JPH04115821A - Wire electric discharge machining device - Google Patents

Abstract

PURPOSE:To surely and smoothly reinitiate machining upon recovery from wire breakage, by performing change-over among several kinds of machining conditions for contact release, which are stored in a memory means, in accordance with a detection signal from an electrode contact detecting means so as to control reinitiation of machining if a wire electrode and a workpiece comes into a recontact condition. CONSTITUTION:When a wire electrode 8 and a workpiece 1 come into contact with each other during performance of wire electric discharge machining under a predetermined NC program, an electrode contact detecting means 11 detects such a contact so as to control the reinitiation of machining. Even if the wire electrode 8 is broken, the control for reinitiation of machining is carried out upon recovery from the breakage of wire electrode. Then, when the wire electrode 8 and the workpiece 1 come into recontact with each other, the control for reinitiation of machining is carried out through change-over among several kinds of machining conditions for contact release which are stored in a memory means 15, in accordance with a detection signal from the electrode contact detecting means 11.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wire electrical discharge machining device, and in particular, even if a wire electrode comes into contact with a workpiece during electrical discharge machining, machining can be reliably resumed. The present invention relates to a wire electrical discharge machining device that can perform

[Prior Art] As a conventional wire electrical discharge machining device of this type, there is a
The technique disclosed in Japanese Patent No. 127227 can be mentioned.

FIG. 3 is a schematic configuration diagram showing a conventional wire electrical discharge machining apparatus.

In the figure, (1) is a workpiece, (2) is a work table on which workpiece (1) is placed, and (3) is a workpiece.
(4) is a work table small drive motor that drives the work table (2). Table driving means (5) is a machining power source, (6) is a feeder that supplies voltage for electric discharge machining from the machining power source (5), (7)
) is a wire automatic feeding means that sequentially transfers the wire electrode to the workpiece (1), (8) is the wire electrode, and (9) is the workpiece (1).
) and the wire electrode (8).

The conventional wire electric discharge machining apparatus is configured as described above, and performs machining using electric discharge generated between the workpiece (1) and the wire electrode (8).

That is, the wire electrode (8) is sequentially transferred to the workpiece (1),
Electric discharge machining is performed by intermittently applying a predetermined voltage between the wire electrode (8) and the workpiece (1). Note that the processed shape is determined by the movement locus of the wire electrode (8) controlled by the NC means (3). That is,
The NC means (3) controls the drive of the work table driving means (4) and drives the work table (1) on which the work (1) is placed.
2) is moved appropriately and processed into the desired shape. Also, if necessary, the wire electrode (8) can be supplied by the wire automatic supply means (7) controlled by the same (NC means (3))
are automatically connected and disconnected.

Furthermore, the voltage between the workpiece (1) and the wire electrode (8) is constantly detected by the voltage detection means (9), and the moving speed of the worktable (2) is controlled so that this voltage is kept constant. Ru. By each of these controls, a stable electrical discharge is continuously generated between the workpiece (1) and the wire electrode (8), and machining progresses.

In normal machining conditions, machining progresses only by adjusting the movement speed described above, but when the wire electrode (8) and the workpiece (1) come into contact with each other, the wire electrode (8) 8) and the workpiece (1), and it becomes necessary to restart machining by a method other than adjusting the moving speed described above.

Here, the machining operation by the conventional wire electric discharge machining apparatus will be explained, including the case where machining is restarted.

FIG. 4 is a plan view showing a machining trajectory by a conventional wire electric discharge machining device.

In the figure, (20) is the initial hole that is the starting point of machining, (21) is the contact occurrence position where the workpiece (1,) and wire electrode (8) come into contact, and (22) is the point where machining is restarted. shows the position where the machining power source (5) is turned on again. Further, the solid line indicates a trajectory that has already been processed, and the two-dot chain line indicates a trajectory that is to be processed from now on.

