JPS6218296B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric discharge machining device for machining microholes using the electrical discharge machining method, which has good surface roughness and roundness, and a high machining speed.
It is an object of the present invention to provide an electric discharge machining device for machining microholes that forms microholes of about 10 μm to 200 μm.

Conventionally, electrical discharge machining is not suitable for micro-hole machining because machining accuracy such as surface roughness and roundness becomes more problematic as the diameter of the hole to be formed becomes smaller, and it is difficult to feed the electrode in micro steps. It was thought that. However, by reducing the energy per discharge (for example, by reducing the capacitor capacity in an RC discharge circuit), it is possible to reduce the surface roughness to 1 μm or less, and by rotating the electrode with high precision, it is possible to reduce machining debris. Ejection is promoted, roundness,
Machining speed is improved. Furthermore, if a minute step feeding mechanism and a feeding method with good responsiveness can be developed, smooth electrical discharge machining of minute holes will be possible without damaging the minute electrodes since the feed is minute.

However, since conventional electric discharge machines use rolling bearings for rotation, it is inevitable that a deflection of several micrometers will occur, and the electrode part as a whole has a spindle structure, so it becomes large. , the stray capacitance increases, making it impossible to reduce the capacitor capacity as an RC circuit, and when the hole diameter becomes approximately 50 μm, the roundness and surface roughness deteriorate extremely. Furthermore, the weight of the electrode part becomes large, and the response speed of electrode feeding inevitably becomes slow, so smooth machining cannot be achieved, and the practical limit is limited to a hole diameter of about 100 μm.

The present invention was made in order to solve the problems of the conventional apparatus as described above, and by rotating the processing electrode while supporting the processing electrode with a V-shaped structure, the spindle structure is no longer required. The electrode part is made lighter and smaller, and the supporting means can be electrically insulated from other parts to significantly reduce stray capacitance, thus enabling machining with good machining accuracy and machining speed. .

An embodiment of the present invention will be described in detail below using the drawings.

Figure 1 is a circuit diagram showing an electric discharge machining circuit of an electric discharge machining device using an RC discharge circuit, in which 1 is a machining electrode, 2 is a workpiece, 3 is a machining power source, 4 is a capacitor, and 5 is a machining resistor. be. FIG. 2 shows an embodiment of the present invention in which an RC discharge circuit is employed as the processing circuit.

In the figure, 1 is a processing electrode, which is supported by a bearing 6. Since the pulley 9 on the motor 8 side is located above the pulley 7 on the machining electrode 1 side, the machining electrode 1 is pressed against the bearing 6 by the tension of the belt 10 and is further subjected to upward tension, so that the motor 8 Rotation is performed by .
The electrode section consisting of the processing electrode 1, bearing 6, and pulley 7 is connected to the main body 33 by an insulating material 11 such as ceramic.
It is electrically insulated from the power source 21 and connected to a power source 21 by a brush 12.

The electrode 1 is fed by two methods: coarse feeding and fine feeding. Coarse movement is performed by sliding the main body 33 along the column 14 on the base 13, and brings the electrode 1 together with the main body 33 close to the workpiece 16 in the processing tank 15. After that, the pinion gear 17 is rotated by the motor 18, and the gear integrated with the feed screw 19 is rotated.
The feed screw 19 is moved up and down to give minute feed to the electrode 1 via the lever 20.

Regarding the processing circuit, 21 is the DC power supply for processing,
22 is a capacitor, 23 is a resistor, the current monitor 24 detects the machining current flowing through the circuit, and the speed and rotation direction of the motor 18 are controlled via the servo circuit 25 to control the minute feed speed and direction of the electrode 1. It's in control. That is, the processing electrode 1 and the workpiece 1
6, the motor 18 rotates at a constant speed set in the counterclockwise direction to feed the machining electrode 1, and the electrode 1 and the workpiece 16 in the machining tank 15 are short-circuited. In this case, the current monitor 24 detects the short circuit current, and the servo circuit 25
The motor 18 is rotated clockwise at a high speed via the motor 18 to separate the machining electrode 1 from the workpiece 16, and after the short circuit has stopped, the motor 18 is rotated counterclockwise again to feed the workpiece at a set speed. Machining is performed by repeating this operation.

