Creo Simulate > Reference Links > Guidelines for Prescribed Displacement Constraints
  
Guidelines for Prescribed Displacement Constraints
In defining prescribed displacement constraints, be aware of the following:
Do not set a prescribed displacement on a model that conflicts with another constraint in the same constraint set.
If the Z axis of a reference cylindrical or spherical coordinate system touches an entity that you want to constrain, you may not be able to successfully specify a prescribed displacement value for one or more of the directional components. Creo Simulate may display a message informing you of the problem. For FEM mode, you will see the message at run time.
To work around this problem, you can change the coordinate system to a Cartesian coordinate system or re-orient the coordinate system so that the Z axis no longer touches the entity you want to constrain.
Although you can specify prescribed displacements in contact analyses, you should take care not to place these on geometry that is part of the contact.
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