Hydroforming... at least that's what I think I need. 5

[RoarkS]

So thought of the day.

This is a follow on to my other heat treat thread. If I'm forming parts out of .025 and .032 2024... it was brought up that If I heat treat and quench I'll get a W condition that would be the ideal time to do forming. As suggested I've got 10 minutes to do it... got me thinking.

The wing ribs I'm planning on making were intended to be hand hammered to shape. The trick with these is that profile flange of the rib cannot be interrupted like a sheetmetal skinned rib can with where you can use fluting pliers or have relief cuts. This is a fabric covered wing, to my understanding it has to be smooth. I've tried flow forming, and hammering aluminum over a block and have had little success.

So here's the question:

Poor mans hydroforming press for 48" x 6" wing rib.

I've seen plenty of EAA harbor freight presses with rubber blocks and such. Just not big enough.

What I'm thinking...
Pour a concrete block with a 12" x 60" x 2" depression in the middle.

waterjet a top plate that has welded in anchors that go into the concrete block with a cut out for the depression.

The top plate has hinges and bolt downs for the "top box" I'm making this up as I type. Top box is a plate with reinforcements welded to the top, and a frame that holds a rubber sheet. I'm actually seeing the rubber sheet more less flush with the plate. not really a box. but there's a fluid port int the top plate and the rubber is what expands to do the forming.

So I take my nice CNC forms put them in the bottom. Pull the blank out of the oven, quench it, put it on the form. Cover it with a sacrificial sheet of rubber. hinge down the top box, secure it. then pressurize it. Part is formed, open it up pull good part out/repeat.

The question is how much pressure? I don't have specialized forming software. I tried running a Solidworks non-linear FEA to try out various pressures on thin sheet and I didn't get a nicely formed rib.
Obviously how much pressure would also dictate the size of the top box reinforcements.... the concrete I'll double check but I'm guessing it will be over built to begin with. As for a hydraulic source I saw a certain youtube fella do some neat things with a pressure washer.

Thoughts?

/I already had a real aerospace shop quote the job. Not gonna happen. I can buy 2 complete flying planes with for what they wanted. Besides don't tell me this doesn't sound like fun.

 

[verymadmac]

I get 12 but a couple look like the names changed over the years (some titles appear pre war only)
Adhesive Bonding ALCOA Aluminum
ALCOA Aluminum Extruded Shapes
ALCOA Aluminum in aircraft
Brazing ALCOA Aluminum
Combating Chemical Corrosion With ALCOA Aluminum
Finishes for ALCOA Aluminum
Forming ALCOA aluminum
Machining ALCOA Aluminum
Riveting ALCOA aluminum.
Soldering ALCOA Aluminum.
Welding & Brazing ALCOA Aluminum
Welding ALCOA Aluminum

 

[RoarkS]

Berkshire I just got my copy of Sachs second edition... found this on the inside cover:

I have a few of those alcoa manuals. I just got a copy of riveting Alcoa aluminum.

 

[mfgenggear]

When I was at general dynamics a lot of aircraft spars and what not was machined from aluminum plate. Would this be a consideration?
Machine honeycomb or equivlant to strengthen.
The pressing machines Will Taylor spoke of
I had experience with but has been few years.
Rubber pad pressing I believe would be the easiest. Make a bottom die from aluminum.
Add tooling holes normally at each end.
Use a light steel plate over rubber.
Use two hydraulic hand presses with pressure gages. Rolling a bead a round the periphery will be tough. I believe it was hand rolled with roller press.
Some critiquing required.

 

[rb1957]

"Some critiquing required." … not to worry on that score, plenty of critics here !

another day in paradise, or is paradise one day closer ?

 

[mfgenggear]

yeppers
look at this guy

https://www.youtube.com/watch?v=PUgXlYMLAkI

 

[mfgenggear]

https://www.youtube.com/watch?v=skcPu3TQTFU

 

[mfgenggear]

rubber press

https://www.youtube.com/watch?v=xw5yEMsDxR8

 

[RoarkS]

@mfgengear all of those are for metal skin wings. I can't have the relief/metal gathering features.

