JPH0478411B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire cut electrical discharge machining device,
In particular, it relates to position control of the processing electrode.

As shown in FIG. 1, the wire cut electric discharge machining apparatus performs the machining process while moving the machining electrode 1, which is a wire electrode or a tape electrode, in the axial direction between a pair of positioning guides 56, 56 arranged at intervals. The workpiece 57 is moved in a direction perpendicular to the axial direction of the electrode, and a pair of machining fluid spray nozzles (not shown) are arranged on both sides of the workpiece 57, coaxially with the machining electrode and facing each other. The machining electrode 1 is
Intermittent voltage pulses are applied between the workpiece 57 and the workpiece 57, and machining is performed by the generated electric discharge.

When using a wire electrode as a processing electrode,
As the positioning guide 56, as shown in FIG. 2, a diamond die or the like having a circular guide hole 56a in the center is generally used.
In the case of a 0.2 mm wire electrode, the diameter of the guide hole 56a is set to 0.206 to 0.22 mm, for example, so that there is a gap of about 6 to 20 μm, usually about 6 to 12 μm, between the wire electrode 1 and the guide surface of the guide hole 56a. Dies with gaps are used. If the diameter of the guide hole 56a is smaller than this, it becomes difficult for the wire electrode 1 to pass through, and the wire electrode 1 may not be able to come out of the hole due to the spread of the discharge trace or the protrusion of the molten bead, and the wire electrode may be suddenly cut.

Therefore, it is necessary to provide the gap, but as shown in FIG. When drawn to an extreme, the wire electrode 1 is curved as shown at 1', and therefore, as shown in FIG. This type of wire cut electric discharge machining apparatus is designed so that the center of the guide hole 56a is the machining position coordinate.
If the wire electrode deviates by 1'', the machining position will shift by at least the amount of the deviation, resulting in a decrease in machining accuracy.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, it is an object of the present invention to provide a wire-cut electric discharge machining apparatus having a structure that can prevent a decrease in machining accuracy due to deviation of a machining electrode.

In order to achieve this object, the wire cut electric discharge machining apparatus of the present invention is arranged such that the positioning guide, which is the die guide, is positioned at equal angular intervals in the circumferential direction around the guide hole of the positioning guide, and each of the positioning guides is positioned relative to the side surface of the machining electrode from the perpendicular direction. a plurality of detection electrodes for detecting the position of the processing electrode provided so as to face each other, a voltage source connected to flow a current between each of the detection electrodes and the wire electrode, and each detection electrode and the processing electrode; a calculation means for detecting the voltage or current between the two, and determining the distance between the sensing electrode, each of the sensing electrodes, and the processing electrode from the detected voltage or current, and calculating the relative position between the two; and means for controlling the relative position of the machining electrode and the workpiece so that the distance between the machining electrode and each detection electrode is at a fixed position within the guide hole.

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 3 is a diagram showing an example of the configuration around a positioning guide to which the present invention is applied, in which 1 is a wire electrode, 2,
Reference numeral 3 denotes an upper arm and a lower arm to which guide rollers 4 and 5 of the wire electrode 1 are attached, and these are attached to the main body of the apparatus (not shown). Support members 6 and 7 are attached to the arms 2 and 3 so that their vertical positions can be adjusted by manual handles or motors 8 and 9;
Reference numeral 10 denotes a current-carrying pin, which is attached to the support member 6 and serves as an upper current-carrying device that applies a voltage to the wire electrode by contacting the wire electrode 1 which has been pressed and displaced by a wear-resistant and insulating pressing pin 10'. It consists of Reference numeral 11 denotes a current-carrying roller as a lower current-carrying device that also serves as a lower guide roller, and since it is energized by contacting with the wire electrode 1 subjected to wire cut electrical discharge machining, it is a fixed current-carrying pin for the upper clean wire electrode 1. 10 is a rotating roller, and the diameter is made sufficiently large relative to the pin 10 in order to increase the contact area, and the power supply from the wire cut electric discharge machining power source to the current-carrying roller 11 is carried out by the current-carrying roller 11. 11
Or, it is carried out by applying brush current to the rotating shaft.

Reference numerals 12 and 13 indicate hollow cylindrical nozzle bodies that are attached to the supporting members 6 and 7 in a minutely adjustable or fixed manner, and openings 1 are formed in the upper and lower end surfaces of these nozzle bodies 12 and 13, respectively.
4, 15 and 16, 17 are formed, and these openings 14 to 17 are formed approximately at the center axis of the nozzle bodies 12, 13, and the wire electrode 1 between the guide rollers 4, 11 is approximately vertical, Moreover, they are arranged in a positional relationship such that they are inserted linearly and coaxially. Further, guide holders 20 and 21 of the upper and lower positioning guides 18 and 19 are coaxially fixed inside the nozzle bodies 12 and 13, respectively.
Further, the lower end opening 15 of the upper nozzle body 12,
In the upper end opening 17 of the lower nozzle main body 13, nozzles 22 and 23 are fixed coaxially so as to face each other, or are fitted so as to be movable in the axial direction as shown in the figure.

The guide holders 20 and 21 are attached to the nozzle body 1.
2 and 13 are hollow cylinders having holes 20a and 21a through which machining fluid flows, and dice-shaped positioning guides 18 and 19 as shown in FIG. The processed portion 2 of the wire electrode 1 at the upper and lower parts of the workpiece 24 interposed between the nozzles 22 and 23 by the
7 is being positioned. Further, the nozzles 22 and 23 in this example are hollow cylindrical bodies having a desired axial length, inner diameter, and axial diameter restriction, and have flange portions 22a and 23a in the nozzle bodies 12 and 13.
The outer diameter of the nozzle bodies 12, 13 is approximately equal to the inner diameter of the tips of the flanges 22a, 2.
3a prevents it from falling off from the nozzle bodies 12, 13. 22A is a push spring provided as necessary.

Pressurized machining fluid supply hoses 25 and 26 are attached to the nozzle bodies 12 and 13, respectively, from which machining fluid is supplied into the nozzle bodies 12 and 13 at a predetermined pressure and flow rate, and the internal positioning guide 18 , 19, and the upper and lower nozzles 22, 23
upwardly to the processing section 27 of the workpiece 24, respectively.
In addition to ejecting from below, each nozzle body 12, 1
The machining liquid is jetted out from the openings 14 and 16 at the upper and lower ends of 3 and is supplied between the current-carrying pin 10 and the current-carrying roller 11 and the wire electrode 1 to cool the wire electrode 1, the current-carrying pin 10, and the current-carrying roller 11. I'm starting to do that. Reference numeral 30 indicates a machined groove, and 39 and 40 indicate flows of processing fluid ejected from the upper and lower nozzles 22 and 23, respectively.

The workpiece 24 is fixed to a processing table 31, and the processing table 31 is connected to an X-axis motor 32 and a Y-axis motor 32.
The shaft motor 33 allows the wire electrode 1 to be freely moved along a predetermined contour on a plane perpendicular to the axis under the control of a numerical controller. Further, the wire electrode 1 is pulled out from a storage reel provided in a column or the like of the device main body (not shown) via a brake roller or the like, extends downward from the guide roller 4 section, and extends downward from the guide roller 1 of the lower arm 3.
1 and 5, a winding roller (not shown), and then winding up or collection into a winding reel such as a column body or a collection container. and,
Electric discharge machining is performed by applying intermittent voltage pulses between the workpiece 24 and the wire electrode 1.

However, in this embodiment, as shown in FIGS. 4 and 5, a plurality of (four in this embodiment) position detection electrodes (detection The electrodes 41 to 44 are arranged at equal angular intervals in the circumferential direction, for example, by partially screwing into a screw hole 45 provided in the guide holder 20 as shown in the figure. In this embodiment, the arrangement is such that the line connecting the detection electrodes 41 and 43 is in the X direction, and the line connecting the detection electrodes 42 and 44 is in the Y direction. The horizontal distances a between each of the detection electrodes 41 to 44 and the guide surface 18a of the positioning guide 18 are all equal and smaller than the diameter of the wire electrode 1.

These detection electrodes 41 to 44 are, for example, corrosion-resistant (anodic dissolution-resistant) electrodes whose sides except for the tip or tip surface are coated with insulation, and are similar to the wire electrode 1.
The distance between the wire electrode 1 and each of the detection electrodes 41 to 44, which may cause a contact short circuit in some cases, is usually determined by measuring the resistance value (conductivity) of the machining fluid using voltage, current, etc. Each of the detection electrodes 41 to 44 is connected to one end of the resistance measurement circuits 45 to 48, and a voltage source is provided to flow a current between each of the detection electrodes 41 to 44 and the wire electrode 1. The outputs of the resistance measurement circuits 45 and 47 (i.e., the detection electrodes facing each other in the X-axis direction) are 41, 43 and the wire electrode 1 (resistance value, voltage, current value, etc.) of the machining fluid based on the distance between the wire electrode 1 and the wire electrode 1 are input into the comparator circuit 49 so that the deviation thereof becomes zero or a value close to zero.
The processing table 3 is controlled by the X-axis drive control device 51.
The X-axis motor 32 for position control in the X-axis direction of No. 1 is drive-controlled for correction or correction. Similarly, the outputs of the resistance value measurement circuits 46 and 48 (i.e., the resistance value of the machining fluid based on the distance between the detection electrodes 42 and 44 and the wire electrode 1 facing each other in the Y-axis direction, or the voltage, current value, etc.) The Y-axis motor 33 for controlling the position of the processing table 31 in the Y-axis direction is corrected or modified by the Y-axis drive control device 52 so that the deviation becomes zero or a value close to zero. to control the drive. Motor 3 like this
Taking the discharge pressure into consideration, controlling the drives 2 and 33 corresponds to pulling the wire electrode 1 in the direction opposite to the direction in which the machining progresses. In addition, since the wire electrode 1 always passes through a desired position such as the center of the guide hole of the positioning guide 18, high precision processing can be performed. That will happen. In the above case, comparison circuit 4
Instead of outputting the outputs of 9 and 50 to the respective shaft drive control devices 51 and 52 to directly correct or correct the motors 32 and 33, the outputs are outputted to the respective shaft drive control devices 51 and 52 from a numerical control device (not shown). The output signal of the processed contour control trace may be corrected or modified in the numerical control device.

