Powder injection molding process design for UAV engine components using nanoscale silicon nitride powders

The feasibility of powder injection molding to fabricate silicon nitride engine components was evaluated in the presented study. Experiments were carried out on a feedstock consisting of nanoscale silicon nitride powders mixed with magnesia, yttria and a paraffin wax–polypropylene binder system. The measured rheological and thermal properties of feedstock were used to simulate the flow of material during injection molding of a combustion engine for an unmanned aerial vehicle (UAV). Simulations based on the Box–Behnken design were used to identify the critical parameters affecting the injection molding process. The simulation results identified melt temperature as the dominant factor affecting the injection pressure, clamp force, shear stress, sink mark depth, temperature at flow front and volumetric shrinkage. Injection time was found to be the dominant factor affecting the bulk temperature and time at the end of the packing. The optimal injection molding parameters were further estimated using a non-linear programming (NLP) model. It is expected that the engineering community can use the simulation techniques discussed in the study to identify optimum processing conditions for fabricating the complex engine parts, thereby avoiding iterative expensive and time-consuming trials.