RyanMark Posted January 23, 2012 Share Posted January 23, 2012 If I wanted to build a large rolling mill, which roll would bend less, given a 16" length and a force applied to the center: 6.5" diameter 4140 heat treated or, 8.5" diameter 1045. Both would be surface hardened. This is for cold rolling of bronze. Tool steel is too expensive. Thanks! Quote Link to comment Share on other sites More sharing options...
bigfootnampa Posted January 23, 2012 Share Posted January 23, 2012 Simple geometry helps with this. 8.5" diameter steel rod weighs about 200 pounds per lineal foot. 6.5" diameter steel rod weighs about 113 pounds per lineal foot. The difference in alloys is unlikely to have as much effect as the difference in mass and the larger diameter would be stiffer because bending would require more stretching of the outside curve and more compression of the inside curve. To sum up I would expect that the larger diameter rod would be quite a bit stiffer than the smaller one. 4140 is doubtless stronger per pound but not THAT much stronger. The larger mass could also be helpful in other ways... momentum for example. Quote Link to comment Share on other sites More sharing options...
jeremy k Posted January 23, 2012 Share Posted January 23, 2012 I would think you would run into way more of a problem with power turning the rolls, before you bend a 6-1/2" round that is only 16" long during a rolling situation Quote Link to comment Share on other sites More sharing options...
RyanMark Posted January 23, 2012 Author Share Posted January 23, 2012 Thanks. Stiffer is better for me, and If the mill works fine then I might hard-chrome plate the rolls for extra hardness and corrosion protection. I think I'll get another quote (they're going to get tired of me calling, haha...but they'll be happy when I buy). 8.5" is still a tight enough curvature to allow for reduction down to half a millimeter, from what I read somewhere. Another question: Do you guys think I need to drive the other roll? I would like to leave the adjustable roll non-driven for simplicity and less cost. The only mills I've seen that have a single driven roll are the Mcdonald mills. I will probably leave a few inches extra on both rolls for room to attach gears. I might have to push/pull my sheets through. Big gears are expensive! Ryan Jeremy- Power might be an issue, but I will have room on the frame for another reduction stage. At that point, I'd be looking at getting 3phase service hooked up and find a motor. Quote Link to comment Share on other sites More sharing options...
Francis Trez Cole Posted January 23, 2012 Share Posted January 23, 2012 how thick of stock are you going to roll out? the other question bearing and aliment to get the space down to zero gap between the 2 rollers. Quote Link to comment Share on other sites More sharing options...
RyanMark Posted January 23, 2012 Author Share Posted January 23, 2012 I've actually already ordered the bearings, cause I like to put the cart before the horse, haha... They're C954 aluminum bronze sleeve bearings which will slide into bearing blocks that are smaller than the diameter of the rolls, thus I can close the gap all the way. The frame and gap adjustment screws have been pretty much designed already. The rolls' journals will be 4" diamter and 5.5" long. A little small for the application but the largest I can fit into the frame (built with the largest angle and channel steel I can get). It sounds like I'm getting a great price quote on a 62" long drop of 8.5" 1045 but that doesn't leave room for gears to drive the other roll. It would be nice to not have to drive that roll... Quote Link to comment Share on other sites More sharing options...
r smith Posted January 23, 2012 Share Posted January 23, 2012 It sounds like I'm getting a great price quote on a 62" long drop of 8.5" 1045 but that doesn't leave room for gears to drive the other roll. It would be nice to not have to drive that roll... Why can't you weld or bolt a small spud shaft on the end to attach gears to if needed? Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 23, 2012 Share Posted January 23, 2012 Since you are giving some though to the system as a whole---what part are you engineering to break if "everything goes wrong"? Hopefully a cheap easily replaced *safe failure mode* part! Can't recall much in the way of small shop machinery that was more expensive than *one* bad hospital run. Quote Link to comment Share on other sites More sharing options...
RyanMark Posted January 23, 2012 Author Share Posted January 23, 2012 This will be manually powered by turning a huge wheel (the side from a large ditching spool) so all I have to worry about is the momentum of the rollers. I don't plan on touching them with my hands, and I'll lock the wheel when not in use. Hopefully the rolls won't fail, they're the most expensive parts. The sleeve bearings are meant to be worn, to protect the rolls and the bearing blocks. In the drive, I would think that the roller chain will fail before a shaft or sprocket...I might get the teeth hardened, though. A guard will be in order for the chain. And, I think bolting on gears could work. Actually, I just bought the roll material this afternoon. It's the 8.5" 1045 drop that the machine shop had from a recent job. Quote Link to comment Share on other sites More sharing options...
