Alibre
1. File > Export
2. Save As > STL
3. Enter Filename
4. Save

AutoCAD
Note: you can only export 3D solid objects to STL
1. At the command prompt type "FACETRES"
2. Set FACETRES to 10
3. Type "STLOUT"
4. Select the objects
5. Enter Y or hit Enter for Create a binary STL file? [Yes/No] <Yes>
6. Enter Filename
7. Save

Autodesk 3ds Max (3D Studio MAX)
1. File > Export
2. Select type StereoLitho *.stl
3. Enter Filename
4. Save
5. Select Binary
6. OK

More information can be found here.

Bentley Microstation V8
1. File > Export
2. Choose file type STL. A dialog box opens.
3. Set Stroke tolerance to 0.05mm (0.002 in)
4. Select Binary
5. Click Export
6. Enter Filename
7. Click Save

Blender
1. File > Export > STL...
2. Enter Filename
3. Select location
4. Click button Export STL

Cadkey / KeyCreator
1. File > Export > STL
2. Enter Filename > OK
3. In the options dialog:
1. Change Format to Binary
2. Change "Facet Tolerance" if a higher resolution is required

Additional export tolerance options are in the Solids99 Configuration window accessed from the Tolerance section of Configuration.

Catia
The export to the STL format is only possible in the Part Design environment.
If you want to export a complete assembly (CATProduct) as a single stl file, you will have to convert the assembly in the Assembly Design environment to a CATPart as follows:
1. Select the entire product tree
2. Tools > Generate CATPart from Product
3. Enter New Part number
4. do NOT check: Merge all bodies of each part in one body
5. OK
Now you can export the CATPart in the Part Design environment.

The accuracy of the STL file depends on the Display accuracy. First set the display accuracy.
1. Tools > Options...
1. In the tree select General > Display
2. select the Performance tab
3. Under 3D Accuracy select Fixed
4. Set to 0.02 mm (0.0008 in)
5. Adjust Curves' accuracy ratio to 0.2
6. OK
2. File > Save As
3. Enter Filename
4. Select type stl
5. Save

Creo Direct (Creo Elements/Direct, CoCreate, OneSpace, SolidDesigner)
The Express Edition with some limitations is freely available from PTC
1. File > Save
2. Press Select > select the objects (or click All Objects)
3. Select File Type STL (*.stl)
4. Click Options
1. Check Binary
2. Max Deviation Distance: enter 0.025 mm (0.001 in)
3. Angle: enter 30°
5. Enter Filename
6. Save

Creo Parametric (Creo Elements/Pro, Pro/ENGINEER)
1. File > Save a Copy
2. Select type STL > OK
3. Select Coordinate System Standard
4. Check Binary
5. Set Chord Height to 0 (Pro/E changes it to the smallest allowable value)
6. Leave Angle Control at the default
7. Enter Filename > OK

I-DEAS
1. File > Export > Rapid Prototype File
2. Select the part
3. Select Prototype Device > SLA500 > OK
4. Set Absolute Facet Deviation to 0.000395
5. Select Binary > OK

Autodesk Inventor / Mechanical Desktop
You can export individual parts or whole assemblies.
1. Manage tab > Update panel > Rebuild All
2. File > Save as > Save Copy As
3. Select STL
4. Enter Filename
5. Select Options
1. Format > Binary
2. Units > mm or inches
3. Resolution > High
6. Save
More information can be found here.

Ironcad
1. Right Click on the part
2. Part Properties > Rendering
3. Set Facet Smoothing to 150
4. File > Export
5. Select .STL

Autodesk Revit
1. Download the STL Exporter from Autodesk Labs
2. Unzip and install using the installer for your version of Revit
3. Load the 3D model and select a view
4. External Tools > Export
5. Adjust and scale your model using a STL viewer
The STL Exporter exports one STL unit for every foot (304.8 mm) in your model. So use your calculator and carefully check the result in a STL viewer before 3D printing anything.

