JPS6052894B2 - Electrical discharge machining method and equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electric discharge machining method and apparatus, in particular a tool electrode that is fed relative to a workpiece in a main machining direction (hereinafter referred to as the Z axis), and a plane perpendicular to the Z axis (hereinafter referred to as the XY axis). The present invention relates to an improved method and apparatus for performing electric discharge machining between a tool electrode and a workpiece while performing auxiliary machining feed along a plane (referred to as a plane).

Electric discharge machining that provides a main machining feed in the Z-axis direction and an auxiliary machining feed along the XY plane between a tool electrode and a workpiece is well known, and an example thereof is shown in Japanese Patent Publication No. 41-3594.

This conventional method has the advantage that multiple stages of machining such as rough machining, semi-machining, semi-finishing machining, finishing machining, and fine finishing machining can be performed continuously using a single tool electrode. In other words, generally in rough machining, only the main machining feed in the Z-axis direction is given, and at this time electrical discharge machining is performed using a large current, and as a result, it is known that the machining gap is relatively large. On the other hand, the discharge current is controlled to gradually decrease at each machining stage proceeding to the subsequent fine finishing machining, and the machining gap also decreases accordingly, but by applying the auxiliary machining feed along the XY plane mentioned above, A single tool electrode can smooth the machined surface while compensating for the reduction in the machining gap. In addition, according to the conventional equipment provided with auxiliary machining feed, the auxiliary machining feed removes cutting powder from the workpiece that stays in the discharge gap or denatured substances in the insulation working fluid that are thermally decomposed by the high-temperature arc during the discharge. can be removed by the pumping action of the machining fluid, resulting in good surface roughening. FIG. 1 shows a general machining state in a conventional method in which a workpiece 12 is machined by an electrode 10 formed of a scalene triangle. A machining feed is given and the radius of its circular motion is denoted by R.

According to this conventional method, it is possible to obtain the same effect as using an electrode larger than the electrode 10 by an arbitrarily set radius R, but as is clear from FIG. The arc-shaped electrode produces a machining action, and as a result, the shape of the workpiece is significantly different from the shape of the electrode. The drawback was that high-precision electrical discharge machining could not be achieved.
In order to eliminate the drawbacks of the auxiliary machining feed using the revolving circular motion shown in FIG. 1, several auxiliary machining feed methods have been considered, and FIG. 2 shows the electrode 10 at each angle.

A method is shown in which the workpiece 12 is displaced radially equidistantly relative to the workpiece 12. In FIG. 2, the radial displacement of each corner is indicated by a vector, 7, whose magnitude is set to R. However, as is clear from the shape of the workpiece in FIG. 2, even with such radial relative displacement, a shape of the workpiece that is significantly different from the shape of the electrode 10 can be obtained due to the difference in the point angle of each corner. However, it was not possible to obtain high-precision electrical discharge machining. FIG. 3 shows another improved conventional method, in which auxiliary machining feed is shown in which each side A, B, and C are relatively displaced at a ratio of similarity magnification k.

However, even in this conventional method, except in the case of an equilateral triangle, the machining gaps α, β, and γ between the electrode 10 and the workpiece 12 have different values, making it difficult to obtain a workpiece shape corresponding to the shape of the electrode 10. The drawback was that I couldn't do it. That is, according to the conventional method shown in FIG. 3, the expansion widths α, β, and γ that are expanded by the auxiliary machining feed from the actual shape of the electrode 10 are different for each side, and for this reason, it is difficult to perform rough machining to fine machining. A disadvantage has arisen in that uniform machining cannot be obtained in multiple electrical discharge machining operations, and highly accurate electrical discharge machining with good surface roughness cannot be obtained. In view of the above problems, the present inventors proposed the following improved electric discharge machining method.

