# Finding Center of Mass (COM)

• 11-07-2012, 03:37 PM
eficonnection
Finding Center of Mass (COM)
To simplify what I'm trying to do, I've drawn a 4 inch circle with a thickness of 0.25 inch. When I analyze the physical properties of the part, the center of mass is not 0,0,0. I'm sure it's a user issue, but I'm not sure what I'm doing wrong. Any suggestions?

http://www.eficonnection.com/temp/Alibre_COM.png
• 11-07-2012, 08:58 PM
MichaelHenry
Looks like center of mass is X = ~10-16 (darn close to zero), Y = 0 and Z = 0.125. Since you have the floor of your disk at z=0, and the disk is 0.25" thick, the center of the disk in Z would be at 1/2 x 0.25 or 0.125" Therefore, COM = 10-16, 0, 0.125 seems pretty close to reality to me.

Does that help?

Mike
• 11-08-2012, 04:11 AM
dbrija
I was going to blame pi and rounding error as this was a cylinder, but I get the same "non-zero" with any other shape. Though, as was already pointed out, 8 x 10^-17 is certainly close enough to 0 to call it zero. I suspect it is just leftover rounding error that should not be getting reported...

I played with decimal places, precision, etc... but you can only set up to 6 places, and what this is reporting is 12 or more decimal places.