make your own press brake dies

Cold rolled will work, but will distort/deface easier than a heat treated material. I'd suggest some 4140/42 HT. It's tough enough to stand up to the work, but easy enough to machine. By working properly, you can end up with straight, pre-hardened dies that should work well. You'll have to come up with a method of locating and holding the dies. Could be you can make some slotted adapters that mount to the platens. Mild steel would be adequate for them. Should work quite well for bending, especially with the slow moving hydraulics you spoke of.

Harold

The college I went to had a 100 ton platen press that was THE thing for making light plane ribs and formers. They had a 2x2 (3x3?) rubber pad on the upper platen, about 4 inches thick. They used male dies, wood for single use, aluminum for production, with just a couple pins for retainig indexing of the part.

Trim the flat sheet aluminum to size, place on pins, press! Complete formed rib or former. Worked really well. The students there were producing RV-4 aircraft that were destined to be registered and sold, other students were involved in CNC milling of the master forms. All pretty cool stuff.

Betcha it'd make a lot of applesauce! :-)

Cheers Trevor Jones

Why am I thinking "Ultimate cider press"?

Pete C.

I'm using that rubber (it's PU) for my press-brake. The company I bought the PU-sticks from is also making that special PU plates and do have a foil to protect the PU (as a wearing surface). You can even cut sheet metal on "rubber". The huge advantage is, that the dies are damned simple (cutting even works with CRS that is case hardened for short runs), the disadvantage is that you need a lot more pressure. But with 150 tons, I wouldn't worry about it that much. :-)

It seems, that they don't have a representative in the USA, but I bet you'll find something similar "over the ocean".

For those who have missed my posting for the press brake:

Nick

Karl, whatever you do, be CAREFUL. That much power moving slowly can very suddenly cause things to pop sideways with a whole lot of kinetic energy.

GWE

I've not seen this rubber idea at all before. I googled for "Veith Eladur" and see nothing on this side of the pond. Anybody know of a US source for this piece of rubber?

Karl

A big 10-4 here. Now convincing "the kid" about safety and danger is a different matter. He had a skate come out pushing the unit with my forklift. Could have tipped it over. Busted the 10 ton toe jack getting it level. Its sitting in the middle of the room waiting for a 20 ton jack from Ebay. He also dumped the new 10hp air compressor off the pallet when moving it out of the way - busted up a bunch of fittings on the compressor head.

Karl

Karl, this book does a good job of covering rubber in the press from a jewelery approach:

Steve who hasn't tried it either

Karl,

The "kid" sounds like a "chip off the old bull in a apple shop".

Bob Swinney "Karl Townsend" wrote in message news:AN_2h.2214$ snipped-for-privacy@newsread1.news.pas.earthlink.net...

...

Back in 1968, I wrecked my dad's new pickup truck. He was giving me holy hell until gramps said, "Whatever happened to my '36 Ford?" I never did find out about that old Ford, and never got any more trouble about wrecking his pickup. What goes around comes around...

Karl

I didn't check the link, but I get the idea that they're talking about urethane---which is commonly used for such applications.

Harold

...

They do indeed mention polyurethane, and Nick goes on to mention the trick is the hole in the bar. The piece looks to be either 1.5"x1.5" or 2"x2" square with a 3/8" or 1/2" hole all along the length. I'm sure Nick could chime in with the exact dimensions.

I could order urethane stock from McMaster Carr, but I have no idea how to drill a hole two feet long down the center of a small square. Any ideas?

Harold, thanks for the very informative post on my query.

Karl

My Dad had an old book by Alcoa that described this. No ISBN, just copyright dates of 1947 to 1962, titled "Forming Alcoa Aluminum". Maybe a library would have a copy, or maybe Alcoa still publishes it? Paraphrasing, they list two general categories of rubber-die forming: those using only pressure to form a sheet to the shape of the punch - the Guerin and Verson-Wheelon processes; and those using additional blank-holder control - the Marform and Hydroform processes. The Guerin process was the first commercial rubber-die process and was introduced by the Douglas Aircraft Company in 1935. Anyway, searches for those process names might turn up some details. They all used to use real rubber but I guess polyurethanes have taken over :-).

The Guerin process sounds like what Trevor is describing. They describe the pad as several layers of rubber cemented together, housed in a strong steel or cast iron container which is about one-third deeper than the rubber, attached to the upper ram of the press. The dies are simply laid on a platen which must fit snugly into the rubber container to prevent extruding the rubber and damaging it. A side clearance of 1/32 to 1/16" is recommended. The rubber will exert force in all directions like a hydraulic fluid. The forming pressure in psi of the rubber equals the press force in tons times 2000 divided by the platen area in square inches. The max height of the die should not be more than 2/3 of the rubber thickness. A rubber pressure of 500 psi will form 0.032" annealed aluminum, and the max pressure used in Guerin work is about

1500 psi which will form annealed 3/32" sheet.

Thought it sounded very interesting when I first read about it, but I've never found an excuse to set up and try it :-). Oh, a 150 ton press would give a pressure of 1500 psi over a platen area of 200 square inches or about 14x14". I'll leave it as an exercise for the reader to calculate the wall thickness needed for the box to contain the 1500 psi rubber :-).

-- Regards, Carl Ijames carl dott ijames aat verizon dott net (remove nospm or make the obvious changes before replying)

I do this rubber thing... What I use for rubber is new forklift tires before there glued to the rim... They come in 4" x 12" x 5' chunks of really good rubber... The stuff never seems to die...

I have a copy of Forming Alcoa Aluminum, also Soldering Alcoa Aluminum and Machining Alcoa Aluminum. Most can be found at an on-line used book site. There's also Welding Alcoa Aluminum and Brazing Alcoa Aluminum

Those rubber bars look really cool, Nick. Are they expensive?

Best wishes,

Chris

It would be easier to commission someone to cast it. Urethane, depending on the hardness, can be a bitch to machine---the softer it is, the less likely you'll be successful.

If you'd like to research the casting idea, please contact me on the side and I'll provide contact information for a guy in Utah that has spent the last 40 or so years working with the stuff. He was trained in the aero-space industry and is well experienced in casting the material.

You're most welcome. Hope it helps.

Harold

Not really cheap. A bar 250 mm long costs 35$. They have them in 1000 mm too. I just found out. The catalog I had was quite old.

Nick

OK, they increased the product line since I bought that stuff. They have a wide selection of cross sections now:

a and b is width and height e and f is the rectangular bore or the diameter. They now have lengths of

250mm and 1000 mm

a 25 50 50 75 75 75 75 100 100 125 b 25 50 75 75 100 125 150 100 200 125 e 45 40 60 85 100 50 140 75 Ø 10 Ø 25 f 20 40 35 35 35 50 50 75

They also have massive sticks that work to, but require more force and a different bed for the stick to lay in. Maybe easier for you as you can get massive sticks much easier. The bed looks like this.

+----+ +-----+ | | | | | +--\ /--+ | | \ / | | -- | +---------------------+

For 3mm sheet it takes up to 750 kN / m bending. It is OK for up to 4 mm

The bored sticks go up to 8mm sheet metal (400 N/mm^2 strength) They require 750 kN / m bending with 8 mm sheet metal. The bored sticks are much better, because they wrap around the work.

They also have "delta" sticks that go right into a conventional Vee-die.

You find a brochure here:

It is in Kraut-speech, but if you start looking at page 11, you have got enough dimensions and pictures to get ... the picture.

HTH, Nick