FIG. 4 shows the auxiliary machining feed action of the electrode 10 according to this improved method. In FIG. 4, the electrode 10
The shape of the workpiece to be machined is shown by straight lines A'', B'' and C'' that are parallel to each side and spaced a distance R from each side of the electrode 10.The straight lines A'', B'' and C'' are respectively parallel to each side. The intersection of is Pl,
P2 and P3, and the apex of each corner of the electrode 10 is Ql,
In q2 and q3, the angles are 01, θ2, and e3, respectively.
Indicated by In FIG. 4, the auxiliary machining feed vector 7, which is used to obtain a uniform enlarged width R from each side A, B, and C of the electrode 10, will be explained using a vector vector as an example. Now, vertex q
From 1, draw a perpendicular line on straight lines A'' and B'' and point their intersection at R.
2,rl, its length is equal to the enlarged width R.
Here, triangle Pl, r2, ql and triangle Pl, rl, ql
shares one side Pl, ql, and the other side R2, ql and R
Since the lengths of l and ql are equal, they are a right triangle, so they are congruent, and the straight lines Pl and ql, that is, the vector word . becomes the bisector of angles Rl, pl, r2. Therefore, when there is a displacement of vector i, the locus of vertex Q2 also moves in parallel to Q2'', and the angle at the apex angle Q2 of parallelogram Pl, ql, q2, q2'' is indicated by I, and from this, vector i The azimuth is θ2+! , and its magnitude can be found by Mldr.

Similarly, other displacement vectors F. F can also be determined by simple calculations, and each vector J, 7, has the azimuth and magnitude shown in FIG. Therefore, the relative displacement between the electrode 10 and the workpiece 12 is expressed as vector i, 10,
If the auxiliary processing feed is performed along the XY plane according to 7, electrode 1
It is possible to obtain a good workpiece shape that conforms to the shape of 0 and whose corners also correspond to the electrode shape. FIG. 6 shows an auxiliary machining feed vector obtained by converting the vectors 7 and 7 in FIG. 5 into mutually continuous vectors. By applying relative displacement, it is possible to obtain a desired shape of the workpiece.

As described above, according to the method proposed by the present inventors, it is possible to obtain a desired enlarged workpiece shape corresponding to the electrode shape, but it is possible to simply use the vector in FIG. 6 as an auxiliary machining feed. A problem has arisen in that it is not possible to obtain uniform machining, particularly uniform wear of the electrode 10, in actual electrical discharge machining by simply applying the method.

Fig. 7 shows the force-receiving portion (machining allowance) when the electrode 10 is sequentially fed along the vector A, stone, and 7, and first, according to the auxiliary machining feed of the vector, the broken line hunting is shown. It is understood that the area 101 shown is machined, and that this amount of machining occupies more than half of the total machined area, and that the electrode surface of the electrode 10 facing the area 101 is significantly worn during the auxiliary machining feed of vector a. Ru. In addition, when the auxiliary force of the vector is applied, processing is performed in the area 102 shown by the solid line hunting in FIG. The electrode surface facing the electrode is subject to significant wear. It is understood that only the area 103 of the non-hunting portion is processed when the assist force of vector 7 is fed, and the amount of processing at this time is extremely small, and the wear on the electrode surface facing the area 103 is small. As mentioned above, in the method shown in Figure 7,
In principle, it is possible to perform extremely good electrical discharge machining, but in practice, electrode wear or deterioration due to thermal effects of the electrode differs markedly depending on each electrode part, and as a result, it is impossible to perform excellent electrical discharge machining. It was hot.

The present invention was made in view of the above-mentioned conventional problems, and uses a single electrode to combine the main machining feed and the auxiliary machining feed along a plane almost perpendicular to the main machining feed to achieve good discharge with uniform electrode wear. It is an object of the present invention to provide an improved electric discharge machining method and apparatus that can perform machining.

In order to achieve the above object, the method according to the present invention supplies electricity through a machining fluid to the opposing gap between an electrode and a workpiece, and there is a main gap between the electrode and the workpiece along the main machining direction. In the electric discharge machining method, an auxiliary machining feed along a plane substantially perpendicular to the machining feed is provided, and a gap between the electrode and the workpiece is controlled to a discharge sustaining gap with respect to the auxiliary machining feed plane. The auxiliary machining feed is a revolution machining process in which most of the desired machining area is machined while relatively feeding the electrode and the workpiece according to an eccentric circular motion, and a revolution machining process in which the electrode and the workpiece are relatively fed along a predetermined vector. It includes a vector machining process in which the machining process is performed by feeding and electrical discharge machining the machining remaining thickness of the revolution machining process.

In the present invention, it is preferable that the revolution machining process is formed by an eccentric circular motion in which the radius of rotation gradually expands from the initial position, and when an abnormal electrical discharge occurs during the revolution machining process, the eccentric circular motion returns to the initial position. However, it is preferable to return to the original processing position after the abnormality is resolved.