Note that various mounting structures can be selected for the detection electrode, and the mounting location may also be on the positioning guide 18 itself instead of the guide holder 20. Figure 6 shows the area around the guide hole of the positioning guide 18.
Conductive and corrosion-resistant detection electrode 5 made of Pt, TiC, TiN, etc.
3 is fixed by ion plating or vapor deposition. With this structure, the position of the detection electrode 53 can be made accurate. Further, the number of detection electrodes may be three or more, but the detection accuracy improves as the number increases. Furthermore, the detection electrodes are not provided only on the positioning guide 18 on one side of the workpiece 24 as in the embodiment, but on the positioning guides 18 and 19 on both sides.
Alternatively, the position may be controlled using the average value of the position coordinates of the wire electrode 1 within the positioning guide determined by both detection electrodes. Also,
The relative position between the wire electrode 1 and the workpiece 24 may be controlled not only by controlling the position of the workpiece 24 as in the embodiment, but also by controlling the position of the wire electrode 1 itself. Alternatively, the position of the workpiece 24 may be controlled in one axis (for example, the X-axis), and the position of the wire electrode 1 may be controlled in the other axis (Y-axis). Furthermore, in the present invention, the target position within the guide hole of the positioning guide of the wire electrode 1 does not necessarily have to be at the center;
If it is not the center, position control will be performed while correcting the coordinate values. Furthermore, the present invention
It can also be applied when the processing electrode is a tape-shaped electrode.

According to an experimental example of the present invention, a gear with 12 teeth and a tip circle diameter of 1.2 mm was made from S55C material with a plate thickness of 6 mm.
Corner part (surface part at the root of the tooth) when cutting out using a 0.05mmφ tungsten wire electrode
When we measured the dimensional accuracy of , we found that when using a conventional precision mold processing machine, the average dimensional accuracy was ±3 μm and the maximum error was ±5 μm, but according to the present invention, the average dimensional accuracy was ±2 μm and the maximum error was approximately ±3 μm. ±3μm
I was able to do this.

As described above, in the present invention, the relative position of the machining electrode and the workpiece is controlled so that the position of the machining electrode is at a fixed position within the guide hole of the positioning guide. This is especially true when there are many inflection points because the electrode must be machined in a straight line as much as possible to prevent it from curving, and the electrode must always pass through a fixed position in the guide hole of the positioning guide. This means that high-precision machining can be performed. Further, according to the present invention, high-precision machining can be performed even if the diameter of the guide hole of the positioning guide is made large, so the guide hole can be made large, thereby making it easier to insert the machining electrode into the guide hole. can be facilitated.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a wire-cut electrical discharge machining device to which the present invention is applied, FIG. 2 is an example of the wire electrode, and FIG. 3 is a longitudinal sectional view showing an example of the wire-cut electrical discharge machining device to which the present invention is applied. FIG. 4 is a longitudinal cross-sectional view of the positioning guide and its surroundings showing one embodiment of the present invention, FIG. 5 is a cross-sectional view taken along line A-A in FIG. 4, and FIG. This is a corresponding diagram. DESCRIPTION OF SYMBOLS 1... Wire electrode, 18, 19... Positioning guide, 24... Workpiece, 31... Processing table, 32
...X-axis motor, 33...Y-axis motor, 41 to 44,
53...Detection electrode, 45-48...Resistance value measurement circuit,
49, 50... Comparison circuit, 51... X-axis drive control device, 52... Y-axis drive control device.

Claims (1)

[Claims] 1. While moving a machining electrode made of a wire electrode or a tape electrode in the axial direction between a pair of positioning guides arranged at intervals, the workpiece is moved relative to the direction perpendicular to the axial direction of the machining electrode. A wire-cut electric discharge machining apparatus that applies intermittent voltage pulses between the machining electrode and the workpiece while moving the workpiece and intervening machining liquid to the machining part where the two face each other, and performs machining by the generated electric discharge. In the
The positioning guide is a die guide, and the machining electrodes are positioned around the guide hole of the guide at equal angular intervals in the circumferential direction, and each of the machining electrodes is provided so as to face the side surface of the machining electrode from the perpendicular direction. a plurality of detection electrodes for position detection; a voltage source connected to flow a current between each of the detection electrodes and the wire electrode; and a voltage or current detected between each of the detection electrodes and the processing electrode. and calculating means for determining the distance between each of the detection electrodes and the processing electrode from the detected voltage or current and calculating the relative position between the two;
Wire-cut electrical discharge machining characterized by comprising means for controlling the relative position of the machining electrode and the workpiece so that the distance between the machining electrode and each detection electrode is at a fixed position within the guide hole. Device.