roll forming capacity question

M. Moore · Jul 22, 2017

Hello,
I have an opportunity to buy an old set of rolls that are 6' long.
The spec on the machine says that it will roll 6' x 1/4".
My question is what thickness will it roll if you go narrower?
Can it roll 3/8" x 30"?
With reasonable regularity I need to roll 3/8" x 28-30" material into gently radius'd parts.
Thanks for your help,

Michael

Dave G. · Jul 22, 2017

What are you rolling? Steel, aluminum, copper, C276? What is the tensile strength/heat treat condition? What is the ratio of the thickness to the "gently radius'd" part?

M. Moore · Jul 22, 2017

Dave,
Sorry for the lack of info.
I would normally be bending mild steel and occasionally aluminum.
The radius would be in the 24 to 32" range for the bends.

Michael

Dave G. · Jul 22, 2017

I found a table that listed the forces required to bend mild steel plate in a PRESS BRAKE using three point bending. The forces for a 1/4" thick x 72" plate were almost the same as a 3/8" x 30", so that's OK. But that's just the forces, the rolls in your roll former might not be stiff enough for a 3/8" plate. You may need larger rolls or to reduce the width of the machine - both sound like deal killers. Aluminum is normally low enough yield that it should be OK.

Ries · Jul 22, 2017

depends on the rolls- generally the answer is, yes, sorta.
older rolls are built beefy- and can take a certain amount of overbending. Unlike a brake, you cant "spring" a set of rolls, generally the gear train breaks first. Which happens, believe me. I have had to make a custom gear for a 100 year old set of 18 gage rolls that some fool tried to roll 1/8" in.
a six foot 1/4" roll ought to have 8" diameter rolls, and be around 10hp or more. First thing to check is if they are already exaggerating its capacity, which often happens.
then check the gear train for chipped or missing teeth. check how high it opens before the gears dont mesh anymore- thats the absolute physical limit on thickness, which is often less than you wish it was. Many rolls simply wont get far enough apart to roll really thick stuff, even if its annealed pure aluminum thats really soft.

I think unless its a super beefy roll, expecting it to roll half the width in 3/8" is probably gonna be too much. Remember that the force required goes up with the square of the increase in thickness- that is, it takes 4 times the force, mass, and power to roll 1/4" as it does 1/8"- NOT twice.

adama · Jul 22, 2017

Im in the you might be able to do it camp, that said its far better and more controllable to have bending gear with some decent head room.But taken with a few passes and not being too greedy you may well be just fine. Do to how bending works the shallower the radius the less force it takes. On rolls this is even more pronounced as a shallow bend and your still riding the tops of the rollers and that means a wider V which means more leverage and hence less tonnage. Trade off is bigger flats at the ends!

M. Moore · Jul 22, 2017

Excellent info here guys, thank you for the responses.
I was in a bit of a hurry so I didn't take any measurements or fully inspect the gears, a quick look and the gears seemed fine.
The owner insisted it works but it has been sitting outside for a few years and the rolls are pretty rusty, not sure if anything is rusted solid or if everything moves as it should. Thieves cut the main power cord off the machine but we could jerry rig up some power to test.
I am guessing that the rolls are at least 8" and it is a 7.5 hp motor. It has an air cylinder to lift the top roll, not sure exactly how that works and the valve seems to be stuck or stiff.
With the above comments I think it wise to get power to it and see if it will roll the 3/8" plate, is there any downside?
Breaking gears is not good obviously, what should I watch for otherwise?

Michael

ps, I am pretty sure it is a "Webb"

LKeithR · Jul 22, 2017

IF the rolls truly are 8" diameter then 30" of 3/8 MS shouldn't be an issue--those would be pretty large rollers for a machine of that size.
I would try contacting Ecco Machinery in Langley or Modern Tool in Coquitlam. Ask them about the capacities and roll sizes of the ones
they sell--should give you an idea of the relative capacity of the machine you're looking at...

M. Moore · Jul 22, 2017

Lkeith,
She is a big old girl, very beefy overall and close to 10,000 pds.
I will check the roll diameter. I did see a few similar machines for sale, the Webb make appears to be a good machine. Its got the power up and down back roll and air powered drop end.
It is new enough to have a foot safety switch at the front for sure, can't remember if it had one on the back side.
As Adama said it will probably do the bend, just need to roll it several times which I would be quite happy to do, having this capability in house is a huge time saver.

