Web Winders, Rewinders and Unwinders Information
Web winders, web rewinders and web unwinders are used for winding, rewinding, and unwinding webs made of paper, film, foil, nonwovens and textiles. These automatic machines are designed to handle web materials of a predetermined length, and may include multiple modules or assemblies.
With web winders and web rewinders, a positioner feeds the web into a mandrel assembly via a feed-through slot. An apron assembly then directs the lead end of the web. At the end of each cycle, a resolver indicates the angular position. When necessary, the feed is adjusted to achieve the shortest angular motion.
Some web winders, rewinders and unwinders have roll ejector assemblies for ejecting the web at the end of the cycle. These assemblies may be activated by the movement of a bearing support assembly, which is moved from one end of the mandrel to release the web.
Many web winders, web rewinders and web unwinders use proportional, integral and derivative control (PID control), a three-function algorithm for automatically matching the control output to a set value of interest. Components and subsystems include dancers, moving roller sensor that provide feedback about web tension; idler rollers, web rollers that are driven by the web rather than by an electric motor, belt, or other external means; and rollers, rotating cylinders that are used for web transport. Web winders, rewinders and unwinders with sample-and-hold, soft start, taper tension, and other control features are also available.
Web winders, web rewinders and web unwinders differ in terms of operation, but are designed to maintain the proper tension during winding and unwinding activities. They may be used with web tension amplifiers, web tension controllers, web tension indicators, and web tension transducers. Web unwinders with pneumatic brakes are also available. Typically, these web dereelers are used by printers or converters. Unlike other web braking systems, which may cause web materials to snap, pneumatic brakes are designed to apply proper specific amounts of torque only when necessary. Heat dissipation, cylinder actuation, and ease of friction pad removal are important considerations when selecting pneumatic brakes for web unwinders. For each product line, suppliers of web winders, rewinders and unwinders also provide many additional specifications.