I’ve turned my post about the Shoch Absorber into a detailed blog post. 

The coil spring of the shock absorber on my RC car, which I previously designed using SolidWorks and xDesign and produced with a 3D printer, has reached the end of its life. The coil spring, which I printed using PETG filament, lost its elasticity. Actually, it had a soft spring rate. While revising the RC car, I decided to improve this part as well. My goal was to increase the stroke travel of the spring, and to obtain a spring with a higher spring rate. 

This improvement process actually turned into a complete Design for Additive Manufacturing (DfAM) application. In this blog post, we will examine everything in detail, from how an appropriate coil spring design for 3D printing should be, to what the spring rate depends on, and the filaments that should be used for printing.

Slot Profile Coil Spring Design

Traditional springs have a circular profile. When you want to produce a spring using FDM technology, you will see that circular profile springs do not perform very well. Especially minimal springs used for an RC car become excessively fragile. Another problem is that their contact area with the printer bed is very small, making printing difficult. As I showed in the slicer software, the first layer contact of a circular profile spring is very minimal, which makes printing difficult. Here, of course, we can solve the problem by adding a brim and supports to provide better bed adhesion.

As a result of my tests, I observed both that bed adhesion is difficult and that the spring breaks after a few compression cycles. To overcome this problem, I decided to change the design of the spring profile. When I used a slot spring profile instead of a circular profile, I achieved better bed adhesion and a stronger spring thanks to the flat surfaces. I showed the differences between the spring profiles in the image below.