OPTIMISATION OF PROCESS CONDITIONS IN POWDER INJECTION MOULDING OF MICROSYSTEM COMPONENTS USING A ROBUST DESIGN METHOD: PART I. PRIMARY DESIGN PARAMETERS

Abstract

Powder injection moulding (PIM) is a net fabrication technique that combines the complex shape forming ability of plastic injection moulding, the precision of die casting, and the material selection flexibility of powder metallurgy. For this study, the design issues related to PIM for the fabrication of thin walled, high aspect ratio geometries were investigated. These types of geometries are typical to the field of microtechnology based electro chemical, mechanical and biological systems, which are multiscale (sizes in at least two or more different length scale regimes) fluidic devices working on the principle of heat and mass transfer through embedded micro- and nanoscale features. Stainless steel was the material chosen for the investigations because of its high temperature resistivity and chemical inertness necessary for typical microfluidic applications. The investigations for the study were performed using the state of the art computer aided engineering design tool, PIMSolver. The effect of reducing part thickness on the process parameters, including melt temperature, mould temperature, fill time and switchover position, during the mould filling stage of the injection moulding cycle was investigated. The design of experiments was conducted using the Taguchi method. It was found that the process variability generally increased with reduction in thickness. Mould temperature played the most significant role in controlling the mould filling behaviour as the part thickness reduced.