JPH03149134A - Electrode position control method for electric discharge machine - Google Patents

Abstract

PURPOSE:To efficiently perform stable machining with an abnormal discharge condition of short-circuiting or the like quickly eliminated without destructing an electrode and a workpiece by eliminating the abnormal discharge condition with the electrode retracted in a prestored direction while reversely fed from the point end of a machining locus in the point of time the abnormal discharge condition is detected. CONSTITUTION:In a process where a workpiece 1 is electric discharge-machined while relatively moving an electrode 4 for the workpiece 1 along a predetermined machining locus, when machining is performed while retracting the electrode 4 in a direction of eliminating an abnormal discharge condition when it is detected, a direction of retracting the electrode 4 is previously stored in a memory 23 simultaneously with the machining locus left as stored following relative movement. Next at the point of time when the abnormal discharge condition is detected, the electrode 4, while it is reversely fed from the point end of the stored machining locus, is retracted in the prestored direction, so as to eliminate the abnormal discharge condition.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrode position control method for stabilizing machining and improving machining speed in an electrical discharge machining apparatus.

[Conventional technology] FIG. 4 is a configuration diagram showing the operating principle of the electrical discharge machining apparatus.

In the figure, (l) is the workpiece, which is the processing tank (2)
The processing electrode (
4) It is facing. The relative movement between the workpiece (1) and the electrode (4) is controlled by the table (5) on which the workpiece (1) is placed.
) and the vertical movement of the electrode (4). That is, the table (5) is moved in a plane by an X-axis drive actuator (6) and a Y-axis drive actuator (7). Further, the vertical movement of the electrode (4) is driven by a Z-axis drive actuator (8). With the above configuration, the workpiece (1) and the electrode (4) can move relative to each other in three dimensions. Note that these actuators are controlled by a numerical control device (9). Also, (l
O) is a processing power source that supplies electrical energy required for processing to the workpiece (1) and the electrode (4).

Next, the operation will be explained. During machining in an electric discharge machining device, a machining power source (
By applying a pulsed voltage (1)) using lO), a discharge is generated between the electrode (4) and the workpiece (1), and the shape of the electrode (4) is formed on the workpiece (1). Perform the transfer process.

In order to maintain a stable discharge state in an electrical discharge machining device, the gap between the electrode (4) and the workpiece (1) must be reduced by a gap servo that controls the position of the electrode (4) according to the voltage between the edges. It is necessary to maintain proper spacing. The operation of a general pole-to-pole servo will be explained below.

The gap servo inputs the gap voltage V between the electrode (4) and the workpiece (1), calculates the difference voltage V e = V - V s from a predetermined reference voltage VS, and calculates the difference. Voltage Ve
The electrode (4) and the workpiece [1] are moved relative to each other by an amount of movement corresponding to . That is, when the state between the electrodes is a short-circuit state, the amount of movement is created so as to increase the relative distance between the electrode (4) and the workpiece (1), while when the state between the electrodes is an oven state. The amount of movement is created so as to reduce the relative distance between the electrode [4] and the workpiece (1). Here, when the machining is in progress, the electrode (4) moves along the specified machining trajectory based on the amount of movement, but when the state between the electrodes becomes a short circuit state, the electrode (4) moves based on the amount of movement. By retracting, a short circuit state is avoided, and when the machining gap state becomes an oven state, the machining machine returns to the retraction start position based on the amount of movement and performs processing again.

Conventionally, the operation of the electrode (4) when the electrode (4) retreats and returns to the retreat start position when the inter-electrode state becomes a short-circuit state is shown in FIG. 5(b) or FIG. 5(c). Such an electrode position control method is used.

That is, in FIG. 5, the workpiece (1) is connected to the electrode (4).
) When a short circuit occurs when machining the trajectory A-B in Figure 5(b), the electrode (4) moves in one predetermined direction (
12) By performing retreat and return, the distance between the poles in the bottom direction is changed, thereby eliminating the short circuit. In addition, in Fig. 5(c), by memorizing the specified machining trajectory, the machining distance in the machining direction can be changed by backing up and returning to the right on the already machined trajectory (13). This will eliminate the short circuit.

Also. Electrodes (4
) in the normal direction of the tip movement trajectory, or combine the normal direction avoidance movement with the electrode avoidance movement in the direction perpendicular to the tangent and normal of the electrode tip trajectory, and the electrode avoidance movement in the direction perpendicular to the tangent to the electrode tip trajectory and the normal line. A method has been considered in which the short circuit between the electrode (4) and the workpiece (1) is eliminated. FIG. 6 shows the movement of the electrode (4) when a short circuit occurs in this Japanese Unexamined Patent Publication No. 59-30622.

In FIG. 6, processing is performed by moving the tip of the electrode (4) within the xy plane so as to form a contour line M on the surface of the workpiece (1). When a short circuit occurs, the electrode (4) S moves toward the workpiece (1) in the normal direction perpendicular to the tangent T of the electrode tip movement locus.
) and performs an avoidance movement by ΔN in the direction away from the target. An even more effective method is to perform an avoidance movement by ΔZ in a direction perpendicular to the main plane, that is, in the Z-axis direction, in synchronization with ΔN, thereby resulting in an avoidance movement in the direction of the resultant vector ΔL.

[Problem to be solved by the invention]

Since the conventional electrode position control method of the electrical discharge machining apparatus is configured as described above, when a short circuit occurs between the electrode (4) and the workpiece (1), the short circuit shown in FIG. 5(b) occurs. In such an electrode position control method, the distance between the electrodes in the direction of the bottom surface increases, but the distance between the electrodes in the direction of machining progress does not change. On the other hand, Fig. 5 (c
), the distance between the electrodes in the direction of machining progress increases, but the distance between the electrodes in the direction of the bottom surface does not change.

Therefore, since it is slow to eliminate the short circuit, machining becomes unstable and the machining speed decreases, or the short circuit cannot be eliminated and a steady arc occurs. In addition, the electrode (4) can be avoided in a direction normal to the tangent to its tip movement locus, or the normal avoidance movement is perpendicular to the direction perpendicular to the tangent and normal to the electrode tip locus. In the method of eliminating the short circuit between the electrode (4) and the workpiece (1) by combining the electrode avoidance movement in the direction shown in FIG. ”, and the electrode (4) is connected to the workpiece (1
) is effective as shown in Fig. 7(c), but it is effective when machining does not cause biting against Figure 7 (
As shown in d), the electrode (4) and workpiece (1) collide due to the electrode avoidance movement, and the electrode (4) and workpiece (1) collide.
will be destroyed. Therefore, in the method in which the electrode (4) is avoided in the normal direction of the locus of movement of its tip end, the feed amount for machining can only be extremely small, resulting in extremely low machining efficiency, which is a problem that needs to be solved.

This invention was made to solve the above-mentioned problems. It quickly eliminates abnormal discharge conditions such as short circuits without destroying the electrode or workpiece, allows stable machining, and efficiently discharges sludge. The purpose of this invention is to obtain a method for controlling the electrode position of an electrical discharge machining device with high machining efficiency.

[Means for Solving the Problems] A method for controlling the electrode position of an electric discharge machining apparatus according to the present invention moves the electrode relative to the workpiece along a predetermined machining trajectory while moving the workpiece. In the method of performing machining while retracting the electrode in a direction to eliminate the abnormal discharge state when an abnormal discharge state is detected in the process of electrical discharge machining, the step of memorizing in advance the direction in which the electrode is retracted; A step of memorizing the machining trajectory as the machine moves.

When the abnormal discharge state is detected, the electrode is moved backward from the tip of the memorized machining trajectory and retreated in the pre-stored direction to eliminate the abnormal discharge state. .

Further, an electrode position control method for an electrical discharge machining apparatus according to another aspect of the present invention includes a process of electrical discharge machining the workpiece while moving the electrode relative to the workpiece along a predetermined machining trajectory. In the method of retracting the electrode in a direction to eliminate the abnormal discharge state when an abnormal discharge state is detected, and then moving the electrode in the machining progress direction, the method includes a step of storing in advance a method for moving the electrode. , in the step of memorizing the machining trajectory along with the relative movement, and at the time when the abnormal discharge state is resolved, the electrode is moved in the direction of its tip along the memorized machining trajectory while and moving in the memorized direction.

Further, a method for controlling the electrode position of an electrical discharge machining apparatus according to still another aspect of the present invention includes electrical discharge machining the workpiece while moving the electrode relative to the workpiece along a predetermined machining trajectory. In the process, when an abnormal discharge state is detected, a method of performing processing while retracting the electrode in a direction to eliminate the abnormal discharge state includes a step of memorizing in advance the direction in which the electrode is to be retracted, and a step of memorizing in advance the direction in which the electrode is to be retracted; At the step of memorizing the machining trajectory, and at the time when the abnormal discharge state is detected, the electrode is moved backward from the tip of the memorized machining trajectory and retreated in the pre-memorized direction to discharge the abnormal discharge. At the stage of eliminating the condition and at the time when the abnormal discharge condition is eliminated.

The method comprises the steps of moving the electrode toward its tip along the memorized machining trajectory and in a direction opposite to the previously memorized direction.

[Operation] In the present invention, when an abnormal discharge state is detected in the process of electric discharge machining of the workpiece while moving the electrode relative to the workpiece along a predetermined machining trajectory, the abnormality Storing a direction to eliminate the discharge state When machining is performed while retracting the electrode, the direction in which the electrode is retracted is memorized in advance, and the machining trajectory is memorized along with the relative movement, and the abnormal discharge state is detected. At that point, the electrode is moved backward from the tip of the memorized machining trajectory and retracted in the previously memorized direction to eliminate the abnormal discharge state.

In another aspect of the present invention, when an abnormal electrical discharge state is detected during electric discharge machining of the workpiece while moving the electrode relative to the workpiece along a predetermined machining trajectory, When moving the electrode in the machining progress direction after retracting the electrode in a direction to eliminate the abnormal discharge state,
The direction in which the electrode is moved is memorized in advance, and the machining locus is memorized along with the relative movement, and when the abnormal discharge condition is eliminated, the electrode is moved along the memorized machining locus at its tip. The sludge discharge is facilitated by moving the sludge in the pre-stored direction.

In still another aspect of the present invention, in the process of electric discharge machining the workpiece while moving the electrode relative to the workpiece along a predetermined machining trajectory.

When processing is performed while retracting the electrode in a direction to eliminate the abnormal discharge state when an abnormal discharge state is detected,
The direction in which the electrode is to be retracted is memorized in advance, and the machining trajectory is memorized along with the relative movement. When the abnormal discharge state is detected, the electrode is moved to the tip of the memorized machining trajectory. The abnormal discharge state is resolved by retracting the electrode in the pre-stored direction while reversing the process, and at the time when the abnormal discharge state is resolved, the electrode is moved in the direction of its tip along the memorized machining trajectory. The sludge is moved in the opposite direction to the pre-stored direction while the sludge is being moved in the opposite direction to facilitate the sludge discharge.

[Embodiments of the invention] Below are the fruits of this invention! fll will be explained with reference to the figure.

Fig. 1 is a diagram for explaining the avoidance operation of electrodes when a short circuit occurs in an embodiment of the present invention, Fig. 2 is a flowchart showing the flow of operation in an embodiment of the invention, and Fig. 3 is a diagram of the invention. 3 is a diagram illustrating a hardware configuration for executing the method according to an embodiment, and in FIG. 3, (Is)
is the NC program that commands the machining trajectory, (16)
(17) is the command position for each axis created by the machining trajectory creation unit (16), and (18) is the voltage V between the electrodes.

(19) is the reference voltage Vs, (20) is the electrode-to-electrode voltage V (1
8) and the reference voltage V s (19), a pole-to-pole servo movement amount creation section (21) is an actuator for each axis based on the travel amount created by the pole-to-pole servo travel amount creation section (20). (6) , (7) , and an electrode position control unit that creates output to (g); (22) is a prespecified interpole servo direction vector component for each axis; (23)
is a trajectory memory memory for memorizing the machining trajectory of each axis, (
24) is each actuator (6), (7), (
8). Incidentally, these are performed by a numerical control device (9) shown in FIG. 4, which shows a conventional example.

The machining trajectory is commanded by the NC program (15),
A machining trajectory creation section (16) inputs the NG program, analyzes it, and creates command positions (17) for each axis by linear interpolation or circular interpolation. The inter-electrode servo movement amount creation unit (20) generates an inter-electrode voltage V (18) and a reference voltage V s
(19) is input, and the amount of movement corresponding to the voltage difference between them is created. These are the same as the conventional ones.

