Using scale factors (thermal expansion)
You can scale instances to account for thermal expansion or other cases where a part may change size by applying a scale factor to the instance.
To apply a scale factor to an instance:
- Open an assembly with one or more instances that you want to scale.
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Select the instance to scale, and then select Scale Factor for Instance... from the File menu,
or
Right-click on the instance name in the Model Explorer, and then select Apply Scale Factor.
- In the dialog that opens, type a name for the scale factor. The name must be a valid variable name. A drop-down list of existing variable names will appear as you type the variable name, so you can select a name from the list if desired.
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Press Enter to add the Scale Factor variable to the Parameter table.
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In the Parameter table, enter a value by which to scale the instance or create an equation that calculates the scale factor. To enter a value that decreases the instance size, enter a decimal fraction, such as "0.95". Zero or negative values, such as "-95", are invalid and will result in a solver alert.
The following example shows two scale factor variables applied to two instances in an assembly.
The instance icon in the Model Explorer is shown with an arrow pointing up
to indicate a scale factor that increases the size of the instance (as for "scale factor 1") and an arrow pointing down 
to indicate a scale factor that reduces the size of the instance (as for "scale factor 2" above). 
The Scale Factor variable can be seen in the list of connected objects when the instance is selected.
Example
As illustrated in the following example, you can use equations to set scale factors. In this example, each instance in the Z-Height assembly (Base, Spacer, Block, and Bar) has its own coefficient of thermal expansion factor based on different materials, such as aluminum, steel, etc.
The four equations compute the scale factors for each instance based on the actual temperature and the appropriate coefficient of thermal expansion.
