JPH0433566B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improving the precision of an electric discharge machining apparatus that fills a machining tank with a machining liquid and immerses a workpiece in machining.

[Conventional technology]

FIG. 4 is an explanatory diagram of a conventional wire electric discharge machining apparatus for immersion machining of a workpiece. In the figure, 10
12 is a wire electrode, and 12 is a workpiece placed on a workpiece mounting surface plate 14. 16 is a power source for machining, which supplies discharge power to the workpiece 12 via the wire electrode 10 and the workpiece mounting surface plate 14. 18,
Reference numerals 20 denote upper and lower wire guides, which hold the wire electrode 10 slidably above and below the workpiece 12, and spray machining fluid supplied by a pump 24 from a machining fluid tank 22 into a minute gap. supply 26 is a processing tank, and upper and lower wire guides 1
In addition to receiving the machining fluid spouted from 8 and 20,
It is formed to be filled with a machining liquid in order to immerse the workpiece 12 therein. 28 is an X-Y cross table, which includes a processing tank 26, a workpiece mounting surface plate 14,
While loading the workpiece 12, the ball screw 30
The rotational force of the motor 32 directly connected to it is converted into a linear movement force, and the
- It is formed to be relatively movable in the Y direction. 34
A detector detects the moving speed and coordinate position of the table 28 and provides feedback to the NC control device 36. Reference numeral 38 denotes a bed, which loads and holds the table moving mechanism. The figure shows a structure with only one axis for simplicity. Also, symbols A, B, and C are processing tanks 26
It shows the liquid level height when the machining liquid is filled at different levels.

When machining the workpiece 12 with the conventional wire electrical discharge machining device as described above, the NC control device 36 sends a movement command to the motor 32 according to a preset program, and the rotation angle of the motor 32 is controlled by the ball screw 30. Convert to linear movement amount, X-Y
The workpiece 12 placed on the cross table 28, the processing tank 26, and the workpiece mounting surface plate 14 is
It is moved relative to the wire electrode 10 that is stretched and fed between the lower wire guides 18 and 20. At that time, the upper and lower wire guides 18, 2
The wire electrode 1
Discharge power is supplied from a power source 16 between the cutting machine 0 and the workpiece 12 to generate electric discharge and cutting the workpiece 12 according to the programmed shape.

In addition, when performing high-precision machining, in order to prevent the workpiece 12 from being thermally deformed due to the effect of heat generation due to discharge energy, the machining tank 26 is filled with machining fluid until the workpiece 12 is immersed (in the first step). Perform electrical discharge machining (level A in Figure 4). Further, in the conventional wire electrical discharge machining apparatus, when electrical discharge machining is performed by changing the levels A, B, and C of the machining fluid in the machining tank 26 as described above, the weight of the machining fluid changes. FIG. 5 shows the wire electrode 10 when the machining tank 26 is filled with machining liquid to levels A, B, and C and the X-Y cross table 28 is sent.
FIG. 2 is a diagram showing the error caused between the NC command value and the actual position by the amount of relative movement of the workpiece 12 with respect to the NC command value. In the figure, the horizontal axis is the X-Y cross table 2
8 is shown in the X-axis direction, and the vertical axis shows the feed error.

Note that the curves indicated by symbols A ₁ , B ₁ , and C ₁ are filled with machining fluid up to levels A, B, and C, respectively, and
The case where the Y cross table 28 is sent is shown. Fifth
From the results shown in the figure, if the machining fluid level is high and its weight is large, the X-Y cross table 28 and bed 38
This shows that the amount of static deformation increases and the feed error also increases.

[Problem that the invention seeks to solve]

In conventional wire electrical discharge machining equipment, even if the weight of the machining fluid filled in the machining tank changes and the amount of static deformation of the X-Y cross table 28 and the bed 38 changes, the X-Y cross table 28 remains in that state. Because of this, an error occurs between the actual relative movement amount of the workpiece 12 with respect to the wire electrode 10 and the NC command value, resulting in a problem that stable, high-precision machining cannot be performed.

The present invention was made to solve this problem, and an object of the present invention is to provide an electric discharge machining apparatus that can perform highly accurate machining by correcting NC command values.

[Means for solving problems]

This invention generates an electric discharge while intervening machining fluid in a minute gap between the workpiece and the electrode in a machining tank, and
In an electric discharge machining device that processes the workpiece into a desired shape while relatively moving the workpiece and the electrode according to a command, in order to solve the above problem, the machining fluid in the machining tank is A feed error at each coordinate value during relative movement between the workpiece and the electrode according to the liquid level detection means that detects the surface and the weight of the machining liquid corresponding to the machining liquid level detected by this liquid level detection means. a correction value storage means for storing a correction value corresponding to the correction value; and a correction value storage means for reading the correction value stored in the correction value storage means and correcting the NC command value using the correction value;
The apparatus further includes a control means for controlling relative movement between the workpiece and the electrode.

[Effect]

In this invention, the correction value corresponding to the feed error at each coordinate position during relative movement between the workpiece and the electrode that occurs depending on the liquid volume (weight) in the processing tank is stored in advance in the NC control device. Since the relative movement between the workpiece and the electrode is controlled while correcting the NC command value using the correction value that is input into the means and recalled from the correction value storage means during electrical discharge machining, the relative position between the wire electrode and the workpiece is controlled. The relationship remains constant regardless of the amount (weight) of the machining fluid, allowing highly accurate positioning.

〔Example〕

FIG. 1 is a block diagram of an embodiment of the present invention.
In the figure, the same reference numerals as those of the conventional electric discharge machining apparatus shown in FIG. 4 indicate the same parts. Reference numeral 50 denotes a liquid level detection means, which is configured to detect the liquid amount by detecting the liquid level. The detected liquid amount is fed back to the NC control device 36a.

FIG. 2a is a block diagram schematically showing the processing inside the NC control device 36a. Reference numeral 52 denotes a liquid level counter, which receives a detection signal from the liquid level detecting means 50 and transmits information on the current amount of liquid in the processing tank 26 to the CPU 54. 56 is a current value counter,
The current position information of the table 28 is transmitted to the CPU 54 by receiving signals from the respective detectors 34 directly connected to the axis and Y-axis motors 32 . Reference numeral 58 denotes a correction value storage device, which measures the feed error of each coordinate position of the table 28 corresponding to each data of the liquid level counter 52 and the current value counter 56 in advance using a length measuring device 60 (see FIG. 2b). , and store the correction value created from the result. A drive unit 62 sends an output to each motor 32 in accordance with a movement command issued from the CPU 54 to drive the table 28.

FIG. 2b is a perspective view of the length measuring device 60.

In the wire electrical discharge machining apparatus configured as described above, electrical discharge machining is performed while moving the workpiece 12 relative to the wire electrode 10, as in the conventional case.

At this time, the amount of machining liquid filled in the machining tank 26 is detected by the liquid level detector 50, and the liquid level counter 5
2 to the CPU of the NC control device 36a as liquid volume information.
Sent to 54. Furthermore, each coordinate position of the table 28 that changes sequentially is detected by a detector 34,
The current value counter 56 sends the current value information of the table 28 to the CPU 54. The CPU 54 compares the liquid amount information with the table current value information, and reads the corresponding correction value from the correction value storage device 58. Next, the CPU 54 adds a correction value to the movement command according to the program, and instructs the drive unit 62 so that the relative position between the wire electrode 10 and the workpiece 12 is as specified by the program, and moves the X-axis, Y-axis,
Controls the drive of the axis.

FIG. 3 is a diagram showing the feed error when the X-Y cross table 28 is controlled in this manner. In the figure, the vertical axis is the feed error, and the horizontal axis is X-Y
The X-axis direction of the cross table 28 is shown. code A ₁ ,
B ₁ and C ₁ are placed in the processing tank 26 up to levels A, B, and C.
Each figure shows the case of filling with machining fluid and performing electrical discharge machining.

From the results shown in FIG. 3, it is clear that the feed error is almost eliminated. Although FIG. 3 shows the X-axis, similar results can be obtained for the Y-axis as well.

Although the wire electrical discharge machining apparatus has been described in the above embodiment, a die-sinking electrical discharge machining apparatus may also be used. Also, the first
Although the liquid level detection level in the figure shows a case where detection is performed in three stages, increasing the number of detection levels allows for more detailed correction, which has the effect of enabling more stable and high-precision machining.

〔Effect of the invention〕

As explained above, according to the present invention, a correction value corresponding to the feed error at each coordinate position during relative movement between the workpiece and the electrode, which occurs depending on the amount of liquid (weight) in the processing tank, is stored in advance. Since the relative movement between the workpiece and the electrode is controlled while correcting the NC command value using this correction value, high-precision machining can be performed stably regardless of the amount of liquid in the machining tank. There is an effect that can be achieved.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of an embodiment of the present invention, Fig. 2a is a block diagram showing an outline of the processing inside the NC control device, Fig. 2b is a perspective view of the length measuring device, and Fig. 3 is a feed error. FIG. 4 is an explanatory diagram of a conventional wire electrical discharge machining apparatus, and FIG. 5 is a diagram depicting feed error. In the figure, 10 is a wire electrode, 12 is a workpiece, 18 and 20 are wire guide parts, 26 is a processing tank, 18 is an X-Y cross table, and 36a is an NC
A control device, 50 is a liquid level detection means, 52 is a liquid level counter, 54 is a CPU, 56 is a current value counter, 58 is a correction value storage device, 60 is a length measuring device,
62 is a drive unit. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. Discharge the workpiece while interposing a machining liquid in a micro gap between the workpiece and the electrode in a machining tank, and move the workpiece and the electrode relative to each other according to an NC command. In an electric discharge machining device for machining into a desired shape, a liquid level detection means for detecting the liquid level of the machining fluid in the machining tank, and a machining fluid weight corresponding to the machining fluid level detected by the liquid level detection means are provided. a correction value storage means for storing a correction value corresponding to a feed error at each coordinate value during relative movement between the workpiece and the electrode according to the above; An electric discharge machining apparatus comprising: a control means for correcting an NC command value using a correction value and controlling relative movement between the workpiece and the electrode.