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I have been working on a tube roll bending machine to create long arc radius bends in square tube for gates and a few other projects. I'll post pics here in a bit.My problem is that on a tighter radius, the square tube wants to twist as it is rolled. I understand why it happens, but was wondering how to either prevent it from happening or to correct it after the arc has been created.How do you ornamental guys deal with it? A customer wants a gate with a full moon arc in the top. I am trying to talk her in tu using flat stock instead, but she likes the look of the square tube.KevMiller 210 and 140 MigsBernard Q-Torches on bothMiller Syncrowave 200Spoolmate 3035 for sale, excellent condtion- PM for detailsThermal Dynamics 38XLShop OutFitters 20/20 Bending SystemLots of other cheap and not so cheap tools Still have LOTS to learn, but got some nice stuff to learn on!
Reply:Some pics, showing both the bender and then som of the arc and twist.Miller 210 and 140 MigsBernard Q-Torches on bothMiller Syncrowave 200Spoolmate 3035 for sale, excellent condtion- PM for detailsThermal Dynamics 38XLShop OutFitters 20/20 Bending SystemLots of other cheap and not so cheap tools Still have LOTS to learn, but got some nice stuff to learn on!
Reply:Are you using flat dies, or dies with a shoulder on them?I'm a Lover, Fighter, Wild horse Rider, and a pretty good welding man......
Reply:Not an uncommon problem. You must work it as you roll it. Each time you roll it through you will need to remove it and twist it straight. Lay it on a flat surface to check it. I would suggest you straighten it after each roll after you notice it twisting. Don't wait until the end. Create a place to mount the tubing, then twist the tubing with a pipe wrench or other bending tool.Even with shouldered dies twisting may still occurs. Shoulders are are more for supporting the tubing--to prevent collapsing. Make sure your collars are lined up, too.You could also not bend as tight a radius.
Reply:I had the same problem on a very similar bender. The main drive roller in the middle was not square to the axis of the tube when the other rollers were centered as they should be. I was able to correct it by making a jig that sat against the main roller and showed me the true line through the other rollers that would be perfectly square with the main roller. After adjusting the other rollers so that they fell in this line, instead of each being centered, it worked perfectly.
Reply:Try turning the piece around in the machine after every pass to counteract any parallelism issues you might have in the rollersJimCut an MGB and widened 11" C4 Corvette suspension and LT1 Chevrolet power & 6 spd. Pictures here:Part 1http://forum.britishv8.org/read.php?13,7581Part 2http://forum.britishv8.org/read.php?13,22422
Reply:I tried that with mine, first, also. It made it into a helix and just compounded the problem. Might be worth a shot for his particular machine, though.
Reply:Good suggestions guys, I'll give it a try. The main drive roller is not shouldered, but each of the guide rollers are. Tap, when trying to straighten it back out, do you grab it at the opposite end and twist it back with a pipe wrench or similar, or do you work on it from the middle?KevMiller 210 and 140 MigsBernard Q-Torches on bothMiller Syncrowave 200Spoolmate 3035 for sale, excellent condtion- PM for detailsThermal Dynamics 38XLShop OutFitters 20/20 Bending SystemLots of other cheap and not so cheap tools Still have LOTS to learn, but got some nice stuff to learn on!
Reply:Originally Posted by Dkevdog...when trying to straighten it back out, do you grab it at the opposite end and twist it back with a pipe wrench or similar...?
Reply:Sounds good. I'll let you know how it works out.KevMiller 210 and 140 MigsBernard Q-Torches on bothMiller Syncrowave 200Spoolmate 3035 for sale, excellent condtion- PM for detailsThermal Dynamics 38XLShop OutFitters 20/20 Bending SystemLots of other cheap and not so cheap tools Still have LOTS to learn, but got some nice stuff to learn on!
Reply:When I have to straighten metal I start where the metal is fixed the twist toward the other end. If you attaching point as some type of receiver then you can feed your metal threw. You work along the length of the arc with a bunch of small twists, not just one end. Work small twist almost unnoticeable, it won't untwist with one large twist.My twisting tool is a pipe wrench with a handle welded opposite the original handle. I bend a lot of metal the hard way (on edge) It aways twist. Box stuff should not twist substantially. If pressure is applied evenly. Hence, Mac's suggestion is very good. Definately check for trueness first.Last edited by tapwelder; 05-31-2007 at 08:37 PM.
