JPH0732219A - Wire electric discharge machine - Google Patents

Abstract

PURPOSE:To suppress the quantity of corner cut at a corner part by providing a corner part machining condition setting means for setting stepwise the machining conditions computed by a corner part machining condition computing means from a position, set by a corner part pre-machining condition change position setting means, to the corner part. CONSTITUTION:A corner part to change a machining feed direction by a wire electrode 24 is detected by a corner part detecting means. A machining condition in front of a position set by a corner part pre-machining condition change position setting means 50 is retained by a machining condition retaining means 50, and machining conditions set stepwise from the position, set by the corner part pre-machining condition change position setting means 50, to the corner part are computed by a corner part machining condition computing means 50. The machining conditions computed by the corner machining condition computing means 50 from the position, set by the corner part pre-machining condition change position setting means 50, to the corner part are then set stepwise by the corner part machining condition setting means 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire electric discharge machine for machining a work piece by repeatedly generating pulsed electric discharge between a wire electrode and the work piece.

[0002]

2. Description of the Related Art Generally, a wire for processing a workpiece by relatively moving the wire electrode and the workpiece while repeatedly generating a pulsed discharge between the wire electrode and the workpiece. In the electric discharge machine, as shown in FIG. 3 (a), when the wire electrode 24 advances from the point C to the point D by a distance of δ to machine the workpiece 2, the electric discharge area S 1 causes a new electric discharge. The wire electrode 24 receives the force due to the reaction vector V1 in the DC direction.

However, as shown in FIG. 3B, when the wire electrode 24 advances from C to E by a distance δ to process the workpiece 2 (direction change of 90 °), a new discharge is generated. Since the combined vector V2 due to the processing area S2 acts in the EF direction instead of the EC direction, the wire is deflected by α. As a result, a deviation of β occurs in the direction perpendicular to the vector CE, and as a matter of course, since the vibration vibrates by an amount corresponding to the deviation to perform extra machining, as shown in FIG. Processing progresses in the direction indicated.

For this reason, as a method of controlling electric discharge machining for suppressing the above-mentioned "dag" at the corners, there has been a conventional method such as Japanese Patent Publication No. 63-2728.

In this electric discharge machining control method, when the wire electrode reaches a corner portion of the machining shape on the workpiece, it is regarded as a variation value deviating from the machining condition program based on a change in machining amount at the corner portion. A means for detecting, a means for ranking and storing a plurality of electrical processing conditions, and a means for stepwise switching the electrical processing conditions stored in the storage means based on the detection result of the detection means are provided. When the detection means detects that the machining has proceeded to reach the angular portion, the angular portion is changed from the electrical machining condition among the conditions stored in the storage means by the switching means so as to keep the machining speed constant. The machining state is controlled so as to be sequentially switched to the electrical machining conditions of the next rank until the machining state reaches the set machining state.

[0006]

However, in addition to the above-mentioned causes, there is another possible cause of "dag" at the corners. The cause is shown below.

As described in FIG. 3A among the above causes, when the wire electrode 24 is machined by advancing by a distance δ from the point C to the point D, the electric discharge reaction force is generated by the new electric discharge machining area S1. Is applied to the wire electrode 24 in the DC direction. The shape of the wire electrode 24 at this time is, as shown in FIG. 5, arcuate in the direction opposite to the machining feed direction, and is bent by the deflection amount α. In Figure 5,
The wire electrode 24 is supported by the upper wire guide 30 and the lower wire guide 32, and the wire electrode 24 is the work piece 2
To move from left to right. Wire electrode 2
When the machining feed direction is changed in the state in which the wire 4 is bent like this, the corner portion is machined by the wire electrode 24 having the bow shape, so that "drip" occurs. FIG. 6 shows the locus of movement of the wire electrode 24 at the corner portion.
FIG. 6A shows a movement locus of the upper surface of the workpiece 2, and FIG.
(B) shows a movement locus in a cross section having a height of ½ of the plate thickness of the workpiece 2. "Who" in the corner caused by the above causes
The larger the amount, the closer to the center of the plate thickness of the workpiece 2.

In the conventional control method, the electrical machining conditions are changed immediately after the corner portion is bent and machined. Therefore, even if this control method is used,
At the corner portion, the wire electrode 24 is bent in a bow shape. Therefore, it is not possible to sufficiently remove "who" at the corner.

The present invention has been made in order to solve the above-mentioned problems, and reduces the deflection amount α of the wire electrode before and after the change of the machining feed direction to reduce the "drip" at the corner portion. The purpose is to reduce the amount of machining and perform machining with high machining accuracy.

