How To Create a Good STL File When producing a part from an STL file, it is essential that the part’s geometry is represented as closed surfaces that unambiguously define an enclosed volume. Any gaps, overlapping or missing surfaces can lead to incorrect geometry being built, or can even cause a total build failure. Bad file – Section of an STL file showing ambiguous design intent. Good file – Section of an STL file showing a good part with one integral surface STL Resolution When exporting an STL file from CAD software, the resolution (also known as Tolerance, Chord Height or Facet Deviation) can be specified. Under-faceted STL files will compromise the final part accuracy and will be visible on the final produced item. Over-faceted STL files will increase the time taken to process the part and will not improve the quality of the final part. There is therefore an optimum tolerance for the STL file. From our experience the tolerance is best set to 0.01mm for an STL file, with Binary as the file format – and this is what we recommend to our customers for best results.