Printing a Strong Part

Overview

During the design phase, you can do a lot of things to make your part strong. This can any thing from the orientation, to avoiding stress concentrations, as well as including areas to add metal reinforcement. Knowing how to design a strong part can be crucial to your success with 3D printing parts and prototypes.

Orientation

The easiest way to get strong parts is being mindful of what the print orientation of the part is. This is because 3D printed parts suffer from anisotropy, meaning they are significantly weaker in one direction versus the other (see Figure 1). When you are designing your part, try to keep in mind the forces that might be on the part, then design the part to be printed in the strongest way.

Figure 1. How anisotropy works in 3D printed parts. (Image Source)

Avoiding Stress Concentrations

Another thing to avoid is stress concentrations. Stress concentrations with anisotropy can lead to incredibly weak parts. Something you can do to avoid stress concentrations is by using fillets (see Figure 2).

Figure 2. Using a fillet to avoid a stress concentration, resulting in a much stronger part.

Example

To show how some simple changes can make strong 3D printed parts we are going to use a axle like part with the shown loading condition below (Figure 3). To test the strength of the part, they will be broken and then given a rating on how difficult it was to break on a scale of 1-10.

Figure 3. Axle part with loading condition

Baseline

The baseline part was printed vertically and is the weakest part.

Aftermath of part testing the baseline part.

Overall, the strength required to break this part was about a 2/10.

Orientation

The first thing to try and make a stronger part will be to change the print orientation. This part was printed on its side. This will make the layer lines parallel to the loading condition, making the part strong.

Part before supports were removed.

Part after testing, notice how the layers stuck together and the part took some of the circle face with it.

Overall, the strength required to break this part was a 7/10.

Fillet

This part has a fillet on the edge where the “axle” meets with the wheel. This will mostly eliminate the stress concentration.

The broken filleted part. Notice how the break occurred after the fillet.

Overall, the strength required to break this part was an 8/10.