April 15, 2013

Posted April 15, 2013 by Jim Swain, Synergis Project Manager for Manufacturing Solutions:
I had a case recently where a customer had a complex assembly, made up of several different subassemblies. The center of gravity location that Inventor displayed just didn’t make sense. It just didn’t pass the “sanity check”.

Diving into the assembly I found that the cause was pretty simple, and in hindsight fairly obvious: one of the subassemblies was tagged as Reference in the Bill of Materials.
Changing the subassembly to Default shifts the Center of gravity to a more reasonable location:

So, while there are very good reasons to have subassemblies flagged as reference at the bills of materials level for modeling and costing purposes be aware that to get good center of gravity information you will have to temporarily shift them to Default, then shift them back when you are done.
Be VERY careful if you are displaying the center of gravity in a drawing, as changing the BOM state will change the view’s size and any dimensions placed to the assembly’s center of gravity marker, as shown here:

So, if your center of gravity locations don’t quite seem to make sense in an assembly – check the bill of material structure for the various components.
Until next time,
Jim is Synergis’ Project Manager for Manufacturing Solutions and has been with Synergis since 1997.  Prior to joining Synergis he worked in the consumer electronics and automotive industries as a design engineer, a test engineer, and as a CAD administrator. He has also taught design classes at the college level. Jim’s broad knowledge base helps him to understand customers’ problems and offer appropriate solutions. Jim earned BS and MS degrees in Mechanical Engineering from Lehigh University. Jim is a certified Inventor Expert, having been in the first group of people to take and pass the Autodesk Inventor Certified Expert Exam at Autodesk University in 2003. He has also presented classes at Autodesk University since 2003.  Email Jim with a question or request.
See Jim’s other posts:
Falcon Goes Further – Autodesk Labs Project Falcon Overview
Pinewood Derby in Inventor
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