Fabrication Of Micro-structured Polymer By Micro Injection Molding Based On Precise Micro-machined Mold Core

In this thesis,in order to improve the manufacturing efficiency and form accuracy of micro-structured polymer components,the precision micro-grinding and micro-electrical discharge machining(EDM)technologies were proposed to manufacture the micro-structured mold core with high form accuracy.The micro-structure features derived from mold core surface were replicated onto the polymer surface by micro injection molding process to rapidly produce the micro-structured polymer workpiece.Explore the mass production and manufacturing process and its application of micro-structured polymer components.The micro-EDM and micro-grinding machining technologies were employed to process regular micro-grooved array structures on the surfaces of titanium silicon carbide(Ti₃Si C₂)ceramic with good electrical conductivity and self-lubrication.The relationships between the form accuracies of micro-structured mold cores machined by the two proposed machining methods and replication rates of micro-structured polymers fabricated by micro injection molding were studied.The effects of micro injection molding process parameters on the replication rate and surface roughness of micro-structured polymer were systematically investigated and analyzed.The hydrophobic properties of smooth and micro-structured polymer surfaces were comparatively studied along with the static contact angle and contact angle evolution versus time.The precision trued superhard cubic boron nitride(CBN)milling-grinding tool was used to machine micro-convex array structure with controllable form accuracy on the surface of mould steel mold core.Then the micro injection molding technology was employed to efficiently fabricate polymeric microfluidic chip with micro-groove array structure.The influences of ultrasonic vibration milling-grinding process parameters on the machining quality of microfluidic mould were analyzed.The experimental results show that the hybrid machining method combined with micro-EDM and micro injection molding can efficiently produce hydrophobic polymer surface with rectangular micro-grooved array structures.The maximum contact angle and replication rate can reach up to 127.5°and 99.46%,respectively.The minimum surface roughness R_a at the bottom of micro-structured polymer was 0.805?m.Compared with injection speed and injection temperature,the melt temperature,holding pressure and holding time had more significant effects on the replication rate of micro-structured polymer,while melt temperature and holding pressure had greater effects on the surface roughness of micro-formed polymer.The micro-structured polymer with inverted V-shaped groove array structures can be fabricated by the hybrid machining method of micro-grinding and micro injection molding,leading to a high replication rate of 99.30%.The injection speed had the greatest influence on the micro-forming angle of injection molded workpiece,while the melt temperature had the least influence.The holding pressure had the greatest effect on the micro-forming replication rate of injection molded workpiece,while the melt temperature had the least effect.The minimum surface roughness R_a of injection molded workpiece was 0.052?m,and the minimum micro-forming angle deviation was 1.47°.Compared with the traditional milling-grinding technology,the developed ultrasonic vibration milling-grinding processing technology can effectively improve the surface quality and form accuracy of microfluidic mould.The minimum surface roughness S_a and arc radius at the bottom of micro-structured mould was 0.082?m and 18.121?m,respectively.