The Monkey Spring

The Monkey Spring is a 3D printable, durable parametric compressive spring that can be used just about anywhere. It is lightweight, durable, and parametric! You can size it for just about any application and control how strong it is just by changing a few variables in Monkey Spring.scad (you can even import it as a module and use it in your own OpenSCAD projects).
FEATURES:

Extremely durable. Guaranteed to withstand at least, "a zillion cycles".
Easy to print. No supports necessary!
Completely waterproof (will never rust) and very strong chemical resistance.
Two modes of operation: Can act as a linear spring or a buckling spring (similar to rubber dome).
Does not weaken (significantly) over time!
Useful for a broad array of applications.
Can provide the equivalent to a spring steel spring in a smaller amount of space.

See the Monkey Spring in action:

https://gfycat.com/needydearestbrontosaurus
https://gfycat.com/leadingphonycollie

Print instructionsThe Monkey Spring must be printed in a flexible filament. Softer TPUs (like 85A Ninjaflex) tend to work best but it all depends on your application! Make sure to try out several different springs in your material of choice and see how it goes.
ALWAYS PRINT AT LEAST TWO AT A TIME. Why? Because flexibles typically need to be printed very slowly and when you print really small models (like the Monkey Spring) really slowly the filament may not have enough time to cool and set, resulting in a big blob instead of your model. By printing two at a time you force the nozzle to move away from your model for at least a second or two which provides ample time for cooling.
Remember: The wall thickness and height of the side walls are the biggest factors in the strength of the spring!
Cut off any mess/stringing
Soft, flexible materials tend make a gigantic mess while printing (stringing everywhere and it also likes to bunch up and collect on the sides of your print). Make sure to use your flush cutters to clean that up after your print is done.