JPH0688174B2 - Wire cut electrical discharge machining method and device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a wire-cut electric discharge machining method and apparatus capable of reliably restarting machining even when contact occurs during machining. is there.

[Prior Art] FIG. 4 is a block diagram schematically showing a conventional wire cut electric discharge machine, and FIG. 5 is an explanatory view showing a machining operation of the wire cut electric discharge machine.

In the figure, a work (1) to be electric discharge machined is fixed on a work table (2), and the work table (2) is moved by a motor (4) driven by a command from an NC device (3). A machining power source (5) controlled by the NC device (3) applies a machining voltage through the feeder (6) between the work (1) and the wire electrode (8), and the work (1) and the wire electrode (8). Between the two) causes the electric discharge to occur and the machining proceeds. The voltage between the work (1) and the wire electrode (8) is detected by the voltage detection device (9). The machining shape, that is, the movement locus of the wire electrode (8) is controlled by the NC device (3). Also, if necessary, the wire electrode (8) is controlled by the NC device (3), and the wire automatic supply device (7) is used.
Will automatically connect / disconnect.

In order to continuously and stably generate an electric discharge between the work (1) and the wire electrode (8) to proceed with machining, the voltage between the work (1) and the wire electrode (8) is constantly detected. The moving speed of the work table is adjusted so that this voltage is kept constant.

Normally, it is possible to proceed with the machining only by adjusting the moving speed, but once the contact state is reached, electric discharge does not occur and it is necessary to restart the machining using a method other than adjusting the moving speed. Occurs.

The function of resuming conventional processing will be described below.

In the initial hole (20), the automatic wire feeder (7) operates and the wire electrode (8) is automatically connected according to a command from the NC device (3). The NC device (3) drives the motor (4) according to the pre-programmed trajectory to move the work table (2), and adjusts the moving speed to appropriately adjust the distance between the wire electrode (8) and the work (1). Discharge is generated continuously while maintaining a certain interval,
Advance processing. In FIG. 2, a thick line portion represents a portion which has already been machined, and a thin line portion represents a locus to be machined.

Due to a sudden change in the processing state, a state in which an appropriate distance cannot be maintained between the wire electrode (8) and the work (1) occurs, and the wire electrode (8) and the work (1) are brought to the contact position (21). In the case of contact, the first machining restart control is to reverse the trajectory that has been progressed while machining and release the contact between the wire electrode (8) and the work (1). . Normally, the contact is released by this control and the processing proceeds again.

However, since it is necessary to sequentially store the coordinate values for each unit control time of the NC device (3) in order to follow the trajectory that was proceeding in reverse, a large amount of data is needed to follow the long trajectory in reverse. Requires storage capacity. In addition, since the storage capacity for storing the coordinate values is limited, it is not possible to trace backwards infinitely. Therefore, if the contact is not released even if the contact is reversed by the fixed amount limited by the storage capacity of the NC device (3), the machining cannot be restarted only by this control. In such a case, as the control of the second machining restart, the machining power source (5) is turned off at the contact position (21), the wire electrode (8) is cut, and the initial hole (20) is extended to the initial hole. After returning the path with a short distance, reconnect the wire electrode (8) with the automatic wire feeder (7), and then move forward by following the previously processed path and move it to the contact position (21). Control is performed to turn on the machining electrode (5) and restart machining. In FIG. 2, the trajectory of the dry run is shown by the dotted line. In order to return to the initial hole (20), only the coordinates of the initial hole (20) need to be stored, and in order to follow the trajectory in the forward direction, the machining program can be interpreted and moved again. Therefore, it does not require a large storage capacity.

If the contact is not released even after the second machining restart control is performed, the first and second machining restart controls are repeated again within a predetermined number of times until the machining can be restarted.

[Problems to be Solved by the Invention] In the above-described method of resuming machining of the conventional electric discharge machining apparatus, the machining power re-input position (22) by the second machining resumption control is set to the first contact position ( Since it is the same as that of 21), the contact may occur again, and the contact may not be released even if the control of restarting the first and second machining is repeated a plurality of times. In such a case, there is a problem that it is necessary to stop the automatic operation and release the contact by the operation of the operator, or to perform the machining again from the beginning.

