Hit the brakes! More often than not, the order is shouted, or even barked. Tone and inflection are indicative of one facttime is of the essence. Immediate, swift and critical action is necessary. Without it, bad things are going to happen. In all likelihood, heavy machinerybe it a car or a flexographers presswill come to a screeching halt. Severe damage is a possibility. Watching this scenario unfold, whether on the road or in a pressroom, one can sense the tension in the air.
Nerves become easily frayed as pressure to respond builds. Anxiety is etched on faces. No one, especially a pressman, wants to lose controlof the web, that is. Thankfully, modern-day presses come with modern-day innovations. Devices are available to promote the maintenance of optimum conditions throughout a pressrun. They measure speed, path of direction and other variables that could affect registration.
Sensors, signals, monitors, AC drives and DC drives (motors), clutches and shafts come together in the unwind, rewind and mid-process tension zones to regulate torque (the force exerted on the web), minimize downtime and lower maintenance costs.
Every press operatorfrom Hood Flexible Packaging, Decatur, Ga., to 4 Lakes Labels, Madison, WI; B&W Press, Georgetown, MA; Packaging Specialties, Fayetteville, AR; Bancroft Bag, West Monroe, LA; FlexFab LLC, Hastings, MI; Wolf Packaging, Fort Madison, IA; and Packaging Specialties, Gainesville, GArelies on and appreciates the art and science of tension control. By all accounts, the systems are universally used in converting operations worldwide, whether the shop is dedicated to corrugated, flexible packaging, labels, preprinted linerboard, newspapers and publications or envelopes.
FLEXO® Magazine recently polled select FTA printer membersthose named aboveto compile a short report for this months Ps & Qs column on the importance of tension-control systems and the impact they have had on operations. Opinions expressed were uniform: The devices are critical, important and basic to success. They improve productivity and ensure run-to-run consistency. The exact questions asked were:
- How important are tension-control systems to your operation?
- What impact have they had on waste reduction and quality output?
- What recent technological advancements in the tension-control field have proven most significant?
Attributes Cited
Measurement and control were focal points of every conversation. It was noted for the record that tension-control system manufacturers are proud of their products and the value they deliver to flexographic printing operations. Pneumatic tension breaksmany specifically designed for use in corrugated and paper converting applicationswere said to deliver long life in constant use. Torque range can exceed 15,900 lbs. Effective tension controls are often credited with having helped to increase line speeds up to 1,140 fpm.
Another attribute cited is the fact that out-of-spec readings on a tension monitor can alert the machine operator to make adjustments to equalize side-to-side tension and optimize tonal tension. Systems were reported to have helped prevent web breaks, as minimum and maximum levels can be specified to sound an alarm.
Original equipment manufacturers (OEMs) recognize the essentiality of incorporating tension controls into the presses that they manufacture, according to every printer participating in the survey.
Mike Poole, Bancroft Bag, reported that in his plant, All presses have controls on them. He admitted, New presses feature more automated tension controls, but also said, Basic ingredients of a tension-control system are the same, no matter how old the press
. Our plant houses Windmoeller & Hoelscher presses, the newest installed in 1997 and the oldest in place since 1980. Our greatest challenge in tension control is keeping good register.
Tony Panther, Wolf Packaging, echoed that assessment. Registration is the reason to employ tension controls. At our plant, we apply hot wax. Too much tension will stretch the paper. To that, Eric Schmidt, plant manager, 4 Lakes Label, added, We use an OEM-installed braking system on our newest press. Print results are in much better register with the tension control. Tension control is necessary if you want to produce high-quality product. With the tolerances that we try to hold, its what we need to have."
Consistency & Repeatability
Steve Lee, general manager, Hood Flexible Packaging, stated, You have to have good tension control on a printing press. If youre printing polyethylene, it affects the repeat. If you dont have tension control, you could stretch the web. Tension control keeps everything better registered. Its a basic thing in printing. He later noted, Some people use tension indicators, and not really tension controls. Good tension indication, at the very least, is needed so you can make adjustments.
Mike Throgmorton, general manager, Packaging Specialties, observed, Dancers and transducers keep the constant tension necessary to keep film running through the equipment. On the rewind side, tension control helps with roll conformity.
