How to Make a Helically Twisted Tube?

[mrelet]

I have a plastic tube design with either a hexagonal or octagonal
cross section. Wall thickness is constant. Overall, part is 3" long, 0.48"
major diameter, 0.02" wall. The twist is that the cross section forms a
helical path with a desired constant pitch of between 0.5 to 3.0. The
most important aspect to keep is the internal helix .

I can get a decent prototype with SLA or ABS plastic (fused deposiiton?). I wanted a
smooth metal working model, but machine shops tell me it is not within
their capabilities [ including swiss screw machines]. Assuming any
plastic, anybody know how this can be mass produced ? I have
an Injection Molding quote, but tooling costs are steep. I'm leaning
towards extrusions. But, so far Extruders have nixed it ["haven't done
an internal helix"] Any ideas?
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[insideman]

Yes, tooling costs are high. Fact of life. But piece part costs should be low. Extrusion looks not so good to me because of thin wall making it difficult to get a goodclean cutoff.

 

[nucci]

maybe you could try to have the internal dimensions of the
tube (before it is twisted) made from silicon, insert the silicon insert into the tube, aplly even heat surounding the tube, twist the silicon to the desierd pitch, and air cool, you should be able to pull the insert threw and you will have the tube .