Bending Flat Bar To 16 Inch Diameter?

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Ok, so i watched a guy bend a 16 inch flat bar to 360 degrees(diameter)... he used a piece of paper with what looked like a 1 quarter radius on it... he kept seeing if the radius matched the bend in the steel, he went back and forth over each end of the flat bar, then once both ends were done to the radius he'd do the whole middle..... if i wanted to do one also, how would a person do it? he used a hydraulic bender with rollers which i'll use too.not sure if maths involved with inside radius or outside radius for a formula, or where to start.Thanks!
Reply:I think you answered your own question actually.Cut a paper or cardboard template for comparison.Then follow his example since you also plan to buy the bender.Edit: forgot to add, the bar length is the circumference of the circle + some waste on each end.C=2(pi)rDave J.Beware of false knowledge; it is more dangerous than ignorance. ~George Bernard Shaw~ Syncro 350Invertec v250-sThermal Arc 161 and 300MM210DialarcTried being normal once, didn't take....I think it was a Tuesday.
Reply:Even on big tank and vessels shells they have to pre-bend the ends so they don't have a flat spot on either side of the seam. The flat spot would happen because the plate isn't all the through on both sides of the rollers. Normally to pre-bend on plate rolls, you put the plate through till it's about 1/2 way on the rear roller and uses the rear roller to push the plate up to get the right radius. An accurate template is used to check it. The rear roller has to come up quite a bit more for the pre-bend than it does for doing the rest of the shell.  Here's some links to some plate rolls in my neck of the woods. The first ones are tiny compared to the monster rolls but if you need a shell 12" thick, they could do it.  If you look at some of the projects done at Dacro, my buddy worked on the 400 ton coker's for Suncor. There were 4 of them, pipe welds on 4" double extra heavy wall pipe were nuclear code TIG welded which meant no repairs allowed. If it didn't pass x-ray it had to be cut out and redone from the start.  http://dacro.com/index.php?page=plate-rollshttp://www.edmontonexchanger.com/pre...plate-rolling/Last edited by Welder Dave; 03-06-2015 at 01:37 AM.
Reply:To figure out the length of flatbar or plate depending on what you're rolling, use the nominal diameter. I.E. if you're rolling a piece of 1/4 thick plate to 12" ID use the formula 12.25 x 3.14, if OD 11.75 x 3.14...Mike
Reply:Do you want a full circle or 90-120 degrees? The latter you can actually do on a cheapo HF pipe bender. I do 4"x3/8" for benches using the 2" pipe die. I should have pics on my threads or can repost if you need.
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Reply:Originally Posted by mrmikeyTo figure out the length of flatbar or plate depending on what you're rolling, use the nominal diameter. I.E. if you're rolling a piece of 1/4 thick plate to 12" ID use the formula 12.25 x 3.14, if OD 11.75 x 3.14...Mike
Reply:Originally Posted by Welder DaveWouldn't ID be 12" x 3.14? Taking a 1/4" off for 12" OD makes sense but adding a 1/4" for ID it seems like it would end up 12 1/4" ID?
Reply:I have a small roller for up to 2" flat,  I will normally cut the flat about 6" longer than needed  and roll it to the approx., diameter and then cut off the flat ends and weld it together, Attached Images
Reply:Originally Posted by waginNo. You have to consider the material thickness/placement. To figure a roll diameter you have to calculate based on center of material thickness.   When rolled, a 12" id would measure 12 1/4" dia. from center to center of material thickness.
Reply:Edmonton Exchanger in one of the links I posted that  has hot bending capability where the steel is heated to 1650 deg's. Sure hate to make a mistake rolling 8" to 12" thick plate. Once the shells are made they can match the heads to fit. They also have a 1200 ton and 3000 ton head press.
Reply:Hello SHaw, I'm a little late on this but I finally found a small item that might shed some light on what others have already shared. Hopefully this will attach without size issues and you'll be able to see it. Good luck and best regards, Allan Attached Imagesaevald
Reply:I've never seen material cut off after pre-bending the ends. When you have a thick vessel, they double bevel the ends before rolling. Maybe experience tells them how much to allow? On thinner material it's common to have to "bump" the seam after it's welded because the weld makes it bow up. You take a piece of 1/4" flat bar about 6" wide with a handle welded on and while an operator rolls the shell, you put the flat bar on the seam and it  get rolled in between the 2 front rollers to flatten it back out. I helped do this a lot in one shop. The old guy running the rolls didn't want anyone else to help him except me which made me feel pretty good. Only thing is you couldn't get ahead of him. He had his way of doing things and that was it. He was Polish and lost all of his family except his sister in Nazi concentration camps. A German guy in the shop had an argument with him once! He punched the German guy in the face. They put a new overhead crane in and everybody hated the huge control for it but the plant manager said that's the way it is. The old guy came back from holidays and refused to use that crane until they changed it. It was changed in 2 days!
