How to export surface to .stl file?

[Anonymous]

Hi, I've got a problem to transfer .dwg to .stl file. My drawing is a surface, I know .stl transfer needs a solid but I cannot convert my surface to a solid. Does anyone know how to transfer? Here is my file. Thank you.

[Anonymous · Accepted solution]

THICKEN

[Anonymous]

Thank you so much! It works~