First, in the initial hole (20), the NC means (
In response to the command from 3), the automatic wire supply means (7) operates, and the wire electrodes (8) are automatically connected. The NC means (3) moves the work table (2) appropriately by controlling the drive of the work table drive means (4) so as to follow a preprogrammed machining trajectory, and at the same time adjusts its moving speed. At the same time, while maintaining an appropriate distance between the workpiece (1) and the wire electrode (8), continuous electric discharge is generated to advance machining.

However, if the machining conditions suddenly change, it becomes impossible to maintain an appropriate distance between the wire electrode (8) and the workpiece (1), and the wire electrode (8) and the workpiece (1) come into contact. (Contact occurrence position (21) in Figure 4)
, the machining cannot continue and the machining progress stops. Therefore, when such a situation occurs, the trajectory progressed during machining is traced back in the opposite direction to release the contact state between the wire electrode (8) and the workpiece (1) (first machining restart control). . Normally, this first machining restart control releases the contact between the wire electrode (8) and the workpiece (1), and machining is restarted.

However, in order to trace the trajectory in the opposite direction,
Since it is necessary for the NC means (3) to sequentially store each coordinate value of the trajectory for each unit control time, a large amount of storage capacity is required to trace a long trajectory. However, there is a limit to the storage capacity for storing these coordinate values, and it is not possible to go back infinitely. Therefore, if the contact state between the wire electrode (8) and the workpiece (1) is not released even after going back a certain distance limited by the memory capacity of the NC means (3), the above-mentioned first processing is restarted. Machining cannot be resumed by control alone.

Therefore, in such a case, the processing power source (5) is turned off at the contact occurrence position (21), the wire electrode (8) is cut, and the process returns to the initial hole (20). This return method does not follow the previous machining trajectory, but returns via a short trajectory from the contact occurrence position (21) to the initial hole (20) (
(See the dotted line trajectory in Figure 4). Then, in this initial hole (20), the wire electrode (8) is connected again by the wire automatic supply means (7), and from there, the wire electrode (8) is moved in the forward direction following the already processed trajectory, and the contact occurrence position (21
), the machining power source (5) is turned on again to restart machining (second machining restart control). This second machining restart control releases the contact between the wire electrode (8) and the workpiece (1), and machining is restarted. To return to the initial hole (20), go back to the initial hole (20).
) only need to be stored, and since the machined trajectory can be traced in the forward direction by reinterpreting and moving the cannibal program, a particularly large amount of storage capacity is not required. If the contact state between the wire electrode (8) and the workpiece (1) is not released even after such second machining restart control is performed, the above-described first and The second machining restart control is repeated a predetermined number of times.

By the way, in addition to the case where a contact state between the wire electrode (8) and the workpiece (1) occurs, there is also a case where a disconnection of the wire electrode (8) occurs and this recovery is performed (hereinafter referred to as disconnection recovery).
In this case, processing restart control as described above is required. However, even when the disconnection is restored and processing is to be restarted, the contact state between the wire electrode (8) and the workpiece (1) may not be released. Here, the reason why the wire electrode (8) and the workpiece (1) become electrically short-circuited when the disconnection is restored will be explained.

First, when machining a thick workpiece (1), the wire electrode (8) is deflected due to machining reaction force during machining, and this causes the NC command value (on the NC This is because there may be a difference between the machining position) and the actual machining position. Second, due to a time difference due to a delay in detecting the occurrence of a wire breakage, a difference may occur between the coordinate values when the wire breakage is detected by the NC means (3) and the coordinate values at which the wire breakage actually occurs. be. Thirdly, the width of the processed groove may become narrow due to copper adhesion that occurs during the first cut.

Therefore, what was devised was JP-A-1-127227.
This is the technology published in the publication, and this publication includes wire electrodes (
8) and the workpiece (1), the wire electrode (8) is moved back a certain distance along the machining path, the short circuit is resolved, and the machining process continues along the original path again. A technique for performing this has been disclosed. Figure 5 shows the
FIG. 1 is a block configuration diagram showing a conventional wire electric discharge machining apparatus published in Publication No. 127227. In the drawings, the same reference numerals and symbols as those explained in FIG. 3 above indicate constituent parts that are the same as or correspond to the constituent parts explained in FIG. 3.