Reply:I seem to always be using older machines and I find that doing gradual increases in bend while turning the piece end for end will cancel out any defects in the machine. It is a lot of extra handling but worth it. Since you have already rolled the tube removing the twist is much more difficult. It is nice when you can weld one end to the concrete floor and jack or pry on the twist at the other end.
Reply:Oh yeah, sometimes you can get away with channel instead of tubing. What are you rolling 1" ,1.25?
Reply:Well I tried bending the tube back to try and straighten it out. Holy heck, I couldn't for the life of me do it with a 24" pipe wrench!!Once I cut the tube to exact length though, the twist wasn't as noticeable, so I'm going with it as is. I checked and as Mac suggested, the roller is not completely square with the material- I'm sure that is most of the problem. I have to get this job out though, so rethinking my homemade bender will go back to the drawing board when the paying job is finished. I'm just starting out and I haven't quit my day job yet, so working this one out will have to be done the hardway.The tube is 1.25 x .063 HR. It doesn'gt want to budge once rolled .I need to talk to Zap, because the tube is putting up a strong fight, and winning at the same time.The customer knows about the twists and she seems OK with it. I'm a perfectionist though, even though I seldom get perfection, I do strive for it. I'll post some pics as the gate makes progress and post it up in the projects forum. When I get around to trying to get that rolling machined beefed up and true, I'll be back.Thanks again guys.KevMiller 210 and 140 MigsBernard Q-Torches on bothMiller Syncrowave 200Spoolmate 3035 for sale, excellent condtion- PM for detailsThermal Dynamics 38XLShop OutFitters 20/20 Bending SystemLots of other cheap and not so cheap tools Still have LOTS to learn, but got some nice stuff to learn on!
Reply:The problem is the machine doesnt have any meat on it to resist the twisting, and no secondary rollers to adjust.Thats why the real machines cost so much- they are designed to counteract stuff like this, and it takes mass, machining, and money to do so.Here is a pic of my storebought, 10 thousand dollar roller- notice that it has a long (15" or so) diagonal roller on each side, after the piece goes thru the three rolls- these diagonal rollers have a screw adjustment top and bottom, so not only can you run em in and out, you can adjust the angle- this makes it really easy to untwist things that are already twisted, or to set it properly to begin with and avoid twist. It helps that the machine weighs about 2000lbs, too.But with your little guy, physics says there is no way to avoid some twist.
Reply:Ries- I know my little machine is far from perfect and needs some improvements, but I'm about $9750 ahead of the game so far . I'm not a professional but I try to equip myself with the best tools I can afford. I am getting by with this for now. I found a fab shop to roll my next arc for a driveway gate. I hope to someday be able to afford a professional machine.What is the min/max materials and diameters you can run with that?KevMiller 210 and 140 MigsBernard Q-Torches on bothMiller Syncrowave 200Spoolmate 3035 for sale, excellent condtion- PM for detailsThermal Dynamics 38XLShop OutFitters 20/20 Bending SystemLots of other cheap and not so cheap tools Still have LOTS to learn, but got some nice stuff to learn on!
Reply:Originally Posted by Ries...But with your little guy, physics says there is no way to avoid some twist.
Reply:I didnt mean to say you have to spend a bunch of money- I bought that machine over 5 years ago, when the euro was a lot lower, and paid about 7 grand for it- and I have used it on enough really big jobs that it has more than paid for itself- but I totally understand guys who build a small machine, or buy one, to do the occasional job. There are days when I run stainless thru it all day, and I can justify the expense.As far as twisting goes- the three wheel machines like the one you posted must be perfectly aligned and balance, and even then, there are stresses in many pieces of steel that may cause them to curve anyway. Angle iron, for example, usually needs to have the side pressure rolls adjusted with postive pressure. Sometimes, for no apparent reason, stuff twists on me, where I run two different pieces thru the same settings, and one twists, and one doesnt. The weight of a big piece can start to pull it one way or another, and if you dont have somebody holding it level, once it goes, it can get bad. I find that even from the same batch of steel, sometimes you get variations in how things bend. I dont know why. But I consider bending, and rolling, to be arts, not sciences, and require constant fiddling and tweaking to get good results.With the big machine, they designed in a way of adjusting for curvature- so I can make curves on purpose, like for spiral handrails, or take curves out- we just did a project where welding on one side caused the metal to curve- run it thru the rolls, and it got flat again. The same company that made mine makes a cnc model that will roll spirals and 3d curves to exact profiles.I like mine because I tend to bend things like the 1 1/4" stainless round bar in the picture, or 3" x 1/2" stainless flat bar the hard way- all a bit tough to do without huge shafts, big bearings, and 5hp.That machine will do 2" x 1/4" square tubing, 2" schedule 40 pipe, 2x2 angle, and up to about 4" flat bar the easy way, or the hard way for that matter.Everybody is different , and has different needs and budgets- I was just trying to point out that there are ways of designing a machine so it wont twist the steel, but it costs more.
Reply:I agree. That's why these cheap(er) machines are only good for tubing. But they can still do tubing very well without twisting.
Reply:Originally Posted by RiesEverybody is different , and has different needs and budgets- I was just trying to point out that there are ways of designing a machine so it wont twist the steel, but it costs more.
Reply:DkevdogNice job on the machine. I didn't realize you made it. When I built my roller. had some problems with the roller spreading as I applied pressure. I put a dial indicator on several points inside and found some deflection in the 3/8" plate. I was able to add support where needed. My design is like the style of Ries' A dial indicator might be the way to go test for dynamic changes. I also chose to go with a acme all-thread rod for the down feed. I felt I could counts turns in order to make repeat bends.I think you roller will be alright. You might end up adding some beefier metal in places. My roller work very well for what I do. However there are several changes I would make were I to build another.
Reply:Thanks Tap, I've been dabbling in welding for a while, but this is my first attempt at engineering a machine. Trial and error works, but is time consuming. I know for a fact that I have some deflection as you state, and as Mac pointed out earlier. I need to add some plate to keep the center roller tower supported so it doesn't deflect under a load. I have a few more jobs coming (hopefully) so I need to either get it done soon or just bite the bullet and buy one. I have found a few options from Baileigh and Heller that might be doable. Always fun to build your own though .KevMiller 210 and 140 MigsBernard Q-Torches on bothMiller Syncrowave 200Spoolmate 3035 for sale, excellent condtion- PM for detailsThermal Dynamics 38XLShop OutFitters 20/20 Bending SystemLots of other cheap and not so cheap tools Still have LOTS to learn, but got some nice stuff to learn on!
Reply:My machine is a BPR, which is the Italian brand sold by EAGLE.http://www.eaglebendingmachines.com/Its a really good machine. You mention 3/8" plate deflecting- Yep, thats why my machine has 1" plate- the assembly that holds the shafts for the 3 rolls has gotta weigh 500lbs, minimum.the bottom line is industrial quality machines of any type use lots of metal. Big plates, big shafts, big bearings, big motors.
Reply:When I worked in Los Angeles, the warehouse next to my work, worked on large structural steel building supports, roller coaster tracks, and large ornamental pieces. They had a lot of curved pipe that they worked/welded on all the time. They had another company roll all of the metal, and I would notice they would always blow air thought the rolled work before they would weld to it. One day I went over to see what they where working on. The guys did not speak much English, and I don't speak much Spanish. But what I understood was that they jammed the hollow metal with sand to keep it from warping with the heat from the bending process. This might help.
Reply:All the rolling we are talking about here is done cold.But sometimes, on thin wall tubing, people put sand, or a low melting temp metal alloy called cerrobend, inside the tubing to keep the walls from collapsing.It seems odd that they would do this for structural stuff, though- its usually only needed on 16 ga walls and thinner.One of your dies is miss-shaped or flexing... You can re-grind to correct...
Reply:It's not misshaped. It's not dead perpendicular.
Reply:Originally Posted by DkevdogSome pics, showing both the bender and then som of the arc and twist.
Reply:A low-tech, low-$ method is to use plywood bending curves. I've got a half dozen of various dia. ones and try,if possible to design around what I have. Need a different one, they are easy to make. Use an extension bar for leverage to bend by hand. Don't need no stinkin' bender200amp Air Liquide MIG, Hypertherm Plasma, Harris torches, Optrel helmet, Makita angle grinders, Pre-China Delta chop saw and belt sander, Miller leathers, shop made jigs etc, North- welders backpack.
Reply:I'm the new guy here. Although I have nothing to add to your twisting dilemma I thought I would share my solution to long arc bends. So far I have had no twisting issues at all, just some minor alignment ones. You can view it here;http://gordsgarage.wordpress.com/201...t-outta-shape/Maybe there is something there that you can use.Good Luck!Gordhttp://gordsgarage.wordpress.com/ |
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发表于 2021-8-31 22:36:15