Helical twisting an extrusion 1

[JRNICO]

Hi guys, love the site, so much good information!

Was hoping someone could point me in the right direction for the process I am trying to do.

I have an aluminum extrusion, it is 4inch diameter and has fins, similar to a heatsink.

I am trying to find a machine/process that can twist this extrusion along its central axis.

This is for a lighting fixture heatsink. The part I am having trouble with is finding a shop/machine that will impart a helical twist on an aluminum extrusion.

Ive attached a jpeg of what I am looking to do. Any help is appreciated!

 

[mcgyvr]

yeah good luck with that.
No shop in their right mind would take that on.

Whats the point? aesthetics only?
It's only going to hurt the thermal properties of that extrusion.

 

[KENAT]

How about casting it?

No promises as it's a pretty funky shape and you don't state the size etc. but worth considering.

Maybe either lost wax/investment casting or some variation of the 'rubber plaster mold' process.

Alternative additive methods might be worth considering, sintering or laser sintering though I'm not sure how well the latter works with Aluminum as the couple of shops I know that do laser sintering don't seem to list aluminum.

Also not sure any of the methods above will make the grade of Al you specify.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[hydromarine]

Depending on how many you have to do it may be worthwhile contacting the Hedo machinery company they have some very good bar twisting machinery , your component may be a bit fragile for this process

 

[ornerynorsk]

That's not just a twist, it's a twist with a full reversal. Very difficult, it might not be possible. Investment casting???

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[racookpe1978]

Do what I do when I twist square bars (smaller in cross-section perhaps at 1/2 x 1/2 up to 1x1 mild steel, but Al will twist equally smoothly). Fins will take some experimenting though.

I clamp the middle of the piece in in vise, put a square drive over the steel at the top (+20 inches above midpoint for a 40 inch tall picket for a handrail for example.) Twist the top half.

Reverse the picket, clamp the middle again. Put the sq drive on the "top" again, and twist again. I go around about 1-4 times, depending on what I want the final picket to look like: tight turns, medium, or very little twist all. If you have a lot of these, clamp the top and bottom in two vises, and twist the middle. Only a very few? Do a few by hand rather than automating the process.

Don't try to do it hot: unless you have some way of making absolutely sure the whole heat sink extrusion is exactly the same temperature the whole length, you'll never get a smooth curve.

Look up picket benders, baskets-twisters, or other metal-working items and catalogs for making fences and railings.

 

[swall]

When I was in high school, I worked in an ornamental iron shop and one of my jobs was to twist pickets. We did 1/2" and 7/16" and they were twisted at room temp. The twisting machine was a modified heavy duty pipe threader. One end of the picket was held; the other end went into a square collet on the machine. Pickets were about 27" long and 4 revolutions were required for the desired twist effect. The big problem with trying to do this on the extrusion would be holding it.