In the figure, (10) is a central processing unit (hereinafter referred to as CPU) built in the NC means (3), which moves the work table (2), connects/cuts the wire electrode (8), etc. according to the NC program. Turning on/off the processing power supply (5)
Control the current value etc. as appropriate. (11) is a wire electrode (8)
Electrode contact detection means (12) is a trajectory tracing control means for detecting the contact state between the wire electrode (8) and the workpiece (1), and the electrode contact detection means (11) detects the contact state between the wire electrode (8) and the workpiece (1). When detected, the wire electrode (8) is once traced back along the machining path in the opposite direction, and then trajectory tracing control is performed to continue the machining along the original machining path. (
13) is a keyboard for performing manual input.

Next, machining restart control when recovering from a wire breakage using this wire electric discharge machining apparatus will be explained with reference to a flowchart.

FIG. 6 is a flowchart showing machining restart control when recovering from a wire breakage using a conventional wire electric discharge machining apparatus. This series of operations is executed when disconnection recovery is performed.

First, in step S1, the wire electrode (8) and the workpiece (1)
Determine whether contact with has been detected.

This contact is detected by electrode contact detection means (11).

In the case of non-contact, the machining can be performed normally, so the process advances to step S5 and the normal machining is continued. As a result, the machining restart control upon recovery from wire breakage ends. On the other hand, if contact is detected, step S2
The wire electrode (8) is controlled by the trajectory tracing control means (12) at
trace in the opposite direction along the machining path. And Ste.
Step S3 is used to return the workpiece (1) to the position before the short circuit caused by contact with the wire electrode (8), and step S4
Then, it is determined again whether contact between the wire electrode (8) and the workpiece (1) is detected. In the case of non-contact, step S
The process proceeds to step 5, where normal machining is performed as it is, and the machining restart control upon recovery from wire breakage is completed. If contact is detected in step S4, the process proceeds to step S6, and it is determined whether or not the trajectory retrospective control from step S2 to step S4 has been performed a specified number of times, and if it has not been performed the specified number of times, the process proceeds to step S2 again. Return and repeat the trajectory retrospective control described above.

If the contact state cannot be canceled and the short-circuit state remains even after the trajectory retrospective control is performed a specified number of times, the machining operation by this wire electric discharge machining device is stopped in step S7, and this series of wire breakage recovery steps are performed. The machining restart control in is completed. Note that this designated number of times can be set arbitrarily.

[Problems to be Solved by the Invention] In the conventional wire electric discharge machining apparatus as described above, even when attempting to restart machining after disconnection, the wire electrode (8
) and the workpiece (1) may not be released, and in this case, trajectory retrospective control is performed. That is, the machining path is temporarily traced back in the opposite direction by the trajectory tracing control means (12), and further returned to the position before the short circuit caused by contact between the workpiece (1) and the wire electrode (8), and machining is restarted. was.

However, even after performing the machining restart control as described above, the contact state between the wire electrode (8) and the workpiece (1) may still not be released, and in this case, this trajectory retrospective control may be repeated a specified number of times. However, conventionally, the process was repeated under the same processing conditions (same wire tension, same processing voltage, etc.). Therefore, the probability that the contact state would be canceled and machining would be restarted by repeating this trajectory retrospective control was extremely low. For this reason, machining was often forced to stop midway.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a wire electrical discharge machining apparatus that can reliably and smoothly restart machining by canceling the contact state even if the contact state occurs again in machining restart control when recovering from a wire breakage. This is an issue to be addressed.

