The Home brew press brake

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Roy
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The Home brew press brake

Post by Roy » Mon Jan 19, 2004 3:10 pm

I went today to the fab shop that I always get my steel (usually drops for free) from and we took a look around after his looking at my sketch of what I wanted to make. I eventually wound up using materials he had on hand that could be had for a decent price. What I wound up with is W section beams which are 8" web and flange and 3/8" web and flange thickness. 28 # per foot. NIce and heavy and stout. I will use them for the vertical uprights of the frame as well as the fixed upper and lower beams. Should not have to box em in with reinforcing to reduce flex with that series of beam. The other beams I had seen on the press mine is modeled after were ligher S section beams. For the bottom die I got 2 x 2 x 3/8" angle which will be welded on a piece of 5/8 x 6" flat bar. For the moveable die head beam it will have a 2 x 2 x 3/8" angle welded to a piece of 3/4 x 3" flat which will be welded to a piece of 2 x 4 x 3/8" walled rectanglular tube. POwer is a 30 ton ram from a porta power working of a 10,000 psi 2 speed hand type pump ( all from a Greenlee ridgid type conduit bending set) of which all I have is the 30 ton ram with 8" stroke and the pump assembly, and one or two other die heads for ridgid conduit (3" and 4" IIRC)

I elected to make my width at 50" as 99% of everything I have ever bent up was 48" or less. I decided that if I went to 60" I may as well go to 72" and if I went to 72" I may as well make it 96" so I had to draw the line at 50".

Just experimenting with a small section of the angle iron dies welded up to a piece of flat stock and placed in my bench vise I find I can bend up a U channel pretty easy, as long as the width of the bottom of the U is more or equal to the overall height of the moveable die head.

The original press brake I saw had the bottom angles welded like ^^ so their bottom legs touched to form a V in the middle, but I found if I spaced them apart approximately 3/8" or just enough so the upper angle will just about bottom out on the plate instead of in the valley of those bottom two angles I can get a better bend on heavier material, and I can slip in a piece of 1/8" flat stock to get a closer radius on lighter stuff.

So tomorrow morning I have to head back up the road and we are going to cut it all to size in the yard. Best part is it is all costing me less than $100. Hard price to beat for close to #850 pounds of steel rust free.

Another plus is he (the owner of this fab shop) thinks he has a set of upper and lower dies (Chisel and V type) from an old press brake he used to have around some place, and all he has to do is find them, and I can have em. So the upper and lower dies may eventually get changed to real dies. I don;t think with home shop use though that the angle iron dies will deform or wear out all that quick.

Be a perfect project to start consuming all those 7018AC 3/32 and 1/8" rods I have just laying around gathering dust. I usually always go with 6013 or 7014.

Nothing like starting a new project before the last one is finished, but I need a means for bending up the sheet steel for the covers etc.

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brent
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Re: The Home brew press brake

Post by brent » Tue Jan 20, 2004 7:20 pm

another "type" of die you can make is to use two pieces of round stock laying parallel ,attached at the ends so you can press "through" giving you a tighter than 90 degree bend. I built a 50 ton H frame press, modeled after the enerpac 50 ton, and I used a enerpac 50 ton cylinder and pump. I have bent some 1/2 steel, about 12 " long,she starts taking a LOT of hydraulic pressure to do that. have fun , be careful. Brent

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Doug_C
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Re: The Home brew press brake

Post by Doug_C » Tue Jan 20, 2004 9:19 pm

Sounds like a neat project. Something to keep in mind for the sake of safety, if anything else.

I have always used 1/4" plate as a standard for estimating tonnage per foot required to air bend a 90 deg angle across a lower V die of 8x the material thinckness. 1/2" and above is 10x material thickness. Anything greater will decrease the tonnage. Anything smaller will start to increase it exponentially. Round rods for the lower V die will throw this proven theory out the window as the contact point is ever changing as the material is penetrating between them.

My base is 15 tons per foot for 1/4" mild steel. A-36 is considered mild, but has a spec wide enough to throw in almost anything in the yard short of AR (Abrasion Resistant) plate. Which is another issue....know the material before you continue to bend it. AR can bend like a spring and possibly shatter before it reaches 90. Like hell unleashed if you are in its path.

