Mold filling Simulation in 3D (SIGMAsoft) for PIM Materials

Simulation of the mold-filling process has become an indispensable asset in plastics processing. Optimization of the injection molding process encompasses innovations such as cycle time reduction, improved tool design, a reduction of material expenditure through runner system optimization, and the use of a cooling duct layout and of connecting seam positioning. These forms of optimization for complex components cannot be carried out without computer-based simulations.

The situation is similar in metal injection molding, despite the fact that the processed feedstock behaves entirely differently in certain significant ways: for example, filling a binder system with a low melting point with metal powder will cause thermal conductivities far above the values found in unfilled plastics. Conversely, the so-called MIM / PIM feedstocks display an entirely different PVT-behavior due to their high fill degree of up to 70%Vol ; they exhibit low compressibility, no or minimal volume leaps caused by crystallization, and a relatively broad range of melting points when combining individual binder components.

Furthermore, MIM-typical errors that are extremely rare in these forms in plastics processing (or that are even entirely unknown in plastics) may occur, such as:

  • sloughing of internal structures along the flow path
  • internal cavities without visible external sink marks

Such faults are very difficult to detect by nondestructive means, especially since they are often only visible as unsintered layers within the component after sintering.

Simulation for MIM / PIM

3D model of the standardized MIM tensile test specimen.
© Fraunhofer IFAM
3D model of the standardized MIM tensile test specimen.

The ability to identify the aforementioned potential faults can be illustrated with a standardized MIM tensile test specimen. Despite the fact that the geometry of the specimen shown here is relatively simple, the internal defects described above have indeed been observed in the fabrication of similar tensile specimens.

Using three different feedstock samples, various injection molding parameters and their effect on the possible occurrence of internal defects were studied at the Fraunhofer IFAM.

A summary of the results can be found here: