Thread: Sheetmetal Rollforming mill info required

Wondering if anyone on here has had anything to do with making a rolling mll. The type where sheet metal comes in on a roll, and is then fed through various rollers to come out as a formed sheet, similar to guttering, roofing sheets etc.
I'm more after the information on the rolls themselves than anything else.
Thanks in Advance,
Kryn

Originally Posted by KBs PensNmore

Wondering if anyone on here has had anything to do with making a rolling mill... I'm more after the information on the rolls themselves than anything else.

Such as shape, finish, material, hardness,...?

Michael

Sorry Michael I should have put that into my request.
The shape I know will depend on the profile of the finished item. I was more after the finish of the rolls, which from memory would be an almost mirror finish. I doubt that Mild steel would be up to the task of the rolling profile and same with the hardness, I'd say it would need to be quite hard, otherwise it would wear quite quickly.
I was hoping that someone has had experience making the rolls and I could pick their brains and or open to suggestions how to go about it.
Thanks
Kryn

Is this the type of thing you are talking about Kryn? It states Hardened rolls 58HRC

https://www.machineryhouse.com.au/S730

The surface of the rolls will transfer any blemishes to the metal being rolled, so yes, a polished finish if the part will be visual. If it will then be painted or something, polish is not quite so important.
Hard is nice as that will mean that they won't get damaged so easily but wear resistant material is also important as the material can drag in dust/ grit and so on.
Depends a bit on required roller life too, as obviously long production runs will require more material to be put through than short runs, so wear characteristics become more important

Michael

Sorry, but no. Thanks anyway What I'm looking for, is information on making a machine that roll forms continous lengths of product like guttering and roofing etc.
Kryn

Found this video of a fairly basic looking production machine https://youtu.be/cB_gzxsgsHk No real detail of how it's made, but you do get a decent look at the construction and various stages of rollers for forming the profile

If it's just for small runs, maybe nitrided 4140 rollers?

Typically you use a series of roll pairs that define the features gradually, so if you were making round tube you might start with rolls that turned up the edges to a flat U shape, then the pair might bend the middle of the strip to get a C shape with an opening at the top. Finally another set will close up the gap by rolling on the outside. It's not that simple of course. The tube mill that we had had far more than 3 stands of rolls - probably 6 or 8 (that was 30 years ago...)
It's not really the sort of thing that can be easily put as a formula, but one reason for multiple rolls is to avoid changing the profile enough in one pass such that the strip distorts (creases) as the rolls do their thing. So for example if you wanted to form a strip into a V shape, one roll may distort the strip and make things curve, so you would start gently with maybe a 22 degree bend, then 45 then 67 then 90. Of course if you are forming a work hardening material that makes the gradual approach harder.
The other balancing factor is the material yield strength. For a shape change to be permanent, the material has to reach it's yield strength (that is, plastically deforming). At the same time, if it gets above it's ultimate strength it will fail/ tear. We did a lot of deep drawing tests at one stage and it is remarkable how little things are the difference between success and failure.
With flash CAD programs these days it may have changed but with press operations (and probably roll forming as well), a lot of it was done through experience/ on the job learning. While there are better methods than others and 'standard' ways of achieving some features, I don't think it is one of those 'only one way' processes. It will depend on the designer and where the metal is moving. Designing roll sets from scratch may require making them in MS, seeing how they form and then modifying them if things are not quite right before committing to proper steel.

Michael

A few years ago I got to see a roll forming machine in various stages as it was being constructed, it was for making house framing channel from light gal or ZA. The channel size was 100 x 50 or thereabouts, there may have been a stiffening bead or two rolled into it.

There was probably 15 or so sets of polished rollers which were around 150 dia, very heavy side frames, heavy chain drives to the rollers, 40 or 50 dia pillow block bearings the device was 4 or 5 metres long.

Thanks Michael and Bob, that's the sort of information I was after.
Making the frame we can handle, making the rolls, well that's another story!! We are looking at getting a large lathe as there are several parts of a product we already make, that will be made in house also.
More details on the product, which would be made from probably 1.5 mm galv sheeting, overall finished size would be 800m wide, with 8 Vs formed equally, approximately 15mm high and 2 X 12mm safety folds on the outer edges.
Rolling quantities would be about 100m a month.
Found some information from Canada on the metal they use, D2 (X153CrMoV12)
"D2 steel is an air hardening, high-carbon, high-chromium tool steel. It has high wear and abrasion resistant properties. It is heat treatable and will offer a hardness in the range 55-62 HRC, and is machinable in the annealed condition. D2 steel shows little distortion on correct hardening."
Doesn't sound cheap????
Kryn

Kryn,

Apparently the D2 can be quite brittle in the hardened state. I have read that it is best tempered twice as insurance that you have the drawn back state correct. I have a small amount of it and it is as hard as the hobs of hell in the pre hard state. Old hands reckon that the D stands for dog to work.
For machining I would say stout machinery, high grade carbide tools and plenty of coolant.

Ken

The safety edge is relatively simple - I'd probably start like this. It may be practical to make up an edge rolling machine that even if you form the Vees another way will allow you to walk a sheet along to put the edge on.
Safety edge.jpg
The Vees though are a problem and may need some experimentation to work out the best set up. A Cylindrical grinder will be an important tool.
Vees.jpg
Given that you are only 100m per month, you may be able to get away with 4140 rolls that have been case or nitride hardened.

Michael

I have to agree with Michael, 4140 would probably be a good choice for the rolls EN36a would also work. 100m per month is pretty low volume for a roll forming machine.
As an alternate idea, depending on how long the finished item is, could it be folded in a press brake? The v's are easy, and fold the safe edge as far as possible then finish in a smaller rollformer?

Thanks Michael and Snapatap. 4140 does sound a better proposition. Need to find someone who works in a place that rolls sheets for roofing to find out how it's done, whether it's one flute at a time or multiples?
Unfortunately it can't be done in a brake press, as the pieces required are 8.5m long!!!!
At the moment we're using a 4 panels to do the job, but it's time consuming fitting them, plus the lengths are only 6m, and we need 8.5m.
Kryn

In a facility that is continuously churning out profiled sheets its all done in one pass. To put 8 grooves plus a safety edge in 1.5mm steel in one pass is going to require Serious Amounts of Horsepower.

For a low volume process, it makes a lot of sense to simplify and cheapen the machine, reduce the amount of power required etc by having one set of grooving tools instead of 8. Interesting project!

Thought would need to be given to the fact that you will feed in a flat sheet maybe 900 wide and end up with an 800W sheet but somehow you need to keep one side of that tapering sheet jammed against a fence so that each groove you roll ends up straight. Also, either the position of each successive roller will need to be incrementally closer to the fence or the fence will need be on a taper and the rollers can stay in a straight line. Probably the second method is more practical.

I would imagine that you would have to roll each groove very gently, i.e. lot of rolling stations, so that you don't distort the yet to be grooved portion of the sheet.

I guess a first experiment is to find out what's involved in rolling a groove down the middle of a 100mm wide strip.