| Low pressure powder injection molding using rapid tooling technology is capable of producing sintered ceramic prototypes in less than one week from the design of the part. Prediction of the shrinkage, complicated by anisotropy, makes dimensioning of the tool a critical part of the process. A model has been developed that predicts die dimensions of alumina and zirconia ceramics formed by this process. The model incorporates anisotropic shrinkage that is a result of differential particle packing and orientation due to pressure-driven flow of particles in a suspension. The model can be integrated into the CAD package used to create the mold for the part. As an example, utilization of the model reduces average error from 1.11 mm (.044&inches;) to 0.32 mm (.012&inches;) on fired alumina parts with a flow length of 100 nun (3.94&inches;). This significant reduction in error would lowers the dimensional variation of the part to within industry tolerances of 0.5%. |
