« Favorite Analogies #2: Traction on rollers and cars | Main | Wrinkles at Roll Starts »
October 12, 2005
Pacer Selection: Coater or Laminator?
A recent post in reply to the 'Two Pacers is One Too Many' post asked a pacer-related questions.
In a lamination process that has a reverse roll coater - drying oven - lamination nip rolls. Both the reverse roll coater and the laminating nip are driven with their own drives. We have been using a ratio control between these drives to maintain the web tension in the oven. The ratio control is being replaced with a closed loop automatic tension control system. Based on your experience should the reverse roll coater or the laminating nip be the pacer for this process? (Cont'd...)
In my experience, coater are are pacers much more often than laminating nips. A coating back up roller as follower will be shifting speeds in closed loop control and may create unacceptable speed-variation defects, such as bar marks or chatter. If you coating isn't sensitive to this, I might select the pacer based on which unit has the higher rotational inertia (maybe the laminator) and will be more sluggish to speed changes. The pacer should be used in all web paths, so if you do any coating without laminating, you may prefer a coater pacer.
Lastly, the pacer should be a drive point that you know won't slip. This could be trouble for either the coater or laminator. If the coater backup roller has as small wrap and runs some time with the coating nip open, uh-oh. Regarding the laminator, I like to run a laminator with as low of nip force as possible. If it's a pacer, you may have a tendency to crank up the nip load to get more pull. What's the negative of too much nip load...more product shear, more product compression, wearing out compliance coverings sooner, and more roller deflection.
If I had to choose, I'd go with the coater backup roller and make sure it has enough traction with wrap, tension, and traction coefficient.
tjw
Posted by Tim Walker at October 12, 2005 01:02 PM