The present invention has been made to solve the above problems, and it is an object of the present invention to obtain a wire-cut electric discharge machining method and apparatus capable of reliably restarting machining even if a contact occurs during machining. To aim.

[Means for Solving the Problems] In the wire-cut electric discharge machining method according to the present invention, when the wire electrode comes into contact with a workpiece during electric discharge machining, a predetermined amount of a trajectory that has progressed while machining the wire electrode is reversed. Back, and then trace back the path that has already been machined, and restart the machining by reapplying the power in the vicinity of the previous contact occurrence position, and the contact between the wire electrode and the workpiece by the first machining restart step. If it is not released, the machining power is turned off at the contact occurrence position, the wire electrode is cut off, the initial hole is returned to the initial hole with a short path to the initial hole to reconnect, and the already processed path is traced again. By the second machining restart step in which the power is turned on again to restart the machining near the contact occurrence position and the first machining restart step after the first and second machining restart steps When the contact between the wire electrode and the workpiece is not released, when the wire electrode reaches the vicinity of the previous contact occurrence position by the same procedure as in the second machining restart step, the machining power re-input position is restarted at the second machining last time. A correction second machining restart step of changing to a position before the contact occurrence position in the process and restarting the power supply by restarting the power supply, and after the correction second machining restart step, the contact between the wire electrode and the work is released. Until the first machining restart step and the correction second machining restart step are alternately repeated,
The re-input position of the processing power source during the operation of the process resuming process is set to a position a predetermined distance before the re-input position of the previous operation.

A wire cut electric discharge machine according to another invention is a counter for counting the number of times of contact of a wire electrode detected by an electrode contact detection means by an NC device that controls electric discharge machining, and an electrode contact detection means for the wire contact discharge means during electric discharge machining. When the contact between the electrode and the work is detected, the first storage means that stores a certain amount of machining trajectory before that time, and the counter detects the number of contact times as the first and fourth times when the electrode contact detection means detects the contact. When counting the even number of times thereafter, the wire electrode is first
The first machining restart in which the locus stored by the storage means is traced back and returned, the already-machined locus is traced again by the original machining program, and the machining power is turned on again near the contact occurrence position to start machining. When the wire electrode comes into contact with the workpiece during the electric discharge machining with the control means, the machining power is turned off at the contact occurrence position, the wire electrode is cut, and the wire is returned to the initial hole with a short path to the initial hole for connection. The wire electrode is stored on the basis of the program stored in the second storage means when the counter counts the number of contacts as the second time when the second storage means storing the program and the electrode contact detection means detect the wire electrode. Cutting and returning to the initial hole with a short path to the initial hole and reconnecting, re-connecting the already processed path to the original processing program. The second machining restart control means for restarting the machining power supply to restart the machining in the vicinity of the contact occurrence position and the counter for setting the third contact count when the electrode contact detection means detects the contact. When the wire electrode reaches the vicinity of the previous contact occurrence position by the same control procedure as the second machining restart control means when counting the odd number of times thereafter,
Corrected second machining restart control for changing the power-on position of the machining power source to a position before the contact occurrence position after the operation of the second machining restart control means at the previous time, and restarting the machining power source at the changed position to start the machining. And means.

[Operation] In the wire-cut electric discharge machining and device of the present invention,
If the wire electrode comes into contact with the workpiece during EDM,
On the basis of the memory of the first storage means, the first machining restart control means traces back the trajectory that has progressed while machining the wire electrode by a certain amount, and returns the trajectory that has already been machined based on the original machining program. When the contact is resumed, the power is turned on again in the vicinity of the previous contact occurrence position to restart the machining, and when the contact between the wire electrode and the work is not released by the first machining restart control means, the second machining restart control means causes the second storage. Based on the program memorized by the means, turn off the machining power at the contact occurrence position, cut the wire electrode, return to the initial hole with a short distance to the initial hole and reconnect, and based on the original machining program, The path of machining is traced again, the power is turned on again in the vicinity of the previous contact occurrence position to restart machining, and the first and second machining restart control means are operated, and again. When the contact between the wire electrode and the workpiece is not released by the operation of the first machining restart control means, the correction second machining restart control means performs the same control procedure as the second machining restart control means based on the number of contacts counted by the counter. When the wire electrode reaches the vicinity of the previous contact generation position, the re-input position of the machining power source is changed to a position before the contact generation position after the operation of the second machining resumption control means of the previous time, and the machining power source is changed at the changed position. The machining is started again by re-inputting, and after the operation of the correction second machining restart control means, the first machining restart control means and the corrected second machining restart control means are operated until the contact between the wire electrode and the workpiece is released. Repeatedly operated alternately to continue the electric discharge machining, and the correction is performed. The power-on position of the machining power source during the operation of the second machining restart step is a predetermined distance from the power-on position of the previous operation. And in front of the position.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory view showing a machining operation of a wire cut electric discharge machine.

