CG location assignment 1

[windell]

I'm new to solidworks and I'm attempting to manually assign the CG location of a part. I would also like to assign a mass to the part. The part was imported in the iges format and was saved as a part. I've tried to modify the values under tools->mass properties, but when i change the values and click okay the location doesn't change to what I want it to be.

Does anyone know what I might be doing wrong?

Thank you for your time!

 

[Eltron]

Have you tried changing the material to what you want it to be? That would adjust the mass properties of your part.

Dan

http://www.eltronresearch.com

Dan's Blog

 

[ctopher]

You want to adjust the CG location of the part? Add the material to the part, then show the mass properties, it will give you the CG.
You need to change the part to move the CG.

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 08
ctopher's home (updated Aug 5, 2008)
ctopher's blog
SolidWorks Legion

 

[CorBlimeyLimey]

Does anyone know what I might be doing wrong?

Yes, you are trying to change the laws of physics.

The CoG is determined by the shape and mass of the object.
You need to adjust the distribution of the mass by altering the shape if you want to re-position the CoG. You cannot just arbitrarily set the CoG wherever you want.

 

[GregLocock]

One workaround would be to add six buttons of highly dense material around the thing's periphery, and adjust the volume of each button to get the reported cg of the assembly into the correct place.

This is not really very clever, as the moments of inertia will be wrong, even if you get the mass and cg location right.

I susect that it might be quicker to find out why the calculated cg and mass is wrong.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[SincoTC]

I agree with CBL and GregLocock and others that you shouldn't be messing with the laws of physics and the solid model should reflect the real world, so if it's a simple model, finding out where the geometry is wrong is the way to go.

However, if the solid model represents a bought in manufactured item that contains many items of different materials, then getting the Mass and CG correct can be a frustrating and time consuming business. Thankfully, SolidWorks does allow you to easily handle these circumstances.

Go to Tools > Mass Properties and Tick the third checkbox "Assigned mass properties" then manually enter the total Mass of the assembly and the co-ordinates of the center of gravity relative to the planes, in the pop-up box.

Hope this helps.



Trevor Clarke. (R & D) Scientific Instruments.Somerset. UK

SW2007x64 SP3.0 Pentium P4 3.6Ghz, 4Gb Ram ATI FireGL V7100 Driver: 8.323.0.0
SW2007x32 SP4.0 Pentium P4 3.6Ghz, 2Gb Ram NVIDIA Quadro FX 500 Driver: 6.14.10.7756

 

[GregLocock]

Ah, well there was bound to be a sensible way of doing it!

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.