Shrink analysis

Shrink analysis enables you to determine an appropriate shrinkage allowance to use to cut the mold taking into account the shrinkage characteristics of the material being used to mold the part and the molding conditions.

Every part which is injection molded requires someone to select the dimensions to which the mold must be cut. In the past, many precision parts have required molds to be heavily modified so that tolerances can be met successfully. On some occasions, molds have been scrapped several times over, in order to achieve the required dimensions, incurring huge costs and significant delays in time to market for the product.

How it works

The key features of the Shrink analysis are:

• Calculation of a recommended shrinkage allowance.
• Graphical display indicating whether it is valid to apply this single shrinkage allowance value across the part.
• Optional definition of critical dimensions and their associated tolerances. Where critical dimensions are defined, the Shrink analysis predicts whether the specified tolerances can be met if the recommended shrinkage allowance is used, included detailed dimensional and tolerance information resolved into X, Y and Z directions.

Material shrinkage is defined as the reduction in the size of a molded component in any direction after it has been ejected from the mold. It is related to the flow and cooling conditions under which the component is injection molded. Shrinkage data characterizes this reduction in component size due to shrinkage for a range of different processing conditions. Shrink analysis is available for any material in the Materials Database that has been shrinkage characterized.

Note: Shrinkage is affected greatly by fiber orientation.

Although it is possible to run a Shrink analysis with a fiber-filled material without selecting the Fiber-orientation analysis option, the result will not take orientation into account and will not be as accurate. If you are analyzing a fiber-filled material you should turn on the fiber analysis option in the Fill+Pack process settings.

Tip:

If your material contains anisotropic matrix material properties, warpage and shrinkage values may be more accurately calculated using the Mori-Tanaka micomechanical model.