| Micro injection molding, derived from traditional injection molding technology, is a novel advanced manufacture technology, which takes milligram as part weight tolerance unit, micron as geometry tolerance unit. Due to the advantage of low cost, short production period and easy to realize large-scale production, it becomes one of hot researches of current micro-nano manufacture technology. Micro fluid behaviors in micro injection molding process were studied with theoretic analysis, experimental test and software simulation, which contribute greatly to micro injection mold design and processes optimizing in theoretical and practice meaning.In the study of micro fluid model, Eringen-Okada viscosity model, surface tension-pressure equation and Rosenbaum-Hatzikiriakos wall slip model were introduced, the micro fluid flow model was firstly built which took the molecule dimension effect, surface tension and melt wall slide phenomena into account. And it was solved numerically with FEM and FDM.In the analysis of micro fluid fountain flow, 2D numerical Simulation of Fountain Flow for Newtonian and Nonnewtonian Fluid Front in micro-channel was firstly realized by using CFD software Fidap8.52. The simulation results of the distribution of velocity and pressure in fountain region were showed and the results of micro-channel fluids are according to the research results of macro fluids. In the mean time, for the investigation about surface tension effect on micro fluid fountain flow, the simulation in consideration of surface tension was firstly processed and results show surface tension influence on the distribution of velocity and pressure in fountain region is week, but its tangential stress acting on the fluid front leads to large deformation of the shape of front.In the research of micro fluid contraction flow, 2D numerical simulation of 4:1 non-isothermal planar contraction flow was realized by using CFD software Fidap8.52. The simulation results of velocity, pressure, shear rate distribution trend were presented and the characteristic agreement of micro scale analysis results with macro scale analysis results appears. However, the simulation result of temperature distribution for micro contraction flow has fault, so the energy equation and boundary condition relative to temperature must be modified in non-isothermal micro scale contraction flow behavior study.In the investigation of micro fluid flow capability, in order to find the rule of micro channel section shape influencing non-Newton and non-isothermal fluid flow capability, in the simulation, RPA (means Ratio of the section' s Perimeter to its Area) was firstly raised for changing the section of micro channel into numeric value. The results show that the flow length of micro fluid in micro channels that have different section shape but the same length is in inverse proportion to sections' RPA (RPA means Ratio of the section' s Perimeter to its Area), and the RPA is the smaller the flow length is the longer. In the range of small RPA, the effects of melt temperature and injection pressure on flow length is strong while in the range of large RPA the effect is week. Furthermore, the effect of injection pressure on flow length is stronger than melt temperature whatever the value of RPA is.In the application research of micro injection molding process, the micro injection molding process of guide-light plane was realized with MoldFlow MPI. The simulation results show that the warp of guide-light plane mainly because of shrinkage, not cooling and orientation and the warp trend presents deflection up in corners and down in center field. With rectangular side gate, there are filling imbalance and flow blocking phenomena and required injection pressure is higher. Through optimizing gate design, the filling imbalance and flow block phenomena were improved better and the warp deflection was decreased obviously with slot side gate. |
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