Autodesk Alias: Converting to STL (Open surfaces)


My name is Ankishu Gupta and I am an Automotive Design student. I’d like to share with you my method of converting surface models built in Autodesk Alias to .stl @iles ready for 3D Printing/Rapid Prototyping.

In this short tutorial, I will be using Autodesk Alias Autostudio for modeling and converting, and Netfabb basic for checking the .stl @ile. (Netfabb Basic can be acquired for free at:

Please note that this page is speci@ically for Alias models that are not a closed volume by design, for a closed volume tutorial please see my other tutorial titled: Autodesk Alias: Converting to .stl (Closed Volume)

Few things to keep in mind:

• We need a watertight model for it to be printable.

• The data need to be 3D geometry, since we are converting open surfaces, we will need to add thicknesses.

• Finding a balance between data resolution and @ile size.

Lets get started! I will be using a simple model of a rear door for this demonstration.

1) First, we need to make sure that all our normals are pointing in the same direction. We can view and change this using the Set Orientation (setor) tool under Surface Edit in the palette. Once the tool is selected it will show the normals in blue and yellow. Blue is facing outward whereas yellow is inward. Use the left mouse button to invert yellows to blue, you can also drag select.



2) We need to validate that all our surface boundaries are continuous to at least G0 Position. This can be done using the drop down in the control panel, choosing modelling, and then selecting G0 under check_continuity. Then click on any boundary edges and as long as all the edges show up green, we are good to go. If not re-align the edges.



3) Now we can begin the conversion and exporting process; select all the surfaces you would like to export. Go to File >Export > Rapid Prototype…, a dialogue box will pop up. Make sure the File Format is set to STL and hit accept.



4) The next step is to verify that all our surfaces are showing up as a single shell with a single boundary. We can do this by looking at the prompt line (below the menu bar) As shown in the image, the prompt line states “Created 1 shell with 1 boundary”. This is what we are aiming for. Now we can select “Accept” and the surfaces will be converted into meshes in the viewport.


5) Now we can experiment with the resolution of our mesh. This is important because the denser the mesh, the large the file size and the longer it will take the computer to process it. It will also be a hassle to upload large files for a quote.

Decreasing the Max Edge Length will increase the number of triangles the mesh is made up of. If the data you are wanting to print is made up of many curved surfaces then it is advisable to increase the resolution by decreasing the max edge length. The opposite goes for a model with flatter surfaces.



6) Since the model we started with consisted of open surfaces, we now need to add thickness to the mesh we just created. To do this, simple check the Wall Thickness option and select the required thickness. Once you the mesh meets requirements, just hit export to save the file as a .stl to the PC.



7) Now that the .stl file has saved, open it in Netfabb to make double check that it is printable. If everything is fine then the model will show up green. you can now upload this fine for a quote. All done!