Michael

Ries · Jul 22, 2017

webbs are good machines.
here is their current specs- they say an 8" diameter roll is rated at 5/16" in 6'2" width. So my guess is the rolls on this one are in the 7" - 7 1/2" diameter range, and it should do what you want, intermittently- probably not for production.
http://www.webbcorporation.com/id3.html

here is a vid of a 1/4" x 6' webb- 6' x 1/4" Webb Initial Pinch Plate Bending Roll - YouTube

M. Moore · Jul 22, 2017

Ries,
Thanks for that link, very helpful specs.
The 7.5" rolls at 48" length will do 3/8", so the 6' rolls doing 28" width of 3/8" plate is very close.
At the top of the specs it does say 40,000 yield and 60,000 tensile "in small diameter".
I assume the small diameter means the smallest the machine will roll?
As already said the larger radius of the bends that I want to do should be fine.

Michael

M. Moore · Jul 25, 2017

The rolls are rolling this way today!
I was not able to test under power as they had no 440 at the shop so I bargained down a bit and we agreed on a price. $1500 is a good deal no?
I will have a few questions on rolling techniques once I get it running. It appears to be all free and the big question is the motors that were sitting out in the rain, not sure if they will be ok or not. I think the main motor will be fine but the smaller motor is questionable.

Michael

M. Moore · Jul 27, 2017

The rolls arrived and were unloaded safely.
We worked all afternoon to fix some minor problems and I quickly rigged up the transformer and some cabtire wire for power and she works!

It needs new belts and quite a few other minor things but it does roll once again!
What a well made machine, very nice to work on and impressively built.
Even after years of neglect and sitting outside in the rain (west coast rain btw) it fired up and ran smoothy without too much effort.
The air valve was full of water but cleaned up with a new O ring it works fine without any leaks.
The hinged bearing was a bit stubborn but after a few tries it popped open and functions well.

I included a pic of a small piece of 1/4" plate that I rolled to a 9" diameter, first try, with pretty much zero experience on any rolling machine.
Now the learning begins.

Thanks for the info guys, I will start a new thread with all my rolling questions!

Michael

atomarc · Jul 27, 2017

Michael,

The Gods must be watching over you if you were able to hit a motor with full voltage that has been sitting outside for years in the rain and not have all the magic smoke come out. Buy some lottery tickets sir.

Stuart

M. Moore · Jul 27, 2017

Yes, very lucky!
Why would you start a motor with anything but full voltage? Just wondering.

atomarc · Jul 27, 2017

M. Moore said:
Yes, very lucky!
Why would you start a motor with anything but full voltage? Just wondering.

You wouldn't..what I was attempting to say is that the normal scenario for anything other than a 'known' dry motor would have been to meg it first, dry it if needed, then run it.

A wet motor, when started can 'blow' but the very same motor, when properly dried out will now last forever. You're lucky yours didn't short out on start up.

Stuart

M. Moore · Jul 27, 2017

Not too much luck involved, it is summer here and we have had a long dry spell, that motor has been baking in the heat and direct sun.
Thanks for the info, future motors may benefit!

adama · Jul 27, 2017

Sounds counter intuative, but its not normally rain that fills motors with water, its humidity that does it with condensation, so long as they have a open drain hole being out side does not normally bother them in my experience unless they have sat in puddles.

FYI the rust on the rollers, over here more than a few people i know like em a little rough, whilst smooth polished rolls might be just what you want for jewellery or polished stainless, any std steels and a rusty surface bit of bite sure helps you get some traction!

gbent · Jul 27, 2017

M. Moore said:
$1500 is a good deal no?

$1500 is not a good deal, its a super, smokin' hot deal!

Even better that it works from the start!

M. Moore · Jul 28, 2017

Adama, that sounds reasonable for the motors, I wasn't worried about it when I started these two for the first time in 5-8 years.
I did clean the rolls just to see what the condition was like, some of my work requires a decent finish and I couldn't tell how bad they were with all that rust.

Gbent,
It felt like I was stealing it but it was a bit risky, it could have gotten expensive fast if something major was wrong.
I did email the Webb company to see if I could find out how old this machine is but have had no response yet. I was also wondering how much these machines were new or what they are worth new now? I have no idea as I have never been in the market for one and haven't done any research on them. Recently a smaller capacity machine (different make) sold at auction for about $7000 but it was much newer and in decent shape.

Michael

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