JPH1170412A - Power supply for electric discharge machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compensate the dispersion of a machining speed caused by machining positions and provide uniform machining characteristics by variably controlling the power voltage of a DC power supply according to the compensation value of the peak current value corresponding to the relative positions of an electrode to a work. SOLUTION: This electric discharge machine is a numerical control type. A voltage-variable DC power supply 20 is used for the power supply for electric discharge machining and a memory device 15 which memorizes the compensation value of the peak current value caused by the position on coordinates in the X and Y-axial directions as a matrix data is connected to a numerical controller 5. The numerical controller 5 reads out the peak current compensation value corresponding to the X and Y coordinates detected by encoders 8, 9 from the memory device 15 and variably controls the power voltage of the DC power source 20. This constitution automatically compensates the dispersion of the peak current value caused by the machining positions and the fixing of the peak value of the discharge current pulse provides a fixed machining speed and stabilizes the machining characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for electric discharge machining, and more particularly, to performing a pulse discharge between a machining electrode and a workpiece while controlling a relative position between the machining electrode and the workpiece. The present invention relates to a power supply device of an electric discharge machine for performing electric discharge machining.

[0002]

2. Description of the Related Art FIG.
There is something like that shown in In FIG. 9, reference numeral 1 denotes an electrode (wire electrode), and reference numeral 2 denotes a workpiece placed on the XY table 3 and moving in the X and Y directions. A minute machining gap (hereinafter, referred to as a gap) 4 is formed between the electrode 1 and the workpiece 2, and a pulse discharge is performed in the gap 4. DC power supply 10 is a semiconductor switching element 1 such as a field effect transistor (hereinafter referred to as FET).
The power is intermittently supplied to the electrode power supply point 12 and the table power supply point 13 by turning on / off of 1, and the semiconductor switching element 11 is controlled on / off by the control circuit 14.

In FIG. 9, reference numeral 100 denotes an inductance existing in the switching circuit; 101, an equivalent inductance from the electrode feeding point 12 to the electrode 1;
Reference numeral 2 denotes an equivalent inductance that increases and decreases when the electrode 1 moves relative to the workpiece 2.

Next, the operation will be described. The machining current supplied to the gap 4 formed by the electrode 1 and the workpiece 2 is an intermittent, so-called pulse current, as shown in FIG.

When the semiconductor switching element 11 that is turned on and off by the control circuit 14 is in an on state, the insulating state of the gap 4 is broken and a discharge current flows. The peak value Ip of the machining current at this time is, as shown in FIG. 10A, ignoring the ON voltage of the semiconductor switching element 11 and the arc voltage between the gaps 4, as shown in FIG.
And the ON time ton of the semiconductor switching element 11
And L of the inductance 100, it is expressed by Ip ≒ E · (ton / L). In this case, the slope of the rise of the machining current is Ip / ton ≒ E / L.

However, actually, L1 of the inductance 101 and L2 of the inductance 102 shown in FIG.
Is present, the peak current value Ip is, as shown in FIG. 10B, from Ip ≒ E · ton / (L + L1) to Ip ≒ E · ton / (L
+ L1 + L2), and the slope of the rising of the machining current also changes within the range of E / (L + L1) to E / (L + L1 + L2).

The machining current pulse having the peak current value Ip is supplied to the gap 4 as machining energy, and at the same time, the XY table 3 is driven in the X direction and the Y direction, thereby machining the workpiece 2 into an arbitrary shape. be able to.

In order to make the machining speed of electric discharge machining constant, it is necessary to control the peak current value Ip to a constant value and make the machining energy constant. In order to control the peak current value Ip to a constant value, in addition to the DC power supply voltage E, the ON time ton of the semiconductor switching element, the inductance L present in the switching circuit, the equivalent inductance L1 from the feeding point to the electrode, and the electrode It is necessary to simultaneously control many factors including the equivalent inductance L2 that increases and decreases when the workpiece moves relative to the workpiece. Cannot be controlled, and therefore, variations in the processing speed cannot be suppressed.

