The effect of constitutive description of PIM feedstock viscosity in numerical analysis of the powder injection moulding process

Influence of the feedstock viscosity description has been studied on the potential errors during numerical simulation of the powder injection moulding process. Pressure results obtained from the simulations with ProCAST analysis package using feedstocks that had differently described viscosities have been compared with each other and the experimentally measured pressure. It has been shown that assumption of constant viscosity of the feedstocks leads to erroneous calculation of pressure. If described by the Carreau–Yasuda model, viscosity of the feedstock at the low shear rates is usually extrapolated. Extrapolation should be performed very carefully. Underestimation of viscosity at the low shear rates range does not harm the predicted pressure results, while overestimation may cause numerical problems and unrealistic results. The best results can be obtained if the simulations are performed with the feedstocks that have viscosity based on the experimental data measured in a wide range of shear rates.