Designing the Injection Molding Process

The injection molding design process typically consists of two phases: Definition and Validation.

Definition Phase

During the Definition phase, you define the proper process settings and validate the runner system design. These settings depend on the selected material and the part’s thickness distribution. Typical settings include:
  • Mold and melt temperature
  • Injection speed
  • Fill / Pack switch point
  • Pack and cool time

Validation Phase

During the Validation phase, you check:
  • Whether the defined process settings can fill the part with the specified machine pressure.
  • Whether the part shows fill defects such as burn marks, weld lines, hot spots, or sink marks.
You also need to evaluate:
  • The freezing time of the gate to get the packing time.
  • The freezing time of the part to get the cooling time.
  • The part deformation for shrinkage and warpage caused by residual stresses as the part cools.

During the Validation phase, you identify any part defects and make changes to the process parameters or geometry to improve the product quality. Once the machine ejects the part, you can only evaluate surface part defects that are visible.

You might still need to evaluate the structural properties of the part. For example, if you use a fiber-filled material and your injection speed is too high, it might cause shear effects that cut the fiber length and result in reduced part stiffness.