Good Morning, all
I have a problem when differencing one solid from another. I have to create a shell for foundry purposes. I've done this at least 20 times without problems, but, this one causes me an unexplained problem. I have a basic shape (Shape1) and I create a solid larger (Shape2) than the basic shape by size and thickness. Before the difference command both shapes are solids. I slide Shape1 into Shape2 leaving a border of 1/32". I execute the difference command and all appears to work, but, when I remove the Shape1 from Shape2, the difference is not shown in Shape2, but now Shape2 indicates a "surface" and is no longer a solid. I am baffled. I'm running version 2 of MOI. If confused about shells, it would be the equivalent of pushing shape into wet cement and removing the shape thus leaving the cement with a copy of the shape pushed in.

Hi Bob, well the first thing I'd recommend is trying MoI v3 and see if it works any better. You can get the 30-day trial version from here: http://moi3d.com/download.htm . There were numerous fixes in v3 to all sorts of things.

If that doesn't do any better then it's probably related to something in the structure of these particular objects, if one of the objects contains any degenerate surfaces in it (meaning surfaces collapsed down to just a thin sliver with no real surface area to it), or degenerate trimming boundaries (edges that do some kind of loop-de-loop crossing over themselves), then that can cause problems with mechanisms that try to analyze what volumes things are contained inside of.

I could probably give you better information if I could examine your model file, can you post the 3DM file as a file attachment here or e-mail it to me at moi@moi3d.com if you want to keep it private?

- Michael