Theory Model And Numerical Simulation Of The Filling Of Micro Injection Molding

Due to the increasing demand for micro products along with the development of micro electromechnical system technology, fabricating micro products by traditional microfabrication technology can hardly meet the requirement of microsystem. Nevertheless, fabricating micro parts by micro injection molding technology has become an important development trend for its high efficiency, stable quality and so on.For the miniature of structure size and volume of micro plastics parts, the traditional design theories for injection mold have lost their instructional significance in some sense. New design theories and methods for micro injection mold should be built according to the characteristics of micro injection molding on microscale. So the research of microscale melt flow behavior in mold cavity becomes an important part of micromold design theories very much, in which the key is establishing theory model suited for micro injection molding.According to the basic theories such as plastic rheology, hydrodynamics etc, using the macroscale melt filling flow theory for reference, comparing the micro injection molding technology with the traditional one, and analyzing some possible influencing factors on micro filling process comprehensively, such as non-isothermal feature in flow process, cavity venting, surface roughness of flow channel, surface tension of melt, gravity and inertia, microscale viscosity, viscous heating and viscoelastic effect, etc, the paper establishes a theory model that reflects micro scale melt flow behavior primarily. Then adopting fluid analysis software, such as Polyflow, etc, simulates effect factors in the model, and improves the theory model according to the simulation results further. Finally, the paper cites the experiment results investigated by Liyong Yu, the doctor of the Ohio States University, simulates the filling processes in two kinds of micro channels which are 200μm and 100μm respectively, contrasts simulation results with experiment data, validates the correctness of theory model, and analyzes the reasons for the errors between the simulation results and experiment data.Through analyzing the simulation results, can know that, considering wall slip effect and adopting local heat transfer coefficient can reflect the effects that is temperature change, surface roughness of flow channel and melt elasticity, etc, to micro melt filling flow behavior. The theory model established in this paper is proved its validity for the prediction of fillinglength in micro flow channels better, can reflect melt filling flow behavior in micro mold channels, and establishes valuable foundation for micro injection mold design theories.