In the figure, the same configurations as those of the conventional example are denoted by the same reference numerals, and the description of the duplicated configurations is omitted. (10) is a CPU built into the NC device (3), which moves the work table according to the NC program and automatically connects the wire electrode (8).
It has a function of cutting off, turning on / off of the processing power source (5), a function of controlling the current value, etc. (11) is a wire electrode (8)
And electrode contact detection means for detecting contact between the workpiece and the work (1),
(12) is a counter for counting the number of contact between the wire electrode (8) and the work (1) detected by the electrode contact detection means (11), and (13) is a first storage means for electrode contact detection means during electric discharge machining. When (11) detects the contact between the wire electrode (8) and the workpiece (1), a certain amount of machining locus from that time onwards is stored. (14) is a second storage means for turning off the machining power source (5) and disconnecting the wire electrode (8) at the contact occurrence position when the wire electrode (8) contacts the workpiece (1) during electric discharge machining. The program for returning to the initial hole (20) with a short distance to the initial hole and reconnecting is stored. (15) is a first machining restart control means, which traces back the wire electrode (8) stored in the first storage means (13) in the reverse direction, and traces the already machined trajectory again by the original machining program. The machining power source (5) is turned on again near the contact generation position (21) to control the machining to start. (16) is a second machining restart control means, which is based on the program stored in the second storage means (14),
Cut the wire electrode (8) and return it to the initial hole (20) with a short path to the initial hole, reconnect the wire electrode (8), and trace the already processed path again according to the original machining program. The machining power source (5) is turned on again near the tip contact occurrence position to control the machining to start. (17) is a correction second machining restart control means, in which the counter (12) is the wire electrode (8) and the work (1).
After counting a predetermined number of contact times, the processing power source (5) is restarted when the wire electrode (8) reaches the vicinity of the previous contact occurrence position by the same control procedure as the second processing restart control means (16). The feeding position is changed slightly before the contact occurrence position (22) after the operation of the second machining restart control means (16) at the previous time, and the machining power source (5) is turned on again at the changed position (23) to perform the machining. Control the start. (18) is a keyboard.

Next, the operation of the above embodiment will be described with reference to the flowchart of FIG.

