Why do aluminum extrusions sometimes have small radius grooves? 1

[AaronH]

All,

I don't have any sort of specific application, more just a curiosity. I have seen aluminum extruded profiles that have either a series of small radius grooves or radius ribs. Often they are symmetrical, but I have seen cases where they appear somewhat random in the design. Anyone that designs extruded profiles willing to shed some light on the whys and where-fors? In some cases I could see asthetic reasons. Are they also used to affect the dynamics of the extrusion process (material flow) and/or the surface properties post extrusion? Seems like a lot of extra effort to put those grooves/ribs in the extrusion die, so they must be there for a reason.

Inquiring minds would like to know...

Thanks,
Aaron

 

[drawoh]

AaronH,

Would it not depend on the design requirements?

Some extrusions are designed as electronics enclosures. The grooves are inside, and slightly wider than the thickness of a printed circuit board.

Some grooves are cooling fins.

Some extrusions are part of something that someone must grab and manipulate. Grooves can make the extrusion easier to hang onto.

JHG

 

[CorBlimeyLimey]

Some of them could be screw ports, but they are usually curved to offer better thread grip.

 

[AaronH]

I understand the ones that are obviously functional. The ones that I am talking about are generally small, say 1mm +/- radius. So, the would be maybe 2mm wide and 1mm deep or so. Sorta like the small grooves along some of the 8020 profiles (I'm not talking about the T-slots). I'm looking for a picture online to show the feature, but so far haven't found a good example.

Aaron

 

[Compositepro]

From you description, I tend to agree that they are screw holes. After the extrusion is cut to length, the cut face already has holes for self tapping screws. But the same technique is also used to mount printed circuit boards by sliding them into the groove.

 

[btrueblood]

The grooves on 80/20 profiles - I dunno, I think they are just cosmetic. We use/have used a bunch of the stuff and its associated fittings, none of which appear to engage/employ the grooves you speak of.

 

[Wicsteve]

Guess -- Maybe it has something to do with how thin extrusions interact with the extrusion die either helping fill the extrusion profile or keeping the extrusion straight as it is being extruded.

 

[MiketheEngineer]

Couple of ideas come to mind.

Much less sharp. A perfect square edge can be quite sharp - esp if used on fabric canopies/awnings, etc.
The radius may act as a bit of stress relief - preventing cracks at the edges.

 

[patprimmer]

Weight reduction? if extrusion has wall has a maximum wall section of 3mm but average of 2.5 to get extra stiffness for weight?

Regards
Pat
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[lumenharold]

They are so you can easily tell if it is metric (smooth) or imperial (grooved).



Harold
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[SnTMan]

Shrinkage control? Total guess.

Regards,

Mike

 

[AaronH]

Lumenharold,

I believe, you can now get 8020 imperial and metric with or w/o the small grooves.

I still haven't found a good example. Years ago I worked on a project for 4 season room aluminum extrusions. Those tend to be fairly thin walled. I can remember, though, that they had the very small ribs in seemingly random places. The overall shape would be symmetrical, but the rib locations were not. Seems like they would be, but there must be more to it. I used to have some of those profile drawings kicking around, but I may have deep sixed them. I'll have to do some digging.

Aaron

 

[lumenharold]

They do have a few profiles that do not have the grooves and are from the fractional series. They are the "light" series and typically are thinner walled and are missing other features making them easy to identify.

That is not to say that all manufacturers use the same method for distinguishing the product or that 80/20 might have added smooth fractional parts. I grabbed the image from an older 80/20 catalog. If you search for "8020 garage sale" you will find the ebay store which has a ton of profile images.


Harold
SW2009 SP4.0 OPW2009 SP2 Win XP Pro 2002 SP3
Dell 690, Xeon 5160 @3.00GHz, 3.25GB RAM
nVidia Quadro FX4600

http://www.lumenflow.com

 

[IFRs]

There is often a groove for identification purposes, or a location for holes to help the drill bit start without walking.