When La-Z-Boy, Inc., Monroe, MI, was looking for a new wrapping material to replace the paper and/or bubble wrap it used to protect its chairs during shipping, "tough" and "wide" were primary requirements. The company settled on a three-layer, 9-mil coextruded film from Next Generation Films, Inc. (www.nextgenfilms.com), Lexington, OH. The high-density film, produced on a 103-in.-wide, three-layer Varex blown-film line from Windmoeller & Hoelscher Corp. (www.whcorp.com), consists of two layers of metallocene from Novacor (www.novacor.com) and one layer of high-density polyethylene.

Next Generation specializes in coextruded engineered films, including metallocene, HDPE, low-density PE, linear polypropylene, ethylene-acrylic acid (EAA), ethylene-vinyl acetate (EVA) and nano-composites. A key area is modified-atmosphere film, including films for extended-shelf-life products, and breathable films for fresh produce. "We’re not interested in commodity films," says Next Generation CEO David Frecka. "We work directly with end users. Each of our customers has their own specific needs, and our focus is helping them redesign and reformulate the proper film to meet those needs. Our growth has been through engineered films, and performance and quality are the prime requirements in this market, with price next. This has been a very successful business for us. We started in 1994, and we’re now at $30 million in sales per year."

Next Generation has six other blown-film lines in addition to the W&H line, but the W&H is the most sophisticated. "The segmented automatic die on the W&H line enables us to maintain less than five percent variation around the bubble, which is very important to our customers, and web handling is the best in the industry," opines Frecka.

Modular technology

One of the keys to this line is its modularity, says Jim Ciolino, sales manager—extrusion systems at W&H. The modular construction principle allows the line to be tailored to specific requirements and to be expanded to cover future growth and requirements. Modules incorporated in the Next Generation line include the Optifil P2® automatic film gauge control system, the Optifil Plus® automation module, the Procontrol® operator interface, internal bubble cooling, an oscillating haul-off with horizontal turning bars and gravimetric metering of components.

The line operation starts with gravimetric metering of components into the extruders. The system has three extruders, one for each layer, and each layer can have up to four components, so there are actually 12 separate metering systems for the three modules. The extruders melt and mix the components and then force the molten mixture through the 20-in.-dia three-layer die. The die features a star predistributor, which enables it to produce both asymmetric and simple symmetrical films. Depending on the film being produced, the temperature leaving the die can range from 400 deg F to 450 deg F.

The mixture is blown upward through the film sizing and stabilizing cage to form a 48-ft-high, 100-in.-dia bubble. The bubble passes through an oscillating haul-off and bubble-collapsing system at the top of the tower that utilizes horizontal turning bars to create a double-thickness film web. The oscillating haul-off system continually changes the angle at which the bubble collapses and the film’s orientation as the web forms, to minimize any long-term buildup of a ridge in the film on the final roll. Cooling air is delivered to both the inside and outside of the bubble to cool it to 45 deg F by the time it reaches the top of the tower.

The web travels down the outside of the tower and then enters a W&H Filmatic M dual winder, where it passes over a series of rolls to a slitter that trims off the edges of the film. The two layers are then separated and wound onto two paperboard cores. The winder incorporates three tension-adjusting rollers where dual loadcells measure the tension of the film and adjust the rollers to maintain the proper tension. Tension rollers are placed to regulate the tension in the film coming down the tower, at the slitter and at the finished film roll. Two Pillar Universal corona discharge treaters are mounted onto the winder frame, one for each layer.

Automation systems

The Next Generation system incorporates the Optifil P2 thermal gauge film profile control system, the Optifil Plus process control automation system and the ISP data-recording system. The P2 system combines a segmented die containing 88 heating elements and a capacitance thickness gauge with an accuracy of ±0.1 micron. The gauge traverses around the film bubble near the top of the bubble at a speed of one revolution every two minutes. The gauge transmits the thickness of the film to the Optifil Plus, which adjusts the temperature of individual segments to change the viscosity of the melt leaving that segment and thus the resulting thickness of the film at that point on the circumference. During PD’s visit to Next Generation, the system was maintaining a variation of 4.6 percent from the set thickness.

The Optifil Plus also controls the feed rate of the gravimetric weighing systems to the extruders and the extruder operating parameters, such as temperature and auger speed. It will sound an alarm if a parameter deviates from its setpoint and, at the push of a button, will explain why the alarm went off and will suggest how to correct the error. In addition, the system maintains a record of all the operating parameters of the line, including the winder, for every product. The operator enters the parameters for each product and then gives it a name in the menu, and the system remembers the parameters and sets up the system accordingly when the operator enters the product name.

The ISP is a standalone computer that takes a snapshot every two minutes of all of the operating parameters and data, and records it in memory. This allows an operator to look at historical data if any questions arise or to compare the operation at different times.

"W&H is a great company to work with," says Frecka. "This machine had the smoothest startup we’ve ever had, and we’ve had no problems since. W&H is the best in the market for wide-width blown film."

More information is available:
Films:Next Generation Films, Inc., 419/564-8713. www.nextgenfilms.com. Circle No. 215.
Blown-film line:Windmoeller & Hoelscher Corp., 800/854-8702. www.whcorp.com. Circle No. 216.
Metallocene film:Novacor,
33 (0) 1 41 39 01 61. www.novacor.com. Circle No. 217.
Static treatment:Pillar Technologies, 414/367-3060. www.pillartech.com. Circle No. 218.