Methods of "machining" springs ... 1

[Doppe]

I'm needing to have manufactured a double start, rectangular section, variable pitch and possibly variable thickness/width coil spring to achieve a "progressive" spring rate spring.

Does anyone have any experience/ability in this area?

Note: I am aware of the capabilities of Heli-Cal and their machined springs ...

I was thinking along the lines of CNC wire cutting a tubular blank to form the spring???

Any thoughts would be appreciated ...

 

[israelkk]

Yes. I have designed rectangular section machined spring. depends on the space between the coils some were CNC machined and some were CNC wire EDM machined. Usually, I use them for torsion springs where the spring ends has to be accurately fixed with minimum backlash.

But, remember that these springs are by far more expensive than common coiled springs especially in small quantities.

Heat treatment and the spring material is another "heavy" issue. Spring wires are specially treated using the combination of cold working and heat treatment to achieve the highest strength available from the spring material, where a machined spring gets its strength only from the heat treatment.

Wire springs are specially designed materials for spring making where the material grain are oriented along the wire giving it superior properties. Machined springs use common structural steels and the grains are usually cut during machining.

Springs made of coiled wire has an excellent surface finish while machined springs are not, especially between the coils. This can lead to inferior fatigue life.