In particular, since the values of the equivalent inductances L1 and L2 change depending on the relative position between the feeding point and the processing position, in order to obtain a constant processing speed irrespective of the relative position, a large number of feeding points on the table side are provided. It becomes necessary, and the number of wires to be connected must be similarly increased, which makes mounting difficult.

In order to solve the above-mentioned drawbacks, in the power supply device for electric discharge machining disclosed in JP-A-59-205228, the peak current value of the machining current pulse flowing between the gaps is detected in real time. By comparing the peak current value with a reference value determined only by the ON time of the switching pulse, the dispersion of the peak current value is corrected.

Further, in the electric discharge machining apparatus disclosed in Japanese Patent Application Laid-Open No. H4-226839, the entire periphery of the side of the workpiece is surrounded by a fastener made of a highly conductive material, and power is supplied to the workpiece so that the machining position is reduced. Regardless, the discharge current is kept constant.

[0012]

However, in the power supply device for electric discharge machining disclosed in JP-A-59-205228, since the correction control is always performed while detecting the machining current in real time, the peak current value is detected and input. After that, a delay in the response time during which the correction value is output to the gap always occurs, and it is difficult to control with high accuracy. Also, in the power supply device for electric discharge machining, it is necessary to always connect the current-voltage converter in the switching circuit in series with the gap, so the peak current value is always reduced by the power loss. However, there is a disadvantage that the processing characteristics are deteriorated.

Moreover, in this electric discharge machine power supply device, when detecting the peak value of the high-frequency machining current, the control circuit has sufficient frequency characteristics and measures for preventing malfunction due to harmonic components included in the machining current. And it is practically difficult.

Further, in the electric discharge machining apparatus disclosed in Japanese Patent Application Laid-Open No. 4-26839, the machining current cannot be constant between a position near and far from the highly conductive material as long as there is an inductance in the workpiece. .

The present invention has been made in order to improve the above-mentioned drawbacks of the prior art, and it is intended to surely correct a variation in processing speed which varies depending on a processing position and to perform processing at a constant processing speed. It is another object of the present invention to provide a power supply device for electric discharge machining capable of obtaining uniform machining characteristics irrespective of a machining position.

[0016]

In order to achieve the above-mentioned object, a power supply device for electric discharge machining according to the present invention provides an on-off switching of a semiconductor switching element in a machining gap formed between an electrode and a workpiece. In a power supply unit of an electric discharge machine which performs an electric discharge machining while controlling a relative position between the electrode and the workpiece by a numerical control by supplying an intermittent pulse current by an operation, a voltage variable DC in which a voltage is variably controlled. A power supply, storage means for storing a correction value for correcting the peak current value as matrix data corresponding to the relative position, and a correction value for the peak current value stored in the storage means corresponding to the relative position. And control means for variably controlling the power supply voltage of the DC power supply in accordance with the correction value.

A power supply device for electric discharge machining according to the next invention is:
An intermittent pulse current is supplied to the machining gap formed between the electrode and the workpiece by ON / OFF operation of the semiconductor switching element, and the relative position between the electrode and the workpiece is controlled by numerical control. In a power supply device of an electric discharge machine that performs electric discharge machining, a storage unit that stores a correction value for correcting a peak current value as matrix data corresponding to the relative position, and a peak current value stored in the storage unit. Control means for reading out the correction value corresponding to the relative position from the storage means, converting the correction value into the on-time of the semiconductor switching element, and controlling the on-time of the semiconductor switching element. Is what it is.

A power supply device for electric discharge machining according to the next invention is:
An intermittent pulse current is supplied to the machining gap formed between the electrode and the workpiece by ON / OFF operation of the semiconductor switching element, and the relative position between the electrode and the workpiece is controlled by numerical control. In a power supply device of an electric discharge machine that performs electric discharge machining, a storage unit that stores a correction value for correcting a peak current value as matrix data corresponding to the relative position, and a peak current value stored in the storage unit. A correction value corresponding to the relative position is read out from the storage means, and a switching frequency of the semiconductor switching element is controlled in accordance with the correction value.

