Bending boxes

Nice, clean bends in 0.063 aluminum, homemade hardwood bender. Anything work better than 6061-T6?

Reply to
Frank
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I always got some corner cracking when I bent up 6061. I think the 'pure' 1100 works well... going to Mcmaster-Carr catalog they also list 5052 as excellent and 3003,5005, 5086, 5205 as Good.

George H.

Reply to
George Herold

Eased radius?

Thanks.

Reply to
Frank

You'll get corner cracks if you use the common bending brake. The inside of the bend radius gets compressed, but the outside is stretched causing the cracking. Where you get into trouble is that

6061-T6 will crack unless the bend radius is fairly large. My guess(tm) is about 2-3 times the sheet metal thickness. If you use an industrial strength press, with a V-bender die set, you can get a much sharper bend radius. The pressure between the punch and the die compresses the bend area, making more of the bend in compression, and less on the outside that gets stretched. The bend area does get slightly thinner, but even with a smaller amount of stretch, it still will crack slightly.

I'm not so sure about using dead soft 1100 aluminum sheet. The stuff is not very durable and is easily scratched, dinged or dented. However, I haven't tried using it, so I'll remain neutral.

Most of the chassis I've worked with use 5052-H32:

Rapid Sheet Metal® - Rapid Tech Tip: 6061-T6 vs. 5052-H32

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Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

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You should drill/punch a hole at the corner of the bend and let the 
metal stretch instead of tear.
Reply to
John Fields

3003 and soft 5052. bends like butter. The 3003 is so soft you can bend it with your hands, which can be a disadvantage. But, it bends very well in a brake.

Jon

Reply to
Jon Elson

Synthesizer modules. Just the long edges need to be bent, no corners to drill.

Reply to
Frank

The minimum bend radius of 6061-T6 is 3-4 times the material thickness. The other readily available alloy that's much better for bending is 5052, usually H32 or half hard. Minimum bend radius is just over the material thickness, about 3/4 the strength of 6061T6, as weldable, and both take anodizing well. Biggest difference is 6061 can be heat treated for more strength (T0 is annealed, T6 is the common heat treated material) while 5052 is annealed with heat but can only be strengthened by work hardening. I buy from McMaster Carr all the time at work for items they make sense for, but if you need more than a few square feet you need to find a local metal supplier since you can easily halve the McMC price and any good supplier will shear a large 4x8 or 5x10' sheet into whatever pieces you need for very little extra cost. (I say readily available because while McMC lists several alloys in their catalog, if you go to a local metal supplier almost anything but 6061 and 5052 in sheet is going to be a special order with a big minimum so in practice you just ignore everything else :-).) Where are you? If you are near Baltimore I can recommend some suppliers.

Nice, clean bends in 0.063 aluminum, homemade hardwood bender. Anything work better than 6061-T6?

Reply to
Carl Ijames

No, just what ever metal break was in the machine shop.

George H.

Reply to
George Herold

ng work better than 6061-T6?

e' 1100 works well... going to Mcmaster-Carr catalog they also list 5052 as excellent

Grin, I'm not claiming it makes the best boxes, but it's easy to put a bend in it. George H.

Reply to
George Herold

Bendability, ductility?? whatever they call it. Don't you have a McMaster catalog?

George H.

Reply to
George Herold

I use 1100-T0 sheet a lot in prototypes--it's easy to tinsmith it into various mounts, lens holders, etc.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Reply to
Phil Hobbs

Well, there is one place where dead soft aluminum shines. VCO's that have microphonic problems. I had to deal with a radio where the designer (not me) threw in such a high divider ratio in the PLL phase lock loops that it was almost impossible to remove the microphonics from the system. My job was to fix the microphonics problem without changing anything, spending any money, delaying deliveries, or precipitating an FCC re-certification. Right, no problem...

I made some major improvements with Q dope, parts spacers, bees wax, hot melt glue, and the blobs of silicon rubber goo, but it wasn't enough. I coined and stiffened the tin covers on the VCO and glued down any loose wires, but still not good enough. I then did some vibration analysis (beat on the box with a small hammer and look at what came out of the receiver on a scope) and found that the main chassis was poorly stiffened and trying to "oil drum". The mechanical resonance of the chassis was about the same as the microphonically induced audio oscillations. Hmmm... I first tried to stiffen the chassis with various brackets, but that only made it worse. What I needed was a way to deaden the resonances. A sheet lead chassis would probably have been best, but that was obviously unacceptable. So, I convinced the fab shop to make a chassis out of 1xxx series 0.063 dead soft aluminum. A hint is the "dead" in dead soft really means that it's acoustically dead. Bingo. No more howling out of the speaker and no more drum amplifier.

After they delivered a few such radios, I didn't hear any complaints coming back so I assumed all was well. In reality, the design had numerous other deficiencies that made a redesign necessary. However, since I complained so much about the design and construction while I was fixing the microphonics, the design job went to someone else. At least I got paid.

So, if the synthesizer design has a microphonics problem, and the usual fixes don't quite work, you can try dead soft aluminum for the cans or that case.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

Baltimore.

Reply to
Frank

Sounds useful for mounting piezo pickups.

Reply to
Frank

Baltimore. ]

Now that's funny :-). We mostly buy sheet aluminum (and steel) from High Steel in Lancaster, PA, plus BMG south of Baltimore on Rt 1, and Pennsylvania Steel in York, PA. Of course, we usually buy enough at a time to get free delivery. You will have to call around and shop for price and convenience. It all depends on how much you can buy at one shot.

----- Regards, Carl Ijames

Reply to
Carl Ijames

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I have an account, but I don't have catalogs. 

I gave them up as wasteful since everything in them is described in 
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Reply to
John Fields

On Tue, 02 Jul 2013 12:14:48 -0700 in sci.electronics.design, Jeff Liebermann wrote,

Heat the bend line with a propane torch until it is no longer -T6

Reply to
David Harmon

Or use 21 gauge instead of 16. Or design around the large radius instead of driving yourself nuts trying to force it.

Reply to
Frank

I'll bet Uri Geller could do it better. He should start a company doing that.

Reply to
John S

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