JPH08141847A - Electric discharge gap control method for die sinking electric discharge machine - Google Patents

Abstract

PURPOSE: To make the escape direction of an electrode during electric discharge gap control a direction of not interfering with a workpiece in the electric discharge gap control of a die sinking electric discharge machine. CONSTITUTION: Whenever movement based on a machining program 1a is commanded to a digital servo device 2, the coordinate value after the command is stored as a path point in a memory 1d. Hereupon, if there is the retreat demand of an electrode from a machining power supply 4, a retreat direction along a tool path is determined referring to the path point stored in the memory 1d, and the retreat movement is directly commanded to the digital servo device 2. The movement of the electrode during electric discharge gap control is in a machining completed path direction, so that the electrode does not interfere at all with a workpiece.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an electric discharge gap of a die-sinking electric discharge machine, and particularly, it is effective when the discharge direction of the electrode is restricted by controlling the electric discharge gap between the electrode and the work. The present invention relates to a discharge gap control method for a processing machine.

[0002]

2. Description of the Related Art In a die-sinking electric discharge machine, an electric discharge is generated between an electrode and a work, and the work is gradually removed by the electric discharge. In the numerical controller, the command to move the electrode based on the machining program is distributed and then sent to the digital servo means. The digital servo means is composed of a servo control circuit and a servo motor, and controls the feed of the electrode or the work according to the movement command. The machining power supply controls machining conditions between the electrode and the work, and monitors the discharge state between the electrode and the work.If the electrode is too close to or far from the work, A command to move away from or close to the work is issued to the numerical controller, and when performing distribution, the numerical controller makes a command to separate from or approach the machining program and instructs the digital servo means.

In this case, the control in which the command from the machining power source is reflected is restricted by the distribution cycle of the numerical controller. That is, since the request from the machining power source is transmitted to the digital servo means only in the cycle in which the numerical controller performs the process of distribution, the response speed to the machining power source cannot be improved beyond the distribution cycle of the numerical controller.

Therefore, EDM (Electric Discharge Mac)
hining) Controller is used to pre-command which direction the electrode should be moved in response to a request from the machining power supply. For example, if the machining power supply requests a retreat, the retraction commanded in advance is used. A command to retract the electrode in that direction is directly issued to the digital servo means, and the digital servo means immediately causes the electrode to retract in that direction. As a result, the gap between the electrode and the work can be adjusted to the optimum state in a short time according to the discharge state.

[0005]

However, the EDM controller is instructed in advance in which direction the electrodes should be moved, and the digital servo means is made to move the electrodes in the direction instructed in advance in response to a request from the machining power source. Although the command is given, it may not be possible to move the electrode in the previously commanded direction depending on the machining shape of the work. For example, the direction previously commanded to the EDM controller is the Z-axis direction and the shape of the electrodes is L.
In case of machining in a curved shape of the electrode in the middle of machining, even if there is a request to let the electrode escape from the machining power source, if the electrode is moved in the Z-axis direction, it becomes a work piece. There is a problem in that the electrodes cannot escape in the direction commanded in advance because of interference.

The present invention has been made in view of such a point, and it is not necessary to previously command the escape direction of the electrode by controlling the discharge gap, and the escape direction of the electrode affects the machining shape of the work. It is an object of the present invention to provide a method for controlling an electric discharge gap of a die-sinking electric discharge machine that does not occur.

[0007]

In order to solve the above problems, the present invention is directed to a die-sinking electric discharge machine for controlling an electric discharge gap between an electrode and a work in the die-sinking electric discharge machine according to an electric discharge state therebetween. In the discharge gap control method, the coordinate value after the command is stored in the memory as a path point every time the movement based on the machining program is instructed to the digital servo device, and the memory is responsive to the retraction request of the electrode from the machining power source in the memory. A die-sinking electric discharge machine characterized in that the stored path point is read out, the escape direction and escape amount of the electrode along the path point are obtained, and a backward movement command is directly issued to the digital servo device. A discharge gap control method is provided.

