On a Calender Stack am I right in saying that yuo do not want 2 rolls in nip that are exactly the same diameter. Lets say 2 thermo rolls one 30.021 inches in diameter and another 30.019 Inches in diameter. Wouldn't you want one roll to be lets say 30.019 and theother maby 30.500, this should help with barring , am I right. Also when you have 3 sets of thermo rolls you don't really want to put the same rolls in the same spot change after change. Isn't it better to mix them up between sets. Maby I said all that right..

Mike

Hi Mike,
You are correct as far as I know. You may be able to get around that by offsetting the rolls so the paper path length nip to nip is different but it is still not good to have 2 rolls the same diameter as any roll order vibration can get imprinted on the other roll. I have heard 0.5mm difference is a rule of thumb.

Hello Mike
You are right in your assessment two rolls with the same diameter should never be put in nip with each other. I'm not a salesman but VCI sells a program called the Reusch Chart. This chart, will do the callculations for you and tell you what your chances are of barring and the number of bars you will get.All you have to do is put the diameters of the rolls your are looking to put in nip with each other in the program. I have used it in the past.It helped me a lot. Especially when you have five or six rolls in nip. Such as on a Calander Stack.