Electrode position control section (21) having the following features of the present invention:
The operation will be explained using the flowchart shown in FIG. In step (27), the electrode position control unit (21) inputs the movement amount created by the inter-electrode servo movement amount creation unit (20) in step 6 (2g), and in (29) inputs the input movement amount and the current servo movement amount. Depending on the amount of retraction, it is determined whether to perform machining trajectory update movement processing, servo retraction processing, or servo return processing. In branch (30), if the movement amount is a forward command (≧0) and the backward amount is zero, the command created by the machining trajectory creation unit (16) in step C31) is used to update the machining trajectory and proceed with machining. Create outputs to actuators (6), (7), and (8) for each axis so that each axis moves toward position (17). At this time, in order to memorize the machining trajectory in step (32), the actuator (6) of each axis,
(7).

The output xn, yn, zn to [8] is stored in the trajectory memory (2
3). Also, at branch (33).

When the movement amount is a backward command (<0) (when a short circuit occurs), in steps (34) to C36), the inter-pole servo direction specified in advance by the inter-pole servo direction vector component (22) of each axis is Movement amount to P X Interpole servo direction backward gain G
Create a retraction amount Lsb in the interpole servo direction for sb, and further retract on the machining trajectory by the amount of movement on the machining trajectory Create the amount Lkb. Then step (
In step C35) and step (36), the amount of retraction in the machining path servo direction and the amount of retraction on the machining trajectory are combined in step C35) and step (36), and the actuators (6), (7), (
8) Create output to By doing so, as shown in FIG. 1(c), the electrode position can be changed in the direction (25) that is the result of the machining trajectory and a predetermined direction. In addition, as shown in branch (38), when the movement amount is a forward command and the backward amount is not zero (return to the backward start position), the backward gain Gsb in the pole-to-pole servo direction during backward movement
In place of the machining trajectory retraction gain Gkb, the machining servo direction return gain Gsr and machining trajectory return gain Gkr are used, respectively, and the machining servo direction return amount = travel amount x machining servo direction return gain Gsr, machining trajectory retraction A return amount is created as amount=movement amount x return gain on machining trajectory Gkr, and the electrode position is changed in the composite direction as in the case of retreat. By switching the gain during retraction and return in this manner, it is possible to create a path different from the return trajectory (26) shown in FIG. 1. By differentiating the retreat and return paths, agitation of the machining fluid is promoted and the bomb effect is promoted, increasing the ability to discharge sludge between the machining holes, maintaining stable electrical discharge, and increasing machining speed. improves.

In the above embodiment, the case where the number of control axes is three is shown, but if the number of control axes is two or more, the same effect as described above can be obtained.

Further, in the above embodiment, the return path of the electrode (4) is different from the retraction path, but it goes without saying that the return path does not necessarily have to be different and may be the same path.

[Effects of the Invention] As described above, according to the present invention, in the process of electric discharge machining of the workpiece while moving the electrode relative to the workpiece along a predetermined machining trajectory, an abnormal electric discharge state is detected. When machining is performed while retracting the electrode in a direction that eliminates the discharge state above when is detected, the direction in which the electrode is retracted is memorized in advance, and the machining trajectory is memorized along with the relative movement, When the abnormal discharge state is detected, the electrode is moved backward from the tip of the memorized machining trajectory and retreated in the pre-stored direction to eliminate the abnormal discharge state. This has the effect of quickly eliminating abnormal discharge conditions such as short circuits without destroying the workpiece, and allowing stable and efficient machining to be performed.

According to another aspect of the present invention, an abnormal electrical discharge state is detected during electrical discharge machining of the workpiece while moving the electrode relative to the workpiece along a predetermined machining trajectory number. When the electrode is moved in the machining progress direction after retracting the electrode in a direction that eliminates the abnormal discharge state, the direction in which the electrode is moved is memorized in advance, and the machining trajectory is changed along with the relative movement. The electrode is memorized, and when the abnormal discharge state is resolved, the electrode is moved toward its tip along the memorized machining trajectory and moved in the previously memorized direction to facilitate sludge discharge. As a result, unstable machining caused by sludge can be eliminated and stable machining can be performed efficiently.

According to still another aspect of the present invention, an abnormal electrical discharge state occurs during electrical discharge machining of the workpiece while moving the electrode relative to the workpiece along a predetermined machining locus. When machining is performed while retracting the electrode in a direction that eliminates the abnormal discharge state when detected, the direction in which the electrode is retracted is memorized in advance, and the machining trajectory is memorized along with the relative movement, and the When the abnormal discharge state is detected, the electrode is moved backward from the tip of the memorized machining trajectory and retreated in the pre-stored direction to eliminate the abnormal discharge state, and the abnormal discharge state is eliminated. At this point, the electrode was moved in the direction opposite to the previously memorized direction while moving the electrode toward its tip along the memorized machining trajectory to facilitate sludge discharge. It is possible to quickly eliminate abnormal discharge conditions such as short circuits without destroying the workpiece, and it is also possible to eliminate unstable machining conditions caused by sludge.
This has the effect of providing stable and efficient processing.

, Brief Description of the Drawings FIG. 1 is a diagram for explaining a method for controlling the electrode position of an electric discharge machining apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram for explaining the electrode position control method of an electric discharge machining apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram showing hardware for implementing the method for controlling the electrode position of an electric discharge machining apparatus according to an embodiment of the present invention, and FIG. 4 shows a conventional electric discharge machining apparatus. 5 is a diagram for explaining the electrode position control method of a conventional electric discharge machining apparatus, FIG. 6 is a diagram for explaining another conventional electrode position control method of an electric discharge machining apparatus, and FIG.
The figure is a diagram for explaining the drawbacks of the method shown in FIG. 6.

In the figure, (1) is the workpiece, (4) is the electrode, and (15) is the workpiece.
) is the NC program, (1G) is the machining trajectory creation section, (
17) is the command position for each axis, (18) is the inter-electrode voltage V, (19) is the reference voltage Vs, and (20) is the inter-electrode servo movement amount creation section.

121) is an electrode position control unit, (22) is a prespecified interpole servo direction vector component of each axis, (23) is a trajectory memory, and C24) is an output amount to each actuator.

(25) is the backward trajectory, and (26) is the return trajectory.

In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

・

Claims (3)

[Claims] (1) When an abnormal discharge condition is detected during electrical discharge machining of the workpiece while moving the electrode relative to the workpiece along a predetermined machining trajectory, the abnormal discharge condition is resolved. A method for controlling an electrode position of an electrical discharge machining apparatus that performs machining while retracting the electrode in a direction, the method comprising: storing in advance the direction in which the electrode is retracted; and storing the machining trajectory along with the relative movement; When the abnormal discharge state is detected, the electrode is moved backward from the tip of the memorized machining trajectory and retreated in the pre-stored direction to eliminate the abnormal discharge state. Electrode position control method for electric discharge machining equipment. (2) When an abnormal discharge state is detected in the process of electrical discharge machining of the workpiece while moving the electrode relative to the workpiece along a predetermined machining trajectory, the abnormal discharge state is resolved. A method for controlling the electrode position of an electrical discharge machining apparatus in which the electrode is moved in the machining progress direction after the electrode is retracted in the direction, includes a step of storing in advance the direction in which the electrode is to be moved, and a step of storing the machining trajectory in accordance with the relative movement. At the memorization stage and when the abnormal discharge state is resolved,
A method for controlling the electrode position of an electrical discharge machining apparatus, comprising the steps of moving the electrode in the direction stored in advance while moving the electrode toward its tip along the stored machining trajectory. (3) When an abnormal discharge state is detected in the process of electrical discharge machining of the workpiece while moving the electrode relative to the workpiece along a predetermined machining trajectory, the abnormal discharge state is resolved. A method for controlling an electrode position of an electrical discharge machining apparatus that performs machining while retracting the electrode in a direction, the method comprising: storing in advance the direction in which the electrode is retracted; and storing the machining trajectory along with the relative movement; When the abnormal discharge state is detected, the electrode is moved backward from the tip of the memorized machining trajectory and retreated in the pre-stored direction to eliminate the abnormal discharge state; an electric discharge machining apparatus comprising the step of moving the electrode toward its tip along the memorized machining trajectory and in a direction opposite to the previously memorized direction at the time when this is resolved. Electrode position control method.