[0008]

According to the above means, every time a movement command is issued based on the machining program, the coordinate value after the command, that is, the current position is stored in the memory as a route point. If there is a request for the electrode to move backward, the backward direction is determined by referring to the path point stored in the memory and the movement of the backward movement is directly instructed to the digital servo device to move the electrode during discharge gap control. Is toward the processed path.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a flow chart showing the procedure of a discharge gap control method for a die-sinking electric discharge machine.

According to this flow chart, in the method of controlling the discharge gap between the electrode and the work in the die-sinking electric discharge machine according to the discharge state between them, first, the movement based on the machining program is instructed to the digital servo device. Each time, the coordinate value of the current position after the command is stored in the memory as a route point (step S1). Next, when there is a request from the machining power supply to retract the electrode due to deterioration of the discharge state, etc., the processed route point stored in the memory is read out, and the electrode escape direction and escape along the processed route point are read. The amount is calculated and directly instructed to the digital servo device (step S2).

As a result, when the discharge state between the electrode and the work deteriorates during machining of the workpiece, the digital servo device is instructed to retract the electrode in the direction of the machined path stored in the memory. It will be. Therefore, since the command for the escape direction of the electrode is given along the route that has been machined, machining is possible without worrying about the machining shape of the workpiece, even when machining the electrode cannot escape in one predetermined direction. Will be able to.

FIG. 2 is a conceptual diagram of a die-sinking electric discharge machine to which the method of the present invention is applied. In this figure, 1 is a numerical controller (CNC), 2 is a digital servo device, 3 is a die-sinking electric discharge machine, 4 is a machining power source, and 5 is an EDM controller.

In the numerical controller 1, the machining program 1a
The relative movement of the electrode and the work based on the above is commanded to the digital servo device 2 by the distribution device 1b. The movement command from the distribution device 1b is issued, for example, in a cycle of 8 milliseconds, and in each cycle, a command to move or not to move by 5 microns (μm) is issued. The distribution device 1b also issues a movement command to the digital servo device 2 and also to the current position display device 1c and the route point memory 1d. The current position display device 1c is a CRT (Cathode RayTub).
The position coordinates instructed to the digital servo device 2 are displayed on the display device such as e). The route point memory 1d stores coordinate values after the command, and can remember some past route points, for example, 1000 points, and can be configured by a ring buffer memory.

The digital servo device 2 is a numerical control device 1.
In accordance with the movement command from, the control is performed so as to move the electrode and the work in the die-sinking electric discharge machine 3. Processing power supply 4
Applies a voltage to the electrode and the work, or monitors a discharge state generated between them, and requests the EDM controller 5 to bring the electrode closer to the work or separate the electrode from the work depending on the discharge state. To put out.

In the EDM controller 5, when a forward / backward request is issued from the machining power source 4, the movement command generator 5a.
Reads the latest path point and the previous and next path points from the path point memory 1d in which the path points are stored, obtains the forward / backward directions and movement amounts of the electrodes, and instructs the digital servo device 2. The command value is input to the retreat amount calculation unit 5b and used when the digital servo device 2 is commanded next.

FIG. 3 is a diagram showing an example of a machining route by a machining program, and FIG. 4 is a diagram showing an example of saving in a route point memory. In FIG. 3, the processing start point is indicated by A, and from this point onward, path points B, C, and 5
... In the illustrated example, it is assumed that processing has started from the route point A to the route point N of the processing route, and the processed route points are indicated by black circles. These route points are sequentially stored in the route point memory 1d. That is,
As shown in FIG. 4, the coordinate value of the route point A is stored in the address "n" of the route point memory 1d, and the address "2" is stored.
The coordinate value of the route point B is stored in “n”, and the coordinate value of the route point N is stored in the address “XXn”.
At the head of the route point memory 1d, the address where the coordinate value of the newest route point, here the route point N, is stored is input.

