OkiePC
Lifetime Supporting Member
Hi all... I have a machine that processes rolls of rubber coated fabric product through a slitter and rewinds the slit stock. The current PLC code doesn't do a very good job of controlling letoff tension and has several other problems, so I am working up a new program for it. I have a very accurate speed feedback signal that tells me the surface speed of the "main pull rolls" (0-400fpm). I know the diameters of the letoff and rewinder rolls both empty and full. I am accurately calculating the length of stock that has been processed (and resetting it as each roll is changed) based on the main pull roll speed feedback. I would like to be able to calculate the diameter of the rewind rolls at any point in the cycle based on the number of linear feet in the roll and the known empty and full roll diameters. I know since the circumference is constantly changing that it's not a linear relationship between feet of stock and diameter. What should the formula look like to do this?
Example values:
Roll length = 1650 feet
Rewind core diameter = 3.5"
Rewind full diameter = 28"
Stock thickness = 0.031" *
The thickness of the stock can be inconsistent, so I'd prefer not to use that value unless absolutely necessary. The final calculation doesn't have to be perfect, but obviously the more accurate it is, the better the final result will be.
Once I have this formula figured out, I will do the same to calculate the diameter of the letoff roll and web rewind rolls. All of this information will be applied to controlling speed and tension to make the machine more user friendly. Currently, the operator has to frequently adjust tension values to keep the machine running well, and if they are running an oddball sized letoff core, the speed control is all out of whack.
Thanks in advance...Paul C.
P.S. adding a device to measure the diameter is not an option on this machine.
Example values:
Roll length = 1650 feet
Rewind core diameter = 3.5"
Rewind full diameter = 28"
Stock thickness = 0.031" *
The thickness of the stock can be inconsistent, so I'd prefer not to use that value unless absolutely necessary. The final calculation doesn't have to be perfect, but obviously the more accurate it is, the better the final result will be.
Once I have this formula figured out, I will do the same to calculate the diameter of the letoff roll and web rewind rolls. All of this information will be applied to controlling speed and tension to make the machine more user friendly. Currently, the operator has to frequently adjust tension values to keep the machine running well, and if they are running an oddball sized letoff core, the speed control is all out of whack.
Thanks in advance...Paul C.
P.S. adding a device to measure the diameter is not an option on this machine.