About Injection Locations

Injection locations define where the plastic enters the part cavity. You must have at least one injection location.

This page discusses:

See Also
Defining an Injection Location
Defining Injection Locations Automatically

Plastic material at the specified melt temperature (see Process Settings) is introduced into the plastic part through injection locations. Each injection location is defined by a surface or a point.

Surface

For surface-based injection locations, the plastic enters the part from the entire surface you select.

If your model has a runner system, select the top of the sprue as your injection location.

Point

For point-based injection locations, the plastic enters the part at a location that you specify.

If your model does not have a surface that represents your injection location, specify any location on a surface as the center of a circular area through which the plastic is injected.

Note: By not modeling the runner system, the effects on the plastic temperature and flow are ignored.

Typically, the diameter of the injection location should be 60-80% of the part thickness.

Automatic Creation of Injection Locations

If you created your part geometry and injection locations using Functional Plastic Parts, Plastic Injection creates those injection locations in the simulation automatically. You can delete these injection locations or add more of them, but these changes do not automatically propagate back to the Functional Plastic Parts app.

If you create injection locations automatically using Plastic Injection, as opposed to inheriting them from Functional Plastic Parts, the app uses an algorithm to approximate the ideal injection locations. The algorithm works in the following manner:

  1. The algorithm finds N random positions on the selected body's outer surface, where N is the number of injection locations you specify to create.
  2. Each random position locates the closest solid element, called a "pivot."
  3. Each pivot iteratively propagates to its nonoccupied neighboring elements until all of the body's elements are occupied. While this process mimics a simple flow pattern, the algorithm does not involve any flow calculations.
  4. For each pivot's distribution of occupied elements, the algorithm determines the center of gravity.
  5. For each pivot's center of gravity, the algorithm locates the closest solid element at the surface of the body.
  6. The algorithm defines this solid element as the new pivot.
  7. The algorithm repeats this process defined in steps 3 through 6 until it converges on a solution or it reaches a defined maximum number of iterations.

The plastic part below, which is an unusual geometry, demonstrates the importance of using the center of gravity of the distribution of occupied elements when determining the injection locations automatically. The different colors represent regions of the part filled by different injection locations.