 

[mfgenggear]

@roarks please provide a blow up of the edge detail. so we may better under stand

 

[berkshire]

Part of the problem with the forming methods that mfgenggear has shown, which are quite popular hand forming methods, is that the rib RoarkS wants to make has a flat surface with no flutes or crimps in its edge. Hand forming this type of rib requires that the excess metal be removed by shrinking or tucking. This can be done by forming a tuck in the part, then hammering that out with a boxwood or hard plastic mallet, working from the inside edge to the outside, or by using a shrinking machine which grabs the metal and forces it in on itself. Whilst the rib shown in the picture looks simple to make, forming it without getting a sideways bend in it is anything but. The true hydroform press with enough tonnage has the ability to shrink those flanges, however even though the flange has been cut down around the leading edge, there is still a good chance of getting wrinkling there, which will have to be removed by hand straightening. Forming 2024 in the AQ (W) temper usually does not leave enough time for a subsequent hand straightening operation, requiring a second heat and quench for hand straightening after forming.
Can you do a material substitution to 7075 this will give you similar strength, with a lot longer working time from the AQ condition, corrosion properties may be more of a problem, but with etched and chromated parts followed by primer should be manageable .
B.E.

You are judged not by what you know, but by what you can do.

 

[mfgenggear]

may be able to bead roll it than hammer over wire like this guy does

https://www.youtube.com/watch?v=eOcZwr-1Y1E

 

[mfgenggear]

why not start wit -o temper then heat treat. typically forming required sub sequent heat treating to prevent cracking.
it may need multiple forming and heat treating. this is standard practice.

 

[berkshire]

Here is another of the

https://www.youtube.com/watch?v=aD0KsVmHc-w

videos showing a shrinker in action, this machine can form the 90 degree flange straight and true. What you are seeing here is the ability of the machine to pull in and gather the excess metal, in this case the operator is using mild steel , when forming aluminum a double folded sheet of Aluminum oxide paper is used in the jaws to avoid slippage and prevent tool marks on the part. Normally the flange would be pre-bent to 90 degrees then the excess material shrunk in on itself to make the flange straight . When I worked as a hand straightener at General dynamic this machine was quite often used to get that final tweek to get a rib or fuselage former straight. It does however require a certain amount of innate skill to do that.
B.E.

You are judged not by what you know, but by what you can do.

 

[WKTaylor]

MFE...

CAUTION.
Thin clad aluminum sheet is allowed only [1] exposure to SHT temperatures... and anneal temperatures are in this same temperature range.

NO re-SHT or re-anneal would be allowed. These high temperatures migrate the low-alloy clad aluminum into the structural aluminum degrading mechanical properties... and intended [cladding] corrosion resistance.

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[mfgenggear]

Do not buy clad material use bare aluminum.
Brush coat with chem film

 

[RoarkS]

Berkshire... I have to try the Aluminum oxide paper in the shrinker jaws!!! I've never seen that and wondered how they are used on aluminum without making a mess. The one I have has serrated jaws and destroys the alclad. Looks like Lazze fellas shrinker (in your youtube link) doesn't mangle the metal anywhere as bad as mine.

Re 7075, I figured that would be cost prohibitive and hadn't considered it. I can do whatever I want with it really... My dream is to completely replace the assembly with composite wings. Have you guys seen how DarkAero has built up their wings... WOW. But they haven't written the complete idiots guide to building honeycomb sandwich rib wings design and construction yet. Anyway Back in dayjob world Stress-corrosion-cracking issues have always steered my higher ups away from us using 7xxx in structural applications so I really don't have too much experience playing with it.

mfgengear berkshire nailed it as far as no flutes or crimps in its edge.

WKTaylor I've got "Forming Alcoa Aluminum" ALCOA 1962 in front of me...

"reheating of the naturally aged products of 2014 and 2024 alloys is not recommended unless it is definitely known that the part will subsequently be completely aged to the -T6 temper. Otherwise a reheating that is sufficient to obtain a material improvement of the formability of the alloys will seriously lower their resistance to corrosion."​

I'm assuming since 1962 someone read that with the upmost conservative interpretation and wrote a spec (??) that you're referencing prohibiting re-SHT or re-anneal.

mfgenggear... where does one buy non-clad 2024 sheet I didn't know that was a thing? Bar and shapes no problem. Bralco metals is the only distributor that normally stocks alclad in my part of the world... and even then my volume with them is so low I usually end up getting sheets from Aircraft spruce for the price.

 

[mfgenggear]

@roark
What part of the world are you at.
Scroll down to the .063 thick 0 temper, bare aluminium.

https://www.twmetals.com/products/coil-and-sheet/aluminum-alloys-sheet/2024.html?p=2

A 90 degree rounded should no problem with 2-4 forming operations. Trial and error
Each time the material will work harden.
There fore will require solution heat treat. I done a lot more severe draws, but had ovens and presses at my disposal.
With out notches or reliefs.plus very well rounded fabricators.
I still think this can easily be done with the rubber gurin process just not in one press, make two or three dies.