Whilst creating a sketch, Inventor will very helpfully automatically constrain each line, arc and point as you lay it down. However Autodesk Inventor doesn’t always pick the constraint you would expect…
If you’ve used AutoCAD then you may be familiar with Autodesk Inventor’s ‘Inferred Constraints’ – You would know them as ‘OSNAPS’.
Inferred constraints temporarily hold your geometry to a given point, Line or Arc. When used in conjunction with Constraint Persistence, Inferred constraints are a very quick way of sketching and constraining geometry.
Occasionally you will want more control and to apply those constraints yourself. There is a quick and easy way of toggling Inventor’s Constraint Persistence on and off.
You can pick which constraints are inferred by right clicking whilst in sketch mode, while no command is active and picking ‘Constrain Options’ from the short cut menu.
‘Scrubbing’ over geometry to infer a constraint
You can ‘force’ a particular constraint by ‘scrubbing’ your cursor over the relevant geometry whilst sketching.
Toggle Inferred Constraints on and off
You can toggle Constraint Inference and Constraint Persistence from the constraints tab on the sketching panel.
Tip: You can temporarily turn off inferred constraints for each line that you sketch by pressing the CTRL key as you sketch.
This doesn’t effect coincident constraints, so your loops should still close…
Update for Inventor 2011
Constraint inference and constraint persistence can be toggled on and off whilst sketching using the toggles on the ‘Constraints’ panel. In Inventor 2011 these controls have moved down to the fly out panel.