconnection of the wire electrode (1) is checked (S4), and if not disconnected, the movement of the wire electrode (1) is continued (S5). The operation of this step (S4) and (S5) is the wire electrode (1)
Is repeated until the wire break position (4) is reached (S
6). When the wire electrode (1) reaches the wire disconnection position (4), a control signal is sent from the control device (11a) to the machining power source (8), the machining power source (8) is turned on, and machining is restarted. (S7).

However, if there is a portion where the processed groove width: g <wire electrode: d while moving the wire electrode (1) according to the already processed locus (6), the wire electrode (1) will be broken. When the wire electrode is broken, the rotation of the guide pulley (9) in FIG. 1 stops, and the output of the rotary encoder (10) connected to the guide pulley (9) is not sent to the control device (16).
It is detected when the count number of the output pulse train of the rotary encoder (10), that is, the count value of the counter circuit (32) does not reach a certain specified number even after a certain period of time. When the control device (16) detects disconnection of the wire electrode (1), the wire electrode (1) is returned to the processing start point (5) again (S8), and the wire electrode (1) is repaired there (S9). Next, the machining program of the machining trajectory in the reverse direction is read from the user memory RAM (13B), and machining of the trajectory (6 ') in FIG. 1 is continued according to the machining program (S10).

In the above, both the initial wire breakage and the wire breakage after repair are detected via the control device (16), but these are in the middle of returning to the wire breakage position after the wire repair operation in the control device (11a) or It is distinguished by whether the wire breaks immediately after that.

Further, in the above-mentioned embodiment, if there is a wire breakage after repairing once, the machining program of the machining trajectory in the opposite direction is read out next, but after the wire electrode (1) is broken several times ( (See the broken line in FIG. 5) It is also possible to shift to the above machining program. Further, the control device (16) has the structure shown in FIG. 4, but the ROM (28) in FIG.
An appropriate program corresponding to the operation of the circuit of FIG. 4 may be stored in and stored in a part of the control device (11a).

[Effects of the Invention] As described above, according to the present invention, when the wire electrode is broken during wire electric discharge machining, if the workpiece is distorted due to release of internal stress, the wire electrode cannot pass through the machining groove. Since it is determined that the machining path is in the opposite direction and machining is continued, even if the wire electrode is broken during machining, unmanned machining can be completed and the reliability is significantly improved. ing.

[Brief description of drawings]

FIG. 1 is an explanatory view of a wire cut electric discharge machining apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram showing a hardware configuration of a control device (11a) of FIG. 1, and FIG. 3 is a machining trajectory in a forward direction. 4 is a block diagram of the control device (16) in FIG. 1, FIG. 5 is a flow chart showing the operation of the above embodiment, and FIG. 6 is a conventional wire cutting. FIG. 7 is an explanatory view of the electric discharge machine, and FIG. 7 is an explanatory view showing a cause of disconnection of the wire electrode. In the figure, (1) is a wire electrode, (2) is an X-axis drive device, (3) is a Y-axis drive device, (4) is a wire electrode disconnection position, (5) is a machining start position, and (6) is an existing position. Processing locus,
(7) is a machining groove, (8) is a machining power source, (9) is a guide pulley, (10) is a rotary encoder, (11) is a controller,
(12) is a workpiece, (13) is a user memory, (14) is a machining NC tape, (15) is a reverse trajectory machining NC tape, and (16) is a controller. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (3)

[Claims] 1. A wire electrode is made to face a conductive work piece with a minute gap, and the work piece is cut by electric discharge energy generated below a medium of a working liquid supplied to the minute gap. At the same time, when the wire electrode is cut, the wire electrode is automatically moved to the machining start position via the XY cross table, and the wire electrode is repaired at the machining start position, and then the machining groove is formed in accordance with the machining path. While passing the wire electrode, return to the above wire electrode disconnection position,
In a wire-cut electric discharge machine that subsequently generates electric discharge energy to continue machining, a wire-break electric discharge detecting means for detecting a wire break while the wire electrode is moving from the machining start position to the wire electrode wire break position, and the wire break detection. When the detection signal from the means is input, the wire electrode is returned to the machining start position again, and the wire electrode is moved from that position in the direction opposite to the forward direction of the machining trajectory, and the machining means is continued. Wire cut electric discharge machine. 2. The wire cut discharge according to claim 1, wherein the control means is provided with a storage means for storing a machining program for a machining trajectory in a forward direction and a machining program for a machining trajectory in a reverse direction. Processing equipment. 3. The control means moves the wire electrode in a direction opposite to the forward direction of the machining locus to continue machining,
The wire cut electric discharge machining apparatus according to claim 2, wherein the control is performed based on a machining program of a machining trajectory in the opposite direction.