Currently quilts can not be exported as STLs as is documented in https://support.ptc.com/appserver/cs/view/solution.jsp?n=CS67713&lang=en&source=snippet . This appears to be a restriction based on the original intended use of STLs for stereolithography. STLs have since been applied to other use cases, including ones that require STLs generated from surfaces, not just STLs generated from solids. Nearly every other CAD package includes support for STLs generated from surfaces. Adding support for STL generation from surfaces would be beneficial and help keep Creo on par or ahead of other packages.