A power supply device for electric discharge machining according to the present invention
In the power supply device for electric discharge machining according to the above invention, the control means calculates an off time of the semiconductor switching element from a correction value read from the storage means, and controls the off time of the semiconductor switching element to control the semiconductor switching. This is for variably controlling the switching frequency of the element.

A power supply device for electric discharge machining according to the present invention
In the power supply device for electric discharge machining according to the above invention, the correction value is determined according to the maximum value or the minimum value of the peak current value at all the relative positions before, and the peak current value is set to the maximum value or the minimum value over the entire machining path. The value is kept constant.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a power supply unit of an electric discharge machine according to the present invention will be described below in detail with reference to the accompanying drawings. In the embodiments of the present invention described below, the same components as those of the above-described conventional example are denoted by the same reference numerals as those of the above-described conventional example, and description thereof will be omitted.

Embodiment 1 FIG. 1 shows a first embodiment of a power supply device for electric discharge machining according to the present invention. The electric discharge machine to which the power supply device for electric discharge machining is applied is of a numerical control type, and a numerical controller 5 controls an X-axis servo motor 6 for driving the XY table 3 in the X-axis direction and a XY table 3. A position command is output to a Y-axis servomotor 7 driven in the Y-axis direction, and the rotation position of each servomotor is determined by encoders 8 and 9 provided in association with the X-axis servomotor 6 and the Y-axis servo 7, respectively. Input the signal.

In this power supply device for electric discharge machining, a DC power supply 20 of variable voltage is used, and a storage device 15 for storing, as matrix data, a correction value of a peak current value according to a position on a coordinate in the X-axis direction and the Y-axis direction. It is connected to the numerical controller 5. The numerical controller 5 reads a peak current correction value corresponding to the X coordinate and the Y coordinate detected by the encoders 8 and 9 from the storage device 15, and variably controls the power supply voltage of the DC power supply 20 based on the peak current correction value.

Next, the operation of the first embodiment will be described. First, a procedure for creating matrix data of peak current correction values stored in the storage device 15 will be described with reference to FIG.

First, the on-time ton of the semiconductor switching element 11 is made constant before the correction control of the peak current value, and the electric discharge machining is performed from the point where the X, Y coordinates are (0, 0) to the point (Xm, 0). , And as shown in FIG.
Data of the peak current value Ip is obtained using the coordinate values as parameters. Similarly, from (0, Y1) to (Xm, Y1),
Data is taken from (0, Y2) to (Xm, Y2), (0, Y3) to ... (Xm, Ym), and the peak current value of an arbitrary coordinate point (Xn, Yn) is calculated as Ip (Xn , Y
n).

Next, the minimum value Ip (min) of the peak current is determined, and Ip (m
in) is subtracted. That is, by setting all the Ip data as Ip (Xn, Yn) -Ip (min), these values are used as the correction value ΔIp (Xn, Yn) of the peak current value Ip at each coordinate point.

Therefore, the correction value ΔIp (Xm, Ym) at the coordinate point indicating the minimum value of the peak current is zero as shown in the equation (2), and the correction value ΔIp at the other coordinate points is It has a positive value as shown in equation (1).

ΔIp (Xn, Yn) = Ip (Xn, Yn) −Ip (min)> 0 (1) ΔIp (Xm, Ym) = Ip (Xm, Ym) −Ip (min) = 0. (2)

The correction value ΔIp (Xn, Yn), which is two-dimensional data determined by the X and Y coordinate values, is represented in the form of a two-dimensional matrix as shown in FIG. 15 is matrix data to be written. In addition,
When the data of the peak current value is first obtained using the X coordinate value as a parameter, there is no problem since the Y coordinate value is also used as a parameter.