RyanMark Posted January 23, 2012 Author Share Posted January 23, 2012 I think I found suitable gears on ebay, a pair of spur gears with the right outer and pitch diamters. I'd be varying the center distance by 1/4" which is going to create backlash and put much stress on the teeth, but I rather not have idler gears if I don't have to. Transferring motion to the other roll is more like an "assist", the way I see it. I'm just making it's friction work for me instead of against me, so I don't think the forces on the gears will be as great as will be on the sprockets on the primary drive side. So you think someone could weld a piece of 1-7/8" keyed shaft to the ends of the rolls? That's the bore of the gears. I'm guessing it should be done before any heat treating? I read that welding carbon steel requires a preheat and slow cool. Quote Link to comment Share on other sites More sharing options...
r smith Posted January 24, 2012 Share Posted January 24, 2012 It seems that you should bore a 1 7/8 hole in the end of the roller shaft, that will keep it centered and straight. I do not know if that hole could easily have a keyway added to it, machine shop question. Or my other thought is to weld a flange on the end of the 1 7/8 machine it square to the centerline of the shaft and bolt that to the roller. I would want the flange to sit is shallow recess on the end of the shaft to keep it centered, maybe a 3 1/2" flange, or put a 1" hole in the end of the roller and have them leave a short 1" spud on the end when the flange is squared up. I hope that makes sense. Sounds like your rollers will be quite nice. smith out I think I like the bolt on flange idea best, if you ever need to modify or upgrade it is easy to do compared to having a welded on shaft. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted January 24, 2012 Share Posted January 24, 2012 Truing them up after welding is what I'd worry about. Welding tends to shift things around---ever take a long bar and weld the end of it to a plate with one finger on the top to keep it from falling over? Moves all over the place as you weld the base! Quote Link to comment Share on other sites More sharing options...
Ric Furrer Posted January 25, 2012 Share Posted January 25, 2012 Ryan, I have been studying rolling mills for a time (got several books on the tool and own two of them). I think you will not be able to reduce the material very much...maybe 0.001 per pass or so...when you have it 16" wide. The torque required is rather vast. If you are using a large ships wheel and hand power you will need a lot of gear reduction...many hundreds of times. Have you run any calculations as to yield of the material being rolled and area of contact for the rolls? The numbers get into big foot pounds and tonnages fast. In general if you double the diameter of the roll you double the torque required as you will be increasing the surface area of contact. If you double the speed..likewise you are doubling the torque required. you will be slow, but still need high torque. I do not think you will need to worry about a failure point in the system as Thomas suggests..in this case...it is the human power which is the limiting factor. I know the term can be put many ways and the numbers can be fudged, but humans can make about 1/2 hp for a while.....you will need hundreds to do what you are thinking about. edit: you can add a large weight..i.e. a fly wheel....this will get you into more energy when it is needed....at that point you are multiplying your own energy with inertia/momentum....you could peddle it up to speed with a bicycle and then jump off an feed the billet through....of course at that point its all or none..if you stall the fly wheel with a jerk...the energy wants to continue in a rotation and bad things can happen. Question: Will you power only one roll or do you have meshed bull gears in the plan? Ric Quote Link to comment Share on other sites More sharing options...
RyanMark Posted January 25, 2012 Author Share Posted January 25, 2012 Ric, I sent you a PM. Sounds like I should plan on adding that extra reduction stage. It could get me up to 4500 ft-lbs. The max working load for size 100 roller chain is over 5,000 lbs so I should be good. Worried about bearings again but too late. As far as gears, I was about to pull the trigger on a pair of Martin C540's but besides them maybe not being strong enough, I think my plan to operate them a few hundreths of an inch outside the correct pitch diameter might be stupid, especially for my application. How is the best way to put a pair of idler gears on an adjustable plane? Quote Link to comment Share on other sites More sharing options...
r smith Posted January 25, 2012 Share Posted January 25, 2012 Your chain should work Quote Link to comment Share on other sites More sharing options...