The apparatus according to the present invention includes an electrode that is relatively fed in the main machining direction with respect to the workpiece, a power source that supplies discharge power between the electrode and the workpiece, and a power source that connects the electrode and the workpiece to the main machining direction. In an electrical discharge machining apparatus including a feeding device that performs auxiliary machining feed along a plane substantially perpendicular to the machining direction, a function memory that outputs a sine wave signal and a cosine wave signal in accordance with an instruction angle signal, and a temporal a moving angle signal supplier that supplies an angular signal that changes to a fixed angle signal supplier that supplies an azimuth signal of a predetermined vector to the function memory, a setting device that sets a machining width in auxiliary machining feed, and an electrode. and a servo control device that supplies the sine wave signal and cosine wave signal of the function memory to the auxiliary processing feed device depending on the relative position in the auxiliary processing feed direction with respect to the workpiece.

Preferred embodiments of the present invention will be described below based on the drawings.

The machining method of the present invention includes a revolution machining process in which the electrode is auxiliary machining fed along an eccentric circular motion along the XY plane, and a vector machining process in which the electrode is auxiliary machining fed along a predetermined vector. Circular motion is indicated at 200 and vector feed at -J, stone, 7. Since the revolution machining process consists of eccentric rotational movement, it is extremely easy to control the auxiliary machining feed of the electrode 10, and most of the necessary electrical discharge machining can be performed in this revolution machining process, and the electrode 10 at this time It has the advantage that wear and tear can be made extremely uniform. Furthermore, the eccentric circular motion 20 in FIG.
0, to gradually and automatically increase the radius of rotation from the eccentric circular motion 200 with respect to the final machining width R? y't) The amount of machining can be limited by one eccentric circular motion, the entire electrode surface can be uniformly opposed to the surface to be machined, and local deformation of the electrode 10 can be prevented. . Eccentric circular motion 20 in the revolution machining process
When the radius of 0 reaches the desired machining width R, the electrode returns to the initial position again, and then the vector machining steps indicated by vectors A, A, and 7 described above are performed. As mentioned above, the azimuth and size of each vector in the vector processing process are determined so that its force width is equidistant from each side of the electrode 10, and as a result, the final result is as shown in FIG. It is possible to obtain the desired shape of the workpiece surrounded by the broken line shown in FIG.

FIG. 9 shows a slightly modified embodiment of the revolution machining process according to the present invention. According to this embodiment, when a short circuit occurs between the electrode and the workpiece during the revolution machining process, the electrode The state is shown in which it is returned to its initial position.

Similar to the embodiment shown in FIG. 8, the electrode starts the revolution machining process from the initial position 1 inch and gradually increases its radius. If a short circuit occurs between the electrode and the workpiece at 1J, rOJ, ``C., R.-Yo'' in each locus, the electrode immediately retracts and returns to the initial position 1Ao. As a result, the machining gap between the electrode and the workpiece is expanded, and the short circuit can be quickly eliminated. After the short circuit is eliminated, the electrode is moved again to the locus at the time of each short circuit, and the revolution machining process is resumed along the eccentric circular motion 200. Therefore, according to the embodiment shown in FIG. 9, wear of the electrode due to short circuits and machining marks on the machined surface can be significantly reduced, and it is possible to obtain good electrical discharge machining quality. FIG. 10 shows an embodiment of an electric discharge machining apparatus suitable for the present invention.

In FIG. 10, the electrode 10 is arranged opposite to a workpiece 12 fixedly held on a table 14, and is given main machining feed in the Z direction.

A pulsed electric discharge machining voltage Vg is applied from an electrode 16 between the electrode 10 and the workpiece 12, and electric discharge machining is performed in the gap between the two. The table 14 is provided with an X-axis drive motor 18 and a Y-axis drive motor 20, and by supplying drive signals for revolution machining and vector machining according to the present invention to both motors 18 and 20, the electrode 10 and the workpiece 12 are The desired auxiliary machining feed is applied during this period. An auxiliary machining feed control circuit is provided to supply predetermined auxiliary machining feed signals to the motors 18 and 20, and this auxiliary machining feed control circuit includes a sine function memory 22 and a cosine function memory 24, both memories 22 , 24 consists of a ROM (read only memory) that stores a sine function and a cosine function for each angle.

The count value of the presettable counter 28 is output as a command angle signal to both function memories 22 and 24 via an address line 26, and the counting action of the counter 28 is performed by a clock signal of an oscillator 30 forming a moving angle signal supplier. The controlled, time-varying angle signal returns to O degrees by counting 359 degrees. The clock signal of the oscillator 30 is connected to the gate 32.
The output of the comparator 34 is supplied to the other input of the gate 32. A digital switch 36 forming a fixed angle signal supplier is connected to the presettable counter 28, and the counter 28 can be arbitrarily preset from the outside in order to supply an azimuth signal of a predetermined vector. The memories 22 and 24 output a sine function value and a cosine function value in accordance with the angle signal applied from the counter 28 via the address line 26, and these output values are sent to the DA converter 42 and DA converter 42 via the data buses 33 and 40, respectively. 44 and output to comparators 46 and 48 as a sine wave signal VO and a cosine wave signal Vy consisting of analog values. Reference voltage E of both DA converters 42, 44,
The difference between the inter-electrode voltage V, and the reference value ■ consists of a voltage given as a positive value signal via the auxiliary processing feed adjustment amplifier 50 and the diode 52, and as a result, the sine wave of each DA converter 42, 44 The signal Vx and the cosine wave signal Vy are expressed by the following equations. Note that K is the amplification constant of the amplifier 50, and φ is the count value given by the counter 28,
It takes a value between 0 and 359 degrees.

The comparators 46 and 48 are supplied with detection signals from position detectors 54 and 56, which are composed of actuating transformers connected to the table 14, and the difference voltage between this detection signal and the sine wave signal ■o and the cosine wave signal ■8 is supplied to the comparators 46 and 48. is supplied to the x-axis drive motor 18 and the Y-axis drive motor 20 via the drive amplifiers 58 and 60, and the relative auxiliary machining feed between the electrode 10 and the workpiece 12 along the XY plane is controlled by the DA converter 42, Servo control is performed to follow the output of 44.

The differential pressure between the discharge voltage ■8 and the reference value ■ is supplied to the comparator 34 and compared with zero volts, and if the differential voltage is greater than zero volts, that is, in a normal electric discharge machining state, the gate 32
The gate 32 is opened and the clock signal of the oscillator 30 is supplied to the counter 28, while the gate 32 is closed when the differential voltage is equal to or lower than zero volts, that is, in the event of an abnormal drop in the interelectrode discharge voltage Vg or a short circuit. The output ψ of 28 is fixed to the value at that time.

The embodiment of the present invention has the above configuration, and its operation will be explained below.

In order to perform the revolution machining process including eccentric circular motion, the auxiliary machining feed setting value K of the auxiliary device 50 of the amplifier 50 is set corresponding to the desired enlargement width R, and the digital switch 36 is disabled in the vector machining process. A clock signal, which is a time-varying angle signal, is supplied from the oscillator 3σ to the counter 28.

Therefore, both memories 22 and 24 output a sine wave signal Vx and a cosine wave signal V which are counted by the clock signal of the oscillator 30.
, are outputted via the converters 42 and 44, and as a result, the X-axis drive motor 18 and the Y-axis drive motor 20 impart a desired eccentric circular motion to the workpiece 12 along the XY plane. The rotation radius of the eccentric circular motion at this time is set to a value that balances the detection signals from the position detectors 54 and 56 with the sine wave signal Vx and the cosine wave signal V, and the power source 16 is connected to the electrode 10 and the workpiece 12. The interelectrode discharge voltage V supplied between
The radius of rotation of the eccentric circular motion is set so that g provides the gap length at which electrical discharge machining can be performed under optimal conditions. amplifier 50
In the embodiment, in order to set the differential voltage supplied to
By setting the value to about 0%, a good revolution machining process can be obtained, and this revolution machining process is continued until the machining of the enlarged width R of the electrode 10 is completed, but nothing happens during this revolution machining process. If a short circuit or other abnormality occurs between the electrode 10 and the workpiece 12 for some reason, the comparator 34 sends a signal to the gate 32.
A gate-off signal is supplied to the counter 28, and the count value of the counter 28 is held at the current value.

At the same time, a return signal is supplied to the motors 18 and 20, and the workpiece 12 returns once to its initial position, quickly eliminating the short circuit. Thereafter, the workpiece 12 moves again to the revolution machining position corresponding to the value held by the counter 28, and the revolution machining process described above continues. After the revolution processing process is performed until the expanded width R of the electrode 10 is reached,
Digital switch 36 to perform vector processing process
An azimuth signal of a predetermined vector is supplied to the counter 28, and at this time, the supply of the clock signal from the oscillator 30 is disabled.

At the same time, the setting value K of the amplifier 50 is also set corresponding to the desired vector. For example, in the case of the vector H in FIG. The value K is set to +/-. As a result, SinO-h result, motor 1
8 and 20 give an auxiliary machining feed corresponding to the vector blindness to the workpiece 12, and thereafter the workpiece 12 is subjected to vector machining along the vectors f and 7 in the same manner.

As explained above, according to the present invention, electric discharge machining during auxiliary machining feed is performed by a revolution machining process including an eccentric circular motion, and since this revolution machining process consists of an easily controllable circular motion, accurate and high-precision auxiliary work can be achieved. Processing feed can be performed.

In the revolution machining process at this time, it is preferable to gradually increase the radius of rotation and perform the desired electrical discharge machining in multiple rotations. This allows the electrode to be used uniformly, and the workpiece powder that remains in the discharge gap is suitable. Alternatively, denatured substances and the like can be quickly removed by pumping action. A vector machining process is performed after the revolution machining process described above, and the remaining thickness due to the revolution machining can be reliably removed and a desired machining shape corresponding to the electrode can be obtained with high precision. Although analog control is performed in the embodiment, it is also possible to program the locus in advance and digitally control the auxiliary machining feed using numerical control.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the state of electrical discharge machining by conventional auxiliary machining feed using revolving circular motion, Fig. 2 is an explanatory diagram showing the machining state by another conventional method, and Fig. 3 is an explanatory diagram showing the machining state by another conventional method. FIG. 4 is an explanatory diagram showing the machining state using the method, FIG. 4 is an explanatory diagram showing the machining principle using vector machining used in the present invention, FIG. 5 is a vector diagram showing the relative displacement in FIG.
The figure is a modified vector diagram of FIG. 5, FIG. 7 is an explanatory diagram showing the drawbacks of electrical discharge machining using the principle of FIG. 4, and FIG. 8 is a machining of a preferred embodiment of the electrical discharge machining method according to the present invention FIG. 9 is an explanatory diagram showing another embodiment of the revolution machining process shown in FIG. 8, and FIG. 10 is a block diagram showing a preferred embodiment of the electrical discharge machining apparatus according to the present invention. be. The same members in each figure are denoted by the same symbols, 10 is an electrode, 12
is the workpiece, 16 is the power supply, 18 is the X-axis drive motor, 20
22 is a sine function memory, 24 is a cosine function motor, 22 is a sine function memory, 24 is a cosine function memory, 30 is an oscillator, and 36 is a digital switch.

Claims (1)

[Claims] 1. Electricity is supplied through a machining fluid to the opposing gap between the electrode and the workpiece, and there is a main machining feed along the main machining direction and a main machining feed between the electrode and the workpiece. In the electrical discharge machining method, an auxiliary machining feed is provided along a plane substantially perpendicular to the auxiliary machining feed surface, and a gap between the electrode and the workpiece is controlled to a discharge maintaining gap with respect to the auxiliary machining feed surface. There is a revolution machining process in which most of the desired machining area is machined while the electrode and the workpiece are fed relative to each other along an eccentric circular motion, and a revolution machining process in which the electrode and the workpiece are fed relative to each other along a predetermined vector. An electric discharge machining method including a vector machining step of performing electric discharge machining on the machining remaining material of the revolution machining step. 2. The electric discharge machining method according to claim 1, wherein the revolution machining step consists of an eccentric circular motion in which the radius of rotation gradually increases from an initial position. 3. The electric discharge machining method according to claim 1, wherein the eccentric circular motion returns to the initial position when an abnormal electric discharge occurs during the revolution machining process, and returns to the original machining position after the abnormality is resolved. 4. An electrode that is fed relative to the workpiece in the main machining direction, a power supply that supplies discharge power between the electrode and the workpiece, and an electrode that is moved approximately perpendicular to the main machining direction between the electrode and the workpiece. An electric discharge machining apparatus including a feeding device for auxiliary machining feeding along a plane, a function memory for outputting a sine wave signal and a cosine wave signal according to a commanded angle signal, and a function memory for outputting an angle signal that changes over time. a moving angle signal supplier for supplying;
A fixed angle signal supply device that supplies an azimuth signal of a predetermined vector to the function memory, a setting device that sets the machining width in the auxiliary machining feed, and a relative position of the electrode and the workpiece in the auxiliary machining feed direction A servo control device that supplies a sine wave signal and a cosine wave signal of a memory to an auxiliary machining feed device.