DEVELOPMENT OF A MICRO DIAMOND GRINDING

Micro-manufacturing processes are not only used for the production of micro-systems but increasingly also for the machining of surfaces, the surface being influenced by the dimensions and the shape of the integrated structures. They are applied in optical, electronic, precise tools, medical instruments and communications systems, these micro-parts and structures are required to develop and fabricate low-cost tools that are micro-sized and have increased wear resistance. A machining mechanism cannot be applied to micro-parts and structures due to thermal stress, thermal deformation and the surface degenerating layer of the machined material. The production of these components is usually done by manufacturing technologies originated in semiconductor processing. To avoid the technological and economical limitations of these processes, cutting and non-conventional processes well known from the macroscopic world are increasingly applied in micro-technology.

This study presents the development of a high-speed electroformed micro diamond grinding tool with thick nickel-diamond coatings with micro-Electron Discharge Machining (micro-EDM). The developed micro-tool is utilized to machine hard and brittle materials, such as optical glass, fine ceramics, and tungsten carbide, and for micro-cutting or nano-grinding. The tool shaft surface provides a reposed base for the floating diamonds. Nickel ions and diamond grains are combined via an electrochemical mechanism to a composite electroformed layer that has two phases: the continuous phase of the metal bonder made of pure nickel, and the discontinuous phase of grinding grain which is fixed with a micro-diamond.

To increase the diamonds per unit area and the amount of exposed cutting edge thereby improving the cutting properties and tool life, a diamond grain 0–2µm in diameter is employed. This reduces micro-miniaturizing of tool and increases the lifetime of the tool. The combined force of the diamond can be enhanced by nickel due to ions piling up one by one. Additionally, micro-tool strength is increased. The fixed diamond with the nickel layer for cementing forms the cutter. To increase the strength of the proposed micro-grinding tool, the tool shaft is made of tungsten carbide in ultra-fine particles. Its diameter is reduced to only 50µm by micro-EDM

CONCLUSIONS

The development of integrates micro-Electron Discharge Machining (micro-EDM) with precision composite electroforming technique was conducted to efficiently produce a micro-grinding tool. The experiment is carried out in two stages. First, the micro-tool shaft is cut using micro-EDM. Second, the micro-diamond grain is plated on the shaft by composite electroforming.

Fine tungsten carbide is machined using micro EDM in a tabletop machining center. A composite working tank is constructed to increase the quantity of the electroformed diamond grains on the substrate. The partition in the tank is reduces flushing, minimizes turbulent flow, improves deposition efficiency in the cathode, sufficiently mixes the electroforming solution and saves diamond grains. The best circularity is improved by using the spherules array in the anode. To increase the amount and the distribution rate of the diamond grains on the cathode a novel miniature funnel mold is developed. By means of the proposed composite electroforming tank and funnel mold, the nickel ions and diamond grains are smoothly and tightly plated on to the substrate surface. Due to the nickel ions piling up one by one, a good combined strength between the micro-diamond grain and the nickel layer can be achieved.

The developed technology is verified on the ceramic component and it is successful to obtain a good surface roughness on the micro component. And can be applied quickly and cost-effectively when fabricating miniature and precise dies, tools and parts. It is also used for the flexible manufacture of cylindrical hole components of hard materials, which are used for the mass production of micro-structured components by forming processes as forming tools.