[0010]

A wire electric discharge machine according to the present invention, which has been made to achieve the above object, has a machining condition setting means for setting machining conditions and the like concerning a workpiece as shown in FIG. Based on the electrical processing conditions set by the processing condition setting means, a discharge control means for applying a pulsed voltage between the wire electrode and the workpiece, and an average between the wire electrode and the workpiece The machining gap voltage detecting means for detecting the machining gap voltage, the relative moving means for relatively moving the wire electrode and the workpiece, and the average machining gap voltage detected by the machining gap voltage detecting means are set for the machining condition setting. The relative movement means is controlled so that the target inter-electrode voltage set by the means or the relative movement speed between the wire electrode and the workpiece becomes the feed speed set by the processing condition setting means. That a moving speed control means performs a processing of a workpiece by repeatedly generating pulsed discharge between a wire electrode and a workpiece.

[0011] Then, a corner portion detecting means for detecting a corner portion for changing the machining feed direction, and a corner portion pre-machining condition changing position setting means for setting a position to start changing the machining conditions before the corner portion, Machining condition storage means for storing the machining condition before the position set by the corner part premachining condition change position setting means, and from the position set by the corner part premachining condition change position setting means to the corner part Corner machining conditions calculating means for calculating machining conditions set stepwise, and the corner machining conditions between the position set by the corner pre-machining condition changing position setting means and the corner The corner portion machining condition setting means for gradually setting the machining conditions calculated by the calculating means, and the above-mentioned corner condition storing means which is stored by the machining condition storage means after passing through the corner portion. And a machining condition returning means for returning the engineering conditions.

[0012]

In the wire electric discharge machine of the present invention having the above-mentioned structure, since the machining conditions are changed from before the corner portion to reduce the electric discharge reaction force, the bending amount α of the wire electrode is minimized at the corner portion. When the machining feed direction is changed in this state, the "drip" of the corner portion due to the deflection of the wire electrode can be minimized. Further, since the machining is performed with the machining conditions changed even after the corner portion, it is possible to minimize the "drip" of the corner portion caused by the discharge reaction force due to the variation of the machining area. As described above, highly accurate machining at the corner can be realized.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic configuration diagram showing the overall configuration of a wire electric discharge machine to which the present invention is applied.

As shown in FIG. 2, the wire electric discharge machine of this embodiment has a movable table 4 for fixing the workpiece 2.
Is provided. The movable table 4 is provided in a processing tank 8 in which the processing liquid 6 is stored, and is moved in the X-axis direction and the Y-axis direction by an X-axis servomotor 10 and a Y-axis servomotor 12 as relative moving means, respectively. To be done.

The machining liquid 6 is pumped out of the machining liquid tank 16 by the pump 14, supplied to the machining portion of the workpiece 2 through the machining liquid supply section 18, and stored in the machining tank 8. Then, the used working liquid 6 overflowing from the working tank 8
Is returned to the processing liquid tank 16 through the drainage pipe 20, and is pumped out again by the pump 14 through the filter 22 for filtration.

Next, the wire electrode 24 for processing the work piece 2 is fed out from the wire bobbin 28 and supported by the upper wire guide 30 and the lower wire guide 32 arranged above and below the work piece 2. Then, the wire drive motor 34 and the tension roller 36 are caused to travel while generating tension. And the wire electrode 24 after use
Is discharged to the waste wire discharging section 38.

The upper wire guide 3 of the wire electrode 24
An upper power feeding section 40 and a lower power feeding section 42 for applying a pulse voltage for discharge to the wire electrode 24 are respectively provided in a moving path above 0 and a moving path below the lower wire guide 32.
Is provided. These power supply units 40 and 42 are connected to the processing power supply unit 44, and between the power supply unit 44 and the movable table 4 between the power supply units 40 and 42.
When the pulse voltage is applied, electric discharge is generated between the wire electrode 24 and the workpiece 2, and the workpiece 2 is processed.

Further, the processing power source section 44 includes a control device 50.
From the machining power supply unit 44 to the wire electrode 24 as a discharge control unit for controlling the generation interval (discharge cycle) of the pulse signal generated to allow the generation of discharge according to the control signal from A peak current control unit 54 that controls the flowing peak current (discharge energy), and an average inter-electrode voltage between the wire electrode 24 and the workpiece 2 (hereinafter,
It is simply called the voltage between contacts. ) Is connected to the inter-electrode voltage detection circuit 56 as the inter-electrode voltage detection means.

The controller 50, as shown in FIG.
The U60, the display device 62, the ROM 64, the RAM 66, the input / output port 68, and the like are configured as a well-known microcomputer, and various processing conditions (that is, processing) input through the operation panel 58 as processing condition setting means. The X-axis servomotor 10 and the Y-axis servomotor 12 based on the program such as the shape, the electric machining conditions such as the discharge cycle, the discharge energy, etc.) and the inter-electrode voltage detected by the inter-electrode voltage detection circuit 56. , A pump 14, a wire drive motor 34, a tension roller 36, a processing power supply 44, a discharge pulse controller 52, a peak current controller 54, and the like, and outputs a control signal.
The above-mentioned units are drive-controlled.

That is, the control device 50 has the following (1)-
Execute (5) and so on.

(1) The X-axis servomotor 10 and Y are arranged so that the actual inter-electrode voltage detected by the inter-electrode voltage detection circuit 56 becomes the target inter-electrode voltage input through the operation panel 58.
By controlling the rotation speed of the axis servo motor 12,
Moving speed control as moving speed control means for controlling the moving speed of the movable table 4, and thus the workpiece 2.

(2) Machining shape control for driving and controlling the X-axis servomotor 10 and the Y-axis servomotor 12 according to the machining shape of the workpiece 2 input through the operation panel 58.

(3) Machining liquid circulation control for driving the pump 14 to circulate the machining liquid 6.

(4) Electrode transfer control for driving the wire drive motor 34 and the tension roller 36 to move the wire electrode 24.

(5) A control signal is output to the discharge pulse control section 52 based on the discharge cycle, the target electrode voltage, the discharge energy, etc. input via the operation panel 58, and the machining power supply section 44.
Discharge cycle control that controls the discharge cycle at which the discharge pulse is generated.

When the program operation is started, the controller 5
0 starts the following processing. The first block of the NC program stored in the RAM 66 is read and analyzed to analyze the X-axis servomotor 10 and the Y-axis servomotor 1.
2 outputs a control signal. By this processing, the movable table 4 starts to move. At this time, the working fluid 6 is the pump 1
4, the wire electrode 24 is run by the wire drive motor 34 and the tension roller 36, and the discharge pulse control section 52 and the machining power supply section 44 generate a discharge pulse between the electrodes. . Therefore, electric discharge is generated between the wire electrode 24 and the workpiece 2,
Processing starts. Then, when the machining is started, the moving speed is controlled so that the inter-electrode voltage becomes the set target inter-electrode voltage.

On the other hand, the CPU 60 during processing analyzes the processing shape of the workpiece 2 input via the operation panel 58. Then, when the corner portion which is the joint of the blocks is detected, the control device 50 starts the corner sag prevention control. here,
It may be determined whether or not the corner sag prevention control is executed, depending on the angle formed by the block seam. The concept of corner sag prevention control, which is the main processing related to the present invention, among the various controls executed by the control device 50, and the actual flow of control will be described below with reference to the flowchart of FIG.

As described above, when the corner portion is processed in a state where the wire electrode 24 is bent in a bow shape, since the corner portion is processed by the bow-shaped wire electrode 24, "drip" occurs at the corner portion. Will end up. To reduce the amount of "drooping" at this corner, the wire electrode 24
It is necessary to remove the deflection. The deflection amount α of the wire electrode 24 is generally given by the following equation.

[0030]

[Equation 1]

The discharge reaction force P has a correlation with the processing conditions, and when the processing conditions are changed, the discharge reaction force acting on the wire electrode 24 changes. For example, when the discharge cycle is considered as an example of the machining condition, the discharge reaction force also decreases because the number of discharge pulses per unit time decreases by increasing the discharge cycle.

That is, by increasing the discharge cycle as a processing condition, the discharge reaction force is reduced and the wire electrode 24
Deflection α of can be removed.

The machining conditions include discharge energy and voltage between electrodes in addition to the discharge cycle. However, in the case of the corner sag prevention control, the best method is to change the discharge cycle while keeping the discharge energy and the voltage between electrodes constant. This is because when the discharge energy and the inter-electrode voltage are changed, the discharge gap changes, and the machining groove width W shown in FIG. 4 also changes accordingly, and the machining shape collapses. After that, the discharge energy,
An example of changing the discharge cycle while keeping the voltage between contacts constant will be described.

As described above, before processing the corner portion,
By increasing the discharge cycle and removing the bending of the wire electrode, it is possible to reduce the "droop" at the corners. However, since the actual machining state is delayed with respect to the change in the machining conditions, the deflection amount α of the wire electrode 24 cannot be removed immediately after the discharge cycle is increased, but after the discharge cycle is increased. It is empirically known that the deflection amount α of the wire electrode 24 can be removed by processing the distance. A graph of this relationship is shown in FIG. It has also been experimentally found that if the discharge cycle is suddenly increased during machining, the wire electrode 24 and the workpiece 2 are likely to be short-circuited. From the above, in order to reduce the "drip" of the corner portion, it is necessary to increase the discharge cycle stepwise in front of the corner portion and provide a section for removing the deflection of the wire electrode 24. The section from the position where the discharge cycle is gradually increased to the corner is referred to as section A.

After the program operation is started as described above and the CPU 60 detects the corner portion, the section A is set in S114. Here, the distance of the section A, the plurality of discharge cycles that are gradually increased in the section A, and the discharge cycle when machining the corner portion can be input through the operation panel 58. It is also possible to calculate all or part by the control device 50. here,
As an example, a method of inputting a discharge cycle when machining a corner portion through the operation panel 58 and calculating another value by the control device 50 will be described.

The discharge cycle which is gradually increased in the section A is given by, for example, equation (2).

[0037]

[Equation 2]

Next, a method of calculating the distance in the section A when the discharge cycle is increased stepwise based on the equation 2 will be described.

The time required to move in one step of the discharge cycle in the section A is defined as Ts, and the time required to change to n steps is T.
If n, then the following equation holds.

[0040]

[Equation 3]

The following equation is obtained from the equations 2 and 3.

[0042]

[Equation 4]

From the equation (4), the time Tt required to move the section A is given by the following equation.

[0044]

[Equation 5]

Further, it has been experimentally proved that the moving speed and the discharge cycle are in inverse proportion to each other, and therefore the following equation is established.

[0046]

[Equation 6]

Therefore, the following equation is obtained from the equations 2, 3, and 6.

[0048]

[Equation 7]

In order to obtain the distance in the section A, the moving speed F (n) may be integrated over time. Therefore, the distance in the section A can be calculated by the following formula.

[0050]

[Equation 8]

Here, F (0) can be obtained by calculating the average speed per unit time of the moving speed before entering the section A, which is controlled by the moving speed control.

As described above, the discharge period is changed by using the formula 2 and the distance in the section A is obtained by using the formula 8 to obtain the target discharge period before the corner portion, and the deflection amount of the wire electrode 24 is obtained. Can be removed.

In this embodiment, the electric discharge cycle set at the corner is input through the operation panel 58.
It is also possible to calculate the discharge cycle when machining the corner portion by inputting the material, plate thickness, and the amount of "drip" of the corner portion that is allowed in the workpiece 2 through the operation panel 58. Is.

Further, as the method of changing the discharge cycle stepwise, the equation 2 is used, but the following equation 9 may be used. Further, although the calculation is performed by using Expression 8 for setting the distance in the section A, it may be input via the operation panel 58.

[0055]

[Equation 9]

After setting the distance of section A in S114, S
At 116, the position Pa at which the change of the discharge cycle is started is calculated. This position Pa is a position in front of the corner portion set by the CPU 60 by the distance of the section A.

Next, in S118 and S120, the machining is continued until the section A is entered. When the section A is entered, the discharge cycle SC (0) set before the section A is stored in the RAM 66 in S121. Then S1
22 starts changing the discharge cycle. This changing method is performed according to the above-mentioned two equations.

When the discharge cycle is changed and the operation of the block before the corner is completed (S124), the operation of the block after the next corner is started (S126).

At the time when the operation of the block after cornering is started in S126, the discharge period is changed to the changed value (SC
(T)). Next, in S127, in order to prevent corner sagging caused by the vibration of the wire electrode 24, a machining distance is set while the discharge cycle is set to SC (t). The section of this distance will be described as section B. It has been experimentally found that there is a correlation between the distance in the section B and the amount L3 of sag of the corner portion 13 shown in FIG. This relationship is shown in FIG. From FIG.
It can be seen that by setting the section B longer, the amount L3 of sag of the corner portion 13 decreases, but even if the section B is set longer than a certain section, the amount L3 of the corner portion 13 does not decrease.
It has also been experimentally found that 0.2 to 0.3 mm is suitable as the distance in the B section. Here, as an example, the distance in section B is set to 0.3 mm in advance in the control device 50.

At S128, the position Pb for returning the discharge cycle to the original state is calculated. This position Pb is a position behind the start point of the block after the corner started in S126 by the distance of section B.

Next, in S130 and S132, the processing is continued until the section B is exited. When you leave section B, S134
Resets the discharge cycle to the original state. In this case, if the discharge cycle is sharply reduced during machining, the wire electrode 24 and the workpiece 2 are likely to be in a short circuit state, and the wire electrode 2
It has been experimentally found that the wire No. 4 is easily broken. Therefore,
After returning from the section B, when returning the discharge cycle to the original state, it is necessary to change it stepwise. Here, as an example, the changing method is performed according to the following formula.

[0062]

[Equation 10]

Finally, when the discharge cycle returns to the value stored in the RAM 66 and set before entering the section A, a series of corner sag prevention control ends.

The series of control procedures described above are repeatedly executed every time the corner is detected until the program operation is completed.

In this embodiment, the distance of the section B is set in the control device 50 in advance.
It is also possible to set the distance of the section. Further, although the formula 10 is used as a method of changing the discharge cycle stepwise,
You may use the following 11 type | formulas.

[0066]

[Equation 11]

[0067]

As is clear from the above description, according to the wire electric discharge machine of the present invention, it is possible to suppress the amount of "drip" at the corner portion and perform machining with high corner precision. Is possible.

[Brief description of drawings]

FIG. 1 is a block diagram illustrating a configuration of the present invention.

FIG. 2 is a schematic configuration diagram showing the overall configuration of a wire electric discharge machine according to an embodiment.

FIG. 3A is a diagram showing an electric discharge reaction force when electric discharge machining is performed on a linear shape. (B) It is a figure which shows the electric discharge reaction force at the time of carrying out the electric discharge machining of the corner part.

FIG. 4 is a diagram showing “dag” when a corner portion is machined by a conventional wire electric discharge machine.

FIG. 5 is a diagram showing deflection of a wire electrode during electric discharge machining.

FIG. 6A is a diagram showing a machining locus on the upper surface of a workpiece when a corner portion is machined by a conventional wire electric discharge machine. (B) It is a figure which shows the processing locus | trajectory of the cross section of the height of 1/2 of the plate thickness of a to-be-processed object when processing a corner part with the conventional wire electric discharge machine.

FIG. 7 is a block diagram of the inside of a control device.

FIG. 8 is a flowchart showing a corner control process executed by the control device 50.

FIG. 9 is a graph showing the relationship between the processing distance after increasing the discharge cycle and the amount of bending of the wire electrode.

FIG. 10 is a graph showing the relationship between the distance in section B and the amount of corner sag.

[Explanation of symbols]

 2 Workpiece 4 Movable table 10 X-axis servo motor 12 Y-axis servo motor 24 Wire electrode 40 Upper power supply section 42 Lower power supply section 44 Processing power supply section 50 Control device 52 Discharge pulse control section 56 Electrode voltage detection circuit 58 Operation panel

Claims (1)

[Claims] 1. A pulse condition between a wire electrode and a workpiece based on machining condition setting means for setting machining conditions and the like relating to a workpiece, and electrical machining conditions set by the machining condition setting means. Discharge control means for applying the voltage between the wire electrode and the workpiece, an inter-electrode voltage detecting means for detecting an average inter-electrode voltage between the wire electrode and the workpiece, and a relative moving means for relatively moving the wire electrode and the workpiece. And so that the average inter-electrode voltage detected by the inter-electrode voltage detecting means becomes the target inter-electrode voltage set by the processing condition setting means, or the relative moving speed between the wire electrode and the workpiece is A moving speed control means for controlling the relative moving means is provided so that the feed speed set by the processing condition setting means is provided, and pulsed electric discharge is repeatedly generated between the wire electrode and the workpiece. In a wire electric discharge machine for machining a work piece by means of a corner portion detecting means for detecting a corner portion for changing the machining feed direction, and a corner portion for setting a position before the corner portion to start changing the machining conditions. Pre-machining condition change position setting means, machining condition storage means for saving machining conditions before the position set by the corner part pre-machining condition change position setting means, and setting by the corner part pre-machining condition change position setting means From the position set by the corner part pre-machining condition change position setting means to the corner part Until the corner portion machining condition setting means for gradually setting the machining conditions calculated by the corner portion machining condition calculating means, and the machining after passing through the corner portion. A wire electric discharge machine, comprising: machining condition restoring means for returning the machining conditions saved by the condition saving means.