3D - 2

What is the purpose of constraints in an AutoCAD 2D sketch/ 3D model?

I am trying to teach myself how to model 3D objects in AutoDesk Inventor 2010. I am working through the provided tutorials, and I understand how you go about constraining a 2D sketch. I don't quite understand, however, WHY constraints are necessary? I notice that when I constrain a sketch, there is a notice at the bottom that says for example, "3 Dimensions needed." However, I am still able to perform model functions on the object without fully constraining it. Why is constraining necessary then, if you don't have to fully constrain a sketch before performing modeling functions? Thanks for your help!

Public Comments

1. Parametric models (those changed by inputs into the program by the user after the design process is started) can be handled better by having at least some of the features fixed or constrained. That will lead to better performance of the software and the computer system, as it cuts down on variables. Also, it lends to better designs, as the most critical measures (diameters,spacing, overall dimension) will remain unchanged and accurate for fitting to other components. http://wikihelp.autodesk.com/Product_Help/Autodesk_Inventor/Autodesk_Inventor_2011/101Fundamentals/1177Basic3DWorkflow/11783Dmodelingconcepts http://wikihelp.autodesk.com/Product_Help/Autodesk_Inventor/Autodesk_Inventor_2011/103Parts/1256Constraints/1258Planconstraints