DWH Technical Topic: Winder speed changes when the accumulator empties
By Clarence Klassen, P. Eng.
Accumulators or festoons ahead of a winder create some interesting tension challenges for the winder. The winder is stopped while the accumulator fills, so any tension problems are associated with the accumulator at that time.
To empty the accumulator, the winder must restart in an overspeed condition.
A motor-driven accumulator can be emptied at a constant speed. The speed at which the accumulator empties determines the overspeed needed at the winder. The winder's tension control will be needed to keep tension controlled in the zone between the accumulator and the winder.
A pneumatically loaded accumulator can be emptied by reducing its pneumatic pressure (indirect tension). Constant tension at the winder will then draw material out of the accumulator. A load cell or dancer for the winder will keep tension in the zone between the accumulator and the winder controlled. The speed to empty the accumulator will be a result of air pressure settings and will not be directly controlled. Note the winder drive must be capable of pulling tension at the overspeed required.
Most accumulators introduce a tension spike when they empty as the web geometry changes to a flat sheet.