Figures 3a and 4b and Figures 4a to 4c show structural examples of bearings. Figures 3a and 3b show an example in which a machining electrode is supported by a bearing having a V-groove, and Figure 3a
is its plan view, and FIG. 3b is its front view. That is, two V-groove pieces 26 are attached to the support body 27 one above the other, and the machining electrode 1 is pressed and supported in the V-groove portion of the V-groove piece 26. In this embodiment, the material of the V-groove piece 26 is ruby, but other materials with excellent wear resistance such as cemented carbide, sapphire, diamond, and hardened steel can be considered. Also, V groove piece 2
6 and the support body 27 may be integrally constructed and made of the same material.

4a to 4c show an example in which the processing electrode is supported by a pivot bearing; FIG. 4a is a plan view thereof, FIG. 4b is a front view thereof, and FIG. 4c is a sectional view of a main part. That is, by attaching two protrusions 28 each having a spherical tip to the inner surface of a support body 29 having a V-shape, the processing electrode 1 can have a total of 4 protrusions.
The processing electrode 1 is supported by each of the protrusions 28. The V-groove angle α of the support body 29 is preferably between 30° and 150°. FIG. 4c is a side sectional view of the protrusion 28.
The protrusion 28 consists of a spherical member 30 at the tip and a sheathing member 31 that covers it. 30 comes from ruby. The material to be embedded in the cover 31 instead of the ruby in this embodiment is preferably a highly wear-resistant material similar to that used in the case of support by the V-groove piece in the previous embodiment, and the tip shape may be flat. .

FIG. 5 shows details of the minute feed mechanism, and the lever lever 32 has a fulcrum C serving as a pivot support lever. The contact side of the processing electrode 1 and the feed screw 19 with the lever lever is spherical or conical;
The contact portion 321 on the lever side is made of a highly wear-resistant material and is a pivot contact. In this embodiment, a sapphire block is attached to the contact portion, but other materials such as ruby, diamond, super steel, hardened steel, etc. are also conceivable.

The lower part of the feed screw 19 has a male thread and is engaged with the female thread of the main body 33. The pinion gear 17 is rotated by the motor 18, and the gear of the feed screw 19 that meshes with the pinion gear 17 also rotates, and the feed screw 19 moves vertically by its own screw while changing its meshing position with the pinion gear 17. The amount of movement of the feed screw 19 is transmitted to the machining electrode 1 through the lever 32, and the machining electrode 1 is fed.

In this embodiment, the gear ratio between the gear of the feed screw 19 and the pinion gear 17 is 5:1, the male thread of the feed screw 19 is a right-hand thread with a pitch of 0.5 mm, and the tooth width of the pinion gear 17 is 10 mm. When the motor 18 rotates counterclockwise, the rotational speed of the feed screw 19 is reduced to 1/5 and rotates clockwise, moving upward by 0.1 mm per rotation of the motor 18. (The maximum movement width is determined by the pinion tooth width). As a result, the A side of the lever lever 32 is lifted upward by 0.1 mm, and since l ₁ :l ₂ =1:1 in this embodiment, the B side of the lever lever 32 is lifted downward by 0.1 mm. Being pushed down.

Since the electrode 1 is connected to the motor 8 by the pulley 7 and the belt 10 and rotates, and receives upward tension from the belt 10, it is constantly in contact with the lever lever 32, and the amount of movement of the lever A side is equal to the processing electrode 1. The feed amount will be . The above is a case of feeding in a stable discharge state, but when there is a short circuit between the workpiece 16 and the machining electrode 1, the machining electrode 1 is pulled up by the same mechanism as described above by rotating the motor 18 clockwise. . In this case, the tension on the belt 10 can be reduced by attaching a weight 34 to the A side of the lever 32.

FIG. 6 shows an insulation state and a brush contact state for reducing stray capacitance.

The main body 33 is insulated from the machining electrode 1 and the bearing 6 by an insulating material 11 (ceramic in this embodiment, but paper, vinyl, glass, etc. are also conceivable), and the brush 12 connects the machining electrode 1 to the machining power source. The electrical conduction is directly achieved, and the discharge circuit system is made smaller to reduce stray capacitance that affects electrical discharge machining.

