ProE

Once the part or assembly is created in 3D and is in positive space:
  1. File > Export > Model
  2. STL
  3. Set chord height to 0. The field will be replaced by minimum acceptable value.
  4. Set Angle Control to 1
  5. OK
For additional questions refer to your manual, MIS department or the Maker of the software: PTC

Select your CAD program in the pulldown menu to view the recommended settings for exporting an STL file