In many production facilities today, high-speed converting is essential for greater productivity. Unfortunately, high speeds can also be counterproductive because roll quality can suffer. At higher speeds, air is entrapped between the incoming web and the surface of the roll, resulting in air pockets and bubbles that allow the roll layers to shift against each other.
The industry’s answer to this problem is the top-riding roll, a welcome refinement to winder and slitter rewinder applications. A top-riding roller prevents air from entering between the incoming web and the layer below it by maintaining constant contact directly on top of the web as it converges with the wound roll, in effect squeezing out air that would otherwise become entrapped. At low web speeds (under 300 fpm) top-riding rollers can be as simple as paper cores mounted on aluminum shafts. Higher speed applications require balanced top-riding rolls manufactured using a variety of application-specific materials. Each type has its pros and cons and is useful for different kinds of materials and process conditions.
Top-riding rolls can also vary from a common roll across the full web width to individual top-riding rolls across slit packages in order to accommodate web thickness variation across the web. Both common and individual top-riding rolls are also useful in obtaining straight, smooth-sided rewound rolls at both high and low speeds. They’re particularly valuable when working with high-slip, light-tension materials that tend to be problematic during the slitting and rewinding process.
Although top-riding rolls are an added expense, they can be a worthwhile tool for keeping roll quality high and minimizing down time and waste.
Here's an important tip: The incoming web should come into contact with the rewinding roll at the point of contact with the top-riding roll or ideally, it should wrap around the top-riding roll, which is how certain Dusenbery® slitter rewinders are designed. If the incoming web touches the rewind roll ahead of the top-riding roll, the tracking, guiding and entrapped air reduction benefit is lost.
For more information please view the Dusenbery® Slitting Techniques Guide.