7 Helpful Numbers Quantify Design Rules for Additive Manufacturing

Greg Thompson, 3D printing global product manager for Proto Labs, gave an informative presentation on the design considerations for additive parts at the most recent Additive Manufacturing Conference. Specifically addressing DMLS and SLS, his talk about best practices included various numbers defining rules of thumb for these processes. Here are a few:

1. Minimum feature size. While these AM processes can produce small features, there is a limit. Results are best if features are at least 0.006 inch in their smallest dimension.
2. Maximum wall height. For the straightness of thin walls, keep to a maximum wall height-to-thickness ratio of 40:1.
3. Quantity of supports. The optimal number of support structures is zero, if that is possible. These sacrificial features can be challenging to remove and they affect the quality of the part. Design the part and its build orientation to require as few supports as possible.
4. Unsupported angle. A feature 45° from horizontal can be trusted to support itself. At a smaller angle, supports are likely to be needed.
5. Unsupported overhang. The next layer can be larger than the previous layer by up to 0.020 inch. More overhang than this and support will be needed.
6. Unsupported bridge. The material stretching from one feature to the next can be up to 0.080 inch in span without support.
7. Font size. For text grown into the part, use the Arial typeface for clarity, with at least a 16-point font size.