The model that you plan to 3D print should be completely closed and water tight. The easiest way to accomplish this is to be a meticulous 3D modeler - paying close attention to seams and joins in your model.
Suggestions for Successfully Creating a 3D Digital Model:
Use SNAPS and OBJECT SNAPS while modeling so that you can line up objects according to their endpoints or other geometrical identifiers.
- Join curves and surfaces as you build them. Keeping things joined as you work will help you know that your objects are truly coincident and closed. The JOIN command will not work if things are not lined up properly so this is a good check.
- Cylindrical features are more accurate when the cylindrical axis is parallel to the z-axis.
- Make sure that a flat surface is not made up of multiple geometries as this can cause it to print incorrectly.
- Make sure your file is set to INCHES
- Every element of the model must have thickness.
Exporting from Rhino for 3D Printing
Quick tips for cleaner modeling in Rhino3D
1- Always model using OSNAPs turned on. This stands for Object Snap and allows you to move geometry using its exact geometric attributes.
2- Turn the Near from the OSNAP off to decrease the possibility of having an open object. We use Near only if it is necessary.
3- If possible, always build closed geometry as you work. Regularly employing the Join for surfaces and Boolean Union or Boolean difference for 3d object. Failure of these commands is a fast indicator your 3D model is not watertight!
- List of useful commands to create closed NURBS volumes:
ExtrudeSrf + Cap (to close it)
ExtrudeCrv (must be closed curve)
4- After you finish modeling, the first thing you should do is to use ShowEdges command to make sure the object is closed. The image below shows an open object vs a closed object. The open surfaces are shown with purple edges in Rhino after you use ShowEdges. Remember to choose Naked Edges in the list of ShowEdges Command.
5- If your 3d model was carefully built in Rhino3D using NURBS geometry the first step in preparing a print file is to convert the model into a mesh using the “mesh” command. The main difference between a NURBS surface and a mesh is that the former is defined by curve functions rather than simple planar polygons. NURBS (non-uniform rational bsplines) volumes are usually computationally much heavier than meshes and therefore meshes are used to create file paths for 3dprinting. Thus when converting a NURBS model to mesh you must define resolution at which to replicate the original geometry using simple planar polygons. Ideally, you would aim to use the fewest amount of polygons to complete the desired geometry. (ie. sinuous surfaces will require much more polygons than flat straight surfaces)
a. this command will usually open a quick dialogue box that gives you the option of defining the resolution at which your model will be converted into meshes.
6- After your model has been converted to a mesh with the desired resolution (may take several attempts) you will run the “ShowEdges” command. If your geometry was built properly you will have no naked edges or non-manifold edges and may proceed to Step
7- Ok you, trouble makers. You’re here because your model had either naked edges, non-manifold edges or a combination of both. It is now the time to use your modeling discretion to asses the problem and decide whether it is better/easier/faster to correct the issue in its current mesh state or return to the original NURBS geometry and remodel components.
a. A NURBS remodel solution
i. This is usually the best option when dealing with naked edges/non-manifold edge counts over 100. A quick inspection of the highlighted edges may show how a quick remodel of a surface may dramatically decrease this error result. If this is the case, you simply need to undo the meshing process and correct the problem areas.
b. A mesh remodel solution
i. Many times “ShowEdges” results will be rather low (ex. ranges from 120). In this case, it may be easier/faster to edit the mesh directly. Once converted to a mesh there are many more possible options for correcting open geometry due to the fact you are able to manipulate polygons independently.
ii. List of useful commands to create closed mesh volumes:
MeshRepair (this command was created as a consolidation of many mesh tools and has a more interface friendly guide than most commands, although may produce undesired results due to its preset settings and therefore must be used with precaution)
iii. In rare occasions, complex geometry may produce errors that in turn cause glitches within rhino3D and prevent you from creating fully closed or functioning volumes. As a last resort, you may try to use https://netfabb.azurewebsites.net/
This a free service software produced by Microsoft for repairing 3D models. Essentially, you upload your 3d model (.stl, .obj, .3mf and others available) and download a newly repaired version. Unfortunately, results highly vary and extra precaution must be taken after attempting this course of action. (an inspection within Rhino3d afterward is recommended. Please note that a Microsoft account is required to use service)
8- You may now seamlessly export and convert your model into the format required by 3dPrinting filepath software. (usually .stl or .obj) Select geometry and run the “Export” command.
Now we know our object is closed and we export our object to STL by selecting the object and go to File>Export Selected > Choose STL* > choose a file name > Save > Binary + uncheck export open objects > ok
- Binary or ASCII
STL files can store information in two different ways. These are Binary encoding and ASCII encoding. Binary files are smaller and easier to share while ASCII files are visually easy to read and check.
Binary format is recommended to use for 3D printing. However, ASCII format is suggested for those who want to manually inspect STL file for debugging.
Tip for files that exceed the max file size in Shapeways:
Reduce mesh command in Rhino: ReduceMesh command
Exporting from Revit for 3D Printing
This details the process for exporting a Revit file containing masses (such as a parametric object made up of multiple instances of a solid component). This process is not intended for traditional Revit geometries, such as buildings containing doors, windows, roofs, ceilings, etc., although it may be applicable.
If you follow this process, it will result in an optimized .stl file that will increase the likelihood of a successful print and will reduce the time and cost required to print your model.
Exporting the Model from Revit
- Open a 3D view of your model
- Select File->Export->CAD Formats->DWG
- The DWG Export window will appear as below:
- Click the "..." button next to export setup.
- Under the "Solids" tab, select "ACIS Solids", then click "OK"
- Click "Next", then save the file. Be sure to select AutoCAD version 2007 for the file type.
Processing the file in Rhino
- Open your .dwg file in Rhino
- Select and delete any lines, text, dimension strings, etc. that are not part of the model that you want 3D Printed
- Select all of the model objects.
- Type "Explode" and press Enter. You should now have one or more closed polysurfaces (you can verify this by selecting an object and looking at its "type" in the properties window)
- Select all objects and scale them to the desired size. UPrint maximum print size is 8 in x 8 in x 6 in.
- Select all objects and click File->Export Selected and choose the ".stl" type from the dropdown. Give your file a name and click "Save."
- The "STL Mesh Export Options" window will appear. Leave the defaults unless you have experience tweaking these numbers. Click OK
- The "STL Export Options" window will appear. Select Binary and click OK. Your file is now ready to be evaluated and submitted for 3D Printing.
Exporting from Sketchup for 3D Printing
For help exporting from Sketchup to .stl please follow this link: