Design Guide

Manufacturing Considerations

Computer Simulation for Defect Avoidance

The success of MIM is linked to its ability to generate precise, complex shapes at the molding machine and then to sinter that shape to the target size and specifications. This requires quality tooling and excellent process control. Computer software is used to simulate molding, tool design, de-binding, and sintering. Several simulations are available.

The computer programs emphasize a combination of mold filling, packing, and cooling simulations. Such packages allow process evaluation prior to commitment to tooling or manufacturing equipment. Cost evaluations are possible based on differences in raw materials, the number of tool cavities, and options on processing cycles.

Cooling Simulation
Cooling Simulation

Short Shot " Simulation
Short Shot " Simulation

Often subtle variations exist in sintering shrinkage that need to be predicted to minimize tool construction errors. For example, non-uniform density in molding leads to distortion in sintering. Further, subtle factors such as gravitational forces in sintering and polymer orientation in molding cause subtle anisotropic shrinkages that contribute to dimensional variations. The desire is to have computer software incorporate these factors into the tool design to help place runners, gates, vents, and cooling paths. Once the shape and gradients, or stresses, are known in the molded body, then finite element computer simulation tools allow prediction of final sintered size and shape.

These simulations require a database of material properties, component specific details, and process details. Unfortunately, many of the modeling parameters are not known with precision and are estimated. For well-controlled operations, computer-assisted design is an inexpensive way to explore options before mold production.