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Having trouble making a shell out of a part

Question asked by Alex Powers on Apr 16, 2018

I've got a model of the spine I'm trying to use for an FEA, and because the human spine is a thin shell of one type of dense outer bone (cortical) outside an inner core of spongy (trabecular) bone, I've been trying to model a part as a shell with an inner core so I can make it 2 different materials. One of the models I'm working on (I'm looking at a few) is an stl I'm using MeshLab to reduce down to a mesh with 10000 faces and importing into SolidWorks (I tried to make it up to 50000 faces but SolidWorks crashed whenever trying to deal with more than 10000- I don't know if this makes a difference here but I have the student version). I've been able to easily import it as a solid or as a surface, but no matter how I import it, I'm having a lot of issues making it into a shell. I've tried using the shell feature with a solid body, the extend surface feature, and the offset surface feature, but all of them fail, and I'm not sure what to do or if I'm going to be able to use this model without some major editing.


I suspect that the laminae might be contributing heavily to the problem, because they're pretty complex surfaces with some pretty sharp curves (both convex and concave). For the purposes of my model, it doesn't really matter if the laminae are shells with two different types of material or solids with a single material, but the body of the vertebrae need to be an outer shell about .29 mm thick of one material and an inner core of another material. I've tried removing the laminae but have had issues doing that successfully, partially because of the sheer number of faces and partially because I'm having trouble getting it to cut out the laminae without also cutting out part of the disk. I've tried shelling inwards and outwards, and SolidWorks says it can't shell or offset the surface or whatever it is I'm trying to do every time, and when I use offset surfaces it tells me to try to use a smaller offset distance. Does anyone have any suggestions as to how I could make this model work, or is it a lost cause?


I've attached the models of the two disks with 10000 faces each and the original models I was trying to use with 50000 faces.