For the average A-36 I would use 20 tons/ft, so by 1/8" increments you can guess what the tonnage across the required die should be. Taking into account what die is available and/or feasible. 1/2" material should take 40 tons/ft as 3/8 will be 30 tons/ft using the proper dies. Aluminums can be .7 times that and stainless can be 1.6 times that base.

This is a generalization, but now take into account what your home made dies can handle. Even many OEM manufactured lower V dies below 2" wide are not capable of much greater than 40 tons/ft.

The wrong mix of material thickness and die width can be an accident waiting to happen. Knowing the tooling and material to keep tonnages under control, is what this is all about.

Brent's suggestion for anyone doing press work, to be CAREFUL should not be under estimated.

DC

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Roy
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Re: The Home brew press brake

Post by Roy » Wed Jan 21, 2004 12:08 am

I don't anticipate ever having to bend much thicker material than 11 ga sheet steel. If I need to bend 1/4" it would only be narrow widths no more than maybe 8 or 10 inches wide. The majority of things I usually bend up is 14 ga and smaller, and I do believe this is going to handle 14 ga up to 48" wide.

I have an Enerpac 30 ton hydraulic system (badged Greenlee) that will supply the hydraulic pressure.

I have the frame all welded up and standing on its own. A bear to do by yourself. Presently working on the dies which brings a question up. On the original press I seen it had angles welded on a 1/2" thick x 6" plate to form the lower V die. This plate was then welded to the I beam that formed the lower fixed table. Welding to me is permanent, so I thought about bolting that 1/2" steel plate to the I beam and having the p[late drilled and tapped and run the bolts in from under it through the beams flange. This way I can always change out or experiment with different dies, and also use it as a conventional press to some degree.

The fellow at the job shop has a set of old but good dies (chisel type upper and multi groove lower die block 6' long) that he said I can have when he finds it, so I would like to leave the lower fixed table free for future modification if he ever finds those dies. Plan is to mount that set of dies in the press someday, and utilize the 2 foot drop in a heavier duty narrow press later on.

So how about my idea on bolting that lower die plate to the beam instead of welding it. I don't see where any stress would cause a problem with the bolts unless the beam bows and bends, and then odds are I have other prooblems as well, but really don't see that happening with the gauge metals I work with. Of course I may be wrong on this idea as well. Opinions appreciated.

Attached is an image of my frame so far. I have to mill out a plate so I can slide in the hydraulic cylinder, and also cut some 3/4 or 1" plate to back up under the hydraulic cylinder on the upper beam and the moveable beam. This time tomorrow it should have been bending some metal I hope.

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Doug_C
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Re: The Home brew press brake

Post by Doug_C » Wed Jan 21, 2004 1:40 am

Hi Roy,

Well, our 50 ton H frame Dake press is about that stout. I can't say that you would stress it at 30 tons. Not to be critical, but the upper ram bar does not appear to be worthy of the 20 tons it will likely take to bend 48" of 14ga. I just don't know for certain. Time will tell. There are a few guys here that can shed some light on this here, I think....

I'm not sure if there is much need to bolt the die down unless warpage is a problem.

One thought could be to weld strips on to the bed top along both side of your V die to form a channel that the die sets into. Should be sufficient. Then it would be easy to change dies with other shapes quickly.

With a couple 3/4" or thicker plates welded in place, you could simulate a standard filler block with set screws for holding the tongue of standard press brake dies. Sky's the limit I guess.

Here is a good link for verifying my tonnage estimates. Check out the effects of V die width on 1 foot of material using the known factors I gave in my previous post. Even though the base is 15 tons for 1/4", I up that to 20 for hedging my bets that the material may be harder than mild steel.

Press Brake Tonnage Calculator

I just acquired an 11 ton Dreis and Krump. I think it is a 3 or 4 foot Machine. I liked it because it was single phase.....oh and free! [img]/ubb/images/graemlins/blush.gif"%20alt="[/img]


DC

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Roy
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Re: The Home brew press brake

Post by Roy » Wed Jan 21, 2004 10:48 pm

Doug
Are you saying that you do not think that my upper I beam will take the pressure? Or are you referring to the portion with the single die attached to the bottom of the ram itself. I upped the pice of steel from 1/2 x 3 to 5/8 x 3 and now the walls in the 3 x 3 tube are 3/8", along with the angle die being 2 x 2 x 3/8"

I never would have thought it would take 20 ton to bend 14 ga. Odds are I won;t even be dong a lot of 14 ga that width, but just as long as I can bend up my 16 ga x 36" wide for my saw covers I'll be a happy camper. Anything else will be gravy. I don;t think it will have problems doing the 16 ga stuff.

Have to go and check out that link

Thanks

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Doug_C
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Re: The Home brew press brake

Post by Doug_C » Thu Jan 22, 2004 1:40 am

If there were a cylinder at each end, or to distribute the load more evenly, this would be less of an issue.

The single die at the end of the cylinder rod, if that is what will be used. You may experience inconsistant bends over the full 48 inches. Where the ends are open greater than the center.

This will be the first culprit to suspect. I was hoping someone else could do the load calculations to estimate the deflection. Ultimately, that will determine what the capacity of the project. Weakest link..so to speak? Your frame looks pretty beefy. As long as you trust your welds.

There is a risk of the upper die not being aligned while being under load. So as it presses, it will attempt to align itself.

A thought on the upper die alignment to the lower die. If you had channel sections on the ends of the upper die holder(Ram) that would ride the I-beam support housings as it strokes. A liner of disk brake pads on the faces of the channel sections would keep it from rubbing metal to metal.

Having the cylinder as the only means of restraining all the tonnage, may prove to be taking chance too.

I was thinking of ways to convert this 11 ton that I will have, to CNC fluid controls. Yours would be cool with a PLC too! [img]/ubb/images/graemlins/grin.gif"%20alt="[/img]

DC

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Roy
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Re: The Home brew press brake

Post by Roy » Thu Jan 22, 2004 11:59 pm

I understand what you were saying now. I agree, twin rams on the ends would be better, but I only had one ram. I do think I may add a power hydraulic unit to it and invest in two cylinders. The way I have it made and assembled its only a simple matter to make the change when I find the right cylinders. Its fully functional as of tonight, so tomorrow I hope to bend up the covers and get my saw finished. I had a couple of drops of 14 and 11 ga material that Iplayed with. Mostly strips 4 to 5 inches wife in 8 and 10 foot lengths I cut up in 24, 36 and 48 inch lenghts just to see what it would or would not brake. It handles 14 ga without a problem the entire span of 48 inches I can bend the 11 ga up to about 36 and have a uniform bend along the entire length, but over the 36 and the ends of the piece are not quite the same radius but still very well useable. After I finish my covers and have some time to play, I am going to experiment with round stock for the lower dies, and perhaps a good piece of harder steel in chisel form for the upper die.

The original press brake I seen had two telescoping tubes to algin the uipper andlower dies, but it hindered removing the upper die head to use it as a conventional hyd shop press.......so for now I clamped some 1 x 1 x 1/8" pieces of angle iron to guide the upper die into the lower die, and it seems to work fine. I was concerned about metal to metal scrubbing, and like the idea of a brake pad material. I have a used but like new clutch plate I can probably salvage some nice sections of lining from that should work ok. I think it really has potential if used within its build and design specs. I sort of proof tested it tonight and bowed upon the handle pretty good on the pump. Everything looks fine. I have never had a weld break yet on me, but there is always a first time......but its all put together with 8018 rods and the wel;ds look great so I am pretty trusting in that aspect.
Time and use will tell the big story down the road though. I'll post some pics of it when I get caught up.
I really apprciate your insight and info on press brakes.

For the most part I think its a worthwhile project and not a hard project to make. It sure is going to beat a bench vise and pair of angle irons and a big hammer, thats for sure, and its a lot more sturdy than the average apron type brake, but still not a replacement for one in some applications. But I think I can now get by with a small perhaps 12 or 18 inch apron type brake for small light stuff.

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Doug_C
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Re: The Home brew press brake

Post by Doug_C » Fri Jan 23, 2004 2:33 am

Nothing like proof in the successful bends.

If your cylinder bore is known, you can add a pressure gage to the line and calculate a gage scale on PSI converted to actual tonnage applied. A travel indicator clamped on the cylinder rod will give some simulation to reference repeatable bends once you find 90 degrees too. Between pressure and ram position indications, you should have a reliable bending system.

Hard to beat the price on that deal.

DC

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