The Unwinding Story
- Published: April 01, 2002, By Nsenga Byrd Thompson, Staff Editor
Sometimes purchasing a “simple” thing, like a pair of bluejeans, can be overwhelming. Unwinders are such a standard piece of equipment in a converting plant that it may be very difficult trying to decide which one is the right fit for you. But if you keep your specific operation — and budget — in mind, you'll find that, along with the many new trends in unwinders, there are still basic factors to consider.
“The first decision to make is what automatic features are required, specifically, whether or not automatic splicing is justifiable,” says Jim Ward, VP of light web products at Martin Automatic Inc., Rockford, IL. “Most processes generate a significant amount of waste as they accelerate and decelerate. This usually means that keeping the process running at full speed by incorporating automatic splicing can have a very quick return on investment.”
Jim Stobvie, sales manager at Macro Engineering & Technology Inc., Mississauga, Ont., Canada, says a key factor today is ergonomics. One of the major improvements in this area, he notes, is the use of shaftless unwinders. “If you do need a shaft,” says Stobvie, “there are [products] made with modern material composites that are very lightweight but strong enough to handle the big weights and roll diameters demanded by the processors.”
Perhaps the most important factor in unwind equipment is tension. Ward says converters must ask themselves what tension range is required and how accurate the tension delivered to the process has to be to maintain registration or control the web width of an extensible substrate.
Stobvie adds, “You may want an unwinder that can handle materials that run with relatively high tensions, like paper or a thicker board. And, you may have to run a very thin, extensible film. You need an unwinder that can operate efficiently at those very different tensions.”
Like all converting machinery, unwinders have evolved. One of the most significant changes in recent years, according to Jack Santa Jucia, president of Independent Machine Co., Fairfield, NJ, has been replacing DC motor-driven unwinds with today's AC motor-driven unwinds. “With the development of the AC digital flux vector drive, higher speeds, wider tension ranges, and response of the control system to process changes are now possible while eliminating DC motor brush replacement.”
Adolpho Edgar, area sales manager at Macro Engineering, says, “The focus has always been on longer run lengths with higher speeds and less scrap. The way to [achieve that] is to go with larger roll diameters and automatic splicing from roll to roll, so you don't have to stop the line to change the roll, and you obtain that with a dual-spindle unwind.
“Traditionally,” says Edgar, “you would see a lot of three-inch cores being used; now the trend is to use six-inch cores, because you have an advantage in that scrap left on the tail of the roll is not crushed or wrinkled as would normally happen with material that is close to the core on a three-inch core.”
Also significant, says Ward, “has been the trend toward tapeless splicing with the use of heat seal splicing methods for use with poly-based films, nonwovens, and foams. When applied correctly, these types of systems can significantly reduce or eliminate the waste associated with taped splices.”
Ward has seen a rise in the need for in-register splicing systems for preprinted or die-cut materials. “Keeping the splice automatically registered within a given tolerance during a roll change can reduce waste significantly. [Today's systems] can operate at significantly lower tension levels, provide better tension accuracy, and operate at much higher speeds than previous generations.”
Restrictions of time and space limit the number of companies, products, and trends that we can discuss in these reports. For additional information, see PFFC's features and departments each month, consult the June Buyers Guide, and check pffc-online.com.
