3D Modeling

In order to make things from either 3D printers (or CNC routers/mills that have 3 or more degrees of movement), you need a 3D model.

While your first experience with one of these machines may use an existing test model or one you've downloaded from a site like Thingiverse, eventually you may want to create things of your own.

The general workflow for 3D modeling and printing is: first, model the part, second, turn it into instructions suitable for the machine you're using to make the part, then third, feed the instructions to the machine and fabricate the part.

This page will only deal with the first step; how to model a part, and it will not cover how to use specific software.

Here is a very out-of-date list of some free 3D modeling applications: 25 free 3D modeling applications

This page deals with 3D modeling with the intent of printing the part on a 3D printer like our LulzBot and Makerbot Replicator printers, and not 3D modeling for CNC fabrication.

Regardless of what modeling software the model you use, there are a few considerations you must make:

Minimum size. The part may not be larger than the printable area of the printer you are using. Larger items can be made by dividing your object into components that are assembled after printing.

Minimum size. Parts must be large enough to resolve, large enough for the print-head to extrude something that holds together.

Parts must be manifold. Manifold is a term that means the surface of the part is contiguous and complete, and with regards to 3d printing, also not zero thickness. Imagine a soccer ball shape: that would be 'manifold,' but if the soccer ball were missing one polygon, it would not be manifold. In order to print such a shape, either the walls of the part need to be thickened, or the gaps or holes need to be patched. Some models created with common software, particularly SketchUp, can be impossible to print without serious repair and reworking, because the models include many holes or gaps and are often composed of zero-thickness planes rather than solid shapes with volume. 'Manifold' is also referred to as 'water-tight.'

Designing 3D Models

Page in progress to describe 3D modeling.

3D models for printing should be saved in the STL format (binary or ascii). Your model should be "watertight" (the mesh has a mathematically determinable interior), correct normals, and a manifold topology. Shapeways has a nice tutorial explaining this.

All software suggestions in this section are open source, and are available for free.

• For individuals new to 3D modeling software, Blender is a good tool for designing models for 3D printing, as well as for debugging fussy models (Blender can highlight the parts of a model which make it non-manifold). Blender recently had a total overhaul of its codebase and user interface, and has become quite user friendly. Additionally, the Blender foundation produces and sells video tutorials. The video tutorials are distributed on dvd data disks, but are creative commons licensed, and so you may legally download them for free online. The videos are created by artists, and cover a wide array of topics from basic usage of the program, modeling techniques, and the more advanced capabilities of Blender.

• Meshlab is an open source tool for repairing 3D models.

• FreeCad is a general purpose feature-based, parametric 3D modeler for CAD, MCAD, CAx, CAE and PLM, aimed directly at mechanical engineering and product design but also fits a wider range of uses in engineering, such as architecture or other engineering specialties.

• OpenSCAD is a different take to 3D modeling. OpenSCAD is a programming language that generates parametric 3D models.

After the part is modeled it needs to be turned into commands the 3D printer can recognize, a step called 'slicing' since it turns the solid shape into a series of paths and printer commands to move and start and stop the extruder, that build up the part layer by layer. The final step in 3D modeling, then, is to save the part in a format that the slicing software can recognize. Common formats include STL, but vary depending on the specific software and workflow you will be using.