What is a Differential Friction Rewind Shaft?
Differences in material thickness and winding tension often arise when rewinding foils, laminates, plastics and other materials. These variations can result in different lengths and tension requirements when rewinding smaller rolls on the same rewind shaft. After only a few winding rotations the centre of some small rolls may be too tight while others may show sagging, making the quality of the end product unacceptable.
A Differential Rewind Friction Shaft overcomes these issues by maintaining proper tension on all rolls throughout the winding operation, ensuring the web material does not sag, stretch, or tear and, the rolls are uniformly wound. In order to perform this function the centre shaft is required to rotate at a higher rate than the Differential Friction Rings. All of the cores are required to slip continuously, however, some will slip more than others in order to maintain the same tension. Control of the slippage and the web tension is achieved by varying the air supply to the centre shaft, so a constant air supply needs to be available, ideally between 20 and 60 psi (1 – 4 Bar). As the roll size increase during the winding process the speed of the Differential Shaft needs to be decreased in order to maintain the same over speed rate.
The Friction Rings are available in a very wide variety of diameters from 50mm Diameter up to over 400mm Diameter. The Inside diameter of the Friction Rings depends on the diameter of shaft which you currently used, and in most instances we can supply the rings to suit your existing shaft.
For more details on the Differential Winding Shafts which we offer then click here