KR20000071399A - Plasma discharge truing apparatus and fine-machining methods using the apparatus - Google Patents

Abstract

Discharging electrode 14 having a disk having a conductive grinding wheel 12, an outer peripheral edge 14a accessible to the machining surface 12a of the grinding wheel, an electrode rotating device 16, and an outer peripheral edge of the electrode and the grinding wheel A position control device 18 for controlling the position, a voltage applying device 20 for applying a voltage pulse between the grindstone and the electrode and a mist supply device 22 for supplying a pressurized mist between the grindstone and the electrode are provided. do. The pressurized mist is a mixture of weakly conductive aqueous solution and compressed air. Plasma discharge is generated between the whetstone and the electrode through the pressurized mist, and the whetstone is truing. In this way, the eccentricity and vibration of the whetstone can be effectively removed, high precision grinding is performed without the deformation of the whetstone itself, and the power equipment is small and small output is sufficient, no complicated control circuit or control device is needed, and electrodes It is easy to manufacture and reprocess consumables.

Description

Plasma discharge truing device and microfabrication method using the device {PLASMA DISCHARGE TRUING APPARATUS AND FINE-MACHINING METHODS USING THE APPARATUS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase plasma discharge truing apparatus for grinding a conductive grindstone having a very fine and thin special shape on a machine, and a fine processing method using the apparatus.

With the rapid advancement of optical communication systems and optical technologies, hard brittle materials such as fine ceramics, optical glass, optical crystals, and semiconductor single crystals have been widely used. Therefore, there is a strong demand in the production field for a technique for efficiently and precisely cutting or molding the hard brittle material.

As a processing method particularly suitable for the molding of such hard brittle materials, electrolytic in-process dressing grinding method (hereinafter referred to as ELID grinding method) has attracted attention. ELID grinding method uses very fine and thin conductive grindstones containing fine diamond particles, and processes workpieces when electrolytically dressing the grindstone, and has high processing precision, high quality surface roughness, and hard 3 It is characterized by relatively easy processing of dimensional shaped parts.

Even grinding wheels with very fine or very thin special shapes for application to micro micromachining may cause eccentricity or vibration in the production. Therefore, it is necessary to remove eccentricity or vibration by truing before applying it to precision machining such as ELID grinding.

However, since the metal bond grindstone used for ELID grinding has a high hardness of the bond material, it is difficult to apply the conventional truing method because the correction efficiency is low and the correction accuracy is limited. Furthermore, if the grindstones applied to hard brittle materials are very fine and thin (eg less than 1 mm in diameter, less than 1 mm in thickness) and have special shapes, if the tool comes into contact with the grindstone during mechanical truing, Since the whetstone itself is deformed, there is a problem that precise truing is not made.

On the other hand, electric discharge machining (Electric Discharge Machining), such as a processing method for processing a workpiece in a non-contact manner is known. In this processing method, the workpiece and the processing electrode are positioned to face each other in the insulating processing liquid at predetermined intervals, and the excess portion of the workpiece is removed by repeating the pulse arc discharge for a short time.

However, the above processing method requires (1) the shape of the electrode to be adjusted in advance according to the desired processing shape, (2) precise position control to maintain a constant gap between the electrode and the workpiece, and (3) the electrode and the It is necessary to supply a large current pulse between the workpieces, a large and complicated power supply equipment is required, and (4) there is a problem of frequent replacement of the electrodes because the electrode shape changes due to the electrode consumption.

The present invention has been devised to solve the above problems. Therefore, an object of the present invention is to efficiently remove the eccentricity and vibration of the grinding wheel having a very small or thin special shape, high-precision trueing without deformation of the grinding wheel itself, and requires a small power output equipment The present invention provides a plasma discharge truing device that does not require complicated control circuits or control devices, and is easy to manufacture / reprocess consumables such as electrodes and a microfabrication method using the device.

The inventors of the present invention generate a uniform and highly efficient spark (plasma discharge) between the outer periphery of the electrode and the grindstone while rotating the electrode on the disk, thereby making contactless and highly efficient and accurate truing possible. It was possible to reduce the shape change due to electrode consumption. In other words, the conductivity of the metal-bonded grindstone used for ELID grinding is used, but the plasma bond phenomenon is caused to occur in the micro-gap between the grindstone and the electrode, thereby precisely dissolving and removing the metal-bonded portion, thereby removing the grindstone surface. Can be modified with

Specifically, according to the present invention, a disc-shaped discharge electrode 14 having a conductive grindstone 12 for processing the work 1 and an outer peripheral edge 14a accessible to the machining surface 12a of the conductive grindstone And an electrode rotating device 16 for rotating the discharge electrode about its axis Z, a position control device 18 for controlling the relative position of the outer periphery of the electrode and the grindstone, and between the grindstone and the electrode. A plasma discharge truing apparatus is provided, comprising: a voltage application device 20 for applying a predetermined voltage pulsed; and a mist supply device 22 for supplying a pressurized mist between a grindstone and an electrode.

According to the above-described configuration of the present invention, a voltage applying device is provided between the outer periphery of the rotating electrode 14 on the rotating disk and the machining surface 12a of the conductive grindstone 12 whose position is controlled by the position control device 18. Since 20 can stably generate the above-described spark (plasma discharge), the metal bond portion of the conductive grindstone can be dissolved and removed accurately and efficiently without contact, and the grindstone surface can be modified to a desired shape.

In addition, since the discharge electrode 14 rotates about the axis Z by the electrode rotating device 16, an appropriate roundness can be maintained even when consumed by plasma discharge, and continuous use for a long time is possible.

In addition, since the pressurized mist (more preferably, a mixture of weakly conductive aqueous solution and compressed air) is supplied between the grindstone and the electrode through the mist supply device 22, compared with the case where the dry state or the insulating liquid is directly supplied, It is possible to stably generate high-current plasma discharge at low voltage, and to reduce the power output of the power supply. Moreover, the experimental results confirmed that the efficiency and accuracy of truing can be increased when the above-mentioned pressurized mist is used.

Further, according to the present invention, (A) a disk-shaped discharge electrode 14 having an outer periphery 14a accessible to the machining surface 12a of the conductive grindstone 12, and the discharge electrode is centered on the axis Z. And an electrode rotating device (16) for rotationally driving the plasma discharge, and supplying a pressurized mist between the grindstone and the electrode while applying a DC voltage between the conductive grindstone and the discharge electrode in a pulse to form a working surface by discharge. Truing process; (B) a dressing electrode 28 having an opposing surface 28a separated from the working surface of the conductive grindstone 12, and between the conductive grindstone and the dressing electrode while supplying a conductive liquid between the grindstone and the dressing electrode; An electrolytic dressing process of electrolytically dressing the conductive whetstone by applying a DC voltage; (C) It provides a micro-processing method comprising a grinding step of processing the workpiece with a conductive whetstone.

According to the present invention, the electrolytic dressing process (B) and the grinding process (C) are simultaneously carried out on the same machine by using a conductive grinding wheel having a very fine or thin special shape in which eccentricity or vibration is eliminated by the plasma discharge truing process (A). Alternatively, it is possible to prevent the adverse effects of eccentricity and vibration, and to prevent the positioning error that may occur when the workpiece is remounted, so that the hard brittle material can be processed efficiently and accurately.

Furthermore, since discharge truing is performed by supplying pressurized mist, as described above, the efficiency and precision of truing can be improved.

Other objects and advantageous features of the present invention will become apparent from the following description with reference to the accompanying drawings.

1 is a view showing the overall configuration of a plasma discharge grinding device according to the present invention,

2 is a view showing the principle of the plasma discharge,

3 is a view comparing a critical discharge gap,

4 is a diagram comparing actual input voltages;

5 is a diagram illustrating a relationship between input voltage and grinding efficiency,

6 is a diagram comparing grinding precision.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Common parts in the drawings are given the same numbers, and duplicate descriptions are omitted.

1 is an overall configuration diagram of a plasma discharge truing apparatus according to the present invention. As shown in FIG. 1, the plasma discharge truing apparatus 10 of the present invention is a conductive grindstone 12, a discharge electrode 14 on a disc, an electrode rotating device 16, a position control device 18, and a voltage applied thereto. Apparatus 20 and mist feeder 22 are provided.

In the present embodiment, the conductive grindstone 12 is a metal bonded grindstone using fine diamond particles, and when moving to the left side of the drawing, the workpiece 1 is grooved or sliced or molded. In addition, the conductive grindstone 12 is rotated about its axis, and the relative position of the outer periphery 14a of the electrode 14 and the grindstone 12 is controlled by the position controller 18.

The thickness of the metal bond whetstone may be any value, for example 1 mm or less. In addition, the conductive grindstone 12 may be a very compact metal bond grindstone.

The disc-shaped discharge electrode 14 has an outer periphery 14a accessible to the machining surface 12a of the conductive grindstone 12 (sharp edged grindston). The outer circumferential edge 14a of the discharge electrode 14 forms a perfect circle around its axis Z. The thickness of the discharge electrode 14 should be as thin as possible to maintain the roundness to achieve a stable plasma discharge, for example 2 mm or less.

The discharge electrode 14 is mounted on a rotating shaft of the electrode rotating device 16 (for example, an electric motor), and can be rotated about the axis Z.

The voltage application device 20 includes a DC power supply 24, a pulse discharge circuit 25, and a current supply line 26. The DC power supply 24 generates a predetermined DC voltage (for example, DC 60 to 100V) and applies it to the input terminal of the pulse discharge circuit 25. In addition, the current supply line 26 of the brush 26a (feeder) in sliding contact with the rotating shaft of the grindstone 12 and the surface of the discharge electrode 14, and of the brush 26a and the pulse discharge circuit 25 And a connecting line 26b for electrically connecting the output terminal, the anode of the output terminal being connected to a whetstone and the cathode connected to the electrode.

The mist supply device 22 supplies the pressurized mist between the grindstone 12 and the electrode 14. The pressurized mist is preferably, for example, a mixture of a water-soluble grinding liquid and compressed air used for ELID grinding. In addition, the liquid is not a complete insulating liquid, but has a certain electrical conductivity (for example, 1300 to 1800 kcal / cm), and has a function of reducing electrical resistance between the grindstone 12 and the electrode 14. It is preferably a weakly conductive solution.

2 shows the principle of plasma discharge. As shown, when the whetstone 12 is applied to the anode and the electrode 14 is applied to the cathode, the metal part 12A of the whetstone is granulated (ionized) and dissociated with high efficiency in the plasma state. When conductive mist particles exist between the grindstone 12 and the electrode 14 in this state, the current routine therebetween is stably ensured, and the discharge phenomenon is stabilized. As a result, since it becomes a high energy state and the temperature between electrodes can be raised easily, truing efficiency rises rapidly and discharge truing is performed as it becomes a plasma state.

In the configuration of the plasma discharge truing apparatus 10 shown in FIG. 1, the discharge electrode 14 is rotated at a constant circumferential speed. Further, the grindstone 12 is rotated at another constant circumferential speed, and is reciprocated in the axial direction by the position control device 18 and moved radially at a predetermined speed. In addition, a constant interval is maintained between the grindstone 12 and the electrode 14, a pressurized mist is supplied, a stable discharge spark is generated, and plasma discharge truing is performed.

According to the configuration of the present invention described above, a voltage is applied between the outer periphery 14a of the rotating discharge electrode 14 and the machining surface 12a of the conductive grindstone 12 whose position is controlled by the position control device 18. By stably generating sparks (plasma discharge), the device 20 can dissolve and remove the metal-bonded portion of the conductive grindstone 12 accurately and non-contact efficiently, thereby modifying the grindstone surface to a desired shape.

In addition, since the discharge electrode 14 rotates about the axis Z by the electrode rotating device 16, the roundness can be maintained even when consumed by plasma discharge, and can be used continuously for a long time.

Moreover, since the pressurized mist is supplied between the grindstone and the electrode by the mist supply device 22, compared with the case where a dry state or an insulating liquid is supplied, it is possible to stably generate a high current plasma discharge at a low voltage, It is possible to reduce the power of a small equipment.

Example

Hereinafter, embodiments of the present invention will be described.

As shown in Fig. 1, the plasma discharge truing apparatus 10 of the present invention includes a disc-shaped discharge electrode 14 which is rotationally driven by a DC pulsed power supply (voltage application device) 20 and an electric motor 16. do. Further, a reciprocating truing mode is adopted in which the grindstone 12 is reciprocated in the axial direction, and the true circumferential surface of the grindstone overlaps with the outer circumferential surface of the electrode.

In addition, as a truing medium used for discharge truing, (1) AFG-M (weakly conductive solution used for ELID grinding), (2) pressurized mist which mistized AFG-M with compressed air, and (3) pressurization Compared to the case of using air and not using these media (4), ie the air gap.

In accordance with basic theories of electrochemistry, electroprocessing modes such as the systems described above involve the interaction of truing whetstones, electrodes and working media. In addition, the truing mechanism using conductive aqueous solution (AFG-M) is described as a complex process in which various electroprocessing actions coexist. Since the object of the plasma discharge truing apparatus of the present invention and the microfabrication method using the apparatus is to provide a truing process that meets the processing purpose, it is understood as a system for optimizing the efficiency by controlling the mechanism of electric truing. Can be. In conclusion, it can be applied to similar kinds of tools.

(Process characteristics)

In order to study the processor characteristics, the above-described truing system was mounted in a vertical machining center and various experiments were conducted. In the experiment, a # 2000 cast iron bond diamond whetstone with a thickness of 1 mm and a diameter of 150 mm was trued. During the experiment, the grindstone was rotated at 200 rpm, reciprocated at 100 mm / min in the Z direction, and the truing electrode was rotated at 100 rpm.

(Critical discharge gap)

Figure 3 shows the critical discharge gaps for four types of working medium: air, AFG-M, pressurized mist and pressurized air. The gap is as large as g _air <g _pair <g _mist <g _APG .

(Voltage drop)

4 shows actual voltages for four types of working media under the same conditions. The voltage drop is useful for truing with AFG-M and pressurized mist. This is the result of a separate electrical machining action at the same time.

(Truing efficiency)

Fig. 5 shows the relationship between the input voltage and the truing efficiency for four kinds of operating media under the same conditions. The gap between the grindstone and the electrode was set constant at 30 μm. The experimental results clearly show that the true efficiency increases as the input voltage increases for the four types of working medium. Also, when pressurized mist, pressurized air and AFG-M are used as the working medium, the truing efficiency is larger than when using air in that order, and this tendency becomes more pronounced as the input voltage increases.

(True accuracy)

6 shows truing precision for four types of working media. The truing precision using pressurized mist as the working medium is the highest, and other working mediums can achieve almost similar precision.

According to the present invention, it is confirmed that by applying plasma discharge truing as an electrical truing means, and precisely performing fine truing of the metal bond grindstone used for micro grinding, it is possible to secure the processing precision required for ELID grinding. It was.

In addition, by applying the plasma discharge truing described above, the following advantages have been found to be available.

1. Applicable to the truing of conductive bond whetstones such as metal bonds or resin-metal composite bonds.

2. Since the electric truing method provides a non-contact processing method, precise truing of small diameter grinding wheel and thin grinding wheel is possible.

3. The NC machine enables the truing of grinding wheels with complex surface shapes.

4. The electric truing can remove the vibration of the grindstone, and the large grindstone particles can also be projected from the bond part, so that it is possible to precisely grind the surfaces with complex shapes while maintaining the grindstone shape.

Therefore, since the plasma discharge truing apparatus of the present invention and the microfabrication method using the apparatus can effectively remove eccentricity or vibration of very small or thin grinding wheels, precise truing is possible without deformation of the grinding wheel body, and If the equipment is small and small output is sufficient, there is no need for a complicated control circuit or control device, there is an effect that the production / re-processing of consumables such as electrodes is easy.

On the other hand, while the present invention has been described with reference to the preferred embodiment, it will be understood that the scope of rights included in the present invention is not limited to the embodiment. On the contrary, the scope of the present invention includes all modifications, modifications, and equivalents included in the appended claims.

Claims (3)

A disc-shaped discharge electrode 14 having a conductive grindstone 12 for processing the work 1, an outer periphery 14a accessible to the machining surface 12a of the conductive grindstone, and the discharge electrode An electrode rotating device 16 for rotationally driving around (Z), a position control device 18 for controlling the relative position of the outer periphery of the electrode and the grindstone, and a predetermined voltage is applied pulsed between the grindstone and the electrode And a mist supply device (22) for supplying pressurized mist between the grindstone and the electrode. The plasma discharge truing apparatus according to claim 1, wherein the pressurized mist is a mixture of a weakly conductive aqueous solution and compressed air. (A) A disk-shaped discharge electrode 14 having an outer periphery 14a accessible to the machining surface 12a of the conductive grindstone 12, and an electrode rotating device for rotating the discharge electrode about the axis Z. A plasma discharge truing process, comprising: (16), supplying a pressurized mist between the whetstone and the electrode, and applying a DC voltage between the conductive whetstone and the discharge electrode pulsed to form a working surface by discharge; (B) a dressing electrode 28 having an opposing surface 28a separated from the working surface of the conductive grindstone 12, and between the conductive grindstone and the dressing electrode while supplying a conductive liquid between the grindstone and the dressing electrode; An electrolytic dressing process of electrolytically dressing the conductive whetstone by applying a DC voltage; And (C) a fine processing method comprising a grinding step of processing the workpiece with the conductive whetstone.