7 and 8 are schematic diagrams of the control circuit of the motor 18. The part surrounded by the broken line is the electrical discharge machining circuit, and the other parts are the motor control circuit.

In FIGS. 7 and 8, 1 is a machining electrode, 16 is a workpiece, 4 is a capacitor, 5 is a machining resistor, and 3 is a machining power source. Further, 35 is a resistor for monitoring the machining current, 36 is a resistor for detecting the reference voltage, and resistor 3 is a resistor for monitoring the machining current.
A comparator 37 compares the voltages generated by 5 and 36.

FIG. 7 is a schematic circuit diagram when the pulse motor 18 is used as a motor for feeding the machining electrode. In FIG. 7, 38 is a low-speed rotation gate;
9 is a gate for high-speed reversal in the event of a short circuit, 40 is a reference rotation signal oscillator, 41 is a 1/N counter, and 42 is a driver amplifier.

That is, during normal discharge, the signal from the oscillator 40 is frequency-divided by the 1/N counter 41, and the signal is input from the low-speed rotation gate 38 to the driver amplifier 42 to rotate the motor 18 at a constant speed.

When the comparator 37 generates a short circuit signal, the gate is switched to a high-speed reversal gate, and the motor rotates in a high-speed reverse direction.

FIG. 8 is a schematic circuit diagram showing the configuration when a DC motor is used as the machining electrode feeding motor. 43 is a setting circuit for high-speed reversal, 44 is a setting circuit for low-speed rotation, 45 is a power amplifier for driving the DC motor 18, and 46 is a tacho generator which applies a servo through a comparator 47 so that the DC motor 18 rotates at a constant speed.

The drive system is similar to the case of the pulse motor shown in Fig. 7, in which the speed and rotation direction setting circuits are switched by the comparator 37, and the DC motor 18 is used during normal discharge.
rotates at a low constant speed, and the machining electrode 1 and workpiece 1
When 6 is short-circuited, high-speed reverse rotation is performed.

As described above, the present invention electrically insulates the supporting means having a V-shaped pressure receiving surface from the main body to reduce stray capacitance as an electric discharge machining circuit, and also uses a reduction gear as an electrode moving means. Using a highly responsive minute feed mechanism using a lever and
Furthermore, by adopting a rotating means that rotates the machining electrode while pressing it against the pressure-receiving surface of the support means, there is no runout, improving rotation accuracy and simplifying the electrode part, resulting in good surface roughness and roundness, and machining speed. It also has the advantage of being able to process microholes quickly and with high precision.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the general configuration of an RC discharge circuit, FIG. 2 is an overall configuration diagram showing a micro-hole electrical discharge machining device in an embodiment of the present invention, and FIGS. 3 a and b are support means in the same device. FIGS. 4a to 4c are plan views, front views, and sectional views of essential parts showing other configuration examples of the same means; FIGS.
FIG. 6 is a block diagram of a main part of a micro-hole electrical discharge machining apparatus according to an embodiment of the present invention, and FIGS. 7 and 8 are circuit diagrams showing examples of the structure of a discharge circuit in the same apparatus. 1... Processing electrode, 6... Support means, 7, 9...
Pulley, 8, 18...Motor, 10...Belt, 11...Insulating plate, 12...Brush, 13...
Base, 14... Support, 15... Processing tank, 16...
... Workpiece, 17 ... Pinion gear, 19 ... Feed screw, 20 ... Lever, 21 ... DC power supply for processing.

Claims (1)

[Scope of Claims] 1 A machining electrode that generates electrical discharge between the workpiece and a pressure receiving surface that supports the machining electrode has a V-shape, and two pairs of electrically insulated from the main body. a support means consisting of a bearing; one end located on the processing electrode and the other end located on a feed screw coupled to a motor that provides rotational driving force through a reduction gear; a moving means for moving the machining electrode relative to the workpiece by vertical movement of a feed screw by rotation of a motor using a lever having a fulcrum therebetween; A microhole characterized by comprising a rotating means that presses the processing electrode against a pressure-receiving surface of the means and at the same time applies a pressing force to constantly press the processing electrode on the opposite side of the workpiece to the lever. Electrical discharge machining equipment. 2. The micro-hole electric discharge machining apparatus according to claim 1, wherein the supporting means is formed by providing a protrusion on a V-shaped pressure receiving surface.