# Hydroforming

Discussion in 'Workshop Tips and Secrets / Tools' started by Kyle Boatright, Apr 3, 2013.

1. Apr 3, 2013

### Kyle Boatright

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I have access to the CNC equipment to create male (or female) dies for nosebowls for a couple of pre-war Aeronca projects I own. In addition, I have acces to a large hydroform press. What I don't have is any practical knowlege of the hydroforming process, particularly for large complex shapes which require shrinking for the major "bowl" shape of the nosebowl AND stretching for the air inlets.

Questions which come to mind are:

How do you deal with springback?

At what point do you need multiple dies?

Does anyone know of useful how-to resources for this kind of thing? BTW, I saw EAA's video on hydroforming small parts, but I assume the degree of difficulty for something like a nosebowl is much higher.

Thanks for the help.

Kyle

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2. Apr 3, 2013

### cvairwerks

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Kyle: Kent White has done a nice video on low pressure hydroforming with a cheap high pressure washer.
He shows how he did the wheel pants for the Hughes Racer replica. Well worth the price for a copy
of the video.
See his website @ tinmantech.com

3. Apr 4, 2013

### Marc Bourget

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Go to Amazon or other online used book websites (abebooks.com) and see if you can find an Alcoca Tech book "Forming Alcoa Aluminum"

What's the machine's capacity for depth? There are other processes that may be more efficient, but the relatively high pressure of a true hydroforming machine permits you to pretty much "net" the tool.

Have you considered explosive forming? I undertand there's someone already forming nose bowls using gasoline fumes in a hole. Some use water pools to dampen, as well. Check YouTube.

mjb

4. Apr 4, 2013

### Brian Clayton

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I saw some forming once that was done in a buried 55 gal drum, filled with water. Converted ac compressor for a vacuum pump and fireworks for the explosive charge. In Bangladesh if I remember right, forming a sheet metal dome for the displacer in a 5hp stirling engine. They had to fiddle with the dies some, to get the material to lay out right (without wrinkles or creases), but eventually got it to work. I think the book detailing the process was "how I built a 5hp stirling" or something like that.

5. Apr 5, 2013

### Kyle Boatright

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I'm gonna rent that right after SnF. If it is good, I'll just keep it and pay the difference in price. I like how he does that...

6. Apr 5, 2013

### Brian Clayton

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The hydroformed parts I have seen dont use multiple dies. I think you just have a female die, with a sealing ring around the outer perimeter. Clamp your plate to the face of the die, and pump out the air on the other side. Have not seen the low pressure forming. Nose bowls would seem to be much easier to make using conventional metal shaping....were the originals formed this way?

7. Apr 5, 2013

### Kyle Boatright

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My thought process is that conventional metal shaping requires skill and dexterity which take a long time to develop. Hydroforming requires getting a hard tool right once and learning how to properly use it. Also, once you get it right, you can make multiple copies or help others in the community make copies. All of the pre-war nosebowls are in rough shape.

Since I have access to the right tools, why not use 'em?

My guess is that the originals were made using hard tooling - hydroforming, stretch forming, etc. Something involving hard tooling and a big machine that would mash your hand pretty badly. ;-)

8. Apr 5, 2013

### Brian Clayton

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Maybe, but dont forget that era of metal working is gone. It hard to even find a good tool and die maker in the states nowadays. Body men dont fix panels anymore, they replace them. Hand forming metal is a art......and becoming lost. I would guess that they were formed by hand, probably checked over a wooden buck. Big press dies would only have been worthwhile for the auto manufactuers. 10,000 cars vs 100 airplanes. If pressed, you need a male and female die, and probably several different ones for different operations. I looked at buying some equiptment out of the old murray lawnmower plant, and the big presses there stood around 3 stories high. Just a little too big for my shop.......

9. Apr 5, 2013

### Pops

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I used to work in a major auto company's stamping plant. Designed automation for the presses, among other things. Just the top portion of a press (crown) of some of the presses can weigh 200 ton and yes,they can be 3 stories high. Type of press to stamp a complete auto body side, etc. 5 presses in a row with the first press with a draw die installed. One part about every 18 seconds. Had 50 of these types of presses.
Smallest press that they had was a small portable press that weighted 30 ton. They had about 75 of those. Take a 200 ton overhead crane and move then around where needed. Dan

10. Apr 6, 2013

### Brian Clayton

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I always wanted to remake a few old ford parts, aluminum bumpers, aluminum bumper brackets, aluminum inner fenders. It just didnt seem practical after see how big the equipment was. Even bought at scrap price, a million pound machine adds up fast. I can understand the draw of the idea to "stamp out" a part, just not sure how practical. Even with cnc machining of the die, the initial cnc program has to be done.... not easy for a multi compound part like a nose bowl. Even using to make a master or buck to form the part too might far outweigh a small run of parts. They guy making the static display on the other thread might have a few ideas..... I would **** sure call him a expert on the matter.

11. Apr 6, 2013

### cvairwerks

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Doing a wood die for hydroforming a few nosebowls is not that hard. A decent Cad/Cam operator can have the file ready to export to a POST processor in a few hours or less, depending on the complexity of the contours. At that point, your time controller is how big of a mill you have and how fast the material can be removed from the blank and getting it to the hand finishing stage.

12. Apr 7, 2013

### Kyle Boatright

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An ex aircraft partner is a computer whiz and is finishing his 4 axis mill and profilograph (or whatever it is called). He wants to do a few fun things before he tries to make  with the setup. He's doing the nosebowl plug for me...

It is good to end your aircraft partnership and keep the friendship in good standing.

We're thinking corian for the initial die, although he says he can make it out of aluminum if I want.

13. Apr 7, 2013

### Brian Clayton

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one problem with not using your final material, is that all of your feed rates and cutter speeds will be wrong.... say between wood and aluminum. Unless time does not equal money in your case, might be cheaper to just do it one time. especially if all of the tool setups have to be changed too.

14. Apr 7, 2013

### PTAirco

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Last time I looked Corian was phenomenally expensive, but that was a few years ago. A long time ago I had a lot sheet metal ribs pressed on a huge rubber press and used a material called Jabroc, a compressed plywood, for the dies. They were like granite. That stuff is sold under different names, in Germany it was Panzerholz.
Seemed a great material for dies, since it also had a slick, low friction finish that let the metal slide nicely as it was being formed.

The press, incidentally, was at the old Miles Aircraft factory in England and was capable of 5,000 tons! It used a 12'x12' bed.

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15. Apr 7, 2013

### Brian Clayton

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If you look at some say, mid 60's full frame cars. Look at the inner fender/splash guard panel under the hood. Several large radius, compound bends that are made in a press. If you look at the areas that need to be shrunk, you can get an idea of how the die needs to be made in that area. Kind of like flutes on rib flanges. That is probably the hardest thing to figure on press dies is where and how to make the dies shrink the material. To figure how much, you can lay a sheet of tissue paper over your original part, and "draw up" and fold the areas that need to be shrunk, and even cut the paper where they stretch. If done right, you can get the paper to lay flat against your compound curves, and then you can see exactly where the material has to "move".

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16. Apr 7, 2013

### BBerson

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Do they still use drop hammers? (I think Univair has an old drop hammer for this)

17. Apr 7, 2013

### cvairwerks

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Drop hammers have their place for doing a lot of forming, but hydroforming has taken over for a lot of short run stuff. If you are going to form a few thousand or more parts, then the hammer is probably way cheaper to run. Hydro really shines in short run or prototyping as you can machine dies out of inexpensive materials that will hold up for a while. Hammers still need kirsite dies and all the accompaning expense of a tool and die crew to build and maintain them as well as experienced hammer operators. Hydro dies can be run on a CNC center and be nearly ready to use when unloaded. Once it's set up, a hydro unit just needs a button pusher to load and unload material and parts.

We phased out our hammer house and the die people about 15 years ago as the company chose to farm out most of our forming work. For nearly 40 years we even had a rivet manufacturing shop inhouse. Now the bean counters just the see basic cost between doing things inhouse and farming it out and have killed off and disposed of most of our specialized capabilities. They never see the expense of the wasted time if we need something special that has be obtained from outside.

18. Apr 7, 2013

### Pops

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Say a 800-etc, ton Danly press. The press has an electric motor turning a large flywheel to a certain rpm. The flywheel was a clutch and brake built into one side. When you hit the run button the brake is released by air, and the clutched in engage by air and the flywheel turns large herringbone gears that turns 2 large crankshafts on each end of the crown (top) of the press. Large rods are connected to the crankshaft,(Just like in your auto engine) The lower end of the 4 rods are connected to the ram,( the top part of the die is bolted to the ram). The ram can be lowered or raised by electric motors in relation to the end of the rods, to adjust the bottom stroke of the ram and the top part of the die. The bottom of the die is bolted to a large steel plate called the bolster plate, the bolster plate is setting on 3 large air cylinder that extend down to a lower floor level. The clamping pressure of the die can be set by varying the bottom stroke of the ram and the air pressure in the lower air cylinders. A draw press has another ram inside the main ram. The outer ram clamps the metal and the inner ram comes down and draws the metal. After the press go past BDC on the stroke the ram goes back up and stops at TDC when the clutch disengages and the brake engages
Just a very short description.

19. Apr 8, 2013

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