Title: Why does SHELL sometimes remove the wrong face from a 3D solid?

[indiancad]

Have you ever used SHELL on a 3D solid, expecting to create a hollow part, but ended up with an unexpected opening?

One thing I check first is whether I selected the correct face to remove. The face selection determines where the solid opens, while the shell thickness controls the remaining wall thickness.

For a more predictable result, I inspect the model from different viewing angles before applying the operation. I also check whether the chosen thickness is suitable for the size and shape of the part.

A small selection mistake can change the entire result.

When creating hollow 3D parts, do you prefer SHELL or do you usually model the inner geometry and use SUBTRACT?