Waste Not, Wobble Not
Web guiding and tension control help converters control waste as well as the web’s “wobble” as it comes off the roll.
February 2007 by Chris Mc Loone
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Web handling is a broad category of products that can range from slitters/rewinders, web guides, register, tension controls, and web inspection. Web guiding and tension control are two factors that help converters control waste as well as the web’s “wobble” as it comes off the roll. In the case of tension control, sensor selection is a major factor. Using low-cost sensors that require constant recalibration is no longer acceptable to converters.
Tension Control Issues
Although some converters may be intimidated by the tension control concept, the waste reduction and improvement in product quality are more than worth the investment. “Tension control is perhaps the most critical part of a web process because the precision it yields reduces waste and improves product quality,” says Brett Hardy, marketing manager, DoubleE USA. “Unfortunately, its importance is often overlooked or avoided because controlling tension seems like a complex issue. A simple conversation with a trusted vendor to review the customer’s operating conditions would quickly reveal which type of tension control system would be most appropriate. The customers should not need to specify a system for themselves,” he adds.
Higher demands are being put on tension sensors for accuracy, repeatability, wide measurement range, and stability over the long term. Ensuring you have the right sensors for the job is also critical. “Machine designers require higher product diversity, production speed, acceleration rates, and to this end we see more process automation and especially direct coupled drives,” says Bob Sarnelli, marketing manager, ABB. “Sensor feedback to the drives for web tension control is critical in order to maintain product quality during fast acceleration and high production speeds.” Hardy adds, “There are many new sensors and controllers which are available in the marketplace today. Many end users are replacing dancer systems with advanced load cells, and generally taking advantage of improved technology. User-friendly controllers make custom programming and constant monitoring simple and easy.
Tension controls evolve as the industry does. Higher speeds and larger rolls are the norm today. Many converters want to run larger diameter rolls on existing equipment to make the machine more efficient (fewer roll changes and splices). “Improvements in efficiency can be offset by the waste that is created with a machine that doesn’t have the range of tension controllability necessary to control the unwind from full roll to core due to large roll build ratios,” says Chris Harper, district manager for Maxcess. “Converters may find that they are throwing away usable material before the end of a run because a single gain value type of controller that worked at full roll becomes unstable as the run gets closer to the core. Multiple gain points will fix this issue.”
Tension Control Issues
Although some converters may be intimidated by the tension control concept, the waste reduction and improvement in product quality are more than worth the investment. “Tension control is perhaps the most critical part of a web process because the precision it yields reduces waste and improves product quality,” says Brett Hardy, marketing manager, DoubleE USA. “Unfortunately, its importance is often overlooked or avoided because controlling tension seems like a complex issue. A simple conversation with a trusted vendor to review the customer’s operating conditions would quickly reveal which type of tension control system would be most appropriate. The customers should not need to specify a system for themselves,” he adds.
Higher demands are being put on tension sensors for accuracy, repeatability, wide measurement range, and stability over the long term. Ensuring you have the right sensors for the job is also critical. “Machine designers require higher product diversity, production speed, acceleration rates, and to this end we see more process automation and especially direct coupled drives,” says Bob Sarnelli, marketing manager, ABB. “Sensor feedback to the drives for web tension control is critical in order to maintain product quality during fast acceleration and high production speeds.” Hardy adds, “There are many new sensors and controllers which are available in the marketplace today. Many end users are replacing dancer systems with advanced load cells, and generally taking advantage of improved technology. User-friendly controllers make custom programming and constant monitoring simple and easy.
Tension controls evolve as the industry does. Higher speeds and larger rolls are the norm today. Many converters want to run larger diameter rolls on existing equipment to make the machine more efficient (fewer roll changes and splices). “Improvements in efficiency can be offset by the waste that is created with a machine that doesn’t have the range of tension controllability necessary to control the unwind from full roll to core due to large roll build ratios,” says Chris Harper, district manager for Maxcess. “Converters may find that they are throwing away usable material before the end of a run because a single gain value type of controller that worked at full roll becomes unstable as the run gets closer to the core. Multiple gain points will fix this issue.”
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