A specific discharge gap control will be described in detail with reference to FIGS. 2 to 4. First, the numerical control device 1 uses the machining program 1a to output a G code indicating the discharge gap control according to the method of the present invention, that is, "G7".
When "0" is instructed, the distribution device 1b performs processing such that the movement command for each distribution cycle becomes 5 μm, issues the movement command to the digital servo device 2, and sets the coordinate values after the command. As shown in FIG. 4, they are sequentially stored in the route point memory 1d.

Here, it is assumed that, when the electrode is at the path point N, there is a demand for retracting the electrode from the machining power source 4 by, for example, 10 μm due to deterioration of the discharge state. At this time, each coordinate value up to the route point N and the address where the coordinate value of the route point N is stored at the head of the memory are set in the route point memory 1d.

The EDM controller 5, which is processed independently of the numerical controller 1, switches the electrodes from the route point N to the route point L (since the route point interval is 5 μm, the moving distance of 10 μm is L before the two route points). To read the coordinate values of the route point N at the current position and the route point L before the retreat amount from the route point memory 1d, and include the escape direction and the escape amount of the electrode in the movement command generation device 5a. A movement command is generated and the digital servo device 2 is instructed. In addition, the command value at this time is stored in the backward movement amount calculation unit 5b as the backward movement amount. As a result, the electrode is retracted from the route point N to the route point L, which is two route points before.

Since the electrode retreats to the path point L, the discharge state is improved and the machining power supply 4 requests the electrode to advance again. Based on the request from the machining power source 4, the EDM controller 5 issues an electrode movement command to the digital servo device 2 so as to move from the route point L to the route point M toward the route point N, and the command value is given each time. Subtract from the amount of retreat. The EDM controller 5 can issue a forward command by referring to the path point memory 1d until the backward movement amount becomes zero.

On the other hand, while the EDM controller 5 moves the electrode from the route point L to the route point M and then to the route point N, the numerical controller 1 causes the distributor 1b to perform the distribution at intervals of 5 μm. . Now, when the electrode is at the route point M, it is assumed that a new movement command is issued by the numerical controller 1 and the route point O is completed. As a result, the electrode comes too close to the workpiece, and the machining power source 4 again requests the electrode to retract by 10 μm.

Then, the numerical controller 1 sets the electrode to the path point O.
However, the EDM controller 5 commands the retreat amount of 5 μm in the direction from the route point N to the route point M. 1 more in this state
To retract the 0 μm electrode, 15 μ from the path point O
The electrode is set back to the path point L (m3 path points before) m before. By the EDM controller 5 commanding a value obtained by subtracting the already commanded movement from the route point N to the route point M from the movement from the route point O to the route point L, the electrode moves to the route point L, Further, when the command amount is added to the backward movement amount, the backward movement amount becomes the distance from the route point O to the route point L.

By repeating these operations, the numerical controller 1
Is continuing the movement command for machining regardless of the control of the discharge gap by the EDM controller 5, and the retreat amount of the retreat amount calculation unit 5b reaches a certain value, for example, 40 μm or more, the EDM controller 5 displays a numerical value. Control device 1
Is interlocked to stop the distribution by the distribution device 1b. As a result, new route points are not updated. Then, the EDM controller 5 uses the route point memory 1d.
While reading, the forward command is given until the backward amount becomes small. During this time, if there is a backward movement request from the machining power source 4, the route point memory 1d is read again and the backward movement process is performed.

When the backward movement amount in the backward movement calculation unit 5b becomes small, the interlock of the numerical control device 1 is released again, and the numerical control device 1 restarts the distribution. By repeating the above operation, the discharge gap control along the machining path is performed.

FIG. 5 is a flowchart showing the processing of the EDM controller. The EDM controller 5 first determines whether or not the request from the machining power source 4 is a backward movement (step S11). If it is a backward movement request, it is judged whether or not the backward movement amount in the backward movement amount calculation unit 5b is a certain value or more (step S12). Here, when the amount of retreat is equal to or greater than a certain value, the distribution of the movement command in the numerical controller 1 is stopped (step S13). Step S
In the judgment of 12, if the amount of retreat is less than the fixed value, the distribution point memory 1d is read without stopping the distribution (step S14). After that, a movement command for retracting the electrode in the direction along the processed route point read from the route point memory 1d and by the amount required by the machining power source 4 is output to the digital servo device 2 (step S).
15). Then, the command value at that time is used as the backward movement amount calculation unit 5b.
Is added to the backward movement amount in step S16 (step S16).

