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# Understanding Shrinkage

You can apply shrinkage to a model to compensate for the
shrinkage that tends to occur as a molded part cools.
• There are two methods to
apply shrinkage:
– Shrinkage by Scale
– Shrinkage by Dimension
• Formula options:
– 1+S
– 1/1–S
– Where S is the shrinkage
ratio
• You can view the Shrink Info
for the applied shrinkage.
Understanding Shrinkage

Figure 1 – Shrinkage Dialog Boxes
When a molded part is removed from a mold, it tends to shrink in size as it
cools down to room temperature. The amount of shrinkage that occurs in
a molding is highly dependent on part geometry, mold configuration, and
processing conditions. Because the mold components are designed from
the reference model, you must consider the shrinkage of the material in the
reference model before you proceed with the rest of the mold design process.
This typically means that you proportionally increase dimensions of the
reference model so that the mold components created are of the pre-shrunk
molding size.
You can apply shrinkage to the reference model in Mold mode. Depending
on the method of applying shrinkage and the method used to assemble the
reference model, the shrinkage feature may propagate to the design model.
Creo Parametric uses the following formulae to calculate shrinkage:
• 1+S — Uses a precalculated shrinkage factor that is based on the original
geometry of the reference model.
• 1/(1–S) — Enables you to specify a shrinkage factor that is based upon the
final geometry of the reference model once shrinkage is applied.
In the above formulae, S is the shrinkage ratio specified.
There are two different methods to apply shrinkage:
• Shrinkage by Dimension
• Shrinkage by Scale
Viewing Shrinkage Information
When shrinkage has been applied to a reference model, you can view the
information regarding the shrinkage by clicking the Analysis group drop-down
appears, providing you with the following details:
. An information window
• Model name — Specifies the name of the model that shrinkage was
applied to.
• Shrinkage method — Specifies whether the model is shrunk by scaling
or by dimension.
• Shrinkage formula — Specifies which formula was used to apply the
shrinkage to the model.
• Model Dimensions and Shrinkage Value — When shrinkage has been
applied by dimensions, these specify which dimensions the shrinkage was
applied to and the shrinkage value applied to each dimension.
• Shrink coordinate system — Specifies the coordinate system specified
when shrinkage is applied by scaling.
• Shrink factors — Specifies the shrink scaling factors used when shrinkage
is applied by scaling