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Plate Rolling Formula(3)

I ran across this formula, but it is only good up to 180Degrees? (.01743xrad)x degree of circle
And I beleive this is not true as well: given Rollout flat pattern: OD = 6.375 material .375 steel Cir. 6.375 x 3.1415 = 20.027 Formula: (.01745xR) (180 Degrees)x2 = (.01745x3.1875) x (180)x2 = (.055621875) x 180 x2 = 10.11937 x2 = 20.023875, which is the same as cir.??
A better formula appears to be: but for alum. only?? (I dont know where the .0078 factor cam from)
(.01745xR)(.0078xT)x(180 Degrees)x2= (.055621875)(.002925)x180x2 = (.052696875)x180x2 = 9.4854375x2 = 18.970875
But evern better "I hope" is AutoCad's factor formula: (for mild steel: A36) By AutoCAD: using .407 factor Times thickness = .0763 of the 3/8 Then offset from the insideat this factor, you get: Length was a total of 19.329"
This seems closer to a real stretchout pattern!
Can anyone confirm??


cloa (Petroleum) 
29 Jan 09 19:39 
Good for you to supply some specific numbers but what is your situation that you want help with? 

the second formula you gave will work with steel if you modify the the (.0078xt)in your formula,This is the neutral line, the point where the metal neither stretches nor shrinks. For a large radius this point, sometimes called the K factor is closer to the middle of the metal thickness. not the inside edge. Here is a link to a bend program that can be downloaded http://www.ciri.org.nz/bendworks/bending.pdfB.E. 

I understand the bending formula quite well, except rolling. Are you say that the bend formula is the same for rolling as well?? This the neutral axis of bending the same as rolling?? 

TheTick (Mechanical) 
30 Jan 09 11:13 
(.01743xrad)x degree of circle = ???
It's not a formula until there's something on both sides of the equal sign. 

SnTMan (Mechanical) 
30 Jan 09 12:33 
windseaker1, what is mostly used for rolling a cylinder from flat plate is the finished mean diameter, pi*(ODt), or pi*(ID+t). Some add allowance for weld seam shrinkage (1/8" typical), some don't.
Regards
Mike 

windseaker1 Sorry for being late getting back, yes the bend formula works for rolling as well, when you roll a plate you are bending it on a large radius, the metal still has to shrink on the inside of the neutral line and stretch on the outside.To get a finished diameter that you want, you have to compensate by adding or subtracting part of the metal thickness from the neutral line. B.E. 



