What is better for tension feedback, a load cell or dancer roller?

This is one of the oldest debates in web handling. Early in my web handling career, I asked many people this question. Based on the input from many people and seeing many applications, here are my key thoughts on this debate and how I answer the question:

Advantages – Load Cell Roller

  • Actually measures tension
  • Often small wrap angles and one-sided contact
  • Fast and accurate Low maintenance

Disadvantages – Load Cell Roller

  • Small accumulation, web path changes create large tension changes
  • Poor response to high frequency upsets

Advantages – Dancer Roller

  • Accumulation
  • Minimal tension change with web path changes.
  • Compensates for poor motor control.

Disadvantages – Dancer Roller

  • Doesn’t measure tension
  • Large wrap angle + difficult to align = wrinkle sensitive
  • Creates tension variation from friction and inertia
  • Poor response at high or resonant frequencies
  • Higher maintenance

I think dancer rollers are over-used. Dancer rollers are a mechanical system used to compensate for mediocre controls. In most cases, today’s motors and control systems don’t need dancers, but many suppliers and converters stay with dancers based on poor experiences with load cells many years ago.

My advice:

  1. If you can afford it, install load cell rollers in every tension zone, if not for closed-loop control, to monitor your process.
  2. Ensure your load-cell rollers are properly calibrated.
  3. If your process will have section to section speed differential of magnitude and time to require accumulation and dispensing of web, use a dancer roller.
  4. I support using dancers on winders and unwinders to absorb speed variations from out-of-round rolls and speed variations of automatic splicing processes.