Web accumulators and coil accumulators are used to control the tension of materials in continuous manufacturing processes. They are different than fluid-line pressure controllers and the accumulators used to control conveyor feed systems.
Web accumulators are used to control the tension of materials such as film, foil, fabric, textiles, and paper. They include a carriage, cage, and one or more sets of metal rollers. Coil accumulators or strip accumulators are used in continuous processes such as painting, tube welding, and extrusion. Both vertical coil accumulators and horizontal coil accumulators are commonly available. Web accumulators are available in vertical or horizontal designs and are either free-standing or equipped with a mounting plate for installation on another machine.
Specifications for web accumulators include: capacity, roller type, and number of passes. Festoon web accumulators are designed to store web material during roll changes or web payout. High-capacity web accumulators feature two sets of idlers that allow a festooned web to move through an outer set of rolls before reversing direction and returning to a nested position within the first set of idlers. Medium-capacity web accumulators are single-pass, self-threading machines with a driven pull-roll. They often include a potentiometer to indicate full or empty conditions. Narrow web accumulators are self-threading devices that use a mechanical counterweight to counterbalance the carriage and load the web. Specifications for coil accumulators include: direction of travel, coil outer diameter, coil inner diameter, material thickness, material width, yield strength, line speed, control voltage, and floor space required. The direction of travel for a coil accumulator can be clockwise (left-to-right) or counter-clockwise (right-to-left). Measurements such as coil outer diameter and coil inner diameter are expressed in either millimeters (mm) or inches (in). Yield strength is the stress at which a material exhibits a specified deviation from proportionality of stress and strain. Line speed for coil accumulators is measured in either meters per minute or feet per minute.
With regard to applications, coil accumulators are often used in continuous processes such as roll forming and tube welding. Vertical loops or festoons are used mainly in strip processing lines, but can also be used with light-gauge lines such as roll formers and stamping machines.