Micro wire EDM for high aspect ratio 3D microstructuring of ceramics and metals

Abstract

Components for microsystems are basically produced using processes from the semiconductor technology or by LIGA. Silicon serves as basic material for this components. The material properties of silicon often don't achieve the demands of for example: micro-surgery, biotechnology, fluidics or high temperature environments. High volume production by replication techniques also needs tool materials with more adapted properties and high lifetime. Therefore materials such as polymers, metals, composits and ceramics becoming more and more important in MST and there is an increasing requirement of suitable manufacturing techniques and processes for this materials. For complex-shapes electro-dischargemachining (EDM) can be applied. Wire EDM (WEDM) is usefull for cutting shapes in materials with an minimum conductivity of about 0,01 s/cm. In our department we use wire diameters down to 20 lm. We will show the newest application from our department made by very fine wires on an universal WEDM machine. IntroductionIn MST there are only few technologies and processes for threedimensional structuring of complex shapes with good surface quality in a variety of materials. One of the most important is wire EDM (WEDM). WEDM is useful for cutting complex 3D shapes in materials with an minimum conductivity of about 0.01 s/cm [1][2][3][4][5][6][7]. In the middle of the ninety, first groups start also using electro-discharge-diesinking to produce microstructures in very robust materials, useful for microreactors [6]. This groups adopt LIGA electrodes for EDM structuring of high aspect ratio structures in different metals. So the electroplating materials of LIGA can be expanded. Tools for replication techniques are complex and therefore there are different processes to make them.The department of process technology-IMTEK of the university of freiburg apply ultra precision milling/turning/planing/drilling and UV-LIGA for electrode making and WEDM and ECM for injection moulding and embossing tools. Together with the metrology and design tools, the complete process chain is available for prototyping and upscaling to medium and high volume production. Especially WEDM and ECM is appropriate for economic prototyping and production of microparts in high stressed materials. Microparts made by WEDM in metalsAim by this application was the developing of polymer micro-structures with hydrophilic materials and no dewetting of the surface, like for the nature example lady's mantle (Alechemilla vulgaris). The hair geometry for the example are: diameter 20 lm, height 1 mm and average distance 500 lm. SEM Fig. 1 shows the first results for the mould tool in steel.In Fig. 2 are the moulded and demoulded structure shown. The material was an DMMA Monomer polymerised by 45°C with an 1.2% EGDM Crosslinker and AIBN used as initiator.For gears in an lot of micromotors applications, to reduce the rotation speed and increase the torque, ductile high tensile materials are necessary. Threedimensional tooth shapes with freeform surfaces reduce the abrasion of the...

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