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Mesh Movement and Its Impact on Screen Tension, Part Two

(April 2003) posted on Thu Oct 29, 2015

Dr. Anderson's sage advice still rings true today with this flashback to 2003.

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By John Anderson

Vibration during stretching As a mesh is stretched, the motion between threads reduces friction forces at thread intersections. This allows some fiber realignment to occur automatically during the tensioning process. To break these friction bonds more rapidly, it could be useful to add vibration to the mesh, either applying it through the tensioning-system clamps or some other method. However, because mesh stretching is a dynamic process, adding vibration with current stretching techniques may have limited benefits while creating a more complex stretching process.

Vibration between stretching stages Friction between threads is the dominant force that resists fiber realignment during the rest periods in multistage stretching. However, applying vibration during these periods may assist in increasing the local tension forces and breaking the contact between the mesh threads. Once this contact is broken, the fibers will be free to move, encouraging and accelerating tension loss as thread positions stabilize.

As simple as this concept sounds, putting it into practice remains difficult. One problem is that fiber realignment is greatest at the edges of the mesh. This means that the forces acting upon the mesh are not equal at all locations. Consequently, no single vibration frequency can be used to break all the friction bonds that keep the threads deflected. Additionally, screen mesh is excellent at absorbing and dissipating vibration energy, so using vibration forces alone to break these bonds is unlikely to give you the desired results.

I would recommend an alternative procedure: During the rest period between tensioning stages, apply a continuous vibration/deflection cycle at multiple points around the mesh, staying with 5 to 15 percent (relative to mesh width) of the screen’s edges. The vibration and deflection should be random in amplitude, frequency, and direction, and be applied for 90 percent of the rest time between each and every stretching cycle. This would provide enough variance in additional applied forces to trigger thread realignment regardless of the location of deflected threads. The rest periods that result with the procedure would be shorter than with conventional multistage tensioning practices and lead to more consistent and stable tension levels.


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