Ric Furrer Posted January 25, 2012 Share Posted January 25, 2012 Ric, I sent you a PM. Sounds like I should plan on adding that extra reduction stage. It could get me up to 4500 ft-lbs. The max working load for size 100 roller chain is over 5,000 lbs so I should be good. Worried about bearings again but too late. As far as gears, I was about to pull the trigger on a pair of Martin C540's but besides them maybe not being strong enough, I think my plan to operate them a few hundreths of an inch outside the correct pitch diameter might be stupid, especially for my application. How is the best way to put a pair of idler gears on an adjustable plane? How do you get 4500 foot pounds (54,000 inch pounds) with human power? That is the same torque as a 270 or so HP motor at 30rpm. I do not see how you are working your numbers. Even at 1rpm you are looking at a 150hp motor or so...and massive gear reduction. Maybe inside a 30 foot walking crane you could get that force built up, but with a four foot lever?..I do not see it. I am not all that good at math and physics, but I simply do not understand. Ric Quote Link to comment Share on other sites More sharing options...
RyanMark Posted January 25, 2012 Author Share Posted January 25, 2012 Me neither, I guess...lol. Quote Link to comment Share on other sites More sharing options...
Dillon Sculpture Posted January 25, 2012 Share Posted January 25, 2012 Why cant you hammer the billets to the desired gage? Is a mill preferred? I don't know much about cymbals. Edit: Just watched the Istanbul vids I guess you would prefer a mill. Quote Link to comment Share on other sites More sharing options...
Ric Furrer Posted January 26, 2012 Share Posted January 26, 2012 Michael, We would both prefer one of every tool.... For many generations these were pounded out by hand...I picture those Mexican copper smiths who have demoed at several events in the US...and then with power hammers. BUT a rolling mill is the modern answer...the question is can one be made or found and then paid for with use? Unlike a hammer a rolling mill is a single use tool...it only makes things thinner. Ric Quote Link to comment Share on other sites More sharing options...
basher Posted January 27, 2012 Share Posted January 27, 2012 If your gears are driving 8" rolls from a 1 7/8" spindle you made made your point of failure . really you need to have the bearings and drive as close to the roll size as possable ,2/3 being an optimum (think I got that figure from Ric) , from my real life experience when I had my drive spindle at 50% of the roll size on a macdonald mill it failed frequently ( 40mm shaft 75mm role ) destroying keys and Keyways and remedial welds . calculated torque around 800ftlb . gears teeth and stretched chain as well. you are asking a lot from your mill. all the best Owen Quote Link to comment Share on other sites More sharing options...
RyanMark Posted January 28, 2012 Author Share Posted January 28, 2012 I've decided to make a 4-hi mill. 16.5" working width. 8.25" diameter hardened 1045 backup rolls (my stock wasn't quite 8.5" but I kinda knew that). 3.25" diameter work rolls: 4140 prehard with suface hardening, chrome plated. Or D2, whichever is less expensive in the end. This design calls for only the bottom work roll to be driven directly by the last sprocket (a Martin 100F70) and disregarding torque for the time being, I'm worried about slippage. What do you all think about a 4-Hi doing cold rolling with only the bottom work roll driven? No gears. If it matters, the bearings for the work rolls will only have to deal with rotation and keeping the rolls in place. The seperating force will be handled by the backup rolls' bearings, which are less than the 2/3 ratio mentioned. Backup roll journals are 4" diameter by 5.25" wide, bearings are C954 aluminum bronze 1/4" thick bushings inside steel blocks. Quote Link to comment Share on other sites More sharing options...
Ric Furrer Posted January 28, 2012 Share Posted January 28, 2012 According to the modern industry rolling mill books (after skimming some 3,000 pages and photos and diagrams at the engineering library at UW-Madison and the ten or so mill books I have here) the rules seem to be: --no wider than 1.6 times the diameter of the roll --journals (bearing ends) no smaller than 50% the roll diameter --even hard rolls compress a bit when working --very hard rolls can heat check under the strain of the metal and the heat --it it rather important to have both rolls powered or the extra torque is lost as it has to pass through the work into the other roll....not efficient and can lead to premature slip. --the smaller the roll diam the greater the pressure and the less the force needed....which is why they use 20 hi cluster mills.. the contact roll is less than 1" diameter and supported by a large mass of "bowling pin" stacked rolls...they swap out the contact roll every shift in the large sheet metal mills. --the shear points are usually a pin located past the drive train or the connecting links after the bull gear (the part that turns the one motor into driving both rolls. --double the speed or roll diam and then you need to double the torque --roll as hot or as annealed as possible --the max infeed angle to the roll is about 15 degrees..more than that and the metal will not be bitten and pulled through --forward slip occurs on the upper and lower outside parts of the metal then a neutral and some of the center is actually being moved backwards and then is fed thorugh ...what this means is that large reductions are VERY stressfull on the metal and can shear even good billets of metal. If you are to be fed into the machine by accident ...go head first as it hurts less. There is a lot more to this when you actually "engineer" a rolling mill, but for us it comes down to vast power, a planned failure point, over building everything else and staying well away from the moving parts of the machine or though shall be eaten. Ric Quote Link to comment Share on other sites More sharing options...
Ric Furrer Posted January 28, 2012 Share Posted January 28, 2012 I've decided to make a 4-hi mill. 16.5" working width. 8.25" diameter hardened 1045 backup rolls (my stock wasn't quite 8.5" but I kinda knew that). 3.25" diameter work rolls: 4140 prehard with suface hardening, chrome plated. Or D2, whichever is less expensive in the end. This design calls for only the bottom work roll to be driven directly by the last sprocket (a Martin 100F70) and disregarding torque for the time being, I'm worried about slippage. What do you all think about a 4-Hi doing cold rolling with only the bottom work roll driven? No gears. If it matters, the bearings for the work rolls will only have to deal with rotation and keeping the rolls in place. The seperating force will be handled by the backup rolls' bearings, which are less than the 2/3 ratio mentioned. Backup roll journals are 4" diameter by 5.25" wide, bearings are C954 aluminum bronze 1/4" thick bushings inside steel blocks. There is ALWAYS side forces..both ways X and Y. If you think there are not then you assume your Z axis..the stacked rolls are perfectly stacked and remain so....its like assuming the seal can balance the balls on its nose without moving its head. When you engage the metal to be rolled you have a lever...this forces side loads on the rolls....NOT in the Z axis. there is also loads which the frame reacts to as well as the bearing surfaces....a shifting load of maybe 80 tons. I am not saying you should not build this machine. What I am saying is that the rolls themselves are not the only parts you need to worry about Ric Quote Link to comment Share on other sites More sharing options...
Ric Furrer Posted January 28, 2012 Share Posted January 28, 2012 You could make a 2" or 3" contact roll from hardened tool steel with a cradle of back-up rolls....two of them with the roll nested between them. Two gear reduced motors..one attached to each roll..one on the left and one on the right so as not to be in each other's way. The entire motor drive on the upper could move with the roll. If the same model/serial numbers they will rotate close enough to not need any more co-ordination or alteration. Be nice to have a fly wheel in there for momentum, but... Failure could be a linkage between gear box and roll...shear pin, gear sprocket and chain? The lager back-up rolls could be set in a babbitt cradle and cast as a unit..maybe a secondary set up to rotate them a bit under load...could be a simple chain drive and 2hp motor to another gear box as they rotate at a fraction of the contact wheel rpm. The smaller contact wheel takes a HUGE amount of torque off the drive train and though it limits your reduction possibility as the slip angle is much less (15degrees of 2" vs 4 or 8.5") to be frank you were not going to have the power to take advantage of the large reduction potential anyway. Ric Quote Link to comment Share on other sites More sharing options...
RyanMark Posted January 28, 2012 Author Share Posted January 28, 2012 Thanks again, Ric! I appreciate your time and input. This bronze doesn't like to be reducted too much anyways or it will start to crack. Which reminds me: Is there a relationship between the shape of a material's edge and the ability to be drawn without cracking? Someone told me that of two shapes, a circle and a square, that the circle will be the shape most likely to split at the edge when drawn out. I know a mechanical engineer who designs wings for Boeing. He's coming up from Wichita next weekend to visit some friends here in KC and he's told our mutual friend that he would love to see what I'm trying to do and help me out with it. It's not his specialty but maybe he has some more advice. Quote Link to comment Share on other sites More sharing options...
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