If the request from the machining power source 4 is forward in the determination in step S11, it is determined whether or not the backward movement amount in the backward movement calculation unit 5b is a certain value or more (step S12). Here, when the amount of retreat is less than the fixed value, the distribution of the movement command in the numerical controller 1 is restarted (step S18). If it is determined in step S17 that the amount of retreat is greater than or equal to a certain value, the route point memory 1d is read without restarting the distribution (step S19). After that, a movement command for advancing the electrode in the direction along the processed route point read from the route point memory 1d and by the amount required by the machining power source 4 is output to the digital servo device 2 (step S15). Is added to the backward movement amount in the backward movement amount calculation unit 5b, that is, the instruction value is subtracted from the backward movement amount (step S16).

[0027]

As described above, according to the present invention, the movement based on the machining program is instructed to the digital servo device, and at the same time, the coordinate values after the instruction are stored in the memory at several points in the past so that the electric power is discharged from the machining power source. The EDM controller reads the path point from the memory and outputs a command to move backward along the processed path point directly to the digital servo device when a request for the electrode to move backward due to the deterioration of the condition is issued.

As a result, in the control of the discharge gap, the electrode can always escape in the direction along the processed path, so that the machining can be performed when the escape direction of the electrode cannot be uniquely determined. Become.

[Brief description of drawings]

FIG. 1 is a flowchart showing a procedure of a discharge gap control method of a die-sinking electric discharge machine.

FIG. 2 is a conceptual diagram of a die-sinking electric discharge machine to which the method of the present invention is applied.

FIG. 3 is a diagram showing an example of a machining path according to a machining program.

FIG. 4 is a diagram showing a storage example of a route point memory.

FIG. 5 is a flowchart showing processing of an EDM controller.

[Explanation of symbols]

 1 Numerical Control Device 1a Machining Program 1b Distributor 1c Current Position Display Device 1d Path Point Memory 2 Digital Servo Device 3 Die-sinker EDM Machine 4 Machining Power Supply 5 EDM Controller 5a Movement Command Generator 5b Recession Calculator

Claims (6)

[Claims] 1. A method of controlling a discharge gap between an electrode and a work in a die-sinker electric discharge machine according to an electric discharge state therebetween, wherein a movement based on a machining program is performed by a digital servo. Each time the machine is commanded, the coordinate values after commanding are saved in the memory as path points, and the path points saved in the memory are read out in response to a retraction request of the electrode from the machining power supply, and the electrodes along the path points are read. A discharge gap control method for a die-sinking electric discharge machine, comprising: directing a backward movement command to a digital servo device by obtaining a clearance direction and a clearance amount. 2. When the machining power supply requests an electrode retreat, the movement command is distributed to the digital servo device based on the machining program when the amount of retreat due to the electrode retraction request from the machining power supply is a certain value or more. The method according to claim 1, further comprising a step of stopping. 3. The die-sinking electric discharge machine according to claim 1, further comprising the step of adding a backward movement amount commanded to the digital servo device after a backward movement command is given to the digital servo device. Discharge gap control method. 4. A path point stored in the memory is read in response to an electrode advance request from the machining power source, an electrode advance direction and an amount of advance along the path point are obtained, and an advance movement command is issued. 2. The method for controlling a discharge gap of a die-sinking EDM machine according to claim 1, further comprising the step of directly instructing the digital servo device. 5. The die-sinking electric discharge machine according to claim 3, wherein when the electrode is requested to move forward from the machining power source, the amount of forward movement commanded to the digital servo device is subtracted from the added backward movement amount. Discharge gap control method. 6. The method further comprises the step of resuming the movement command distribution to the digital servo device when the machining power source makes a request for advancing the electrode and the added retreat amount is equal to or less than a predetermined value. The discharge gap control method for a die-sinking EDM machine according to claim 5.