Simulation of Particle Migration of Powder-Resin System in Injection Molding

Powder injection molding is an important processing method for producing precision metallic or ceramic parts. Experience, intuition and trial-and-error have been the practice for the design and process optimization of such molding operations. However, this practice is becoming increasingly inefficient and impractical for the molding of larger, more complicated and more costly parts. In this investigation, a numerical method for simulating the mold-filling phase of powder injection molding was developed. The flow was modelled using the Hele-Shaw approach coupled with particle diffusion transport equation for the calculation of powder concentration distribution. The viscosity of the feedstock was evaluated using a power-law type rheological model to account for the viscosity dependency on shear rate and powder concentration. A numerical example is presented and discussed to demonstrate the capabilities and limitations of the simulation algorithm, which has the potential as an analytical tool for the mold designer. The variation of powder density distribution can be predicted, which is ignored by the existing simulation packages. Preliminary simulation indicated that powder concentration variation could be significant. Non-isothermal analysis indicated that most of the key parameters for filling process would change due to a change in powder concentration distribution.