JP2005329511A - Micromachining method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micromachining method for a simple plastic material with high machining property. <P>SOLUTION: An aluminum blank 12 is brought into contact with a forming die 11 having a very small rugged part. Shock wave is generated by performing electric discharge within a closed container 18 provided on a back face of the blank 12 and filled with liquid 22. The blank 12 is formed into a fine shape along the forming die 11 by generation of the shock wave. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for molding or transferring a plastic material using a mold having a fine shape on the order of micrometers.

  In recent years, with the miniaturization and complexity of all devices, there has been a demand for higher precision and higher density of processing in the precision machinery industry and electronics industry. Has been developed. Until now, the development of such micromachining technology has been mainly based on the approach from semiconductor process technology. However, in recent years, micromachining that can realize processing that is difficult with semiconductor process technology has attracted attention. Research into various micromachining technologies such as cutting, coining, forging, drilling, and electrical discharge machining is underway.

  On the other hand, processing methods using hydraulic pressure have been widely used in the field of processing plastic materials such as sheet metal processing. In this method, molding is performed by pressing a plastic material against a die by liquid pressure. As a method of applying pressure to the liquid, in addition to a method of mechanically using a piston, explosives may be exploded in the liquid. (Explosive forming method) and methods using shock waves generated by discharging (in-liquid discharge forming method) have been performed.

  Among these, the explosion molding method and the submerged discharge molding method are classified as high energy speed machining methods, and since molding is performed at a high strain rate and high pressure, there is an advantage that the amount of springback is greatly reduced. This method is preferable not only in terms of efficiency but also in terms of workability with respect to difficult-to-process materials and complex shape molding, as compared with a processing method using hydrostatic pressure generated by a piston or the like.

  However, the explosion molding method has a problem that it is difficult to handle because it is subject to legal restrictions due to the use of explosives. In contrast, the submerged discharge molding method uses a large charge stored in a capacitor or the like as an energy source, discharges it instantaneously in the liquid, and uses the impact pressure wave generated at that time to increase the speed. Since it is not subjected to legal regulations like the explosion molding method, it has a feature that it can be performed relatively easily.

  Since machining by submerged discharge becomes shocking machining, the electric discharge machining method has heretofore been used exclusively for rough machining before strong machining or finish machining.

In order to use this submerged discharge for micromachining (micromachining), the inventor of the present application converges a shock wave generated by underwater discharge with a sonic lens to open a hole in an object in order to concentrate the machining force on a fine region. Micro drilling technology has already been developed.
The present invention further allows the submerged discharge molding method to be applied to high precision micro molding and high precision micro transfer processing without using such a sonic lens. That is, the problem to be solved by the present invention is to provide a processing method capable of performing micrometer-order molding and transfer processing with high speed and high accuracy.

  In order to solve the above problems, a micro machining method according to the present invention includes a plate-shaped workpiece and a fine mold that are brought into contact with each other, and the workpiece and the fine mold are disposed on the upper portion. And generating a shock wave by filling the liquid inside the sealed chamber and discharging in the liquid, and applying a shock wave water pressure from the lower surface of the workpiece or the fine mold, The material is formed into a shape along the mold.

Further, the micromachining method according to the present invention uses an in-plane machining with a machining depth of 100 μm or less with respect to a workpiece by using a transfer die having a fine concavo-convex pattern on the surface as a machining die. (Transfer processing) may be performed.
That is, in the micromachining method according to another aspect of the present invention, a plate-shaped workpiece and a transfer mold having a fine surface pattern are brought into contact with each other, and the workpiece and the transfer mold are arranged on the top to be sealed. Forming a chamber, generating a shock wave by filling the inside of the sealed chamber and discharging in the liquid, and applying a shock wave water pressure from the lower surface of the workpiece or the transfer mold, A fine pattern having a depth of 100 μm or less by the transfer mold is transferred onto the surface of the material.

  In the micromachining method of the present invention, the workpiece may be placed under the molding die or the transfer die, and the workpiece may be pressed against the die by impact hydraulic pressure from below to perform molding / transfer processing. Alternatively, the molding / transfer processing may be performed by placing a molding die or a transfer die below the workpiece and pressing the die against the workpiece by impact hydraulic pressure from below.

  Further, the micromachining apparatus according to the present invention includes: a) a transfer mold having a fine mold or a fine surface pattern disposed so as to be in contact with an upper surface or a lower surface of a plate-like work material; and b) the work material. And a sealed chamber for filling the liquid provided below the fine mold or the transfer mold, c) a discharge electrode provided in the sealed chamber, and d) means for applying a voltage to the discharge electrode. It is characterized by that.

