Waste Not, Wobble Not

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 controls are evolving to meet the needs of printers and converters to run bigger rolls on machines than initially intended by the OEM,” says Darrell Whiteside, distribution channel manager, MAGPOWR. “Introducing a tension control with automatic gain scheduling allows you to run literally any roll build with none of the scrap caused by stability problems associated with having too much gain at the core.”

Hardy adds, “Faster speeds and larger rolls can contribute to more throughput, but they can also be harder to control, so problems can multiply quickly. A good tension control system monitors tension control and keeps it consistent as variables change.”

Web Guiding

To John Thome, general manager, of BST Promark, the inherent benefit provided by a proper web guide system on a converting machine has been taken for granted. “Without a proper web guiding device, machines run slower, output is less, productivity is reduced, downtime is greater, and downstream processing is severely affected in a negative way.” All of these things, according to Thome, are avoidable.

“The web guide remains an essential design element of any effective converting machine,” he says. “Guiding systems themselves have come a long way since the turn of the century in terms of what they can do, the output they provide, how they talk to and control other devices, and a lot more.”

Tom Jonozzo, manager, guiding department, North American Manufacturing Company cites two trends in the industry: the drive to combine previously separate and distinct components into one compact design package fulfills stripping and web guiding; and the need to provide operator control stations that can control all subsystems or components on a line.

Combining components allows “a streamlined and simple machine design, convenience and ease of use for operators, and less manufacturing and assembly time for machinery builders,” he says. Jonozzo cites integrated web guide and splice table units becoming more prevalent on ­flexographic tag and label printing machines as one example.

Mike Flannigan, manager, corporate user accounts, Maxcess, relates that more customers seek to upgrade their existing pneumohydraulic guides with cleaner and more efficient electromechanical systems. According to Flannigan, the existing equipment works fine, but can become a maintenance issue. “To answer this issue, Fife has developed a retrofit program that makes it easy and affordable to switch,” he says. Flannigan states that customers who have made the switch cite many benefits. “Electromechanical systems are easier to use, require less maintenance, are safer, and increase response time.” An increase in response time, he comments, means that the web guide is more accurate. Narrow-web printers typically deal with large-diameter rolls that are more likely to oscillate or wobble. “A 6-inch wide web wound to a diameter of 40 inches is not uncommon,” he says. “A web guide with a faster response time will correct for roll ‘wobble’ and maintain alignment despite this challenge.”

Integrated Tension Control Systems

The Double E / Re Integrated Tension System packages all electrical and pneumatic components in a single ready-to-mount, NEMA-style enclosure. The Model EP.03 is ideal for end users wishing to simplify installation of a new or upgraded closed loop tension control system. It contains the MW.90.10 controller, E/P converter, air pressure gages, and manual override dials, and quickly connects to new or existing pneumatic brakes. DoubleE USA, www.doubleeusa.com

Guide Retrofit Package

Fife Corp. has introduced a program to offset the cost of retrofitting existing web guides, improving accuracy and ease of use. The new retrofit program includes all components necessary to make the switch, as well as cash back for the return of older equipment. Fife retrofit kits include a web guide controller, sensors, electromechanical actuator, mounting bracket and cables to be installed by internal maintenance personnel or local Fife service engineers. Fife Corporation, www.fife.com/retrofit

Tension Control Improves Stability on Large Rolls

Automated functions on the Cygnus tension control maintain constant tension as roll diameter changes, making it easier for narrow web converters to produce large rolls that are solid from full roll to core. Operators can spend time monitoring the entire converting process instead of changing control parameters as the roll diameter changes. Other features like automatic tuning, weightless load cell calibration, and out of round roll compensation (previously only possible with a dancer control) help ensure consistent roll quality. MAGPOWR,
www.magpowr.com/cygnus

Industrial Network Web Guide Controller

North American Manufacturing Company’s H6423 web guide controller is for machines that use operator HMI’s or industrial network communication. The H6423 can accept operator commands directly from a machine HMI or as an addressable networked device when used in conjunction with a North American industrial gateway interface. The unit operates on a 24-VDC power supply, and uses standard SimPlex™ sensors and actuators to deliver precise web control. North American ­Manufacturing Co., www.namfg.com

Web Width and Sleeve Measurement System

BST International has introduced a closed-loop web width measuring system. BST ProTouch integrates BST’s CCD Pro cameras into a web/process management system capable of complex automated applications such as web width measurement, splice control and tire manufacturing. BST ProLogic is for use on extruders, slitters, printing machines, and other converting machinery. It provides continuous graphic display of the actual web width and, when integrated with the exruder, it can provide a complete closed loop web width measurement and control system. BST ­International,
www.bstpromark.com pP