In NX4, in the pull down (Analysis)mass properties,
tab, Create Principal Axes, is that the same as finding the center of gravity? If not, how can I get the C.G.??
Select Measure Bodies, select the body and let the computer crank away for the results. When it's finished, click the Information icon (large lowercase i) and the Center of Gravity will be listed as the Centroid in the upper portion of the Listing Window and also as Center of Mass beneath that.
Same thing John outlined but without creating anything "extra".
I haven't used the Keep Measure since NX3, but the last time I did, it created a point at the Center of Mass (Centroid) and would update after any model revisions. Make it the very last feature if you want this to be associative. Then after your model updates, all you need to do is an Info Object on the point to get the Centroid rather than waiting 2 times for the software to crunch the numbers. (Once for the onscreen information and a second time for the Listing Window information).
To add to what Tim stated, this is what I do with the Keep Measurement point. In my line of work (putter design) weight is a HUGE concern.
When I do my mass measurement, I too keep this feature at the end of the feature tree so it always updates. The beauty for me is that I have the "Details" window open at the bottom of my 'Part Navigator' window, so all I have to do is select the body measurement in the model navigator and the details show up in the Details window. I don't even have to do an Info Object.
Now, you won't get all of the details that you would if you DO perform an Info Object, but for me, this works.
Good Luck!
Chris Cooper
Senior CAD Specialist
Cleveland Golf / Never Compromise