  In the micromachining method of the present invention, the workpiece is deformed at a very high speed using shock waves generated by submerged discharge, so that surface transferability and machining with high dimensional accuracy of the molded product can be performed. it can. In addition, since molding is performed using water pressure, a precision tool or the like is not required as in fine processing by cutting, and the processing apparatus is excellent in terms of durability. In addition, the workpiece and the mold or transfer mold are placed in the upper part of the sealed chamber filled with liquid, and molding is performed by upward shock waves, so that there is a gap between the mold and the workpiece during molding. This makes it easier for air to escape and prevents molding unevenness due to the air.

Hereinafter, the best mode of the present invention will be described using examples.

(Example 1)
An example of the micromachining apparatus according to the present invention is shown in FIG. The micro-processing apparatus 10 includes a cap 13, a mold holder 14 that holds a forming die or transfer die 11, and a metal base plate (blank) 12 that is a workpiece to prevent wrinkles from being generated due to deformation. Wrinkle holding plate 15, blank 12 and blank holder 16 for holding wrinkle holding plate 15, spring 17, sealed container 18 for storing liquid 22, auxiliary piston 19, electrode 20, and electrode are provided. A thin metal wire (conductive wire) 21 is provided. S45C steel was used as the material for the closed container 18, and the closed container 18 was sealed with an O-ring 27. As the liquid 22 used as the pressure medium, it is desirable to use water that can efficiently transmit the shock wave generated by the discharge and the pressure energy of the high temperature / high pressure gas to the blank 12 and can be easily removed after molding. In addition, the electrode 20 preferably uses a method of energizing the conductive wires 21 provided between the electrodes 20 as in the present embodiment from the viewpoint of energy efficiency and discharge stability, but the conductive wires 21 are provided. It is also possible to use a system that performs gap discharge. An aluminum wire having a diameter of 0.25 mm was used as the conducting wire, the distance between the electrodes was 10 mm, the distance from the blank 12 to the conducting wire 21 was 38 mm, and the distance from the blank 12 to the bottom surface was 85 mm.
In this embodiment, the blank 12 is held by pressing the wrinkle holding plate 15 against the blank 12 only by the force of the spring 17, but the impact pressure during discharge also acts on the wrinkle holding plate 15. It is more desirable to arrange a wrinkle pressing plate because the blank 12 can be uniformly pressed using the impact pressure during discharge.

  The electrode 20 is connected to a capacitor 23. After the charge switch 25 is turned on and electric energy is accumulated in the capacitor 23 by a voltage applied from the power source 24, the safety switch 27 is turned on, and the capacitor 23 is accumulated. The generated electrical energy is discharged and supplied to the conductive wire 21 in a short time. As a result, the conductive wire 21 is rapidly melted and evaporated to generate a shock wave, and pressure due to the explosive vaporization of the water between the electrodes 20 is generated, and the blank 12 is formed into a shape that conforms to the shape of the mold 11. . The intensity of such shock waves can be controlled by adjusting the voltage applied to the capacitor 23 by the controller 26.

(Example 2)
A micro-extrusion molding experiment was conducted using the micro-processing apparatus 10 of Example 1 above. The mold 11 used for processing was produced using a focused ion beam device (FB-2000A manufactured by Hitachi High-Technology Corporation). FIG. 2 shows a schematic diagram of the mold and an SEM (Scanning Electron Microscope) photograph. The mold 11 was a cylinder having a diameter of 100 μm and a depth of 50 μm. The shoulder portion of the mold 11 was chamfered by 4 μm, and a hole having a diameter of 10 μm was provided at the bottom of the mold 11 in order to remove air existing between the blank 12 and the mold 11 during molding. At this time, the periphery of the hole was formed in a taper shape so that the air could escape efficiently. The mold 11 was used by being embedded in a mold holder 14. In addition, a hole for venting air was also provided in the upper part of the mold holder 14 in order to let the air escaped from the mold escape to the outside.

  A blank made of pure aluminum having a thickness of 0.025 mm was used as a workpiece. The blank 12 was set so as to be sandwiched between the wrinkle pressing plate 15 placed on the blank holder 16 and the molding die 11. The molding experiment was performed by changing the charging energy from 0 to 1260 J by changing the charging voltage from 0 V to 3000 V by setting the capacitor capacity to a constant value of 280 μF. Moreover, AC100V was used for the power supply 24 of the apparatus.

