Why does a paper roll unwind in jerks?

In summary: This is called resonance. If the frequency of the resonance is close to the natural frequency of the structure (like the fibers in the paper), then the oscillation will be magnified.
  • #1
ubergewehr273
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TL;DR Summary
Paper is rolled into a tube and it unwinds in jerks. Why is it so?
I came across a problem regarding a paper being rolled into a tube. When a piece of paper is rolled into a tube and then left to unwind, it is always seen that the unwinding happens in jerks and not smoothly. Why is it so?

What I have thought (and thanks to some discussions on reddit), that when one rolls a paper into a tube, creases form along the surface which in essence prevent the tube from unwinding smoothly. Potential energy gets stored and is released all at once when the force of friction due to the crease is overcome. This happens in intervals.

I would be glad if someone could correct me on this one and provide some further explanation on this phenomenon.
 
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  • #2
ubergewehr273 said:
.. then left to unwind,...
How exactly? Left in place, so the winding loosens up? Or rolled along the floor?

When it loosens in place, I suspect static friction is responsible for the non-uniform propagation.
 
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  • #3
Nonlinear oscillations are called limit cycles. They can be very difficult to analyze, but at the root there is some kind of dynamic instability.

Are you familiar with differential equations and stability analysis?
 
  • #4
A.T. said:
How exactly? Left in place, so the winding loosens up? Or rolled along the floor?

I'm sorry for not mentioning but the rolled paper tube is placed vertically on a flat surface and left to unwind.
 
  • #5
anorlunda said:
Are you familiar with differential equations and stability analysis?

I'm not familiar with the latter one.
 
  • #6
ubergewehr273 said:
I'm sorry for not mentioning but the rolled paper tube is placed vertically on a flat surface and left to unwind.

OK
then read the second part of @A.T. 's answer :smile:
 
  • #7
ubergewehr273 said:
I'm sorry for not mentioning but the rolled paper tube is placed vertically on a flat surface and left to unwind.
This could be quite complex. As the unwinding propagates around and into the roll, it could interfere with itself, creating phases of faster and slower movement.
 

1. What causes paper roll unwinding in jerks?

Paper roll unwinding in jerks can be caused by a variety of factors, including uneven tension on the roll, debris or imperfections on the surface of the roll, or improper alignment of the roll with the unwinding equipment.

2. How does paper roll unwinding in jerks affect the quality of the paper?

If not addressed, paper roll unwinding in jerks can lead to uneven or wrinkled paper, which can impact the quality of the final product. It can also cause jams or tearing, resulting in wasted paper and production delays.

3. What can be done to prevent paper roll unwinding in jerks?

To prevent paper roll unwinding in jerks, it is important to ensure the roll is properly aligned and that there is even tension throughout the unwinding process. Regular maintenance and cleaning of the unwinding equipment can also help prevent jerking.

4. Can the type of paper affect how it unwinds?

Yes, the type and quality of paper can affect how it unwinds. Thicker or heavier paper may require more tension to unwind smoothly, while thinner or lighter paper may be more prone to jerking if there is too much tension.

5. Are there any technological advancements that can improve paper roll unwinding?

Yes, there are various technologies that can improve paper roll unwinding, such as automatic tension control systems and sensors that detect and adjust for any imperfections on the roll. Additionally, advancements in roll handling and alignment equipment can also help prevent jerking during the unwinding process.

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