JP3007229B2 - Control method of electric discharge machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electric discharge machining, in which an electrode and a workpiece are relatively moved and a machining gap formed between the electrode and the workpiece is discharged through a machining fluid to perform machining. The present invention relates to a method of controlling a machine.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing a configuration of a die-sinking electric discharge machine to which a conventional control method of an electric discharge machine disclosed in Japanese Patent Application Laid-Open No. 4-63623 is applied. This die-sinking electric discharge machine has a machining tank 4 in which a machining fluid is stored in a machine main body 10, and a workpiece W which is a workpiece is mounted in the machining tank 4. Electric discharge machining is performed by the supplied machining electrode 3. The machining electrode 3 is gripped by a chuck device 16 attached via an insulating member 15 to the lower end of a main shaft 14 that has a feed screw mechanism from a drive motor M and performs a feed operation via a feed device 13, and the main shaft 3 According to the up and down movement of 14, the workpiece W is fed toward the workpiece W (negative direction) or in a direction away from the workpiece W (positive direction), and opposes the workpiece W via a discharge gap.

The machining electrode 3 and the workpiece W are connected to a machining power supply 17 via a power supply cable, so that a machining gap is generated by electric pulses for machining supplied from the machining power supply 17 during electric discharge machining. A discharge is caused to occur. At the time of electric discharge machining, the voltage between contacts in the electric discharge machining section between the machining electrode and the workpiece W is constantly monitored and detected by the discharge voltage detection section 5, and the detection data is sent to the numerical control device 20 of the electric discharge machine. . The numerical control device 20 includes an arithmetic unit CPU, a memory device 21 forming storage means, an interface 22, machining information including electric discharge machining data of various workpieces, and correspondence with the machining depth of the workpiece. An operation panel 23, a display device 24, and the like for inputting the reference jump amount data and the like are provided. Therefore, the data detected by the above-described discharge voltage detection unit 5 is input to the arithmetic unit CPU via the interface 22. The numerical controller 2
Numeral 0 is connected to the drive motor M of the feed system of the main shaft 14 via the interface 22 and the rotation detector E of the drive motor M to form a servo system for controlling the feed operation of the main shaft 14, and The feed amount of the machining electrode 3 is controlled via the control unit. That is, the feed amount of the machining electrode 3 is controlled in both positive and negative directions according to the detection data of the gap state in the electric discharge machining section. Further, the numerical control device 20 includes the processing power supply device 1
7 is also connected through an interface 22.
A control signal for controlling the current condition of the discharge pulse current, that is, the pulse width and the pulse pause width, is transmitted according to the gap state of the electric discharge machining portion.

By the way, while the electric discharge machining is performed on the workpiece W by the machining electrode 3, the state of the gap between the machining electrode and the workpiece is detected by the discharge voltage detecting section 5. According to the data, the arithmetic unit CPU of the numerical controller 20 can momentarily calculate the feed operation given to the machining electrode 3 via a feed servo system using the drive motor M as a drive source. By calculating the total feed amount of the machining electrode 3 from the start time of the electric discharge machining performed according to the input electric discharge machining information on the corresponding workpiece W, the machining electrode 3 is now positioned with respect to the position at the start of the electric discharge machining. It can calculate and detect how far it has moved. Further, by integrating the total feed amount of the positive and negative feed operations given to the machining electrode 3 via the feed servo system, it is also possible to calculate data of how deep the electric discharge machining has been performed on the workpiece W. it can. Further, the position and the working depth of the working electrode 3 may be determined by a digital scale (not shown) for detecting the feed movement amount of the working electrode 3 in real time.

[0005] When the electric discharge machining of the workpiece W by the machining electrode 3 is started, a discharge pulse voltage applied from the machining power supply device 17 causes an electric discharge in a discharge machining section where the electrode and the workpiece oppose each other through the machining gap. Is generated, and the electric discharge machining of the workpiece W progresses. At this time, the numerical controller 20 detects the gap state in the electric discharge machining section from the gap voltage data detected by the discharge voltage detection section 5. Then, the machining conditions are adjusted according to the gap state, and control is performed so that a normal electric discharge machining state is maintained. On the other hand, as the processing of the workpiece W progresses, a jump as shown in FIG. 7 or FIG. 8 is made to the processing electrode 3 via the feed servo system in order to remove the processing debris accumulated in the processing recessed portion of the workpiece W. An action is given. This jump operation is set on condition of the amount of jump (the amount of jump) and the length of the repetition period of the jump. When the machining electrode 3 jumps in the machining fluid in the machining tank 4, a pump action is activated, and the workpiece is processed. The processing waste accumulated at the processing dent portion of the object W is removed to promote normal electric discharge machining. FIG. 7 shows a state in which the cycle of the amplitude at which the electrode 3 goes down and up becomes faster, as shown in FIG. 7A, and then the electric discharge machining is stabilized by the jump operation, and FIG. 8 shows a state as shown in FIG. In this state, the amplitude of the rise and fall of the electrode 3 is widened, and the electric discharge machining is stabilized by the jump operation.

[0006] The jump condition is appropriately adjusted in accordance with the progress of the electric discharge machining, and control is performed so that the progress of the electric discharge machining is further optimized. Therefore, in advance, a reference jump amount corresponding to the machining depth when the workpiece W is subjected to electric discharge machining to increase the machining depth is obtained by an experiment, and is set and stored in the numerical control device 20. That is, when the machining depth increases, the jump amount needs to be gradually increased to obtain the pump effect by the jump operation. Such a jump amount is experimentally obtained as data in advance, and the machining depth versus the jump amount is determined. A graph is set from the operation panel 23 in the memory element 21 of the numerical controller 20. Then, the machining depth is detected in the electric discharge machining process to adjust the jump amount.

In this embodiment, the position of the machining electrode 3 is integrated every sampling time from the start of electric discharge machining.
Detect and calculate the processing depth of the workpiece W at the time of detection, detect and send it to the machining electrode 3, set the jump condition through the feed operation of the servo system, and give the jump operation. In addition, the processing conditions of the processing power supply device 17, for example, the pulse pause width are set in accordance with the setting of the jump condition.

[0008]

As described above, according to the conventional control method of the electric discharge machine, the jump amount, the jump period and the pause width of the discharge pulse corresponding to the machining depth are stored in advance, and the actual machining process is performed. The stored condition is read out, and jump control is performed in accordance with the read condition. According to this control, only the control stored in advance is performed, and there is a problem that the control cannot be performed while reflecting the actual processing state. Further, in the conventional apparatus, the machining state is estimated by calculating how much the machining depth has changed from the previous depth to the current depth, and the machining conditions are changed accordingly. Control has been made. However, in this control, in the electric discharge machining in which the electrode 3 is repeatedly moved up and down, it is not possible to know where the electrode is in the vertical amplitude when sampling the machining depth. There is also a problem that it is difficult to determine the processing state due to the instability of the measurement of the processing depth.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and the discharge is unstable based on the amplitude and cycle of the axis operation for controlling the gap to be effective for machining. Judgment whether or not the discharge is unstable, performs the jump operation of the electrode irrespective of the jump operation cycle, promotes the discharge of machining waste, and controls the electric discharge machine to stabilize the discharge The purpose is to provide.

[0010]

SUMMARY OF THE INVENTION The present invention provides
In view of the above-described circumstances, a control device for an electric discharge machine according to the present invention has an electrode for performing discharge, a workpiece to be subjected to electrical discharge machining by discharge from the electrode, and an electrode and the workpiece. Determining whether or not discharge is unstable from a moving means for moving the moving means, a position detector for detecting the position of the moving means, and an amplitude and a cycle of the axis operation of the moving means based on a signal from the position detector. Means, and determines whether or not the discharge is unstable by the determination means, and when it is determined that the discharge is unstable, the machining gap between the electrode and the workpiece is relatively moved at a predetermined speed for a predetermined distance. The moving means is controlled so as to perform a jump operation of expanding and returning to the original position at a predetermined speed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a die-sinking electric discharge machine to which a control method of the electric discharge machine according to the present invention is applied. The electric discharge machine has a machining tank 4 in which a machining fluid is stored in a machine main body 10, and a workpiece W as a workpiece is mounted in the machining tank 4. Electrode machining is performed by the electrode 3. Then, the machining electrode 3 is gripped by a chuck device (not shown) attached to the lower end of the spindle that performs a feed operation from the drive motor M via a feed device 13 having a feed screw mechanism, and is received according to the vertical movement of the spindle. Direction toward workpiece W (negative direction) or direction away from workpiece W (positive direction)
, And is opposed to the workpiece W via the discharge gap. The machining electrode 3 and the workpiece W are connected to a discharge pulse control unit 2 via a power supply cable, and a power supply is connected to the discharge pulse control unit 2. Electric discharge is generated in the machining gap by the machining electric pulse supplied from the section 2.

Further, a discharge voltage detector 5 for detecting a discharge voltage between the processing electrode 3 and the workpiece W is connected to the processing electrode 3 and the workpiece W. V / V which converts the difference between the discharge voltage detected by the discharge voltage detection unit 5 and the voltage suitable for performing machining discharge by pulse conversion.
The F converter 6 is connected. And the V / F converter 6
Is connected to a numerical controller 7 for converting the number of pulses generated by the V / F converter 6 into each axis command value. The numerical controller 7 converts the command value to a command value to the power amplifier 9. Is connected. Further, a position detector E for detecting the rotational position of the drive motor M and a power amplifier 9 are connected to the axis control unit 8, and the drive motor M is connected to the power amplifier 9.

Next, the operation of this embodiment will be described.
In the above-mentioned electric discharge machine, the movement of the electrode 3 is detected by reading the data of the position detector E, so that the machining gap formed between the electrode 3 and the workpiece W is to be widened or narrowed. You can determine whether you are going to. The numerical control device 7 counts the period at a certain time interval with the operation of widening and narrowing the gap as one cycle, and when it exceeds a specified value, it is determined that the discharge has become unstable. That is, as shown in FIG. 2, when the cycle of the amplitude of the electrode 3 falling or rising in the middle of the processing is shortened and the processing is not advanced, it is determined that the discharge is in an unstable state.

Alternatively, the numerical controller 7 stores a position where the machining gap has changed from a state of being widened to a state of being narrowed and a position where the state of the machining gap has been changed from a state of being narrowed to a state where the machining gap is widened, and calculates an amplitude from these two positions. It is determined that the discharge becomes unstable when the value exceeds the specified value. That is, as shown in FIG. 3, when the amplitude of the electrode 3 falling or rising during the processing is wide and the processing is not progressing, it is determined that the discharge is in an unstable state. As a result of this determination, the numerical controller 7 creates an axis command value for the jump, and drives the motor M through the axis controller 8 and the power amplifier 9 to raise the electrode 3 as shown in FIG. Accordingly, convection occurs in the working fluid between the electrode 3 and the workpiece W, thereby facilitating discharge of machining chips and stabilizing discharge. FIG. 4 shows a case where the period of the amplitude at which the electrode 3 is lowered or raised during the processing is short and the processing is not progressing.
FIG. 5 shows a state in which it is determined that the discharge becomes unstable, and a jump operation is performed regardless of the normal jump interval.
Indicates a state in which when the amplitude at which the electrode 3 is lowered or raised during the processing is wide and the processing is not progressing, it is determined that the discharge is unstable, and the jump operation is performed regardless of the normal jump interval.

[0015]

As described above, according to the present invention,
Judgment means judges whether or not the electric discharge is unstable. If it is judged that the electric discharge is unstable, the machining gap between the electrode and the workpiece is relatively widened by a predetermined distance at a predetermined speed, and the original value is increased at a predetermined speed. Since the moving means is controlled so as to perform the jumping operation to return to the position, the discharge can be stabilized, the effective machining time can be lengthened, and the machining speed can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a die-sinking electric discharge machine to which a control method for an electric discharge machine according to the present invention is applied.

FIG. 2 is a diagram showing a state in which processing is not progressing because the cycle of the amplitude at which an electrode is lowered or raised during processing is short.

FIG. 3 is a diagram showing a state in which the amplitude at which an electrode is lowered or raised during processing is increased and processing is not progressing;

FIG. 4 is a diagram showing the operation of the present invention.

FIG. 5 is a diagram showing the operation of the present invention.

FIG. 6 is a block diagram showing a configuration of a die sinking electric discharge machine to which a conventional control method of the electric discharge machine is applied.

FIG. 7 is a diagram showing an operation of a conventional example.

FIG. 8 is a diagram showing an operation of a conventional example.

[Explanation of symbols]

 3 Electrode 5 Discharge voltage detector 7 Numerical controller E Position detector M Drive motor W Workpiece

Claims (1)

(57) [Claims] An electrode for performing discharge, a workpiece to be subjected to electrical discharge machining by discharge from the electrode, and a moving unit for relatively moving the electrode and the workpiece, In a control method of an electric discharge machine for performing electric discharge through a machining fluid in a machining gap formed therebetween, a position detector for detecting a position of the moving means, and an axis of the moving means based on a signal from the position detector. Determination means for determining whether the discharge is unstable based on the amplitude and cycle of the operation, and determining whether the discharge is unstable by the determination means. A machining gap between the workpiece and the workpiece is relatively widened at a predetermined speed by a predetermined distance, and the moving means is controlled to perform an operation of returning to an original position at a predetermined speed.