Not necessarily. It is common OpenSCAD models to have to be repaired before slicing them. You may try repairing with the free MeshLab, or online using the Netfab online service: https://modelrepair.azurewebsites.net/ <https://modelrepair.azurewebsites.net/> Usually it works. On the other hand if you need to render and export an union of previously generated STLs with malformations, usually that will not be so simple and I can't help you, maybe someone in the forum with wider experience can. jpmendes -- View this message in context: http://forum.openscad.org/STL-Exports-Many-need-repair-and-I-can-t-tell-why-tp16463p16469.html Sent from the OpenSCAD mailing list archive at Nabble.com.