First, the NC device (3) is operated according to an NC program to generate an electric discharge between the wire electrode (8) and the work (1) through the initial hole (20) to start electric discharge machining (step (30)). Next, during electrical discharge machining (step (31))
In addition, when the wire electrode (8) comes into contact with the work (1) due to a sudden change in the processing state, the electrode contact detection means (1
1) detects contact between the wire electrode (8) and the work (1) (step (32)). Then, the first machining restart control means (15) operates to restart the machining (step (3
3)). That is, when the electrode contact detection means (11) detects the contact between the wire electrode (8) and the work (1), the first machining restart control means (15) is based on the memory stored in advance by the first storage means (13). , The path that has progressed while processing the wire electrode (8) is reversed and returned, and then the path that has already been processed is followed again based on the original processing program, and processing is performed near the contact occurrence position (21). Reconnect the power supply (5) to restart the machining and continue the discharge (step (3
Four)). Further, when the contact between the wire electrode (8) and the work (1) is not released by the operation of the first machining restart control means (15), the electrode contact detection means (11) again causes the wire electrode (8) and the work (1). ) Contact (step (3
Five)). At this time, the counter (12) is the work electrode (8).
The number of contact times is counted, and it is determined whether the flag is 1 or not. If it is not 1, the flag is set (steps (36) and (37)). When the flag is set, the second
The machining restart control means (16) operates to restart the machining (step (38)). That is, the second machining restart control means (1
6) is based on a program stored in advance in the second storage means (14), and at the contact generation position (22), turns off the machining power source (5), disconnects the wire electrode (8), and cuts the initial hole (20). Back to the initial hole with a short path, reconnect the wire electrode (8), trace the path already processed based on the original machining program again, and process power near the previous contact occurrence position (22). (5) is reintroduced to restart machining, discharge is continued, and the process returns to step (34). When the contact between the wire electrode (8) and the work (1) is not released by the operation of the second machining restart control means (16), the electrode contact detection means (11) also detects the contact between the wire electrode (8) and the work (1). The contact is detected (step (40)). At this time, the process returns to step (33), and the first machining restart control means (15) operates again to restart the machining, and the wire electrode (8) is restarted by the first machining restart control means (15) again.
If the contact between the work (1) and the work (1) is not released, the electrode contact detection means (11) detects the contact between the wire electrode (8) and the work (11) (step (31)). The counter (12) counts the number of contacts of the work electrode (8), judges that the flag is 1 from the number of contacts, and the corrected second machining restart control means (17) operates to restart the machining. (Step (39)). That is, the correction second machining restart control means (17)
Returns the wire electrode (8) to the initial hole (20),
After that, the wire electrode (8) comes first to the contact occurrence position (22).
Until it reaches the vicinity, it operates in the same control procedure as the second machining restart control means (16), and when the wire electrode (8) reaches the vicinity of the previous contact occurrence position (22), the machining power source (5) The re-feeding position of is changed to a position slightly before the contact occurrence position (22) after the operation of the second machining restart control means (16) of the last time,
At the changed position (23), the machining power source (5) is turned on again to resume machining. In this way, the power-on position (23) of the machining power source (5) during the operation of the corrected second machining restart control means (17) is set to the machining power source (5) during the previous operation of the second machining restart control means (16). ) Of the re-injection position (22) to a predetermined distance, the possibility of contact between the wire electrode (8) and the work (1) is reduced,
The resumption of processing can be realized with a higher probability than the conventional method.

Further, when the contact between the wire electrode (8) and the work (1) is not released by the operation of the correction second machining restart control means (17), the electrode contact detection means (11) causes the wire electrode (8) and the work (1) to be released. ) Contact is detected. After that, the first machining restart control means (15) and the corrected second machining restart control means (7) until the contact between the wire electrode (8) and the work (1) is released.
And are alternately repeated to continue the electric discharge machining (step (34)) and end the electric discharge machining (step (4)
1)). In addition, the second correction second machining restart control means (1
When the operation of 7) is performed, the machining power supply (5) is turned on again (24).
Is set to a position a predetermined distance further than the re-input position (23) of the machining power source (5) during the operation of the first correction second machining restart control means (17). By doing so, the probability that the machining can be restarted becomes higher.

[Effects of the Invention] As described above, according to the present invention, when the wire electrode comes into contact with the workpiece during electric discharge machining, the trajectory that has progressed while machining the wire electrode is traced back by a certain amount, and then already machined. A first machining restart step of tracing the trajectory again and restarting the machining by reapplying the power in the vicinity of the previous contact occurrence position, and a contact occurrence position when the contact between the wire electrode and the workpiece is not released by the first machining restart step To turn off the machining power supply, disconnect the wire electrode, return to the initial hole with a short path to the initial hole, reconnect the wire, retrace the already processed path, and restart the power supply near the previous contact occurrence position. The second to put in and restart processing
When the contact between the wire electrode and the work is not released by the machining restarting step and the first machining restarting step after the first and second machining restarting steps, the wire electrode is first moved by the same procedure as the second machining restarting step. A correction second machining resumption process in which when the position near the contact generation position is reached, the machining power re-input position is changed to a position before the contact generation position in the previous second machining resumption process, and the power is re-powered to restart the machining. The machining is restarted with respect to the contact of the work electrode during the electric discharge machining, the first machining restarting step is performed by the first machining restarting control means, and the second machining restarting step is performed by the second machining restarting control means. The machining restart process is performed by the correction second machining restart control means, so that if a contact occurs during electrical discharge machining, the machining can be reliably restarted with a much higher probability than in the past and the automation rate is improved. And, there is an effect that high reliability can be realized machining.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an explanatory view showing a machining operation of a wire cut electric discharge machine.
FIG. 3 is a flow chart showing the operation of resuming machining of the wire cut electric discharge machine, FIG. 4 is a block diagram showing an outline of a conventional wire cut electric discharge machine, and FIG. 5 shows machining operation of the wire cut electric discharge machine. FIG. In the figure, (1) is the work, (3) is the NC device, and (5).
Is a processing power source, (8) is a wire electrode, (10) is a CPU, (1
1) is electrode contact detection means, (12) is counter, (13) is first storage means, (14) is second storage means, (15) is first machining restart control means, and (16) is second machining. Restart control means, (1
7) is a correction second machining restart control means. In each drawing, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A wire discharge for automatically supplying a wire electrode to a work and applying a machining voltage between the wire electrode and the work while moving the work table to generate an electric discharge for electric discharge machining of the work. In the machining method, when the wire electrode comes into contact with the workpiece during electric discharge machining, the trajectory that has progressed while machining the wire electrode is traced back by a certain amount, and then the trajectory that has already been machined is traced again, and the previous contact occurs. When the contact between the wire electrode and the workpiece is not released by the first machining restart step, the machining power is turned off at the contact occurrence position to turn the wire electrode off. Cut and return to the initial hole with a short path to the initial hole, reconnect and retrace the already processed path, and then touch When the contact between the wire electrode and the work is not released by the second machining restart step in which the power is turned on again near the raw position to restart the machining and the first machining restart step after the first and second machining restart steps. When the wire electrode reaches the vicinity of the previous contact occurrence position by the same procedure as in the second machining restart step, the re-entering position of the machining power source is changed to a position before the contact occurrence position in the previous second machining restart step, A correction second machining restart step of restarting the power by turning on the power again at the changed position, and the first machining restart step after the correction second machining restart step until the contact between the wire electrode and the workpiece is released. And the corrected second machining restart step are alternately repeated to continue the electric discharge machining, and the power-on position of the machining power source during the operation of the corrected second machining restart step is a predetermined distance from the reloading position at the previous operation. In front Wire-cut electric discharge machining method being characterized in that so as to position. 2. An automatic wire feeding device for automatically feeding a wire electrode to a work, an electrode contact detection means for detecting a contact between the wire electrode and the work, and a work table moved by an NC program and the wire electrode is automatically moved. In a wire cut electric discharge machining apparatus having a NC device having a function of connecting / disconnecting a wire, a function of controlling a machining power supply, and a function of resuming machining based on an output signal of an electrode contact detection means, the NC device is an electrode. A counter that counts the number of contact of the wire electrode detected by the contact detecting means, and stores a certain amount of machining trajectory from that time when the electrode contact detecting means detects the contact between the wire electrode and the workpiece during electric discharge machining. 1 When the memory means and the electrode contact detection means detect, the counter counts the number of contacts 1st and 4th and even number of times thereafter. At that time, the wire electrode is traced back by tracing back the locus stored by the first storage means, the locus that has already been machined is traced again by the original machining program, and the machining power source is turned on again in the vicinity of the previous contact occurrence position for machining. First machining restart control means for starting, and when the wire electrode comes into contact with the workpiece during electric discharge machining, the machining power is turned off at the contact occurrence position, the wire electrode is cut, and the initial hole has a short distance to the initial hole. Second storage means for storing a program for returning and reconnecting with a locus, and at the time of detection of the electrode contact detection means, the second storage means stores the wire electrode when the counter counts the number of contacts as the second time. Based on the program, cut the wire electrode, return it to the initial hole with a short distance to the initial hole, reconnect it, and reconnect it. When the electrode contact detection means detects the second machining resumption control means that restarts the machining power supply again by re-tracing the traced trajectory according to the original machining program and turning on the machining power source in the vicinity of the previous contact occurrence position, the counter makes contact. When the wire electrode reaches the vicinity of the previous contact occurrence position by the same control procedure as the second machining restart control means when counting the number of times the third time and the odd number of times thereafter, the power-on position of the machining power source is set to the previous time. And a correction second machining restart control means for changing to a position before the contact occurrence position after the operation of the second machining restart control means and restarting the machining at the changed position by restarting the machining power supply. Characteristic wire cut electric discharge machine.