3D Printing, FDM Technology

Which Is Better: Round vs. Diamond Shaped Holes

By Alex Yingst on September 21, 2017

Anyone who prints parts with multiple holes knows the headache that can come from designing and post-processing round shapes. In this blog, we are saying goodbye to traditional round shaped holes and exploring the benefits of 3D printing diamond shaped holes instead. 

Why 3D Print a Different Shaped Hole?

Generally, when 3D printing an overhanging feature, support is required underneath. This means pausing your print to switch between support material and model material, which in-turn, adds extra time to your build. Taking advantage of self-supporting angles can fix this problem. 

Self-supporting angles are those which enable a 3D printer to build successive layers without the need of support material. For FDM, this is usually around 45 degrees. While round holes do not support this method, diamond shaped holes do. Since there is no angle greater than 45 degrees, support is not needed in the hole.

Depending on the project, this tactic can reduce build time, material usage and time at the wash station. Below are some key factors to determine when a diamond hole might be the right choice for your part rather than a round shape hole.

Round Holes

Round shape holes are the most common of the two shapes. One reason for this is because they are simple to bring from a drawing software into Catalyst/Insight and then to a printer. Round holes also work especially great if you are printing with a sparse infill, using it as a conceptual model or don’t mind soaking the part. Since diamond shaped holes only work with FDM technology, round shaped holes are still necessary when printing with PolyJet technology.

Diamond Holes

Unlike round holes, diamond holes are a better option if you plan to use a solid infill or want a functional end-use part. The great thing about this process is that it can be used by any FDM printer, in any material. Aytime there is a vertical hole in a FDM part, consider making it a diamond shape to save on time, material and frustration.

This tactic is especially beneficial in long holes when you need to wash away the supports. The only catch is that diamond shaped holes need to be drilled out instead of soaked. Drilling out the part is not uncommon when using breakaway-style support material like ULTEM or using the same build and support materials like with PLA. Even with materials that do have a soluble support, we see the holes come out oval shaped as if they have been squeezed a little. For many applications this is fine, but for precision work you will need to drill the hole out regardless of the shape. So depending on your project, the cost/benefit can be in favor of diamond holes. 

Comparison Test

From a resources aspect, we wanted to compare the difference between time and materials needed to 3D print round vs diamond holes. As you can see in the sample parts below, using diamond holes saved 1 hour 27 minutes.

Round Shaped Hole Sample Part Diamond Shaped Hole Smaple Part
(Left) Round Shaped Holes, (Right) Diamond Shaped Holes

Rather than soaking for two-four hours, using diamond shaped holes allowsed us to pull the part off the tray immediately. After a  few minutes with a drill, we had a finished part with holes exactly the same size as we needed. Saving a few hours per part is a huge difference when it comes to beating your competition to market.

Want to learn more helpful tips and tricks about 3D printing with FDM technology? Browse our recent blogs.

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