Research On Viscous Dissipation And Heat Transfer In Micro Injection Molding

Micro injection molding is a newly emerging technology that can be utilized to form micro parts in mass production. Comparing with the traditional manufacturing technologies as well as the currently used silicon-based micro processing in fields of micro-electro-mechanical-system (MEMS), micro injection molding is more advantageous in manufacturing cost, productive cycle, reliability of quality, etc.However, during micro injection molding, rheological characterizations of the melted polymer in micro channels are quite different with those of the traditional one because of the scale effect in this process. These differences may lead to quality defects in micro plastic parts if the traditional processing techniques are still used in these cases.Based on theories of plastic rheology, hydrodynamics as well as factor-impact correlation analysis in micro injection molding, a new mathematical model that takes the effects of viscous dissipation and the heat transfer into account was established in this paper. Some key influences during micro injection molding such as temperature of mod cavity and melted polymer, non-isothermal feature in flow process, wall slip, roughness in channels and viscoelastic-effect, were analyzed by using this model. Viscous dissipation and heat transfer effects were then simulated using commercial polymer fluid software, namely, Polyflow ? . The feature dimensions of the micro channels were set to 50μm, 100μm and 200μm, respectively. The simulation results were verified by comparing with the experimental data of filling process as well as viscous dissipation in micro channels in literatures reported by L. Yu and J. H. Chen, respectively.Results of this research show that temperature change of the melted polymer in micro filling process can be more accurately evaluated when consider the effects of viscous dissipation and local heating transfer coefficient. The influences of these two factors, which are described in the mathematical model in this paper, have also been proved by the results of temperature rise and filling length of the melted polymer comes from both simulations and experiments. Finally, researches in this paper may provide valuable references in design, manufacturing and operating of the micro injection mold.