[Means for Solving the Problems] A wire electrical discharge machining apparatus according to the present invention includes a wire electrode (8
) and the workpiece (1), and an electrode contact detection means (11) for detecting the contact state between the workpiece (1) and the workpiece (1), and a machining shape, machining voltage, and wire electrode (8) of the workpiece (1) according to a predetermined NC program.
NC means (3) performs machining restart control based on the disconnection of the wire electrode (8) and the output signal of the electrode contact detection means (11); a processing condition switching means (14) for switching processing conditions based on the output signal of step 11); and a storage means for storing various processing conditions for releasing the contact state between the wire electrode (8) and the workpiece (1). (15).

[Function] In the present invention, when the wire electrode (8) and the workpiece (1) come into contact during wire electric discharge machining according to a predetermined NC program, this contact is detected by the electrode contact detection means ( 11) is detected and processing restart control is performed, but even if a break occurs in the wire electrode (8),
Processing restart control is performed at the time of this disconnection recovery, and when the wire electrode (8) and the workpiece (1) come into contact again, based on the detection signal from the electrode contact detection means (11), Since machining restart control is performed by switching various machining conditions for contact release stored in the storage means (15), the contact state is easily released and the probability of restarting machining is extremely high. There will be no more stopping.

[Example] The present invention will be explained in detail below.

FIG. 1 is a block diagram showing a wire electrical discharge machining apparatus which is an embodiment of the present invention. Note that in the drawings, the same reference numerals and symbols as in the above-mentioned conventional example indicate constituent parts that are the same as or correspond to the constituent parts in the above-mentioned conventional example, and thus redundant explanation will be omitted here.

In the figure, (14) is a processing condition switching means that switches processing conditions based on the output signal of the electrode contact detection means (11) during trajectory retrospective control when the wire electrode (8) recovers from disconnection; ) is a storage means for storing the processing conditions as data.

Note that this processing condition is based on the wire electrode (8) and the workpiece (1).
) are used to release the contact state.

The wire electrical discharge machining apparatus of this embodiment is configured as described above, and as in the conventional case, the wire electrode (8) and the workpiece (
1) Machining is performed using the electrical discharge that occurs between the two. That is, electric discharge machining is performed by sequentially transferring the wire electrode (8) to the workpiece (1) and intermittently applying a predetermined voltage between the wire electrode (8) and the workpiece (1).

If the wire electrode (8) breaks during this electrical discharge machining, it will automatically recover. Note that this disconnection recovery operation itself is the same as that of the conventional example, so a description thereof will be omitted here. Therefore, the schematic configuration diagram of the wire electric discharge machining apparatus of this embodiment is the same as that of the conventional example shown in FIG.

Therefore, here, when the wire electrode (8) returns to the position where the wire breakage occurred after the wire breakage recovery is completed and the machining power source (5) is turned on, the wire electrode (8) and the workpiece (1) are in contact with each other. The following will focus on the machining start control that is performed when .

Next, machining restart control when recovering from a wire breakage by the wire electrical discharge machining apparatus of this embodiment will be explained with reference to a flowchart. FIG. 2 is a flowchart showing an example of machining restart control in recovery from wire breakage by the wire electrical discharge machining apparatus of the present invention. This series of operations is executed when disconnection recovery is performed.

First, in step S1, the wire electrode (8) and the workpiece (1)
It is determined whether or not contact with has been detected, and if there is no contact, the process proceeds to step S5 and normal machining is performed as it is. On the other hand, if contact is detected, in step S2 the wire electrode (8) is traced back along the machining path in the opposite direction. After this, in the conventional example, the work was returned to the position before the short circuit caused by contact between the workpiece (1) and the wire electrode (8) in step S3, but in this example, step S2 and step S3 are In between step 82.
5 is provided, and the machining condition switching means (14) calls up the machining conditions for short-circuit release stored in the storage means (15) and switches the machining conditions. Then, the process proceeds to step S3, where the work is returned to the position before the short circuit occurred due to contact between the workpiece (1) and the wire electrode (8), and the contact between the wire electrode (8) and the workpiece (1) is resumed at step S4. Determine whether or not it has been detected. In the case of non-contact, in the conventional example, step S is immediately performed.
5, and normal machining was performed as it was. However, in this embodiment, the machining conditions were changed in step 82.5, so after returning to the original machining conditions in step 84.5, the process continued in step S5. Proceed to normal processing. If contact is detected in step S4, the process proceeds to step S6, and it is determined whether or not the trajectory retrospective control from step S2 to step S4 has been performed a specified number of times, and if it has not been performed the specified number of times, the process proceeds to step S2 again. Return and repeat the trajectory retrospective control described above. At this time, in step 82.5, switching to other machining conditions is performed again.

Therefore, each machining condition is changed each time the trajectory retrospective control is repeated a specified number of times. If the contact state still cannot be released and the short-circuit state remains even after the trajectory retrospective control has been performed a specified number of times, the machining operation by this wire electric discharge machining device is stopped in step S7, and the series of Processing restart control upon recovery from disconnection ends.

In this way, the flowchart of machining restart control in disconnection recovery shown in FIG. 2 is similar to the conventional flowchart of machining restart control in disconnection recovery shown in FIG.
and step S4.5. That is, in this embodiment, in machining restart control when recovering from wire breakage,
If contact occurs and a short circuit occurs, the processing conditions are changed to release the contact state.

Here, the processing conditions for canceling the short circuit will be explained.

For example, the wire tension of the wire electrode (8) may be lowered than during machining under normal normal conditions.
8) Makes vibration easier to occur. And this wire electrode (
Using the vibration of the wire electrode (8) and the workpiece (1),
) to make it easier to release the contact state. In addition, processing power source (5)
By increasing the machining voltage supplied from the wire electrode (8) and the workpiece (1), the discharge gap between the wire electrode (8) and the workpiece (1) is widened, and contact is prevented from coming into contact again after the contact state has been released. Make it less likely to occur.

By changing the machining conditions in this way, the state in which the wire electrode (8) and the workpiece (1) are in contact can be temporarily released. - When it is temporarily released, the wire electrode (8) and the workpiece (1) are
widen the discharge gap between the two and prevent them from coming into contact again.

Then, when the discharge gap between the wire electrode (8) and the workpiece (1) becomes stable, the machining conditions are returned to the original conditions and machining is restarted. As a result, normal machining can be continued from then on.

Note that a plurality of patterns of machining conditions for short-circuit release are stored in advance in the storage means (15).

Then, when the machining restart control is performed upon recovery from wire breakage, as shown in the explanation of step 82.5 in FIG. Can be switched.

As described above, the wire electrical discharge machining apparatus of this embodiment sequentially transfers the wire electrode (8) to the workpiece (1), and applies a predetermined voltage intermittently between the wire electrode (8) and the workpiece (1). wire electrical discharge machining means for performing electrical discharge machining by applying electric current; electrode contact detection means (11) for detecting the contact state between the wire electrode (8) and the workpiece (1); NC means (3) for controlling the machining shape of the workpiece (1), the application state of the machining voltage, the cutting/connection of the wire electrode (8), and the machining restart control based on the output signal of the electrode contact detection means (11); processing condition switching means (14) for switching processing conditions based on the output signal of the electrode contact detection means (11) when controlling restart of processing due to recovery from disconnection of the wire electrode (8); It is equipped with a storage means (15) for storing various processing conditions for releasing the contact state with the workpiece (1).

When the wire electrode (8) and the workpiece (1) come into contact with each other during wire electric discharge machining according to a predetermined NC program, the electrode contact detection means (11) detects this contact, Machining restart control is performed, and
Even when a break occurs in the wire electrode (8) and recovery is performed (break recovery), processing restart control is performed. Then, in the machining restart control due to this disconnection recovery,
After the wire breakage recovery is completed, place the wire electrode (
8) returns and when the machining power source (5) is turned on, if the wire electrode (8) and the workpiece (1) come into contact again, the detection signal from the electrode contact detection means (11) Based on this, trajectory retrospective control is performed by switching various machining conditions stored in the storage means (15). As a result, the contact state between the wire electrode (8) and the workpiece (1) is temporarily released, and processing is restarted.

Therefore, in the wire electrical discharge machining apparatus of this embodiment, trajectory retrospective control is not repeated a specified number of times under the same machining conditions (same wire tension, same machining voltage, etc.) as in the past, but rather Since trajectory retrospective control is repeated by appropriately switching to machining conditions that facilitate peeling off, the contact state is easily released and the probability that machining will be resumed becomes extremely high.

As a result, unlike in the past, machining does not stop midway, and machining can be restarted reliably and smoothly when the disconnection is restored.

By the way, in the above description of the embodiment, an example was explained in which the trajectory retrospective control and the machining condition switching operation are combined, that is, an example in which the machining conditions are switched every time the trajectory retrospective control is repeated. It is possible to release the contact state to some extent by simply switching the machining conditions without using control.

Further, the timing for changing the machining conditions may be before performing the trace tracing, that is, before step S2 in FIG. 2. moreover,
In the above embodiment, a wire electrical discharge machining apparatus is described in which the machining condition switching means (14) and the storage means (15) are incorporated into the NC means (3), but they may be provided separately.

[Effects of the Invention] As described above, the wire electrical discharge machining apparatus of the present invention includes electrode contact detection means for detecting the contact state between the wire electrode and the workpiece for electrical discharge machining, and various machining controls according to a predetermined NC program. a machining condition switching means for switching machining conditions based on the output signal of the electrode contact detection means; and a storage means for storing various machining conditions; When the wire electrode and the workpiece come into contact, the electrode contact detection means detects this contact and controls the restart of machining. However, even when the wire electrode is broken, this disconnection recovery is performed. When machining restart control is performed at times and the wire electrode and workpiece come into contact again, based on the detection signal from the electrode contact detection means,
By switching the various machining conditions for contact release stored in the storage means and performing machining restart control, the contact state is easily released, the probability of restarting machining is extremely high, and machining is stopped midway. Since there is no need to do this, processing can be restarted reliably and smoothly when the disconnection is restored.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram showing a wire electrical discharge machining apparatus which is an embodiment of the present invention, and FIG. 2 is a flowchart showing an example of machining restart control in recovery from disconnection by the wire electrical discharge machining apparatus which is an embodiment of the invention. FIG. 3 is a schematic configuration diagram showing a conventional wire electrical discharge machining device, FIG. 4 is a plan view showing a machining trajectory by the conventional wire electrical discharge machining device, and FIG. 5 is a block diagram showing a conventional wire electrical discharge machining device. FIG. 6 is a flowchart showing machining restart control when recovering from a wire breakage using a conventional wire electric discharge machining apparatus. In the figure, 1: Work 3: NC means 4: Work table driving means 5: Processing power supply 7: Wire automatic supply means 8: Wire electrode 9: Voltage detection means 10: CPU 11: Electrode contact detection means 12: Trajectory retrospective control means 14: Machining condition switching means 15: Storage means. In the drawings, the same reference numerals and the same symbols indicate the same or equivalent parts. Agent: Patent attorney Masuo Ohne and 2 others 21.22

Claims (1)

[Scope of Claims] Wire electrical discharge machining means for sequentially transferring a wire electrode to a workpiece and applying a predetermined voltage between the wire electrode and the workpiece to perform electrical discharge machining, and a contact state between the wire electrode and the workpiece. an electrode contact detection means for detecting; a numerical control means for controlling resumption of machining according to the machining shape of the workpiece, machining voltage, cutting of the wire electrode, and an output signal of the electrode contact detection means according to a predetermined numerical control program; During machining restart control due to wire electrode disconnection recovery,
It is characterized by comprising a processing condition switching means for switching processing conditions based on the output signal of the electrode contact detection means, and a storage means for storing various processing conditions for releasing the contact state between the wire electrode and the workpiece. Wire electrical discharge machining equipment.