How to Prepare Rhino Files for 3D Printing

Time to read: 9 min

Correctly preparing a solid model file for 3D printing is a critical step in the part-production process. Accurate preparation of a 3D model for 3D printing ensures that the final product is dimensionally correct and meets your desired specifications — the 3D printer will print the model as designed, so any errors will be replicated in the final product. Additionally, a correct model ensures that the printer is used effectively and efficiently, minimizing the risk of over-printing or under-printing due to inaccurate model data. 

For more tips on how to prepare all sorts of files for 3D printing, check out How to Prepare CAD Files for 3D Printing. There are many different types of modeling software for designing and exporting 3D print files, and this article covers Rhinoceros 3D software (aka Rhino) — Rhino requires some unique considerations when preparing 3D print files.

Units and Tolerances

You first need to set correct tolerances before you start modeling by finding the tolerance of the program you are exporting your model to. A good rule of thumb is to set your Rhino tolerance to be 10 times that of the printer tolerance (i.e printer tolerance is 0.1mm, so Rhino tolerance should be set to 0.01mm). 

Rhino file tolerance can be set from the document properties window in the units tab. No matter what units you use to create your model, files exported from Rhino are almost always read as mm, so set your units to mm before exporting your file for printing.

Pro-Tip: Check out our guide on How to Conduct a Tolerance Analysis for 3D Printed Parts if you have complex tolerance requirements and want a simple way to perform a tolerance analysis.

Common 3D Model Mistakes to Avoid

The most common reason models become unprintable is due to bad objects and naked edges. Bad Objects are those that violate NURBS (Non-Uniform Rational B-Splines) rules or have structural problems — they often appear after joining and Boolean operations. Naked Edges are surface edges not connected to other surface edges, which create open meshes that cannot be 3D printed.

For successful 3D prints, the 3D model should be watertight, meaning if you dropped the model in a bath, no water would get inside. To achieve a watertight model, you need a closed polysurface. To close open polysurfaces in Rhino (or convert open polysurface to solid in Rhino), you first find them by selecting Analyze Direction → Show Edges → Select Open Polysurfaces, and then follow the steps below:

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