Next, the operation of the correction control based on the matrix data of the peak current correction value stored in the storage device 15 will be described. When electric discharge machining is started from the point A by the electrode 1 and the X-axis servo motor 6 and the Y-axis servo motor 7 are drive-controlled by the position command of the numerical controller 5, XY
The table 3 moves in the X-axis direction and the Y-axis direction, and the electrode 1 processes an arbitrary shape on the workpiece 2 at an arbitrary point B.
To reach.

Since the XY table 3 moves on a two-dimensional plane in the X and Y directions, all the movement trajectories of the XY table 3 during this time can be represented by X and Y coordinate values. Therefore, the electric discharge machining start point A can be expressed as (0, 0), and an arbitrary arrival point B can be expressed as (Xn, Yn).

Since the numerical controller 5 recognizes the movement amount and speed of the X-axis motor 6 and the Y-axis motor 7 by receiving signals from the encoders 8 and 9, the processing position point B is set to (Xn, Yn). Can be recognized as At this time, the numerical controller 15 specifies the coordinate value (Xn, Yn), and thereby obtains the peak current correction value ΔIp from the matrix data created in advance and stored in the storage device 5.
(Xn, Yn) can be derived. The numerical controller 5 variably controls the power supply voltage of the variable DC power supply 20 according to the correction value ΔIp (Xn, Yn), and
Is defined as E−ΔE (Xn, Yn).

As a result, as shown in FIG.
The peak current value Ip can be corrected to Ip−ΔIp (Xn, Yn). At this time, ΔE (Xn, Yn) is a variable amount of the power supply voltage E and is represented by Expression (3).

ΔE (Xn, Yn) = L · (ΔIp (Xn, Yn) / ton) (3)

The above correction operation is performed at an arbitrary coordinate position (Xn,
Yn), the peak current value can be corrected and controlled to a constant value on all machining trajectories from the machining start point (0, 0) to the machining end point (Xm, Ym). As a result, the processing energy can be made constant over the entire processing locus, and a constant processing speed can be obtained regardless of the processing position.

Embodiment 2 FIG. 5 shows a power supply device for electric discharge machining according to a second embodiment of the present invention. In FIG. 5, portions corresponding to those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and description thereof will be omitted.

In this embodiment, the DC power supply comprises a fixed voltage DC power supply 21 and a variable voltage DC power supply 22 connected in series to the DC power supply 21 to compensate for the fluctuation of the peak current. DC power supply 22 from numerical controller 5
To the DC power supply 2
2 is variably controlled.

Next, the operation of the second embodiment will be described. First, a procedure for creating the matrix data of the peak current correction value stored in the storage device 15 will be described.

In the first embodiment, the correction value ΔIp (Xn, Yn) of the peak current value Ip is used for all peak current values Ip.
The value of the minimum value Ip (min) of the peak current is subtracted from each of p, and ΔIp (Xn, Yn) = Ip (Xn, Yn) −Ip (mi
n), but in the second embodiment, the maximum value Ip (m
ax), and ΔIp (Xn, Yn) = Ip (max) −Ip (Xn, Y
n) ≧ 0.

Therefore, the maximum value of the peak current Ip (ma
The correction value ΔIp (Xn, Yn) at the coordinate point indicating x) is zero, and the correction values ΔIp at the other coordinate points are positive values. As in the first embodiment, these X,
Correction value ΔI which is two-dimensional data determined by the Y coordinate value
p (Xn, Yn) is represented in the form of a two-dimensional matrix, and is assumed to be matrix data to be electronically written to the storage device 15.

Next, the operation of the correction control based on the matrix data of the peak current correction value stored in the storage device 15 will be described. The numerical control device 5 controls the variable voltage DC power supply 2 according to the peak current correction value ΔIp (Xn, Yn).
2 is variably controlled, and the total power supply voltage is added to the power supply voltage E of the DC power supply 21 to obtain E + ΔE (Xn, Yn), thereby correcting the peak current value Ip to Ip + ΔIp (Xn, Yn). I do.

