Finding the Flat Length of a Bent Steel Metal

It has been too many years for me to give specific help but if I recall correctly "K Factor in sheet metal bending" is a term to Google.

Awesome, thanks bruce.. i have started researching it. Still would like a specific walk through on this though if someone has this floating around in their head..could save me some time haha. Thanks again for the info though!

http://www.custompartnet.com/calculator/bend-allowance

That's all very nicely explained. Unfortunately if you try to use just that to calculate the dimensions to cut the flat piece to be bent into the curved piece, it will not yield the correct size flat piece.

This is a core part of our fabrication. We have a analogic controlled 3/4" x 6' capacity pyramid plate roller. Your method is almost exactly what we do. The only additional is we add 6"-8", 3"-4" each end, for trim waste. If "Garrett12345's" fab shop has a 21stC numerically controlled roller there will be less trim waste.

FYI to all yu'al: the pyramid plate (sheet metal) roller was invented by Leonardo Da'Vinci. The only tangible differences between his and a modern machine is his has bronze or wood rollers and uses a hand crank or treadmill powered top roller drive while the best modern machines have hardened steel rollers and use electric over hydraulic bottom (both) rollers drive.

Just need to remember, if he gets rolled, depending on the size of roller, both ends will not get rolled, and will remain flat.

we/I always specify that the ends get bumped.

I have learned this piece is getting rolled. How does this change the situation? Can trimming still be used for a rolled steel plate? Phoenix can you further explain what you mean by this?

Sorry for all the questions. Just very curious on this subject now.

I usually put it on my scope (graphically) as a requirement when I send it to contractor... don’t have with me now.,I’ll post it tomorrow.

but basically, when rolling you have (3) rollovers in a triangle arrangement. (2) rollers on the bottom, and the single roller on the top in the middle (pinch roller).

as the sheet is fed through, when the first part of the sheet does not begin to bend or form untill both bottom rollers are engaged with the sheet.

Same as it exits the rollers.

so basically, you will have a flat area, half the distance between the distance of the (2j bottom rollers and the beginning of the roll, and at the end of the roll.

even with you have to roll it a number of times to come to the required radius.

I would expect the fabricator to know exactly what is required to achieve your desired outcome. Whether they require final trimming and how much trimming will depend on how they do the job and what sort of equipment they use.

The straight line areas would be greatest if they are using a standard 3 roller machine. Pre-bending (either with a separate die or the roller itself) will reduce the straight as will the use of a suitably curved base plate under your sheet, but this effectively doubles the load on the machine for that portion of the bend, ie. they would need a roller with at least a 2" capacity.

Three roll initial pinch and four roll machines also enable reduction of the straight line section as the bottom rollers can be moved closer together for the start and finish of the roll.

If trimming is required, the edge finish that you want and the availability of methods may restrict the possibilities.

I'm not aware of the width of the sheet in question, if it's quite narrow, then a cutoff saw may be adequate, if it's quite wide, then you may need to look at Oxy, Plasma, Waterjet etc.

Is finish of the cut important? - you could leave a little extra and clean the edges after cutting.

Is heat effect from Oxy or Plasma going to be a concern? - then Waterjet may be the answer, but generally expensive.

Your fabricator will know what they can do.

Wow thank you all so much. I have a feeling I’m going to be learning a lot from this community and hopefully I will be able to pitch in to help others (well maybe eventually at least haha).

Thanks again and hope y’all have a good week.

Practically, it is better to bend an oversize piece and trim it to the right length. It is difficult forming accurate bends near the ends of the material properly as these tend to remain straight. Heating it up will also help.

As an illustration, and also a coincidence, a piece of flat 20-thou polystyrene sheet intended for a model refused to bend fully to a curved shape with a radius of about 2.5in last night. The ends stayed straight. The solution was to make it over-long, bend it to shape, and cut the straight ends off to size.

Sort-of felt a similar sort of job...

Another way - trip a hoop off the cylindrical material for the vessel that is going to be put on the saddle, straighten it a bit, and trim it to size.

If you haven't already got your answer, the terms you might Google are Bend Allowance and Setback. Bend Allowance is a computation of how much stretch happens on the outside of the radius and Setback is a measure of the compression on the inside. In Aviation Tech School in the 70s we had to do these calculations in order to determine sheet metal sizes used in constructing aircraft wings. I haven't seen or used the formulas since.

Try this:

if [R_inside = 5' - 1 11/32'' = 61.34375'' = Ri ] => [arc length = S = (central angle, in radians) x (radius, in inches)]

then [S_inside = ( Ri = 61.34375'') x (160 deg x PI/180 deg) = 171.30407'' = (168 + 3.30407)'' = 14' - 3 39/128'' ~ 14' - 3 5/16'']

GA for that response. My first thought was to do it with Radians, but the Op wanted a step by step and - I presume - simple explanation which I felt that method didn't provide.

I still would have added half the material thickness to arrive at a more accurate material length for bending, doing that and using Radians gives a length of 14' 4&3/16"

Thanks for the ''GA''.

If there was such a thing, then I would give you an ''MHE'' for a ''More Helpfull Explanation'' overall...