Dimensions and body constraints can constrain the faces and edges in a model in certain ways, while allowing free-form Direct Manipulation of the model in other ways.
You can use body constraints to constrain faces and edges within a single component, but not between different components.
Body constraints cause the body to change shape to meet the constraints. In contrast, Component (assembly) constraints treat each component rigidly. Inventor Fusion solves body constraints first, and then component constraints. For information about how to constrain or assemble components relative to each other, see Position and Constrain Components.
Inventor Fusion respects the design intent of the constraints when you use the Move and Press/Pull commands, and when you change dimension values. If you move a face that is constrained to another face, then that face moves exactly as you specify, and the other face also moves.
Constraints are propagated through patterns. When you move a face that is part of a pattern, then all corresponding faces in that pattern move in the same way. If any of those faces are constrained to other faces, the other faces also move. If Inventor Fusion cannot find a suitable solution, then the preview stops and the error glyph displays.
You can access the following types of Body constraints from the Constrain command:
- Coplanar: Two planar faces are made to lie in the same plane
- Center: Two cylindrical faces are made to lie along the same axis
- Parallel: Two planar faces are made to be parallel
- Perpendicular: Two planar faces are made to be perpendicular
When you use the Constrain command to create body constraints:
- Only the appropriate types of faces are available for selection (cylindrical for Center constraints, planar for the other types).
- The first face that you select is marked with the Anchor glyph (grounded). The second face that you select is marked with the Non-anchor glyph (not grounded). When you apply a constraint, the grounded face remains where it is, and the other face (or faces, as appropriate) moves.
- You can switch to the grounded face with the Tab key, or click the Anchor or Non-anchor glyph, before you apply the constraint.
- You can change the constraint type before you apply the constraint. Faces that are not valid for the new constrain type are filtered out.
- The grounded state is temporary. After you create the constraint, either or both faces can move to satisfy the constraints. There is no way (nor no need) to make a face permanently grounded. The solver never moves unconstrained faces. (In contrast, assembly components can be grounded.)
NOTE Instead of using body constraints to move a face, you can use the move triad, possibly aligning it to an edge. By selecting the appropriate element of the triad, you can force the face to move in only certain limited directions.
Dimensions can drive the model, or function as pure annotations (non-driving). For more information about dimensions as annotations, see Dimensions.
Dimensions and explicit body constraints are solved together. No precedence is given to one or the other.
You can lock a dimension to force the model to maintain that dimension at the current value, regardless of other changes. Locked dimensions are shown in bold.
Locked dimensions constrain edges. The adjacent faces move to adjust the edges to the correct size and the correct position.
When you pause the cursor over a dimension, a lockable dimension shows a Lock glyph which means the dimension is locked. If it shows an Unlock glyph, the dimension is unlocked.
To lock a dimension, do one of the following:
- Double-click the dimension and change its value (click Enter when done, or Escape to cancel).
- On the context-menu, click the check box for Lock to lock the dimension at its current value. Clear the check box to unlock.
- Click the Lock glyph.
NOTE If a double-click does nothing, the Lock check box is not available on the context menu, and no glyph displays when you pause the cursor over a dimension, then you cannot lock the dimension.
When editing the value of a dimension:
- A preview of the new value displays. A delay in the preview minimizes unnecessary previews of intermediate values as you enter them.
- Most dimensions show an anchor glyph to indicate the grounded side. The other side moves in response to the new value of the dimension. To swap the anchor, move the cursor to the other side. Indicator lines and circles represent the original position of the editing edges. Indicator lines and circles display temporarily when the dimension is in preview mode.
Details and limitations
- Sometimes invisible constraints remain to maintain obvious perpendicularity and parallelism. If the invisible constraint is not appropriate, move the faces slightly before you apply the constraint, or lock the dimension.
- If a Move or Press/Pull operation causes an edge or face to split, and the edge or face has a dimension or constraint attached to it, then the dimension or constraint is automatically applied to one of the resulting entities. The other edge/face does not inherit any constraining behavior from the original. It is not possible to predict or specify which edge or face acquires the constraint.
- You can create a situation where a dimension becomes invalid and changes color during the preview. If you finish the command with dimensions in this state (sick), then the sick dimensions are deleted.
- If you create a set of constraints that cannot be solved, the error glyph appears. Undo or delete constraints to get back to a properly solved model.
- You can save dimensions and body constraints in only the DWG format. They are not saved in any other format.
- Constraints are not respected in the Draft command.
- Under some circumstances, invisible intermediate states can fail for no visible reason. To avoid these situations, by move the elements through a different route, or move a little bit at a time, and accept each move.