Research On The Simulation Of Powder Injection Molding

In this thesis, mold filling and two-phase separation problems were analyzed by means of test and finite element during powder injection molding.The rheological properties of different binder ratio of 316 L stainless steel feedstock were compared. The binder ratio that was suitable for powder injection molding was obtained. The rheological behavior was determined to obtain the relationship between feedstock viscosity and shear rate and temperature. The rheological equation was fitted by MATLAB. Through the orthogonal experiment,effects of various parameters to injection molding are quantified. The results showed that the influence of the injection speed was maximal, and the injection temperature and injection pressure were equivalent, which were greater than the interaction of different factors. Micro pore of products were obtained by metallographic microscope,respectively.Considering the influence of process parameters on the filling process, the main influences, such as injection temperature and injection speed, were simulated with finite element method. In mold filling simulation, feedstock was served as a single fluid to calculate the melt flow front every time step. In Two-phase separation problem, the powder was regarded as pseudo fluid and assuming that the powder size obeys normal distribution. The powder size was obtained by randomly generating normal distribution data. The drag model was closely to the actual injection molding process. The best process parameters for 316 L stainless steel injection molding are:injection pressure of 70 MPa, injection temperature of 140℃, injection speed of 25%.The highest surface average solid volume fraction is 57.68%, which was simulated in FLUENT. In the same way, The best process parameters for alumina injection molding are: injection pressure of 90 MPa, injection temperature of 150℃, injection speed of 35%. The highest surface average solid volume fraction is 61.45%.Result shows that the average solid volume fraction of the simulation results is higher when the product surface pore is smaller and less. The results show that the two results are in good agreement. Then we can estimate the relatively severity of the powder and binder phase separation of different process parameters, and provide some references for the process optimization during the initial stage. It had certain practical significance for the optimization of injection molding process parameters and improving the quality of the injection molding.