# Volume and mass property estimation of shape drawn in GSD

#### rb08

##### Newbie
Hi

I generted a shape by exporting points from excel . It is similar to some airfoil shape. After that I revolved the shape and created a closed volume (I call it V1). Than I gave an offset to the shape and from this I used volume revolve and created a new volume inside the earlier one (I call it V2). (The offset value was very small as compared to the actual dimensions of the body)
Finally I removed the new volume from the earlier created volume(I call it V3). This gave me an airfoil shape with small (very small)thickness. I wanted to measure the mass, volume and inertia properties of this new volume.

According to common sense, V1 - V2 = V3 . But CATIA is giving results different from it. Plz help me to understand if there is any error on my part or this is some mathematical approximations used by CATIA.(Error is close to 20-30 %). I tried to use it for different volumes but the error is still creeping in. Plz help !!

#### MrCATIA

##### Super Moderator
Since the transistion from CATIA V4 to V5, Volumes have not been used very much - V5 solid modeling has almost replaced the need to use Volumes. So, I can't respond to your problem. I just don't have much experience using that type of geometry. And my current employer doesn't use Volumes (and didn't waste their money on the license), so I can't even try to repeat what you have done.

I agree with your steps; V1 minus V2 should equal V3! (assuming V2 is smaller and totally inside V1) I'm not sure why you're not getting the correct results. Does the volume of V2 appear to be correct based on the volume of V1?

Maybe someone else could make up a little surface model, repeat your steps, and let us know the results.

Which release of CATIA are you using?

You could easily perform the same steps with solids, using the Part Design workbench. Might even be easier.

1. revolve the original shape to create a SHAFT feature. The volume of the SHAFT should be the same as the volume of V1.

2. use the SHELL command to hollow out the shaft, leaving the thin-walls on all sides.

3. MEASURE the volume of the PartBody. Should be the correct value of V3.

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#### rollicker

##### Newbie
Hey
How are you removing the volumes? You have to create the volumes V1 and V2 under two separate bodies (for example let V1 be under Body.1 and V2 under Body.2) and then use boolen operation to remove Body.2 from Body.1. Then the resulting Body.1 is your actual V3. If you do by procedure, you will exactly find V1-V2 = V3.
All the best!