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Trying to determine Center of Mass of weldment in order to get crane pick points

Question asked by Dave Krum on Mar 20, 2019
Latest reply on Mar 21, 2019 by Matt Peneguy

Hello. I'm experimenting with the C.O.M. feature to determine the "close enough" pick points to raise a 40,000# weldment and keep it balanced. The shop asked me if Solidworks could do this and I responded that I was pretty sure the ability was there once it was modeled from a supplied drawing. Basically its a tapered fabricated plate girder with 2-1/2" thick flanges top & bottom and 1" web. See below for snips. I've also attached the .sldprt for reference along with all 6 split entities that were created once the Split feature was used. The results are being questioned since the left half side of the C.O.M. calculates to 1,000# heavier than the right side when referencing the C.O.M. point that Solidworks is figuring. First I modeled it then inserted the Center of Mass reference point. From there I sketched a vertical line coincident thru the COM point and used Split to make essentially 2 half weldments (this feature broke it from 3 into 6 bodies). I then used Evaluate to get my weights (used Grade 50 A709 that I created for material which should be about the same as A36 steel) of the 3 parts of the left half and when compared to the weight of the 3 pcs. of the right half, the left weighs over 1,000# more and the guys are questioning why since it would make sense that the sides have equal totaling weights. I've never used the COM feature before but was thinking that the point given by SW for the COM is a drop down height from top flange. Maybe I cannot just sketch a vertical line from this point and cut the weldment in half? But still, 1,000# greater is alot. Looking for comments / suggestions. As always, thanks for the help!


iso view:

front view:

shop snip: