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How to convert a CAD file to an STL file?

Tutorial by GrabCAD Tutorials
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STL is the standard file type used by most or all rapid prototyping systems. A STL is a triangulated representation of a 3D CAD model (figure 1). The triangulation of a surface will cause faceting of the 3D model. The parameters used for outputting a STL will affect how much faceting occurs (figure 2 and 3). You cannot build the model any better or smoother than the STL file, so if the STL is coarse and faceted, that is what you can expect in the final model.

In the CAD package, when exporting to STL, you may see parameters for chord height, deviation, angle tolerance, or something similar. These are the parameters that affect the faceting of the STL.You don’t necessarily want to go too small. The finer the STL the larger the file is in size, which will affect processing time in Insight as well as build time. Below is some information found on the Internet regarding exporting to STL from various CAD packages.

  1. Step 1:

    3D Studio Max

    1. First check for errors
    2. An STL object must define a complete and closed surface. Use STL-Check modifier
    to test your geometry before exporting your object to STL.
    3. Select an object.
    4. Click Modify
    5. Click More ...
    6. Select “STL-Check” under Object-Space Modifiers
    7. Select Check
    8. If there are no errors, continue to export the STL file by:
    9. Clicking File>Export
    10. Select “StereoLitho [*.STL]” in Save as type
    11. Select location in Save in
    12. Enter a name in File name
    13. Click Save; OK
    14. Export To STL dialog:
    15. Object Name: Enter a name for the object you want to save in STL format.
    16. 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.
    17. Selected Only: Exports only objects that you selected in the 3D Studio scene.

  2. Step 2:

    Alibre

    1. File
    2. Export
    3. Save As > STL
    4. Enter File Name
    5. Save

  3. Step 3:

    AutoCAD

    1. Click Output > Send panel > Export. At the Command prompt, enter export.
    2. In the Export Data dialog box, enter a file name.
    3. Under Files of Type, select Lithography (*.stl). Click Save.
    4. Select one or more solid objects. All objects must be entirely within the positive XYZ octant of the world coordinate system (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.

  4. Step 4:

    AutoDesk Inventor

    1. Save Copy As
    2. Select STL
    3. Choose Options > Set to High
    4. Enter Filename
    5. Save

  5. Step 5:

    CADKEY

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

  6. Step 6:

    DataCAD

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

  7. Step 7:

    Deskartes-3D Data Expert

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

  8. Step 8:

    SketchUp

    1. Download Sketchup to DXF or STL plugin.
    2. 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).
    3. 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.
    4. On Mac OSX: The sketchup plugins folder is /Library/Application Support/Google
    SketchUp [VERSION]/SketchUp/Plugins
    5. After copying this file, start Sketchup. You should now have an extra menu option (Export to DXF or STL) in the Sketchup Tools menu.

  9. Step 9:

    IronCAD

    1. Select Part Properties, then Rendering
    2. Set facet surface smoothing to 150
    3. Select File, then Export
    4. Select .STL

  10. Step 10:

    Mechanical 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 is 0.0000, ignored.

  11. Step 11:

    Pro E

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

  12. Step 12:

    Pro E Wildfire

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

  13. Step 13:

    Revit

    Revit doesn’t allow direct export to STL files. First save in dwg file and open in AutoCAD to
    create STL files.
    1. Go to 3D view
    2. Go to File menu , select Export CAD format
    3. A dialog box opens
    4. Select Option
    5. Scroll down the dropdown menu (3D view only) and select 3D polymesh
    6. Select “AutoCAD 2004 DWG” in Save as type
    7. Next, open the saved file AUTO CAD
    8. Enter “Explode” on the command menu
    9. Select the object and press Enter
    10. All the objects are converted into 3D solid
    11. Select a single solid for STL output (must be one solid to export to STL)
    12. Enter “stlout” or “export” on the command menu
    13. Select objects: Use an object selection method and press Enter when you finish
    14. Create a binary STL file? [Yes/No]: Enter y

  14. Step 14:

    Rhino

    1. Open the model design in Rhino.
    2. From the File menu, select Save As. The Save dialog box opens.
    3. In the File name box, enter a name for the new STL file.
    4. In the Save as type box, select Stereolithography [*.stl].
    5. Click Save.
    6. 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.
    7. 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)
    8. Click OK.
    9. In the STL Export Options dialog box, set the file type as Binary and click OK.

  15. Step 15:

    SolidEdge

    1. File > Save As
    2. Set Save As Type to STL
    3. Options
    4. Set Conversion Tolerance to 0.001in or 0.0254mm
    5. Set Surface Plane Angle to 45.00
    6. Save

  16. Step 16:

    SolidWorks

    1. File > Save As
    2. Set Save As Type to STL
    3. Options > Resolution > Fine > OK
    4. Save

  17. Step 17:

    Think3

    1. File>Save As
    2. Set Save As Type to STL
    3. Save

  18. Step 18:

    UGS NX 6

    1. File > Export > STL
    2. Set Output type to Binary
    3. Set Triangle Tolerance to 0.001
    4. Set Adjacency Tolerance to 0.001
    5. Set Auto Normal Gen to On
    6. Set Normal Display to Off
    7. Set Triangle Display to Off

  19. Step 19:

    Unigraphics

    1. File>Export>Rapid Prototyping
    2. Set output type to binary
    3. Set triangle tolerance to 0.0025
    4. Set adjacency tolerance to 0.12
    5. Set auto normal gen to on
    6. Set normal display to off
    7. Set triangle display to on

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