FIG. 3 shows an SEM photograph of a molded product when a molding experiment was performed at a charging voltage of 2400 V, and the result of shape measurement of the molded product. In the molded product, the angle between the flange portion and the side wall portion is almost vertical, and the taper shape of the entrance of the hole is reproduced, and it can be seen that a good molded product along the mold 11 was obtained. Moreover, the unevenness | corrugation of the upper part of a molded product is not a molding defect, and the unevenness | corrugation by the process roughness of a mold bottom part is transcribe | transferred.
From the above results, it was confirmed that the micromachining method by submerged discharge of the present invention has very excellent moldability in 100 μm micro-extrusion molding.

(Example 3)
In Example 2 described above, so-called out-of-plane processing was performed in which the blank was deformed into a shape along the molding die. However, a transfer die in which an uneven pattern sufficiently shallow with respect to the thickness of the blank was applied to the surface as a processing die. By using, in-plane processing can be performed on the blank. Hereinafter, a transfer processing experiment using such a transfer mold will be described.

  A hologram transfer processing experiment was conducted using the micro-processing apparatus 10 of Example 1 above. A hologram is a recording of the wavefront of light reflected from the surface of an object in the form of interference fringes, and has interference fringes at intervals of about 1 μm corresponding to the wavelength of visible light. If this fine stripe shape is duplicated, the original stereoscopic image can be reproduced from the duplicate hologram.

As the transfer mold used in this experiment, a commercially available relief type diffraction grating having fine irregularities on the surface was used. A blank made of pure aluminum having a thickness of 0.1 mm was used as a workpiece.
FIG. 4 shows a transfer mold and a photograph of the transfer product, and FIG. 5 shows an SEM photograph of the surface of the transfer product and a schematic diagram thereof. Radial rainbow color development was confirmed on the transferred blank surface, and SEM photographs confirmed that linear grooves with a 1 μm interval were formed on the surface.
From the above, it was confirmed that the fine concavo-convex shape of the relief type diffraction grating can be transferred to an aluminum blank by the micromachining method by submerged discharge molding according to the present invention. Such a micro-transfer method can be applied to, for example, decoration of aluminum cans or complicated packaging containers utilizing the optical effect of holograms. In addition, a woven fabric or the like can be used as a transfer mold, and the texture pattern can be transferred to a blank.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the micro processing apparatus which concerns on Example 1 of this invention, (a) is an exploded sectional view, (b) is a circuit diagram. The (a) top view and sectional drawing of the shaping | molding die used in the micro shaping | molding experiment which concerns on Example 2 of this invention, (b) SEM photograph. The (a) SEM photograph of the molded product shape | molded in the shaping | molding experiment of the Example, and (b) Shape measurement result. (A) Photo of transfer type and (b) Photo of transfer product in transfer processing experiment according to Example 3 of the present invention. (A) SEM photograph and (b) schematic view of a transfer product transferred in the transfer processing experiment according to the same example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Micro processing apparatus 11 ... Mold, transfer mold 12 ... Blank 13 ... Cap 14 ... Mold holder 15 ... Wrinkle holding plate 16 ... Blank holder 17 ... Spring 18 ... Sealed container 19 ... Auxiliary piston 20 ... Electrode 21 ... Conducting wire 22 ... Liquid 23 ... Capacitor 24 ... Power supply 25 ... Charge switch 26 ... Controller 27 ... Safety switch 28 ... Voltmeter 29 ... Rectifier

Claims (3)

  A plate-shaped workpiece and a fine mold are brought into contact with each other, and the workpiece and the fine mold are arranged at the top to form a sealed chamber. The sealed chamber is filled with a liquid and discharged in the liquid. A plastic material characterized in that a shock wave is generated by performing and a shock wave hydraulic pressure is applied from the lower surface of the workpiece or the fine mold to form the workpiece into a shape along the mold. Micro-machining method.   A plate-shaped workpiece is brought into contact with a transfer mold having a fine surface pattern, the workpiece and the transfer mold are arranged at the top to form a sealed chamber, and the sealed chamber is filled with liquid. A shock wave is generated by discharging in the liquid, and a shock wave water pressure is applied from the lower surface of the workpiece or the transfer mold, whereby a fine pattern having a depth of 100 μm or less by the transfer mold is formed on the surface of the workpiece. A micro-machining method for a plastic material, characterized by transferring the material. a) a fine mold or a transfer mold having a fine surface pattern arranged so as to be in contact with the upper or lower surface of the plate-like workpiece;
b) a sealed chamber for filling a liquid provided below the workpiece and the fine mold or transfer mold;
c) a discharge electrode provided in the sealed chamber;
d) means for applying a voltage to the discharge electrode;
A micromachining apparatus comprising: