Hydroforming

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cudabean
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Hydroforming

Post by cudabean » Tue Nov 18, 2003 6:52 pm

Bruno mentioned Hydroforming, touting it as an inexpensive way to create metal parts. It seems to me like it would be feasible to use it for small run or even one-off manufacturing like making aluminum ribs for a homebuilt, etc. In any case, this process had slipped past my radar (that typically homes in on inexpensive and interesting manufacturing processes) so I did a little searching on the net and found this description:

Hydroforming is the process of using the water to do the work. You don't
always need a die or form at all, but even if you do need the form, it
takes a lot less pressure than a press die. What you do is clamp aluminum
or other malleable metal sheet in between two pieces of a chamber.
High pressure fluid (often water) is injected into one side of the
chamber, forcing the sheet to bend outward, away from the water, into the
other side of the chamber. Usually, there is a form of fairly thick
metal, but not as hard as tool-steel or other exotic alloy, that is a
'female' form for the final piece. This piece has to be made just a
little larger than the desired final size, to accomodate the relaxation
of the stress in the workpiece when the pressure is removed. The whole
process is a lot like blow-molding used to make glass and plastic
bottles, except that the metal is softened by heavy stress, rather than
heating.

This process doesn't take a lot of energy, doesn't use any heat, so it
won't affect heat-sensitive materials, and provides some grain alignment
which strengthens some materials like forging. And, because it doesn't
require press molds made of super-hard steels, the molds can be machined
at much less expense.

A variant of this process, which may have special mettalurgical properties
is explosive hydroforming, where an explosion in the water provides the
pressure in a very intense impulse. The explosion is often produced by
exploding a wire with a massive, instantaneous electrical impulse from
a capacitor bank.

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Post by Mike Everman » Tue Nov 18, 2003 8:32 pm

Found some cool pics of hydroformed parts... The second pic conveniently illustrates the pressures involved, apparently on welded steel exhaust tubing.
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Post by Bruno Ogorelec » Tue Nov 18, 2003 9:29 pm

Mike,

For some things, you don't even need a die. You cut two flat patterns from sheed steel. Say, something looking like your hand. Weld a threaded nipple onto one of the two sheets. Put one sheet atop the other and weld the edges together. Pump water through the nipple.

Presto, you have a steel glove. Without a die. the pattern itself was a die, in a manner of speaking. (Actually the glove is a bit too complex for such basic hydroforming and would not look terribly well, but you could do it.)

You should avoud very tight bends. Also, it takes a lot of practice to cut patterns for bent items in order to get the internal angles right when the thing is pumped up.

Combine cunning pattern-making and simple dies and you can do really amazing things.

Bruno

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Post by Pieter van Boven » Tue Nov 18, 2003 9:38 pm

let,s learn more about it!

http://www.arcelorauto.com

pieter.

cudabean
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Post by cudabean » Tue Nov 18, 2003 9:46 pm

Perhaps worthy of experimentation?

* Carve a foam male part into the shape you want for your hydroformed part.

* Suspend the foam in a waterproof vessel.

* Pour slip-casting clay into the vessel around male mold

* Once clay has hardened, remove male mold and relieve regions in female mold as required for proper hydroforming

* fire it (anticipate shrinkage of 20%)

* Reinforce ceramic mold with close-fitting steel jacket in order to withstand hydroforming pressures.

* Hydroform.

cudabean

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Hydroforming

Post by Mike Kirney » Wed Nov 19, 2003 2:47 am

I too was intrigued by hydroforming, especially pulsejets. I read that it takes quite a lot of pressure (1000 psi) to fabricate stuff that way, but that it wasn't so much that you couldn't hand pump it, given a long enough lever. Perhaps a two-ton jack, an old hydraulic cylinder, a high-pressure check valve, and some good strong hose could be cobbled together to give you titanic metal-forming handpower.

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Post by Mike Everman » Wed Nov 19, 2003 3:33 am

mike k wrote:...I read that it takes quite a lot of pressure (1000 psi) to fabricate stuff that way, but ...
Check the 304L photo above, they wrote the pressures on them, with varying degrees of success following the die. 11,400psi! A blow-out on a cobbled together rig might just cut you in half!
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Post by Viv » Wed Nov 19, 2003 2:10 pm

Mike Everman wrote:
mike k wrote:...I read that it takes quite a lot of pressure (1000 psi) to fabricate stuff that way, but ...
Check the 304L photo above, they wrote the pressures on them, with varying degrees of success following the die. 11,400psi! A blow-out on a cobbled together rig might just cut you in half!
And the gas volume behind the liquid pressure? or pumping capacity to maintain the jet at 11,400psi

Nick Ibbitson completly on his own came up with a hand operated pump and made up a U bend for a BCVP prototype one afternoon!

One day we all spoke about it as a possiblity the next day he sent us a picture of the completed U bend and rig.

Viv
"Sometimes the lies you tell are less frightening than the loneliness you might feel if you stopped telling them" Brock Clarke

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Monsieur le commentaire

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Hydroforming

Post by Mike Kirney » Wed Nov 19, 2003 7:02 pm

It looks like 8000 and 10000 psi gave the best results. The 11,400 psi one looks as though it might have bulged slightly from overpressure and the 5000 psi was obviously underpressured as the steel looks all wrinkled and 'slack'. I don't think a hand-pumped machine would be all that dangerous because if something failed it would just crack or deform. If a hose came loose, it would just pop off, squirt fluid and then droop, and not windmill too much. Energy would be supplied gradually and there would be no excess to fling shrapnel around because you would probably stop pumping when you heard the 'crack' or 'bang' or whatever. You could also tell when things were getting dangerous because it would become progressively harder to pump as the pressure inside the workpiece increased. Would Nick or another one of the Albion team like to describe his apparatus here on the forum?

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Post by Bruno Ogorelec » Thu Nov 20, 2003 8:46 pm

Viv wrote:Nick Ibbitson completly on his own came up with a hand operated pump and made up a U bend for a BCVP prototype one afternoon! One day we all spoke about it as a possiblity the next day he sent us a picture of the completed U bend and rig.
Here's Nick's work. I have already posted it in some other thread, but it may be more relevant here.

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OOPS!

Post by Bruno Ogorelec » Thu Nov 20, 2003 9:37 pm

The Albion Propulsion team has asked me to pull the pictures of Mk. VII off the forum. The first approval of publication was apparently a mistake. They saw it in the forum and said, Ohmigod! and did a bit of quick messaging to make me pull it down. Of course, I demanded a fat check in return. It is in the mail.

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Re: OOPS!

Post by Mark » Thu Nov 20, 2003 10:11 pm

brunoogorelec wrote:The Albion Propulsion team has asked me to pull the pictures of Mk. VII off the forum. The first approval of publication was apparently a mistake. They saw it in the forum and said, Ohmigod! and did a bit of quick messaging to make me pull it down. Of course, I demanded a fat check in return. It is in the mail.
Loose lips sink ships.
Mark

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Re: OOPS!

Post by Bruno Ogorelec » Thu Nov 20, 2003 11:00 pm

Mark wrote:Loose lips sink ships.

Jesus, Mark, you _are_ old. That's World War II, isn't it? The golden age of the propaganda poster.

Bruno

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Post by Mike Everman » Thu Nov 20, 2003 11:23 pm

OK, I have to do this, please forgive me...
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Re: OOPS!

Post by Mark » Fri Nov 21, 2003 3:21 pm

brunoogorelec wrote:
Mark wrote:Loose lips sink ships.

Jesus, Mark, you _are_ old. That's World War II, isn't it? The golden age of the propaganda poster.

Bruno
It was something I saw in a movie, and the days of propaganda were blended in with the documentary film. A silly catch phrase I suppose. Didn't mean to ruffle feathers.
Mark

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