Web-Tension Principle of Winding. When winding elastic films, web tension is the dominant principle of winding used to control roll hardness.
When winding film on a pure center winder as shown in Fig.
For winding on pure center winders, the starting tension should be towards the higher value of the suggested tension range.
In center winding, the spindle torque through the center of the roll provides the web tension.
An advantage of center winding is that this process can wind softer rolls.
When surface winding elastic materials, web tension is the dominant winding principle.
Macro's latest Automax C (center) and S (surface) winders have an optional "kiss" winding mode that uses a special servo-driven lay-on roll to provide very light lay-on force--just enough to remove the air.
Tecno uses AC vector drives on the winding roll and AC servo drives for tension control on other driven rolls.
The dual winding station has a special winding track and shaft movement, which allow the idle shaft to bypass the shaft currently winding and return to the start position near the lay-on roll without disturbing the web.
Addex Inc., Boston - A novel surface/center-assist and gap winder with a special lay-on and cutover capability also can do reverse winding. Developed by Reinhold in Germany, the machine's winding shaft remains fixed, and the contact roll moves in a carriage along a track to maintain tension as the roll increases in diameter.
Both test methods have some limitations, however, since they are testing point loads rather than the uniform loading a core experiences during winding.
Straight cores promote uniform winding tension and thus prevent film from wrinkling.