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Micromachining Seminar Report



Micro parts of various kinds are now in demand for fabricating high-tech products. In order to supply these micro parts, the development of micromachining technology becomes increasingly important. Among the various stages of micromachining, the fabrications of holes and pins are the most basic ones. This paper focuses on the process of making micro pins . Different methods are used to manufacture micro pins. In this paper electro chemical method is used to fabricate extremely thin cylindrical tungsten micro pins. The cylindrical micro pin is obtained by regulating the current density. The current profile for the current density control is obtained with a mathematical model based on the relationship between an electric charge and a surface area.

In recent years, the demand for micro pins has been greatly increasing because of its potential applications in micromachining, electrochemistry, and cell biology. These thin micro pins are often difficult to fabricate by conventional mechanical methods because it has a very small diameter of micron order and is easily bent by the lateral force . Moreover, in many new applications, the materials to be machined are hard and tough, which makes the machining more difficult. Wire electro-discharge grinding (WEDG) is one of the proposed methods to overcome such limitations. However, it takes too long time to fabricate one micro pin by WEDG. There are commercial WEDG machines already available. However, one of the limitations of these machines is that the machined surface has a roughness greater than about 50 nm (Ra) and that the surface is covered with craters. This high roughness and the integration of craters preclude a mirror like surface and give rise to the problems of possible high friction and short fatigue life. Therefore, a smoother and/or craterless surface is desired for such applications as shafts for micro motors, mould inserts for optical parts and punches for micro blanking. In this paper, the improvement of the product’s surface quality is investigated by pursuing the possibility of EDM and by introducing a new process of combined EDM and mechanical polishing. The targeted product size is in the range of 30-100 pm in diameter. Most of these problems may be solved by the electrochemical method. The electrochemical method is a kind of atomic removal process, so it is possible to make a thin and long micro pin regardless of the stiffness of materials. But, this method has not been applied to make such a cylindrical micro pin of uniform diameter until now because of the difficulties for uniform shaping . Unlike the mechanical method, the electrochemical method has advantage in not using any special tools for shaping and open the way for mass production of micro pins inexpensively. In this paper, an electrochemical method using current density control for producing a cylindrical micro pin is proposed. A mathematical model is derived for controlling the current density. The validity of the suggested method is verified through experiments.


MICROMACHINING

Micromachining is the basic technology for fabrication of micro-components of size in the range of 1 to 500 micrometers. Their need arises from miniaturization of various devices in science and engineering, calling for ultra-precision manufacturing and micro-fabrication. Micromachining is used for fabricating micro-channels and micro-grooves in micro-fluidics applications, micro-filters, drug delivery systems, micro-needles, and micro-probes in biotechnology applications. Micro-machined components are crucial for practical advancement in Micro-electromechanical systems (MEMS), Micro-electronics (semiconductor devices and integrated circuit technology) and Nanotechnology. Most methods use silicon as substrate material. Micromachining has evolved greatly in the past few decades, to include various techniques, broadly classified into mask-based and tool-based.







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