At this time, ΔE (Xn, Yn) is a variable amount of the power supply voltage of the variable voltage DC power supply 22, and is represented by the equation (3) as in the first embodiment.

ΔE (Xn, Yn) = L · (ΔIp (Xn, Yn) / ton) (3)

Maximum power supply voltage ΔE of variable voltage DC power supply 22
(max) may be set to the value of ΔE (max) = L · (Ip (max) −Ip (min)) / ton).

Since the above-described correction operation is performed at an arbitrary coordinate position (Xn, Yn) as in the first embodiment, the correction operation is performed from the processing start point (0, 0) to the processing end point (X
m, Ym), the peak current value can be corrected and controlled to a constant value on all machining trajectories. Thus, also in this embodiment, the processing energy can be kept constant over the entire processing locus, and a constant processing speed can be obtained regardless of the processing position.

Further, in the first embodiment, the peak current value to be constant is the minimum value Ip (min), but in the second embodiment, the peak current is the maximum value Ip (max) and the processing speed is constant. You can get speed.

Embodiment 3 FIG. 6 shows a third embodiment of the power supply device for electric discharge machining according to the present invention. In FIG. 6, portions corresponding to those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and description thereof is omitted.

In this embodiment, the numerical controller 5
The peak current correction value stored in the storage device 15 is converted into a correction value of the ON time of the semiconductor switching element 11,
This on-time correction value is output to the control circuit 16 of the semiconductor switching element 11. The control circuit 16 is a numerical controller 5
The on-time of the semiconductor switching element 11 is corrected in accordance with the on-time correction value given by the controller.

Next, the operation of the third embodiment will be described. In the third embodiment, the numerical controller 5 is the storage device 1
5, the peak current correction value ΔIp (Xn, Y
n) is converted to a correction value Δton (Xn, Yn) of the ON time of the semiconductor switching element 11 by the following equation (4).

Δton (Xn, Yn) = L · (ΔIp (Xn, Yn) / E) (4)

The control circuit 16 receives the correction value Δton (Xn, Yn) from the numerical controller 5 and, as shown in FIG. 4, calculates the ON time ton of the semiconductor switching element 11 as ton−Δton (Xn). , Yn) to correct the on-time. Ip−ΔIp (Xn, Yn) = E / L · (ton−Δton
(Xn, Yn)), the current value Ip is corrected to Ip−ΔIp (Xn, Yn) as in the first embodiment, and the peak current value is reduced to the minimum value Ip on all the machining trajectories. Correction control can be performed to a constant value with (min).

Thus, also in this embodiment, the processing energy can be kept constant over the entire processing locus, and a constant processing speed can be obtained irrespective of the processing position.

Further, the on-time is corrected by setting the on-time ton of the semiconductor switching element 11 as ton + Δton (Xn, Yn), and Ip + ΔIp (Xn, Yn) = E / L · (ton + Δton
(Xn, Yn)), the current value Ip may be corrected to Ip + Ip (Xn, Yn), and the peak current value may be corrected and controlled to a constant value at the maximum value Ip (max) on all machining trajectories. it can. In this case, as in the case of the second embodiment, a higher constant processing speed can be obtained with a constant peak current of the maximum value Ip (max).

Embodiment 4 FIG. 7 shows a fourth embodiment of the power supply device for electric discharge machining according to the present invention. In FIG. 7, portions corresponding to those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and description thereof will be omitted.

In this embodiment, the numerical controller 5
The correction value of the off-time of the semiconductor switching element 11 is calculated from the correction coefficient of the peak current value stored in the storage device 15, and the off-time correction value is output to the control circuit 16 of the semiconductor switching element 11. The control circuit 16 corrects the off-time of the semiconductor switching element 11 according to the off-time correction value given from the numerical controller 5. As a result, the switching frequency of the semiconductor switching element 11 is controlled according to the peak current correction value.

Next, the operation of the fourth embodiment will be described. First, a procedure for creating matrix data of a correction coefficient for a peak current value stored in the storage device 15 will be described with reference to FIG.

First, the on-time ton of the semiconductor switching element is made constant before the peak current value correction control,
Electric discharge machining is performed from the point where the X and Y coordinates are (0, 0) to the point (Xm, 0), and as shown in FIG. 2, the data of the peak current value Ip is obtained using the X coordinate value as a parameter. Take. Similarly, from (0, Y1) to (Xm, Y1),
Data from (0, Y2) to (Xm, Y2), (0, Y3) to... (Xm, Ym) is taken, and the peak current value of an arbitrary coordinate point (Xn, Yn) is calculated as Ip (Xn , Y
n).

Next, the maximum value Ip (max) of the peak current is obtained and divided by the respective values of all the peak current values Ip. That is, by setting all Ip data as Ip (max) / Ip (Xn, Yn), the correction coefficient of the peak current value Ip at each coordinate point is defined as K (Xn, Yn). . Therefore, the correction coefficient K (X0, Y0) at the coordinate point showing the maximum value of the peak current is 1 as shown in the equation (6), and the correction coefficient K at the other coordinate points is obtained.
Has a value of 1 or more as shown in Expression (5).

K (Xn, Yn) = Ip (max) / Ip (Xn, Yn) ≧ 1 (5) K (X0, Y0) = Ip (max) / Ip (X0, Y0) = 1 ·・ ・ (6)

The correction coefficient K (Xn, Yn), which is two-dimensional data determined by the X and Y coordinate values, is represented in the form of a two-dimensional matrix, and is assumed to be matrix data that is electronically written to the storage device 15. It should be noted that there is no problem in the case where data of the peak current value is firstly obtained using the X coordinate value as a parameter, since the Y coordinate is also used as a parameter.

Next, the operation of the above-described correction control using the matrix data will be described with reference to FIG. In FIG. 8, the fall time tf of the current of waveform 1 and waveform 2
Is approximated as ton ≒ tf, the area S1 of the waveform 1 and the area S2 of the waveform 2 are expressed by Expressions (7) and (8).

S1 = Ip (max) · ton (7) S2 = Ip (Xn, Yn) · ton (8)

Here, K (Xn, Yn) = Ip (max) /
Since Ip (Xn, Yn) and ton have the same value, equations (9) and (10) hold.

S1 = K (Xn, Yn) · S2 (9) S2 = S1 / K (Xn, Yn) (10)

The cycle T1 of the waveform 1 is T1 = ton + toff. When the area of the waveform 2 is corrected to be the same as the area of the waveform 1 in this one cycle, the cycle T2 of the waveform 2 is set to K
Since it is sufficient to multiply by (Xn, Yn), T1 = K (Xn, Yn) · T2. Here, assuming that the correction value of the off time of the semiconductor switching element 11 is Δtoff (Xn, Yn), the period T
2 can be corrected to T2 = ton + toff−Δtoff (Xn, Yn), and Δtoff (Xn, Yn) can be obtained by the following equation (11).

Δtoff (Xn, Yn) = (ton + toff) · (K (Xn, Yn) −1) / K (Xn, Yn) (11)

When Ip (max), K (X0, Y0) =
Since it is 1, Δtoff = 0.

Next, the operation of the correction control based on the matrix data will be described. The numerical control device 5 receives the correction coefficient K (Xn, Yn) from the storage device 15 and executes the semiconductor switching element 1 by the above (11).
The correction value Δtoff (Xn, Yn) of the off-time of 1 is calculated.

The control circuit 11 receives the correction value Δtoff (Xn, Yn) from the numerical controller 5 and, as shown in FIG. 8, sets the off time toff of the semiconductor switching element 11 to toff-Δtoff (Xn, Xn, Yn) to correct the off-time. In other words, by correcting and controlling the switching frequency of the semiconductor switching element 11, it is possible to correct and control the area of the waveform per cycle, that is, the processing energy, to a constant value even for waveforms having different peak current values.

The above-described correction operation is performed at an arbitrary coordinate position (Xn,
Yn), the machining energy can be corrected and controlled to a constant value on all machining trajectories from the machining start point (0, 0) to the machining end point (Xm, Ym). And a constant processing speed can be obtained.

[0071]

As can be understood from the above description, according to the power supply device for electric discharge machining according to the present invention, the memory means stores the correction value of the peak current value corresponding to the relative position between the electrode and the workpiece. The correction value of the peak current value stored in the storage means, which corresponds to the relative position between the electrode and the workpiece, is read out from the storage means, and a direct current is stored in accordance with the correction value. Since the power supply voltage of the power supply is variably controlled, the variation of the peak current value depending on the machining position can be automatically corrected, and the constant machining current, that is, the constant machining speed can be obtained by keeping the peak value of the discharge current pulse constant. As a result, not only the processing accuracy and surface roughness of the workpiece are improved, but also the reproducibility in the processing is improved, the processing characteristics are stabilized, and the occurrence of disconnection of the wire electrode is suppressed.

According to the power supply device for electric discharge machining according to the next invention, the correction value of the peak current value corresponding to the relative position between the electrode and the workpiece is stored in the storage means in advance as matrix data. Of the correction values of the peak current values stored in the memory means, the one corresponding to the relative position between the electrode and the workpiece is read out from the storage means, and the ON time of the semiconductor switching element is controlled according to the correction value.
The variation of the peak current value due to the machining position can be automatically corrected, and by keeping the peak value of the discharge current pulse constant,
A constant processing energy, that is, a constant processing speed is obtained, which not only improves the processing accuracy and surface roughness of the workpiece, but also improves the reproducibility in processing, stabilizes the processing characteristics, and disconnects the wire electrode. Is suppressed. Also,
In the power supply device for electric discharge machining according to the present invention, there is no need to use a variable voltage DC power supply, so that there is also an effect that it can be realized at low cost.

According to the power supply device for electric discharge machining according to the next invention, the correction value of the peak current value corresponding to the relative position between the electrode and the workpiece is stored in the storage means in advance as matrix data. Of the correction values of the peak current value stored in the memory, a value corresponding to the relative position between the electrode and the workpiece is read out from the storage means, and the switching frequency of the semiconductor switching element is controlled according to the correction value. Variations in peak current value due to machining position can be automatically corrected, and by keeping the peak value of the discharge current pulse constant, constant machining energy, that is, constant machining speed, can be obtained. Not only the roughness is improved, but also the reproducibility in the processing is improved, the processing characteristics are stabilized, and the occurrence of disconnection of the wire electrode is suppressed. Further, the power supply device for electric discharge machining according to the present invention does not require the use of a variable-voltage DC power supply, and thus has the effect of being able to be realized at low cost.

According to the power supply device for electric discharge machining according to the next invention, the off time of the semiconductor switching element is calculated from the correction value read from the storage means, and the off time of the semiconductor switching element is controlled to control the switching of the semiconductor switching element. Since the frequency is variably controlled, the variation of the peak current value depending on the machining position can be automatically corrected,
By making the peak value of the discharge current pulse constant, a constant processing energy, that is, a constant processing speed is obtained, which not only improves the processing accuracy and surface roughness of the workpiece, but also improves the reproducibility in processing. In addition, the processing characteristics are stabilized, and the occurrence of disconnection of the wire electrode is suppressed. Further, the power supply device for electric discharge machining according to the present invention does not require the use of a variable-voltage DC power supply, and thus has the effect of being able to be realized at low cost.

According to the power supply device for electric discharge machining according to the next invention, the correction value is determined according to the maximum value or the minimum value of the peak current value at all relative positions, and the peak current value is determined over the entire machining path. Since the constant value is maintained at the maximum value or the minimum value, a constant processing energy, that is, a constant processing speed can be obtained, which not only improves the processing accuracy and surface roughness of the workpiece, but also improves the reproducibility in processing. In addition, the processing characteristics are stabilized, and the occurrence of disconnection of the wire electrode is suppressed. In particular, by maintaining the peak current value at a constant value based on the maximum value over the entire machining path, a faster constant machining speed can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing Embodiment 1 of a power supply device for electric discharge machining according to the present invention.

