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Just a nice experiment; comment in Russian is obvious
Russian Commentary on Chain Wheel Experiment
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SUMMARY
The discussion centers on a mechanical experiment involving pull rolls for a paper napkin folder. The initial design utilized a pair of 12" diameter rolls covered with tread tape, achieving a coefficient of friction between 1.7 and 2.0. However, when the machine operated at 1000 FPM, the smaller 4" diameter knurled steel rolls failed to maintain tension due to centrifugal force equaling back tension. The final solution involved adjusting the gap between the pull rolls to ensure proper paper nipping, allowing the machine to function effectively despite the design constraints.
PREREQUISITES- Understanding of mechanical engineering principles related to tension and friction
- Familiarity with paper processing machinery and its components
- Knowledge of centrifugal force effects in rotating systems
- Experience with roll design and adjustments in manufacturing processes
- Research the mechanics of centrifugal force in rotating machinery
- Explore advanced techniques for optimizing roll design in paper processing
- Learn about the properties and applications of different roll materials
- Investigate methods for measuring and adjusting tension in manufacturing systems
Mechanical engineers, manufacturing process designers, and professionals involved in paper production and machinery optimization will benefit from this discussion.
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.Scott
Science Advisor
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At highway speeds, steel belted radials are often heavy enough to stay round even after a blow out.
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jrmichler
Mentor
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I once got tripped up by exactly that effect. The project was pull rolls for a paper napkin folder. We did not want to pinch the paper between a pair of rolls because that could squash the emboss pattern, so we tried a pair of S-wrapped rolls similar to the diagram below.
The input roll of the folder grabbed the paper using vacuum, so could only pull with about 0.3 lbs force. The necessary tension at that point was about 3 lbs in order to keep the web taut after the embosser, and pull it over the folding plows. The tension increase is provided by pull rolls. The proof of concept test used a pair of scrounged rolls about 12" diameter covered with tread tape. It worked perfectly. The actual rolls were about 4" diameter knurled steel. The measured coefficient of friction was 1.7 to 2.0 with the tread tape, and about 0.4 with the knurled steel.
When the machine got up to speed, about 1000 FPM, the pull rolls stopped pulling. It turned out that the centrifugal force was equal to the back tension at that speed with the smaller rolls. The design was locked in by that point, so we adjusted the gap between the pull rolls to nip the paper just enough to make it work. We had hoped to eliminate an operator adjustment, but at least the machine worked.
The input roll of the folder grabbed the paper using vacuum, so could only pull with about 0.3 lbs force. The necessary tension at that point was about 3 lbs in order to keep the web taut after the embosser, and pull it over the folding plows. The tension increase is provided by pull rolls. The proof of concept test used a pair of scrounged rolls about 12" diameter covered with tread tape. It worked perfectly. The actual rolls were about 4" diameter knurled steel. The measured coefficient of friction was 1.7 to 2.0 with the tread tape, and about 0.4 with the knurled steel.
When the machine got up to speed, about 1000 FPM, the pull rolls stopped pulling. It turned out that the centrifugal force was equal to the back tension at that speed with the smaller rolls. The design was locked in by that point, so we adjusted the gap between the pull rolls to nip the paper just enough to make it work. We had hoped to eliminate an operator adjustment, but at least the machine worked.
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