Web accumulators can be used to provide several functions, which may be important to your process:
- Tension control. Basically web accumulators are simply dancer roll tension controls with large amounts of material storage. Their operation and control logic is similar to a dancer roll for tension control.
- Stabilize an intermittent feed application. Web accumulators can be utilized in intermittent feed applications where frequent starting / stopping of the web is common. Many times, intermittent feed applications create web handling issues due to momentum and inertia concerns, especially when looking at the unwind or rewind tension zone in the process. Web accumulators can be used as a "shock absorber" to reduce or eliminate unwind and rewind roll starts and stops.
- Run non-stop. At the unwind, accumulators operate by storing the necessary amount of web to allow the machine to continue running while the machine operator makes the splice to a new, full master roll. The accumulator must be designed to store enough material for a splice to be made in a pre-determined amount of time. In other words, if it takes the machine operator one minute to make a splice, the accumulator must store one minute (plus some for a safety factor) worth of web.
Accumulators at the rewind location are similar, except they operate running empty. When a cut-over to an empty core is required, the accumulator fills with web allowing enough time for the cut-over to be made on the fly.
Use of web accumulators can allow you to run the machine continuously, eliminating stops for splices at the unwind and cut-overs at the rewind. Your production will increase; waste due to machine stops will be eliminated. When you consider lost production time during the course of a normal work day for machine stops, you can easily calculate return on investment when utilizing web accumulators.
It is very important to consider the design of your web accumulator. Factors to consider include:
- Ease of threading. Web accumulators may have many rollers and web passes. Choosing a design that is easy to thread your web through will speed up set up time.
- Loading. There are several methods to load a web accumulator. Weight loading air loading are common. Air loading is usually more desirable because it decreases effects of momentum and inertia on the web.
- Cost. Mechanical designs and control logic can be simple to complex depending on what is required for your process. Specify what is needed for your application and consider what design is best for your operation.
Written by Jeff Damour, Converter Accessory Corp.201 Alpha Road, Wind Gap PA 18091 800-433-2413
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