Curved Extrusions

[MadMango]

Material: A356.0-F, 4.5" x 1.9" x 57" long with a radius of 129".

Just curious if this shape is manufacturable, and what level of tolerance can be expected for the radii and length? Cross section is similar to a "C" with fins going with the direction of the radius. If this cannot be extruded as a radius, can it be rolled formed or some other method after extrusion?

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[MikeHalloran]

If I understand the process correctly, extrusions come out of the die in the -0 temper, soft and malleable like lead. So you should be able to get the gentle curvature you've specified just by laying a piece on a curved form/platen, and maybe beating on it with a rubber hammer.

Alloy 356 is almost universally used for sand casting, but not for extruding.

So you could cast the part in linear form, and beat some curvature into it in the same way.



Mike Halloran
Pembroke Pines, FL, USA

 

[arunmrao]

mm,I will go with your suggestion of extruding followed by roll forming. Casting process ,you can definitely opt ,if you could tolerate some of the process inconsistencies.Also casting this would be the cheapest way to get your product.

 

[rb1957]

i don't think mike was advocating casting the product, but rather was suggesting that the material proposed is generally not extruded (and so there could be issues with it).

 

[MadMango]

Sorry about the material, it was a hold over from a previous design, should have caught that. This will be extruded, and material will be 6063A. So it sounds like the extrusion should be fairly easy to shape into this slight curve. Now I'm just curious about how tight of a tolerance can be expected? Arch length end-to-end distance of the radii) and radii is important.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[CoryPad]

What you want is possible and done every day for automobile bumper beams. Take a look at this site:

http://www.sapagroup.com/en/Company...tive-products/Car-products/Impact-Protection/

They have technical information available at their site that may include tolerances.

 

[MikeHalloran]

Roll forming discrete lengths, using three forming rollers, leaves non-ideal tangents at both ends, so you might want to form an overlength blank, then sawcut it to finished length.

The achievable radius tolerance is skill- dependent, because the springback changes with the temper of individual parts. It might work better after tempering to whatever condition you need with a controlled process.

I.e., it might be better to have the extruder supply overlength tempered blanks, to be processed by someone experienced with cold forming of aluminum.

This would be a good time to be talking to actual extruders about your specific part. Some of them just want to handle sticks, some like to also do the secondary operations, but all will need an actual print on which to base a quote. For which purpose they also need a credible estimate of annual production.




Mike Halloran
Pembroke Pines, FL, USA

 

[TheTick]

You might get the 129" radius just from painting one side black and leaving it in the sun.

 

[BluTurtle]

While we are on this topic, I have a question about roll forming this profile to get a nice radius (R 129")

- Will there be a Straight segments at the ends (holding lengths) ? OR can we achieve radius throughout the part?


~ BT

 

[ornerynorsk]

Extrusions are commonly formed. If you can't live with straight tangent sections on each end, you'll need to start with longer pieces and add a trim operation. Any full service extruder should be able to handle the entire thing for you, especially one that does work for the boat or transport industry, or custom architectural.

 

[berkshire]

The other method you can examine is stretch forming. The fins can be packed with blocks to prevent distortion.Or a die can be made to custom fit your extrusion.
A trim operation will be required because a certain amount of straight is required for the jaws to clear the stretch form die.
Stretch forming is most often done in the O or AQ condition.There is some reduction in cross section, but it is no worse than the distortions induced by a 3 roll profile or 4 roll Buffalo roller.
B.E.

 

[berkshire]

The Tick.
The rise over a 57" chord for that Radius is just a little over 3" I think that's a bit much for sun heating
B.E.