Reply:Hello Dave, there are some commercial rolling machines that are designed to be capable of rolling out to the ends of the material and provide an even radius all the way to the end. For those that don't have a machine like that, they may utilize the option that I discussed. As you said, if it is thicker or requires any sort of bevelling I will do that after forming up the ends and before doing the finish rolling. I have also used a sacrificial doubler plate that is thicker than the part that I am rolling and will bridge the span on the rolls and set the ends of the piece that I am rolling on top of that piece and proceed to roll the ends, this will also form the radius on the parts out to the ends. Hope that makes sense. Best regards, Allanaevald
Reply:Here's just a little bit more to add to this thread. For machines that don't have the ability to roll a radius fully to the end of a part without leaving a "flat spot" this may be an option. Best regards, Allan Attached Imagesaevald
Reply:I've worked in a few tank shops that had to pre-bend and never saw them cut material off after pre-bending. Here's another link for Edmonton Exchanger, they don't cut strips off after pre-bending. Maybe they just have better rolls? http://www.edmontonexchanger.com/pre...w-of-services/Last edited by Welder Dave; 03-08-2015 at 03:24 PM.
Reply:I agree Dave, there are units that can roll a radius right up to the end, so I could certainly see where you would do the edge preparation prior to the forming process. I have not had the pleasure of actually working with any of those machines, although I have seen some of them in operation. The largest set that I ever saw was in Cheyenne, Wyoming, as I recall it was capable of rolling 10" thick material, 10'-0" wide. Most of the ones that I have had to add material to in addition to the actual length required it due to the roll configuration. Especially if they are like the drawing in my last post, a Pyramid Configuration. Thanks for including that link. Best regards, Allanaevald
Reply:I think even with 3 roll machines there are different configurations. There are also 4 roll machines but the 3 roll seems more popular. The Davi rolls like Edmonton Exchanger and Dacro have list double pre-bending so you don't have to flip the plate around and pre-bend each side. The shops I worked in always had to do one side then take the plate out and do the other side. The Monster rolls at Exchanger are some the largest in N. America and are serviced by a 100 ton overhead crane. They have other rolls as well but I don't know what brand they are. They do very precise work as does Dacro. My buddy worked at Dacro and said they were so good, they could cut the holes for nozzles in the plate before it was rolled! I went to school with the foreman at Exchanger. He was lucky, went for work experience and got offered an apprenticeship after finishing high school and has been there ever since. Oddly enough he bought one of my lots when I sub-divided. He's not hurting for money. I don't think he remembered me much but was telling me the head press they designed and built at Exchanger has a 6' diameter hydraulic cylinder! It's 4 stories high and develops 3000 tons of pressure. Every size head requires a different die and sometimes multiple dies to form. The shop is quite dirty though because they use a lot of graphite to reduce friction when forming thick steel. I just saw on their website they keep about 30,000 tons of SA516 boiler plate in stock! That's a lot steel and $$$$. The fence around their main shop is steel plate with patterns cut out on a plasma table. They are always busy. I should figure out how to post pictures. I could drive around and take some awe inspiring pics. of some of the big stuff around Edmonton.Here's another shop in Edmonton that does big vessels. All 3 shops are with the Boilermakers union. If Dacro or Cessco need components thicker than they can form themselves, they get them from exchanger. I think the founder of exchanger used to work at Cessco many years ago. http://cessco.ca/Last edited by Welder Dave; 03-08-2015 at 04:25 PM.
Reply:Very cool stuff there Dave, thanks for including those links. The only other sizeable forming rolls that I have been around were some that were used to roll sections of wind towers. In those particular applications they were rolling 2" plate into a slightly tapered configuration and I believe that they were 10'-0" in width and roughly 18'-0" in diameter and believe it or not, this was from a single section of plate, that was in the Moses Lake, WA. area. They had a "huge" plasma table. Always in awe as to the size and extent of some of the metal forming equipment that is out there. Best regards, Allanaevald
Reply:Here's an older link with a pics. of them rolling a thick shell on their "smaller" set of rolls. The ends are pre-bent with a double bevel but maybe ?? they did pre-bend and cut the flat part off? I've never seen strips cut off but I notice that most of these big rollers, the top roller is a bigger diameter than the back roller. That might be the difference? I know that the shells can be ordered straight, beveled and tacked or fully welded. I can't find a picture anywhere of their big head press but read their plasma table cut up to 3" stainless and is 17' x 40'! In the one picture you can see the guy spin forming a large head wearing a high temperature fire suit. Their heat treat is bigger than a garage and I've heard once the plate is hot enough, they have to come in fast with the forklift and the guys wear heat suits and faces shields but the face shields start to melt from the heat. If must be really bad with stainless were it's heated to 1900 deg's. Steel is only 1650 deg's. Dacro has about a 25,000lb capacity welding positioner sitting outside with a bunch of other equipment and tools when they need it. They also have a removable floor in the shop for the big diameter stuff and a huge stress relieving building. I think it's the biggest in N America. This big stuff and how they make it fascinates me. http://edmontonexchanger.com/wp-cont...Components.pdfLast edited by Welder Dave; 03-09-2015 at 02:04 AM.