About Assembly Constraints 

This reference describes what you should know to create assembly constraints:


Setting constraints is rather an easy task. However, you should keep in mind the following::
  • You can apply constraints only between the child components of the active component.
    Do not mistake the active component for the selected component:
    • The active component is blue framed (default color) and underlined. It is activated by double-clicking.
    • The selected component is orange framed (default color). It is selected by clicking.
  • You cannot define constraints between two geometrical elements belonging to the same component.
  • You cannot apply a constraint between two components belonging to the same subassembly if this subassembly is not the active component.
  • If you modified any geometrical elements of a constraint, take care if it already exists to solve the constraint, example, the axis of the spot facing in a counterbored hole disappears when the hole type is changed.
    • There are two offset constraints:
      • Offset.1 between the Part2 and the axis of the hole (sky blue) in Part1.
      • Offset.2 between the Part2 and the axis of the spot facing of the hole (orange) in Part1.

    • When changing the hole type from Counterbored to Simple, the spot facing is deleted as its axis.
      • The Offset.2 constraint is disconnected:

  • The following example illustrates what you are allowed to do:
    • (1) The constraint cannot be applied because Product K does not belong to the active component Product B. To define this constraint, Product A must be made active.
    • (2) The constraint cannot be applied because Product E and Product F both belong to a component other than the active component Product B. To define this constraint, Product D must be made active.
    • (3) The constraint can be applied since Product C belongs to the active component Product B and also Product E is contained within Product D which is contained within the active component Product B.
  • When you set a constraint, there are no rules to define the fixed and the movable component during the selection. If you want to fix a component, use the Fix command. See Fixing a Component.


  The following table lists the symbols used to represent the constraints you can set between your components:
Constraints Symbol used in the geometry area Symbol displayed in the specification tree
Planar Angle
  Note also that deactivated constraints are preceded by the symbol ( ) in the specification tree.


  The name of a constraint displays when passing the mouse over that constraint.


  To set constraints it is possible to select the geometry (plane, line or point) resulting from intersections, projections or offsets from the specification tree. For more about these operations, please refer to Generative Shape Design User's Guide.

Customizing Constraints

  The application lets you customize the creation and the display of constraints. For more information, please refer to Customizing Assembly Constraint and Customizing Constraint Appearance.


  To facilitate alternative selections when the geometry to be constrained is not directly accessible, the Other Selection... contextual command allows to you select the desired geometry.
  In a cone example, its face is selected when you select the Other Selection... contextual command.
  The Other Selections dialog box appears, the Face geometry element is selected.
  In the the dialog box you can directly select the Extremity or the Axis geometry elements of the cone and show this selection in the geometry window as in the following images:

V4 Interoperability

  You can set a constraint on a SOLIDE (solid exact) CATIA V4 feature, but you cannot set set a constraint on a SOLIDM (solid mockup) CATIA V4.