Another bending question

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I'm going to be making a backhoe bucket for a small catagory 1 digger and came up with an idea for forming the main body of the bucket. My goal is to produce these frequently and the hardest part is rolling/forming this one part. I came up with the "die set" below that I'll set a sheet of 11ga in and stamp it into the main body. I need to add more structure to the top die but before I get ahead of myself I thought it best to bring this to the board for feedback. The sketch below is just the 2 dies to show what I am talking about. I haven't given thought yet to mounting and driving the dies or how much force will be needed. Before I spend any more time designing this I'd like to know if it will work. My hope is to get a nice radius curve with the 2 bends shown. The bends are 15 and 20 degrees. At the widest point the part is 20 inches wide, 13 inches at the deepest point. I hope to stamp buckets that are 16 and 20 inches (length of main body). Thoughts? Attached Images
Reply:I don't know much about stamping and how that would work but I would think that if you are going to be producing these a slip roller might be a good way to do it.  Also think that 11 gauge might be a little thin for a bucket like that.
Reply:Your drawing shows how it would be formed if you used a brake to shape it, any reason you couldnt do it that way?Since you already have it drawn out, it would simply be transferring the bend lines and hitting them to the right degree, and in the right sequenceHave we all gone mad?
Reply:Buy a brake instead.There is a reason why they make dies like this from solid blocks of steel that weigh several thousand pounds. These dies will not hold up.And you are talking one VERY big press to do this- in industry, they would probably use a 500 ton to 1000 ton 4 post hydraulic press. Maybe  bigger.Pressing it all at once in a die like this is done when you need hundreds, or thousands, of pieces a day, and its worth spending the time and money on expensive tooling, because you need a very low per part price, and a very high volume.Instead, you should find a small used mechanical press brake- often available for only a couple grand, sometimes just for the price of hauling. Then bend a series of bends, and make your curves.If its only 20" wide 11gage, you could actually do this with a good hand brake- my Chicago D&K is rated 12 gage, but will bend 20" of 11 gage, and I have bent shapes like this pretty quickly.You draw a series of parallel lines on the steel with a silver pencil, then bend, move, bend again.You could make one, by hand in a sturdy enough manual brake, in under ten minutes. And save on gym memberships too...You cant do this on a cheap chinese 16 gage brake- you would need a decent sized one- my 12 gage brake weighs 2000lbs for a 4 foot machine.Much cheaper, though, is just finding some shop with a big old press brake, to knock em out for you- you could probably get em for under 20 bucks each. (not including material)
Reply:Ditto what Ries said re using a brake. Also by pressing it in one shot you have no adjustment to allow for spring back. Different plates differ as to how they bend, some more some less so if you should get a bunch of thicker/thinner, slightly harder/softer plate you'd be up the crick.....Mike
Reply:Thanks guys. I really appreciate the insight. I knew what I was thinking was too simple to actually be practical. I'll explore the hand brake approach which should work fine since each bend is only a couple degrees. Answering the question about 11ga being thick enough, this is for small tractor mount diggers with less than 3000lbs breaking force at the bucket. The bucket body (round piece and sides) is 11ga and the welded on cutting edges (seen in the third pic) are 1/4" AR which weld to three sides of the bucket and tie to another 1/4" plate on the back.
Reply:Even if 11ga can handle the force, it should be plated up really good or youll wear through it in a year. Its only .1196" in thick....
Reply:Originally Posted by RiesBuy a brake instead.There is a reason why they make dies like this from solid blocks of steel that weigh several thousand pounds. These dies will not hold up.And you are talking one VERY big press to do this- in industry, they would probably use a 500 ton to 1000 ton 4 post hydraulic press. Maybe  bigger.Pressing it all at once in a die like this is done when you need hundreds, or thousands, of pieces a day, and its worth spending the time and money on expensive tooling, because you need a very low per part price, and a very high volume.Instead, you should find a small used mechanical press brake- often available for only a couple grand, sometimes just for the price of hauling. Then bend a series of bends, and make your curves.If its only 20" wide 11gage, you could actually do this with a good hand brake- my Chicago D&K is rated 12 gage, but will bend 20" of 11 gage, and I have bent shapes like this pretty quickly.You draw a series of parallel lines on the steel with a silver pencil, then bend, move, bend again.You could make one, by hand in a sturdy enough manual brake, in under ten minutes. And save on gym memberships too...You cant do this on a cheap chinese 16 gage brake- you would need a decent sized one- my 12 gage brake weighs 2000lbs for a 4 foot machine.Much cheaper, though, is just finding some shop with a big old press brake, to knock em out for you- you could probably get em for under 20 bucks each. (not including material)
Reply:Not trying to derail your thread, but what program did you use for your drawings? But back on topic, I agree with farming out the work to a local shop, you will be happy, they will be happy ($$$), supporting local small business is good for the community you live in, you might make a friend/business contact, and more importantly save yourself the trouble of the R&D process.Just another clown trying to be cool
Reply:I'm doing the design work in Google Sketchup. Takes a little bit to get the hang of but once you do it's an amazing FREE tool for quick design work. Based on the feedback I was changing my approach to use a home made style [ame="http://www.youtube.com/watch?v=B9u3QcLdAAE"]press brake[/ame] and do all the bends individually. Sketchup is great as seen below because I can very accurately get all the measurements and angles to bend the piece out. There are 13 bends total to make this piece, I added the measurements for a few of them in the diagram below. I still want to go with my original plan of a home made die set. I would mount the dies in a full sized shop press and keep adjusting the shelf up in the press to compensate for the short stroke of the bottle jack until I have the work piece fully compressed. Then I was planning to tack weld the sides of the bucket on while still compressed in the dies which would prevent any "bow back" when released from the dies. I know 11ga sounds thin for this application but I'm basing it on 10 years experience with a backhoe this size and a bucket that was put through h-e double L from me. The bucket was all 11ga and the only part that really wore down was the teeth and front cutting edge. The cutting edge was 1/4" plate and probably AR. I'm sure the overall bucket was much thinner when I sold it, but it was all together 20+ years old at that point and still digging strong. It sounds like some folks think the press brake is the best way, while others think a die set would work? The reason I like the die set is I can cut 100+ bucket sides from a template and know they will accurately fit the pressed piece every time. If I make 13 manual bends to create each piece then there will be compensations to be made with the bucket sides every time  Attached Images
Reply:If you end up using a press break, you will have variations in the bend angles and each piece will be close but not identical. I dont know if that will mess you up or not. To get your desired radius' and have the shape you want, you will be making many breaks at intervals of 1/4 or 1/2 inch depending on how smooth of a radius you are after. each break will be just a fraction of your bend angle. You would need to re-adjust the break if you changed thickness.I agree that farming it out to fab or machine shop may be the best option.
Reply:If you end up using a press break, you will have variations in the bend angles and each piece will be close but not identical. I dont know if that will mess you up or not. To get your desired radius' and have the shape you want, you will be making many breaks at intervals of 1/4 or 1/2 inch depending on how smooth of a radius you are after. each break will be just a fraction of your bend angle. You would need to re-adjust the break if you changed thickness.I agree that farming it out to fab or machine shop may be the best option.SORRY ABOUT THE DOUBLE POST
Reply:If your decision is to press these all at one time, I'd make the die set and bend one before you cut all you sides. I think it would be a mistake to try and tack the unit before it moves to it's natural position. You'll be locking in a lot of stress in that piece thats trying to peel the bucket apart, then add digging stresses.You would be better off guessing how much spring back there will be, and compensating somewhat in the die so that when it comes out, you are close to for final size. After you bend 2 or 3 and find they come out the same, then start cutting sides to match.I will agree with others the press brake is probably the way to go. even if it's off a tiny bit, it's easy to toss it back in and make an adjustment to get it to what you want. A pattern next to you as you bend will quickly let you check fit. if you wanted to get real fancy, a unit with auto stops would let you crank these out fast. Insert to line, run the press till the preset stop kicks in and then move to the next and repeat as necessary. I'd either count strokes on the press handle with a manual pump, or most likely, I'd get a elect hydraulic pump, or air over hydro, and make up a set of fixed height stops. Hit the pedal and run it down till it bottoms out on the solid stops and then move to the next and repeat. I'd make the stops removable, so if you needed to tweak the bend a tiny bit to fit, you pop out the stops, and do one or two quick bends free hand to get what you want.If anything, I'd build a jig like you inner die, that you can use to set and weld the sides. Set up a few clamps to keep the floor bent in place, and a few to lock the sides. Then roll it over and weld side A, flip and weld side B and you're done.I think you will find that moving the table as you go will end up being a real PITA and a time waster. Remember about spring back. If you get 6" from your ram, then it springs back 2" it's going to take a lot of moves to fully bend that. Each time you have to reset the table, you have to reposition the piece in the fixture. That or bend 10 pieces at height 1 keeping them all aligned the same way, then repeat at height 2 and 3 and so on. I've tried this with running bends before and never had good results on getting exact repeatable bends on each item. In the end it was easier to run each item individually, and make adjustments as needed to get them as close as possible..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan