JPH0468084B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application This invention relates to an electric discharge machining apparatus, and more particularly to a method for controlling the feed of an electrode in an electric discharge machining apparatus.

b. Prior Art In electric discharge machining, the following method is available as a method for controlling the feed of an electrode based on the detection information of the machining state of the electrode gap (the gap between the tool electrode and the workpiece).

(1) For a certain period of time (t), the machining state is detected using, for example, a discharge state determination device.

(2) Based on the above-mentioned detection information, the feeding method is determined to be one of three states: forward, stationary, and backward.

(3) When it is determined that it is moving forward or backward, the unit movement amount (meaning the amount of movement by one command) (△X ) Issue a movement command to move forward or backward.

The above electrode feeding method has the following features.

(1) It is better to set the unit movement amount (ΔX) for a certain period of time (t) to a relatively small value for stability.

(2) When forward commands are issued continuously, the apparent forward speed is maximum, and V _F max = △X/t.

(3) Similarly, when backward commands are issued continuously, the apparent backward speed becomes the maximum, and V _B max = △X/t.

Here, for example, t=1msec, △X=0.5μm
There is an example in which the stability of machining is relatively good when the setting is set as . In this case, V _F max=V _B max=0.5mm/
It becomes sec.

c Problems to be Solved by the Invention In electric discharge machining, for example, when machining a deep hole, a short circuit may occur due to machining debris etc. on the side surface of the deep hole that has already been machined. In such a case, the maximum retraction speed V _B max = 0.5 mm/sec is too slow, and it takes time to release the short circuit.
Also, for this reason, when moving forward after retreating a relatively large distance, forward commands are normally issued consecutively, and the maximum forward speed V _F max should be relatively large to reduce waste of machining time. few.

In the conventional method described above, the unit movement amount ΔX of the electrode once set is fixed, so
Due to the reasons mentioned above, it has not been possible to respond to cases where higher speed is required.

The present invention provides an electrode feed control method for an electrical discharge machining apparatus, which improves the problems of the prior art as described above.
The purpose is to provide

d Means for solving the problem In order to achieve the above object, the present invention detects the machining state of the electrode gap at regular intervals, and based on the detected information, moves the electrode by a unit movement amount, advances or
The gist of the configuration is to increase the unit movement amount up to a preset upper limit unit movement amount when moving backward or standing still, and moving forward or backward for a certain period of time or a certain number of times. be.

e Effect Since it is configured as described above, if a forward or backward command continues for a certain period of time or a certain number of times in the event of a short circuit, etc., the moving speed of the electrode increases and the short circuit etc. can be quickly prevented. It is possible to quickly release and return the electrode after release.

f Example Next, an example of the present invention will be described based on the drawings. FIG. 1 shows how the present invention is applied to an electric discharge machining apparatus controlled by a microcomputer at a period of t.
This is a flowchart for interrupting and executing the main program of the CPU (not shown). When the movement command calculation program is started by an interruption at period t, the following processing as shown in the flowchart is performed.

In step (1), it is determined whether the current command should move forward, stand still, or move backward based on the machining state detection results during the immediately preceding time t. When it is determined that the robot is moving forward, it is checked in step (2) whether the previous movement command was forward, and if it is other than forward (stationary or backward), it means that the current forward movement is not a continuation. Clear the forward continuation counter CF and set the unit movement amount △X to the initial value X. Make it. If it was a forward movement last time, in step (3), the forward movement continuation counter is
Check whether CF has reached the set value CFmax. When CF has not reached CFmax, CF
is incremented, and △X remains unchanged. C.F.
If has reached CFmax, it means that the forward command has continued for more than a certain period of time, so in step (4), the unit movement amount △X is set to the maximum value △
Check whether Xmax has been reached. Maximum value △
If Xmax has been reached, the unit movement amount will not be increased. If the maximum value △Xmax has not been reached, the unit movement amount △X is increased by the set value △x in step (5).

In step (6), a forward command of unit movement amount ΔX is output.

In step (7), a flag indicating the previous movement command direction is set to forward.

If it is determined in step (1) that the object is stationary, a flag indicating the previous direction of movement is set to stationary in step (8).

When it is determined in step (1) that the vehicle is moving backward, the process is similar to the case of moving forward. That is, it is checked whether the previous movement command was for backward movement, and if it is other than backward movement, the backward continuation counter CB is cleared and the unit movement amount △X is set to the initial value △X. Make it. If there was a backward movement last time, the backward continuation counter CB will be set to the set value.
Check whether CBmax has been reached. C.B.
If CBmax has been reached, the unit movement amount △X is increased by the set value △x. However, △X is not increased beyond △Xmax. When CB has not reached CBmax, CB is incremented and △X remains unchanged. Next, a backward command of unit movement amount ΔX is output, and a flag indicating the direction of movement is set to backward.

In this way, the electrode feed can be controlled with a small unit movement amount when the machining state of the electrode gap is normal, and with a large unit movement amount when it is abnormal.

g. Effects of the Invention As understood from the above explanation, the present invention has the structure set forth in the claims, so that when an abnormality such as a short circuit occurs in electrical discharge machining, the moving speed of the electrode is increased. By doing so, it is possible to provide an electrode feed control method for an electric discharge machining apparatus that can quickly cancel an abnormal state and return to a normal state.

[Brief explanation of drawings]

FIG. 1 is an example of a flowchart for interrupts when the present invention is implemented using a computer.

Claims (1)

[Claims] 1 Detect the machining status of the electrode gap at regular intervals,
Based on the detection information, the electrode is moved forward, backward, or stationary by a unit movement amount, and the forward or backward movement is
If it continues for a certain period of time or a certain number of times, up to the preset upper limit unit movement amount,
An electrode feed control method for an electrical discharge machining device, characterized by increasing a unit movement amount.