Creo Topology Optimization > Model Setup > Constraints > To Define Planar Constraints—Topology Optimization
  
To Define Planar Constraints—Topology Optimization
The planar constraint allows full planar movement, but constrains off-plane displacement.
1. Click Home > Constraints > Planar. The Planar Constraint dialog box opens.
2. Specify a Name for the constraint. Click the color swatch next to Name if you want to change the color of the constraint icon.
3. To create a new constraint set, select a constraint set from the Member of Set list, or click New to open the Constraint Sets dialog box.
4. Select the planar surfaces to constrain. You can select the geometry before or after you open the Planar Constraint dialog box. The Surfaces collector shows your selections.
5. Click OK.
For details about constraints, see the Creo Simulate help.