How much force required?

[Hex]

Hi
I`m hoping to tap into your vast experience to help solve a problem.
Plaese note that i`m not a blacksmith, more of a hobbiest, but i`m quite resourceful :wink:

My question is roughly how much force (in tons or kg) is required to press 3mm thick aluminium sheet approx 10" in diameter into a shallow cone?

The angle of the "dish" after pressing will need to be about 12 degrees..but i`m guessing the tooling will need to be at a greater angle to account for springback?

I wondered if this sounds like a remotely workable plan,
My first thought is to use a hydraulic press with a male punch and a female die (hope the terminology is correct)
Essentially the punch pushes the aluminium sheet into the die and forms the shallow cone.
A center hole in the aluminium sheet (and in the punch) placed over a locating pin in the die to keep things aligned during the pressing operation.

Any and all advice appreciated

Regards Colin

[irnsrgn]

about 11 ga. alum I assume, depends on whether its soft or hard alum and the form of the dies.

[Hex]

Hi Irnsrgn
Thanks for the swift reply.

I`m not sure of the grade but softer than T6, I assume it`s a general purpose alum if thats of any help.
I didn`t realise there might be options for the die forms.
I envisaged a cone shaped steel punch and a recessed cone for the die.

I`m not sure of the correct placement though, i presumed the male punch would be on the ram to push the plate into the die, but perhaps the female die should be on the ram to form over the cone shaped punch?

It`s obviously not as simple as i first imagined :wink:

[irnsrgn]

well you gonna need prettys soft alum or its gonna shear instead of bend and crack instead of compress. You will need all corners polished like mirrors and some kind of lubricant. The lips will need to compress and become thicker at as it comes up compresses. cracking from compression is always a problem especially with tough aluminum.

But I am no expert, just a few trials and then no more.

And as far as tonnage, 10 tons should be more than suffiecient for soft aluminum.

[henerythe8th]

You may find, depending on what you need these cones for that it may be easier to cut sheet and form them from flat sheet and rivet or weld them together...

...just a thought, without knowing what you need them for...

henry

[nightwalker]

Hi Hex.... Well I do not know the tonnage or force required, however in my daily delivery dutys I do have access to many industrial shops that make tank heads, one thing they all have in common is that they gradually form the "dish" using huge presses, however they do not press it all at once, well except for the real big one that stamps out two inch thick iron dishes about two feet in diameter in one swelt swoop.. anyway, they start out with a small amount of compression, the hydraulic punch goes up, and they rotate the disc a little with each slow stomp, gradually increasing the " throw" as it starts forming a dish, the bottom is concaved, the top punch is convex, they keep going round and round and gradually increase the throw and shazam... a texas chilie bowl is formed......... they usually have a swatch of carpet on the lower concave die and I have never seen any kind of lubrication used....... I know your application is considerably smaller, however I hope some of this information can be of some use as to your project..... Brian...

[Hex]

Many thanks for the replies, guys.

At least I have more information to go on now..forewarned is forearmed as they say :wink:
Looks like i`ll just have to give it a try and see how things turn out.

Regards Colin

[Chris Pook]

alot of places use rubber or a soft urethane with there dies for shaping stuff.

[Hofi]

you can ''raise'' the cone on the lath with wooden cone mandrel and a roller or round pointed hard wood to press it to the wooden mandrel while runing the lathin high speed.soft allu is a must with the press also.

hofi