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Manufacturing Flat Helical Springs?

Manufacturing Flat Helical Springs?

(OP)
I'm trying to determine if a given shape is possible to manufacture. Specifically, this would be a classic coil compression spring but - rather than formed by bending a round wire - this would be made of flat, foil-thickness material with the wide dimension being radial. So, its not a flat sheet twisted, but rather a cylinder with a helical slice along its length like a flexible coupling.

I envision that a piece of cylindrical stock could be rotated driven into a radius-wide cutting tool set to the desired pitch on a lathe. The flat foil helix would develop from the cut as an endless chip. Is this something that can be or is already manufactured?

RE: Manufacturing Flat Helical Springs?

(OP)
Yes, but physically larger and thinner. Say, 4" OD, 0.25" ID, 4" tall, and 0.015" thick material.

RE: Manufacturing Flat Helical Springs?

Maybe in Delrin, probably not in steel.
The tangential force on the cutting tool, and the bending moment on the workpiece, would be huge.
Not to mention the torque on the workpiece.
Maybe with some kind of stiff roller follower rest on top of the workpiece right above the cut.
Have you got access to a really big lathe?

Mike Halloran
Pembroke Pines, FL, USA

RE: Manufacturing Flat Helical Springs?

Such a spring would probably be made by wire EDM. Have you checked with Heli-Cal to see if they can make it?

RE: Manufacturing Flat Helical Springs?

These guys can make springs (not in the single coil you describe) with that OD and material thickness but you will probably run into problems if you need that small of an ID together with that OD. Any reason for such a big difference? http://smalley.com/

Alternatively, if you are looking for the shape described but for applications other than use as a spring you could look into electroforming. There are limits on what material can be used with that process though. http://en.wikipedia.org/wiki/Electroforming

Doug

RE: Manufacturing Flat Helical Springs?

What if you got a drill bit and just drilled into a material (with a hole already drilled equivalent to the inner diameter of the spring, i.e. 0.25") with a properly lubricated drill bit with a strong cutting tip so you can have high chiploads? A 4" HSS drill bit should be able to make a 0.015" coiled ribbon easily. Material wastage would be much less than just machining a tube or solid rod via EDM.

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