Rhino
1. File > Export Selected or File > Save As
2. Select the objects to be exported
3. Select File Type Stereolithography (*.stl)
4. Enter Filename
5. Save
6. in STL Mesh Export Options
1. Enter Tolerance 0.02 mm (0.0008 inches)
2. OK
7. Alternatively press Detailed Controls... which opens the dialog box Polygon Mesh Detailed Controls
1. Set Maximum angle to 30°
2. Set Maximum distance edge to surface to 0.02 mm (0.0008 inches)
3. Set Minimum intial grid quads to 16
4. Check Refine mesh
5. Leave all other controls at 0 or unchecked
6. OK
8. in STL Export Options
1. Select Binary
2. Uncheck Export Open Objects
3. OK
9. If you get the STL Export Warning dialog, Cancel and fix your modeling errors

Siemens PLM NX (Unigraphics)
1. File > Export > STL
2. Select Output Type Binary
3. Set Triangle Tol to 0.025 mm (0.001 in)
4. Set Adjacency Tol to 0.1 mm (0.04 in)
5. Set Auto Normal Gen to On
6. Set Normal Display to Off
7. Set Triangle Display to On
8. OK
9. Enter Filename > OK

Google Sketchup
Google Sketchup cannot export to STL natively. You will have to install a plugin. Here are the possibilities:
su2stl.rb plugin.
CADspan plugin
Convert Sketchup SKP files to DXF or STL
Sketchup to CNC
STL for Sketchup (stl4su) plugin
Alternatively export to .dae file, then import the .dae (COLLADA) file in Meshlab or Blender and export to .stl file.

Solid Edge (Siemens PLM)
1. File > Save As
2. Set type to STL
3. Click Options
1. Set conversion Tolerance to 0.025 mm (0.001 in)
2. Set Surface Plane Angle to 45.0°
3. Select Binary
4. OK
4. Enter Filename
5. Save

SolidWorks
1. File > Save As...
2. Set type to STL(*.stl)
3. Click Options...
1. Output as: check Binary
2. Unit: > Millimeters or Inches
3. Resolution > Fine
4. OK
4. Enter Filename
5. Save

SolidWorks Student Design Kit
1. File > Save As...
2. Set type to eDrawings(*.eprt)
3. Click Options...
1. Check Allow export to STL for Parts & Assemblies
2. OK
4. Enter Filename
5. Save
6. Open part in eDrawings
7. File > Save as… > select type STL Files (*.stl)
8. Save
Think3
1. File > Save As
2. Set type to STL
3. Save

Vectorworks
Vectorworks only exports the current layer to STL. Please read Tips for Users of VectorWorks.pdf on how to merge the layers into one layer.
1. File > Export > Export Stereolithography (3D Only)
2. In Export STL Options
1. check File Type ASCII
2. adjust the slider Export Quality towards the middle
3. OK
3. Enter Filename
4. Save

Alibre
1. File > Export
2. Save As > STL
3. Enter Filename
4. Save

AutoCAD
Note: you can only export 3D solid objects to STL
1. At the command prompt type "FACETRES"
2. Set FACETRES to 10
3. Type "STLOUT"
4. Select the objects
5. Enter Y or hit Enter for Create a binary STL file? [Yes/No] <Yes>
6. Enter Filename
7. Save

Autodesk 3ds Max (3D Studio MAX)
1. File > Export
2. Select type StereoLitho *.stl
3. Enter Filename
4. Save
5. Select Binary
6. OK

More information can be found here.

Bentley Microstation V8
1. File > Export
2. Choose file type STL. A dialog box opens.
3. Set Stroke tolerance to 0.05mm (0.002 in)
4. Select Binary
5. Click Export
6. Enter Filename
7. Click Save

Blender
1. File > Export > STL...
2. Enter Filename
3. Select location
4. Click button Export STL

Cadkey / KeyCreator
1. File > Export > STL
2. Enter Filename > OK
3. In the options dialog:
1. Change Format to Binary
2. Change "Facet Tolerance" if a higher resolution is required

Additional export tolerance options are in the Solids99 Configuration window accessed from the Tolerance section of Configuration.

Catia
The export to the STL format is only possible in the Part Design environment.
If you want to export a complete assembly (CATProduct) as a single stl file, you will have to convert the assembly in the Assembly Design environment to a CATPart as follows:
1. Select the entire product tree
2. Tools > Generate CATPart from Product
3. Enter New Part number
4. do NOT check: Merge all bodies of each part in one body
5. OK
Now you can export the CATPart in the Part Design environment.

