DWH Technical Topic: Dancer plus load-cell control

By Clarence Klassen, P. Eng.

The jury is still out on whether dancer control or load-cell control for tension is the better solution.

One of the worst solutions is "design-by-committee" in which both a dancer and load cells are installed. I have seen this numerous times over my career. In these cases, the load cells are installed per the published instructions. By that time the budget is used up, and a dancer is slapped in as an afterthought.

We can expect this dancer will have several design deficiencies:

The geometry will not be well designed. A dancer requires three rollers. The motion of the dancer should be linear. That is to say, 1 cm of motion at the slack side should be the same as 1 cm at the tight side. Finally, high-quality cylinders with low stiction (friction) should be used.

Using both the load cell and dancer generally results in oscillations in both measured tension and the dancer's movement. Performance may be improved by increasing pressure on the dancer to pin it on the slack side.

I have seen the combination solution attempted with poor results on:

· A paper off-machine coater unwind
· A tandem off-machine paper coater between the 2nd and 3rd coaters
· A plastic tube printing line winder
· A plastic film turret winder

Instead of providing a valid comparison between load-cell and dancer control, the combination seems to result in neither means of control being optimum.

Please link to Dr. David R. Roisum's blogs and videos related to dancers.

https://www.stevenabbott.co.uk/abbottapps/RL/index.html Search “dancer”

https://www.stevenabbott.co.uk/abbottapps/Web201/index.html Search “dancer”

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