Cad to STL


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If you've ever ordered a prototype or production part online, your part may have looked different than you expected. Why? Because sometimes data is lost when you convert your file from CAD to STL.

Since nearly every rapid prototyping and digital manufacturing (end-use parts) organization uses STL files to build parts, it is important to understand what STL is and what settings you can adjust to get the part you really want.

The .STL file format has turned into the Rapid Prototyping industry's standard data transmission format. This format approximates the surfaces of a solid model with triangles. For a simple model, such as the box shown in figure 1, its surfaces can be approximated with twelve triangles, two on each side, as shown in figure 2. The more complex the surface, the more triangles produced as shown in figure 3.

Rapid prototype CAD file

Almost all of today's CAD systems are capable of producing an STL file. For the user, the process is often as simple as selecting File, Save As and STL. Below are steps for producing high quality STL files from a number of today's leading CAD systems.

General Steps

Most CAD packages will have a couple of options that affect the quality of the STL.

  • Changing a "Deviation" type of value will alter the overall output or tessellation.
  • Changing an "Angle Tolerance" type of value will alter smaller details in your file.

The tighter these parameters, the more triangles placed on the surface of the model.

  • Simple geometries tend to be a few hundred kilobytes in size.
  • Complex models will range from 1-5MB in size and still produce good parts.
  • For many models, files larger then 5MB may be unnecessary and often result in more time to get your quote and models back.

In all cases, export your STL file as a binary file. This saves on time and file size.

Please note, these are general guidelines and may not work or in some cases, produce the best possible STL file. Please consult your user's guide or the software developer's for more information or technical support. Should we determine that your STL file is not adequate for production, we will contact you for an updated file.

PDF Download CAD to STL Guide


  • First check for errors
  • An STL object must define a complete and closed surface. Use STL-Check modifier to test your geometry before exporting your object to STL.
  • Select an object.
  • Click Modify
  • Click More ...
  • Select "STL-Check" under Object-Space Modifiers
  • Select Check
  • If there are no errors, continue to export the STL file by:
  • Clicking File> Export
  • Select "StereoLitho [*.STL]" in Save as type
  • Select location in Save in
  • Enter a name in File name
  • Click Save; OK
  • Export To STL dialog:
  • Object Name: Enter a name for the object you want to save in STL format.
  • Binary/ASCII: Choose whether the STL output file will be binary or ASCII (character) data. ASCII STL files are much larger than binary STL files.
  • Selected Only: Exports only objects that you selected in the 3D Studio scene


  • File
  • Export
  • Save As > STL
  • Enter File Name
  • Save

STL settings: How to change STL settings.

  • Tools > Options
  • File Types tab<
  • Configure File Types: STL
  • Normal Deviation: 5

(Smaller deviations will produce a smoother file, but the file size will get larger)


  • Click Output > Send panel > Export. At the Command prompt, enter export.
  • In the Export Data dialog box, enter a file name.
  • Under Files of Type, select Lithography (*.stl). Click Save.
  • Select one or more solid objects. All objects must be entirely within the positive XYZ octant of the world coordinate systems (WCS). That is, their X, Y, and Z coordinates must be greater than zero.

The file extension .stl is automatically appended to the file name

Autodesk Inventor

  • Save Copy As
  • Select STL
  • Choose Options > Set to High (for highest quality surface)
  • Enter File Name
  • Save

Note: The "High" setting will also produce the largest file size. From Low, Medium to High, the Hairdryer sample file in Inventor went from about 6.7MB to 17.6MB to 50MB. Below are images from this sample file with the various settings:

Low Medium High
Low Medium High


  • File>Export>STL
  • Type a file name and select OK
  • Change format to binary
  • Use default facet tolerance
  • Additional export tolerance options are in the Solids99 Configuration window accessed from the Tolerance section of Configuration.


  • In the File pull-down menu, select Export STL file.
  • Click Save


  • Transfer the data into 3Data Expert through IGES file
  • Give command Solid/Triangulate in 3Data Expert
  • A watertight STL file is generated
  • Surface accuracy control during the process is easy
  • To check for a good STL file:
  • Orient surface normals and check for errors with Solid/Repair command

Google Sketchup

  • Download Sketchup to DXF or STL plugin.
  • To use the plugin, download the file below (skp_to_dxf.rb) to the Sketchup plugins folder on your computer. [VERSION] stands for the Sketchup version number (6, 7 or 8).
  • On a Windows PC: If you’ve installed Sketchup on the C: drive, this folder will be at C:\program files\google\google sketchup [VERSION]\plugins.
  • On Mac OSX: The sketchup plugins folder is /Library/Application Support/Google SketchUp [VERSION]/SketchUp/Plugins
  • After copying this file, start Sketchup. You should now have an extra menu option (Export to DXF or STL) in the Sketchup Tools menu.

Iron Cad

  • Select Part Properties, then Rendering
  • Set facet surface smoothing to 150
  • Select File, then Export
  • Select .STL

Mechanicak Desktop

1. Use the AMSTLOUT command to export your STL file.
2. The following command line options affect the quality of the STL and should be adjusted to produce an acceptable file:

  • Angular Tolerance: This command limits the angle between the normals of adjacent triangles. The default setting is 15 degrees. Reducing the angle will increase the resolution of the STL file.
  • Aspect Ratio: This setting controls the height/width ratio of the facets. A setting of 1 would mean the height of a facet is no greater than its width. The default setting is 0, ignored.
  • Surface Tolerance: This setting controls the greatest distance between the edge of a facet and the actual geometry. A setting of 0.0000 causes this option to be ignored.
  • Vertex Spacing: This option controls the length of the edge of a facet. The default setting


  • File > Export > Model (or File > Save a Copy)
  • Set type to STL
  • Set chord height to 0. The field will be replaced by minimum acceptable value.
  • Set Angle Control to 1
  • Choose File Name

ProE Wildfire

  • File > Save a Copy > Model
  • Change type to STL (*.stl)
  • Set Chord Height to 0. The field will be replaced by minimum acceptable value.
  • Set Angle Control to 1
  • OK


  • Open the model design in Rhino.
  • From the File menu, select Save As. The Save dialog box opens.
  • In the File name box, enter a name for the new STL file.
  • In the Save as type box, select Stereolithography [*.stl].
  • Click Save.
  • In the STL Mesh Export Options dialog box (Simple Controls), set the STL tolerance – the maximum distance allowed between the surface of the design and the polygon mesh of the STL file.
  • In the Polygon Mesh Detailed Options dialog box, set the STL tolerance in the field labeled Maximum distance, edge to surface, as shown in the figure. (please refer to the STL help in Rhino for setting definitions)
  • Click OK.
  • In the STL Export Options dialog box, set the file type as Binary and click OK.

NOTE: In order to build on additive manufacturing technologies, STL files must contain completely closed (watertight) polygon mesh objects. Refer to Rhino’s STL help for more information.


  • File > Save As
  • Set Save As Type to STL
  • Options
  • Set Conversion Tolerance to 0.001in or 0.0254mm
  • Set Surface Plan Angle to 45.00
  • Save


  • File > Save As
  • Set Save As Type to STL
  • Options > Resolution > Fine > OK
  • Save<

STL settings: How to change STL settings.

  • File > Save As
  • STL > Options
  • For a smoother STL file, change the Resolution to Custom
  • Change the deviation to 0.0005in (0.004 mm)
  • Change the angle to 5
(Smaller deviations and angles will produce a smoother file, but the file size will get larger)


  • File > Export > STL
  • Set Output type to Binary
  • Set Triangle Tolerance to 0.001
  • Set Auto Normal Gens to On
  • Set Normal Display to Off
  • Set Triangle Display to Off


  • Select AEC object . Go to 3D SOLID menu & select convert to 3D SOLID  (ENTER)
  • After that you will have an option: Erase selected object [Yes/No]  <Yes>: Enter Y
  • All the objects are converted into 3D Solid using the same procedure for each AEC objects
  • Select a single solid for STL output... (Must be ONE solid to export to STL)
  • Command entry: stlout
  • Select objects: Use an object selection method and press ENTER when you finish
  • Create a binary STL file? [Yes/No] <Yes>: Enter Y


Revit doesn't allow direct export to STL files. We have to first save in dwg file and open in AutoCAD to create STL files.

  • Go to 3D view
  • Go to File menu , select Export CAD format
  • A dialog box opens
  • Select option
  • Scroll down the drop down menu (3D view only) & select 3D polymesh
  • Select “ AutoCAD 2004 DWG “ in <Save as type>
  • Next open the saved file AUTO CAD
  • Enter < Explode > on the command menu
  • Select the object and press <enter>
  • All the objects are converted into 3D solid
  • Select a single solid for STL output... (Must be ONE solid to export to STL)
  • Enter < stlout>  or <export > on the command menu
  • Select objects: Use an object selection method and press < ENTER > when you finish
  • Create a binary STL file? [Yes/No] <Yes>: Enter y
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