FIG. 2 is an explanatory diagram showing a method of calculating a peak current correction value.

FIG. 3 is an explanatory diagram illustrating an example of matrix data of a peak current correction value.

FIG. 4 is an explanatory diagram showing an example of correcting a peak current value.

FIG. 5 is a configuration diagram illustrating a power supply device for electric discharge machining according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram illustrating a power supply device for electric discharge machining according to a third embodiment of the present invention.

FIG. 7 is a configuration diagram showing a third embodiment of the power supply device for electric discharge machining according to the present invention.

FIG. 8 is an explanatory diagram showing correction of processing energy by an off time.

FIG. 9 is a configuration diagram showing a power supply device for electric discharge machining in a conventional example.

FIGS. 10A and 10B are explanatory diagrams showing a machining current pulse waveform and a peak current value.

[Explanation of symbols]

Reference Signs 1 electrode, 2 workpiece, 3 XY table, 4 machining gap (between poles), 5 numerical controller, 6 X-axis servomotor, 7 Y-axis servomotor, 8, 9 encoder, 10
DC power supply, 11 semiconductor switching element, 12 electrode feeding point, 13 table feeding point, 14 control circuit, 15
Storage device, 16 control circuit, 20, 21, 22 DC power supply.

Claims (5)

[Claims] An intermittent pulse current is supplied to a processing gap formed between an electrode and a workpiece by an on / off operation of a semiconductor switching element, and a relative control between the electrode and the workpiece is performed by numerical control. In a power supply device of an electric discharge machine for performing electric discharge machining while controlling a position, a voltage variable DC power supply whose voltage is variably controlled, and a correction value for correcting a peak current value as matrix data corresponding to the relative position. The stored storage means, and among the correction values of the peak current values stored in the storage means, those which correspond to the relative positions are read out from the storage means, and the power supply voltage of the DC power supply is read in accordance with the correction values. A power supply device for electric discharge machining, comprising: control means for performing variable control. 2. An intermittent pulse current is supplied to a machining gap formed between an electrode and a workpiece by an on / off operation of a semiconductor switching element, and a relative control between the electrode and the workpiece is performed by numerical control. In a power supply unit of an electric discharge machine that performs electric discharge machining while controlling a position, a storage unit that stores a correction value for correcting a peak current value as matrix data corresponding to the relative position; Reading out the correction value of the peak current value corresponding to the relative position from the storage means, converting the correction value into the ON time of the semiconductor switching element, and controlling the ON time of the semiconductor switching element. A power supply device for electric discharge machining, comprising: 3. An intermittent pulse current is supplied to a machining gap formed between an electrode and a workpiece by an on / off operation of a semiconductor switching element, and a relative control between the electrode and the workpiece is performed by numerical control. In a power supply unit of an electric discharge machine that performs electric discharge machining while controlling a position, a storage unit that stores a correction value for correcting a peak current value as matrix data corresponding to the relative position; Control means for reading a correction value of the peak current value corresponding to the relative position from the storage means, and controlling a switching frequency of the semiconductor switching element according to the correction value. A power supply device for electric discharge machining characterized by the above-mentioned. 4. The control means calculates an off-time of the semiconductor switching element from a correction value read from the storage means, and varies the switching frequency of the semiconductor switching element by controlling the off-time of the semiconductor switching element. The power supply device for electric discharge machining according to claim 3, wherein the power supply device is controlled. 5. The correction value is determined according to the maximum value or the minimum value of the peak current value at all relative positions, and the peak current value is maintained at a constant value according to the maximum value or the minimum value over the entire machining path. The power supply device for electric discharge machining according to any one of claims 1 to 4, characterized in that: