JPS6026649B2 - Wire cut electrical discharge machining control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire-cut electric discharge machining control method for performing electric discharge machining using a wire electrode.

Wire-cut electric discharge machining uses a metal wire with a diameter of about 0.05 mm to 0.3 mm as an electrode to provide controlled feed in the X and Y directions between the wire and the workpiece to cut the desired contour shape. .

In such a processing method, controlled feed in the x and y directions is usually given with reference to the locus of the center of the wire electrode.

However, if the trajectory of the center of the wire electrode follows the desired contour shape, the workpiece will be machined with dimensions that differ from the desired contour shape by the wire diameter and the amount of machining gap. Therefore, the locus of the middle iD of the wire electrode is shifted by the amount of the wire length and the machining gap so that the dimensions after machining become the desired contour shape.

That is, in FIG. 1, 1 is the desired contour shape,
2 is a trajectory centered on the wire. Further, A is a case where the inside of the wire trajectory 2 is desired after being processed and cut, and B is a case where the outside of the wire trajectory 2 is desired after being processed and cut. Here, the amount of deviation 6 between the desired contour shape and the locus of the center of the wire electrode is referred to as an offset amount. This offset amount was a constant amount that did not change from the beginning to the end of machining in the secondary wire cut electrical discharge machining. Now, when the wire electrode 4 performs electric discharge machining on the workpiece 3 having a thickness change as shown in Fig. 2 in the direction of the arrow in the figure using such a machining method, the outer diameter d of the wire electrode 4 and the electric discharge machining gap The machining groove width S, including the width S, changes from A to B.

Therefore, vertical lines or steps are left on the cut surface after processing, which reduces processing accuracy and reduces the value of the processed product. In order to eliminate the drawbacks of the conventional wire-cut electrical discharge machining method as described above, the present invention detects the machining state and changes the offset amount during machining.

FIG. 3 is a diagram illustrating an embodiment of the method of the present invention.

The workpiece 3 is mounted on an X-Y table 5, and electrical discharge machining is performed between it and a wire electrode 4 by a machining power source 6. Further, the table moving motor 7 is driven by a table control device 8 to enable movement of the table in the x-y directions and control machining of a desired shape. The machining gap state detection device 9 detects the factors that affect the machining groove width of the electric discharge machining, which changes as the electric discharge machining progresses, converts it into an electric signal, and sends it to the offset vector control device 10. The factors that affect the machining groove width in electrical discharge machining, which changes as the electrical discharge machining progresses, are, for example, the pressure between the machining holes, the current between the machining holes, the time from applying a pulse voltage to discharging, machining speed, and machining fluid. It is one or a combination of two or more of electrical conductivity, etc. The offset vector control device 10 controls the absolute value of the offset vector using the signal from the gap state detection device 9, and sends the amount of correction of the wire center trajectory to the table control device 8.
The table control device 8 performs normal trajectory interpolation calculations, changes the trajectory based on commands from the offset vector control device 10, and drives the table moving motor based on the result. At this time, the offset amount for the machining gap state may be selected from a group of pre-stored data based on various machining conditions, or may be simply a simple function, such as a linear function, if high precision is not required. It may be. Here, specific examples of the former include the following.

In other words, the voltage between electrodes is digitized in IV units, and this is converted into VG.
shall be. Here, VG takes a value from 0 to 300. Similarly, the processing speed is digitized at 0.1 skin/min, and this is set as Fc, and this Fc takes a value from 0 to 100. Further, the electrical conductivity of the machining fluid is also digitized in units of IKQ/c and expressed as Rw, where Rw takes a value from 0 to 100. Here, if we consider a three-dimensional array representing the absolute value of the offset vector and let it be OF, OF is, VG, Fc,
It is uniquely determined by specifying Rw.

For example, VG=100. If Fc=20 and Rw=20, OF(100, 20, 20)=180. The OF value of this three-dimensional array (300 x 100
×ION (specific) may be determined in advance by an appropriate value through experiments or the like. Further, specific examples of the latter include the following.

In other words, it has been experimentally confirmed that the length of the machining gap is almost proportional to the voltage between the machining holes, and if you do not want very high accuracy, you can change and control the offset amount so that it is proportional to the voltage between the machining holes. . In this case, it is sufficient to simply set the absolute value of the offset vector=k×voltage between electrodes (k' is a proportionality constant).

FIG. 4 shows the groove width during machining when the control according to the present invention is applied.

2 shows the locus of the center of the wire electrode, and one side of the groove width is almost a straight line.

In other words, the present invention controls the decrease in processing accuracy due to changes in the groove width during processing by changing the offset amount so that even if the groove width itself changes, it does not substantially affect the machined product. There are characteristics in what you do.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram when the locus of the center of the wire electrode is shifted from the desired contour shape by an offset amount. FIG. 2 is an explanatory diagram of how groove width changes in the conventional method, FIG. 3 is an explanatory diagram of the method of the present invention, and FIG. 4 is an explanatory diagram of how groove width changes in the method of the present invention. Note that the same reference numerals in the figures represent the same or corresponding parts. 2... Locus of the center of the wire electrode, 6... Processing power source, 8... Table control device, 9... Inter-electrode state detection device, 10... Offset vector control device. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. Place the wire electrode facing the workpiece through a small gap, repeatedly perform pulse discharge while supplying machining fluid to this small gap, and advance the wire electrode or the workpiece along the planned machining path. A wire-cut electric discharge machining control method for electric discharge machining the workpiece using a wire cut electric discharge machining method, the wire cut electric discharge machining control method comprising: an element that influences the machining groove width of the electric discharge machining, which changes as the electric discharge machining progresses in a minute gap formed between the wire electrode and the workpiece; 1. A wire cut electrical discharge machining control method, comprising: detecting the detection signal, and changing and controlling a relative movement path between a wire electrode and a workpiece in accordance with the detection signal.