Calculating volume of voids can be done fairly easily. In this example we will find the volume of the material removed during the shell.
I know this is pretty basic geometry but the principal is the same.
Create a sketch that fits the inside of the shell, you can convert entities or in this case just draw in a rectangle. Extrude this upto next, make sure to clear the merge result check box.
Now you can select a body to get just that solids information as seen below using the mass properties command to extract volume or mass.
I know now you thinking how would we get all of the voids if we needed the rest of them too? This is a slight modification to the sketch and edit the extrusion end condition to be upto surface and pick the back face of the model.
Now we use the combine feature, subtract. Where is it? Insert, features, combine.
Now we can use mass properties to get the sum of the remaining bodies.
What if it is an odd shape? In some cases you can use just a big box around the whole part, subtract like we did and then delete unnecessary bodies. Or you might have to get creative.
Here I used the body and an extruded surface to help me create a knit surface. Using the try to form solid option allowed me to have a body with the same shape as the original.
Then combine and subtract again.
John Van Engen
CATI Tech Support