Paper Converting

Paper slitting machine using water cooled brakes

Proper tension with WPT Power’s Steel Water Cooled Brakes on slitter application.

Paper converting is an industry centered around taking raw paper products and turning them into finished products. These finished products include books, magazines, newspapers, cards, cardboard, stickers, paper bags, toilet paper, and nearly every other paper product that you use daily. These plain paper products are produced in paper mills and rolled onto large rolls for storage, transport, and later, use in the paper converting process. These rolls of raw paper can weigh tens of thousands of pounds and be as much as 12 feet long and several feet in diameter.

Once the raw paper rolls are created and moved to the production site, they often need to be reduced in length to fit a particular application. This conversion from a long roll to a shorter roll is the source of the term “paper converting.” There are two main methods for shortening the rolls, sawing the entire paper roll in place, and slitting and rewinding the roll.  WPT Power industrial brake products play a significant role in the latter option.

During the slitting and rewinding process, the raw paper is loaded into the slitting machine and fed into a series of cutting blades to reduce the length of the paper to the required size. The reduced length paper product is then rewound for use elsewhere. Keeping proper tension on the source roll is crucial to the slitting and rewinding process.

If you have never had the luxury of working with large industrial-sized sheets of paper rolls, you may not appreciate the challenge of keeping the paper at the proper tension. Too little tension and the paper rolls will begin to unwind in an uncontrolled manner and create a runaway effect that will result in time wasted and potential damage to the plain paper or machine. This would be similar to the rat’s nest that can form in a fishing reel when the line does not have enough tension, just on a larger scale.

The unwinding and slitting machines utilize a dynamic braking system to keep proper tension on the rolls. This brake system comprises a brake, controller, and tension measuring device. The brake can be an air-cooled design for light to medium duty payout or a water-cooled design for medium to heavy-duty payout.

Because the roll changes in weight and diameter as it unwinds, the amount of torque needed to keep constant tension on the paper roll changes over time. Therefore, nearly all brake systems on unwinders and slitters utilize a feedback loop that monitors the tension on the paper roll and adjusts the braking accordingly. The WPT Power Low Inertia (LI) Brake and Low Inertia Steel Water Cooled Brakes (SWCBs) provide the required torque capacity, precision control, and heat dissipation.

Best suited for light to medium duty applications, the WPT LI brake line features premium friction disc linings, ventilated centerplates, and a reinforced neoprene airtube. The friction disc linings are available in Low, Medium, and High coefficients to provide the level of torque needed for every situation. The ventilated center plates offer increased airflow to better dissipate the heat building during the unwind. Finally, the neoprene airtube provides maximum sensitivity by reacting to small pressure changes and offering no resistance to movement. The WPT Low Inertia brake can also be outfitted with a fan to provide forced air cooling. These units are available in 1-, 2-, or 3-plate versions ranging from 6 to 60 inches.

For more demanding industrial applications, the WPT Low Inertia Steel Water Cooled Brake features a unique design that takes the heat dissipation capacity to the next level. The specially designed center plates (or water jackets) utilize a one-piece steel design with integrated cooling ports that allow water to flow through the jacket to an external cooler. This means the brake can achieve extended periods of high speed and high torque slipping without overheating. Upgrading to the WPT SWCB brake is easy because it will mount in the same position as an air-cooled version. They also use the same airtube that allows for precise control and response. The WPT Steel Water Cooled Brake is available from 6 to 30 inches in 1-, 2-, and 3-plate configurations.

For more information on either the WPT Low Inertia Brake or Water Cooled Brake lines, please get in touch with WPT Power.