Project Abstract:

Metal Injection Molding uses the shaping advantage of injection molding to mold metallic as well as ceramic parts. The entire process consists of the following core steps – formation of the feedstock, injection molding, binder removal and sintering. In feedstock formation, fine-grained powders are mixed with a thermoplastic polymer (binder) to form a precise mixture of ingredients that is pelletized (feedstock). During injection molding, the feedstock is heated to melt the binder and a part of the desired geometry is formed. The molded part is known as the green part. The polymeric binder is then removed through heating by a debinding process. While retaining its shape and size, the debound or brown part is a powder skeleton that is very brittle and porous. In the final sintering processing, the brown part is heated, allowing densification and shrinking of the powder into a dense solid.

This project seeks to optimize the feedstock mixing process and the injection molding process with the help of a suitably formulated design of experiment. Factors that have been identified to influence the feedstock homogeneity include processing variables and material variables. Optimization of the mixing process was conducted by performing homogeneity analysis on the feedstock. Thermogravimetric Analysis (TGA) was used to determine its homogeneity. In the injection molding study, injection molding parameters like temperature and flow rate were studied carefully to rectify dimensional defects. The main objective was to control the parameters simultaneously in order to eliminate potential problems associated with the molding cycle.