Rubber forming, aka Guerin process

[Russ Hanscom]

This is forming of metal using rubber as one side of a die, and something hard on the other side. See rubber forming on the internet.

Can anyone suggest a source of practical application information, I want to form thin copper and brass, .020 - .040" thick and since a bunch of related parts are needed, I would rather have something faster than a shot bag and hammer (already made test pieces that way)

Thanks

[whateg0]

At one time, metalmeet had a few discussions about it, I think. I've never used rubber, but have used softwood at times for shallow things. There's also some youtube videos but IIRC, they were rather lacking in details, such as recommended durometer.

For simple shapes, a simple opening and something to push the metal into it works, but obviously for more complex shapes, you need the opposing force everywhere.

Dave

[Russ Hanscom]

I have gleaned a suggestion of 60-70 durometer for the rubber from one vender's site, and I have a source for the proper rubber. Not that expensive so I probably will get some bits and start playing. Fortunately the pieces are for wind sculptures so there are no required tolerances.

[GlennW]

I've done quite a few parts using 1" thick Buna-N 70 durometer sheet on the bed of a 50 ton press.

There are a number of techniques depending on the size and shape of the parts.

I used to run a press brake using 2" square polyurethane bar for a lower die and just push the upper die into it. It made prefect mar free bends in aluminum sheet that matched the form of the upper die. I also used a six inch wide steel flat bar as a lower die along with the 1" rubber to press out smaller parts.

You can also build a stout steel box, fill it with smaller chunks of rubber and ptess your die into that if you need more depth to the parts. The chunks being contained in the steel box causes them to compress all around the part.

[Russ Hanscom]

That is close to what I am thinking. I have a 40 T press and was thinking of building a 6" x 12 box and putting 2" of rubber for testing. I need up to 1" of depth on the parts, but no tight edges.

[GlennW]

If you use the box you can use cut up inner tubes to fill it as they will conform to just about anything and give more even pressure on the form.

[GlennW]

I just googles this up.

You might have already found it...

http://www.eaavideo.org/detail/video/12 ... TOTAL:DESC

[Russ Hanscom]

Been a long time since I saw an inner tube! What with everything being tubeless these days, but we do have several large truck tire repair shops in the area, might give them a visit.

Interesting video, not impressed by his ram tip alignment though. Thanks for the link. Would not have thought of a spray lube - might grab the wife's Pam.

[Bastelmike]

Hi Russ,

I have a 50 page pdf about rubber forming, made by a Company who sells Equipment like those rubber bars. It contain a lot of Information.
Problem: Its in German

I You are interested I would email that to You.

Mike

[Russ Hanscom]

Sure, why not. I might be able to glean a few bits or I might find someone local that knows German. If it can be sent by pdf, I would appreciate a copy. There might even be some online auto translate functions that could get most of the words.

Thanks.

[Russ Hanscom]

Sure, why not. I might be able to glean a few bits or I might find someone local that knows German. If it can be sent by pdf, I would appreciate a copy. There might even be some online auto translate functions that could get most of the words.

Thanks.

For email; use russhanscom@gmail.com

[Russ Hanscom]

Ok, a bit of an update.

I made a sturdy metal box, 6 x 12" inside to take half a sheet of rubber, and multiple layers to get about 2" thick. So far only using a 5 ton press, which is ample for this stock.

Tried a few forms, using an oak male form, and with .02" thick copper, and .03" thick brass. The parts had little wrinkles along the outer edges. Figured the edges needed some support so l I tried a piece of hard rubber as the top layer; that gave much better results, just a hint of wrinkle, so on the right track.

Re the pictures; the oak form has a 1 1/4" cross radius and a 12" long radius. The metal has a plastic protective coating, clear on the copper, and bluish on the brass, most of the wrinkle is in the coating only. Blanks are 2 1/2" wide and 6" long.