Precise control boosts homegrown coater’s productivity, quality

Why go out for hamburger when you can stay home and have steak? Engineers at Wausau Coated Products (Wausau, Wis.) considered this question before deciding to install their own high-performance laminating coater with expanded capabilities.

To produce its laminated, pressure-sensitive labels, Wausau Coated applies silicone film to 3.4 ft wide, 30,000 ft long rolls of 2.5—5.0 mil paper used to line the labels. Several years ago, Wausau Coated’s 100,000 ft2plant was at peak capacity with more than $35 million in revenues, so the company asked its engineers to achieve faster, better production using newer coating processes and control systems.

Wausau Coated’s engineers chose to replace a former water-based, 500 ft/min, emulsion process with a method that could triple production speed. It uses ultraviolet light to trigger a photo-initiator on solid silicone film. Precise control and roller coordination were critical to this new process because improperly cured liner could stick to the rollers or itself; poor control might cause sticky coating imperfections; and uneven roller speeds could create liner web sags, leading to wrinkles, jams, and tears.

Control adds flexibility

To cut dc motor downtime by replacing them with ac motors, Wausau’s engineers finally settled on a system from Rockwell Automation Drive Systems (Mequon, Wis.) that combined field-oriented controlled ac drives, intuitive operator interface terminals, programmable controllers, and single-source engineering and integration support. “We’d been accustomed to using only dc motors and drives because only they were able to deliver the precise speed control and handle the high torque loads needed to produce a quality product,” says Chris Stogbauer, Wausau Coated’s engineering director.

The new system manages rollers with 16 Allen-Bradley (A-B) 1336 Force ac drives that directly control torque and reportedly meet or exceed dc motor and drive performance. The drives communicate with a PLC 5/40 programmable controller through a Data Highway Plus network for information management and via a remote I/O network for normal control functions. Drive-to-drive communication is also available at high speeds.

Wausau Coated’s machine operators found their new system provided greater flexibility to coordinate varying roller speeds at either end of the process because the new drives could be programmed to run at set speeds or at percentages or ratios of line speed. The drives also have enhanced regenerative braking and web tension maintenance down to zero speed, which allow faster and more accurate adjustments. Likewise, controllers can download process parameters to the system more quickly, which means faster converting and order filling.

Two A-B PanelView operator interface terminals now monitor the coating process. To build this system in-house, Wausau Coated’s engineers used A-B’s PanelBuilder software and constructed human-machine interface screens on a Microsoft Windows-based PC. Designs were sent to Rockwell, where control engineers programmed parameters that feed the screens. Rockwell Automation Global Technical Services’ engineers later helped tie the new terminals into the new coater’s controls.

For more information, visit www.controleng.com/info .

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