The accuracy of the STL file depends on the Display accuracy. First set the display accuracy.
1. Tools > Options...
1. In the tree select General > Display
2. select the Performance tab
3. Under 3D Accuracy select Fixed
4. Set to 0.02 mm (0.0008 in)
5. Adjust Curves' accuracy ratio to 0.2
6. OK
2. File > Save As
3. Enter Filename
4. Select type stl
5. Save

Creo Direct (Creo Elements/Direct, CoCreate, OneSpace, SolidDesigner)
The Express Edition with some limitations is freely available from PTC
1. File > Save
2. Press Select > select the objects (or click All Objects)
3. Select File Type STL (*.stl)
4. Click Options
1. Check Binary
2. Max Deviation Distance: enter 0.025 mm (0.001 in)
3. Angle: enter 30°
5. Enter Filename
6. Save

Creo Parametric (Creo Elements/Pro, Pro/ENGINEER)
1. File > Save a Copy
2. Select type STL > OK
3. Select Coordinate System Standard
4. Check Binary
5. Set Chord Height to 0 (Pro/E changes it to the smallest allowable value)
6. Leave Angle Control at the default
7. Enter Filename > OK

I-DEAS
1. File > Export > Rapid Prototype File
2. Select the part
3. Select Prototype Device > SLA500 > OK
4. Set Absolute Facet Deviation to 0.000395
5. Select Binary > OK

Autodesk Inventor / Mechanical Desktop
You can export individual parts or whole assemblies.
1. Manage tab > Update panel > Rebuild All
2. File > Save as > Save Copy As
3. Select STL
4. Enter Filename
5. Select Options
1. Format > Binary
2. Units > mm or inches
3. Resolution > High
6. Save
More information can be found here.

Ironcad
1. Right Click on the part
2. Part Properties > Rendering
3. Set Facet Smoothing to 150
4. File > Export
5. Select .STL

Autodesk Revit
1. Download the STL Exporter from Autodesk Labs
2. Unzip and install using the installer for your version of Revit
3. Load the 3D model and select a view
4. External Tools > Export
5. Adjust and scale your model using a STL viewer
The STL Exporter exports one STL unit for every foot (304.8 mm) in your model. So use your calculator and carefully check the result in a STL viewer before 3D printing anything.

Rhino
1. File > Export Selected or File > Save As
2. Select the objects to be exported
3. Select File Type Stereolithography (*.stl)
4. Enter Filename
5. Save
6. in STL Mesh Export Options
1. Enter Tolerance 0.02 mm (0.0008 inches)
2. OK
7. Alternatively press Detailed Controls... which opens the dialog box Polygon Mesh Detailed Controls
1. Set Maximum angle to 30°
2. Set Maximum distance edge to surface to 0.02 mm (0.0008 inches)
3. Set Minimum intial grid quads to 16
4. Check Refine mesh
5. Leave all other controls at 0 or unchecked
6. OK
8. in STL Export Options
1. Select Binary
2. Uncheck Export Open Objects
3. OK
9. If you get the STL Export Warning dialog, Cancel and fix your modeling errors

Siemens PLM NX (Unigraphics)
1. File > Export > STL
2. Select Output Type Binary
3. Set Triangle Tol to 0.025 mm (0.001 in)
4. Set Adjacency Tol to 0.1 mm (0.04 in)
5. Set Auto Normal Gen to On
6. Set Normal Display to Off
7. Set Triangle Display to On
8. OK
9. Enter Filename > OK

Google Sketchup
Google Sketchup cannot export to STL natively. You will have to install a plugin. Here are the possibilities:
su2stl.rb plugin.
CADspan plugin
Convert Sketchup SKP files to DXF or STL
Sketchup to CNC
STL for Sketchup (stl4su) plugin
Alternatively export to .dae file, then import the .dae (COLLADA) file in Meshlab or Blender and export to .stl file.

Solid Edge (Siemens PLM)
1. File > Save As
2. Set type to STL
3. Click Options
1. Set conversion Tolerance to 0.025 mm (0.001 in)
2. Set Surface Plane Angle to 45.0°
3. Select Binary
4. OK
4. Enter Filename
5. Save

SolidWorks
1. File > Save As...
2. Set type to STL(*.stl)
3. Click Options...
1. Output as: check Binary
2. Unit: > Millimeters or Inches
3. Resolution > Fine
4. OK
4. Enter Filename
5. Save

SolidWorks Student Design Kit
1. File > Save As...
2. Set type to eDrawings(*.eprt)
3. Click Options...
1. Check Allow export to STL for Parts & Assemblies
2. OK
4. Enter Filename
5. Save
6. Open part in eDrawings
7. File > Save as… > select type STL Files (*.stl)
8. Save
Think3
1. File > Save As
2. Set type to STL
3. Save

Vectorworks
Vectorworks only exports the current layer to STL. Please read Tips for Users of VectorWorks.pdf on how to merge the layers into one layer.
1. File > Export > Export Stereolithography (3D Only)
2. In Export STL Options
1. check File Type ASCII
2. adjust the slider Export Quality towards the middle
3. OK
3. Enter Filename
4. Save