- April 01, 1998, Mykytiuk, Andrew
Static electricity was causing big problems for Favorite Plastics. The solution - a Tantec system - was only a phone call away.
Favorite Plastics, a Brooklyn, NY, manufacturer of film for the converting industry, was experiencing problems at the wind-up stands on its Battenfeld Gloucester extrusion equipment. It seems that operators were getting shocked every time they touched or came too close to the winders. Even worse, customers were beginning to complain about high static charge on film rolls. Favorite Plastics found the answer with static control equipment from Tantec Inc.
"A static charge on a roll of film turns it into a dust magnet," says Jim Beres, an engineer with Favorite Plastics. "Once a static charge is imparted, the roll will attract and hold all kinds of dust and dirt just by sitting in the warehouse."
Beres goes on to explain that converting machinery will not work as designed when static is present. "The film has a tendency to stick together and resist unwinding. Our customers use the film we manufacture for all sorts of applications, from bagmaking to processing food packages. A lot of the specialized converting machinery is sensitive as far as the way it unwinds, and if the film we make for them is sticking together, it creates problems as it's being converted, especially if it's being laminated onto something else." For a customer-driven company, this was an unacceptable situation.
Favorite Plastics already had a static control system on its machinery, the type referred to as an ionizing air blower. It was a 5x12x10-in. unit with an integral fan motor designed to blow the ions generated at the static bar toward the windup stand. The problem with this system, explains Beres, was that the static bar was too far from the film, and the farther away from the film, the less effective it is at eliminating static.
Static, Static Everywhere
"Film Can generate static electricity in several ways," says Beres. "We manufacture long lengths of film that have to be guided in a number of different directions by many rollers. Every time the film touches a roller, you're creating friction that generates static, and, as the film travels along the rollers, there always is a slight stretching of the film, which also generates static electricity."
A team of engineers at Favorite Plastics was assembled with the goal of eliminating the static problems at the winder. "We knew about static bars, because we already had been using them," says Beres. "There are many different kinds, so it became a question of finding the product that was right for our application.
"Based on ease of maintenance and durability, our engineers chose a system from Tantec. All static eliminators require periodic maintenance, and the Tantec product is quite easy to clean," notes Beres. "The other thing is that you can grab the static bar itself while the system is on, and you won't get a shock. They're made of a material that does not break very easily. With the older type of static bars, when the film got caught up in it and pulled the bar, it bent, or even broke. The Tantec units can take a fair amount of abuse, and in an industrial environment, the ability to take abuse is important."
Keeping It Close
Solving the problem, however, required more than just selecting a product. The main engineering challenge was how to get the static eliminator bar to within an inch of the film as it was being wound onto the core. One inch is the maximum distance between the static bar and the web; any more than that and effectiveness drops dramatically.
This can be a major problem, because the diameter of the roll increases as the film is wound. If the static bar is mounted conventionally, the standoff between the bar and the roll increases as roll diameter increases, rendering the static control system ineffective. Not only is the distance between the bar and the web important, but the mounting location is important as well. "You want the static bar as close to the winding as possible, because the farther away it is, the more rollers you have in between and the more possible stretching," says Beres. "The static control system becomes less effective the farther up the line you have it away from the roll."
Engineers from Favorite Plastics and Tantec got together and decided to mount the static bar on a lay-on roller so it would follow the diameter of the roll as it grows during winding. The assembly rigidly moves the static bar up/down to accommodate changes in wound-up roll diameters at speeds to 800 fpm. The 1-in. distance is maintained throughout the entire operation.
The incorporation of the Tantec system yielded one more unforeseen benefit to Favorite Plastics: a shielded cable. Not generally found in this type of system, the cable eliminates interference with sensitive electronic equipment such as PLCs, drives, electric motors, or safety sensors.
With the Tantec system, operators are no longer being shocked, and customers are no longer complaining about statically charged rolls of film.
Tantec Inc., Schaumburg, IL; 847/529-5506; fax: 847/529-6956.
Battenfeld Gloucester, Gloucester, MA; 508/281-1800; fax: 508/283-9206.