Processing Magazine

Tougher TPU-coated rollers extend wear-life and productivity

September 29, 2009

Specially formulated thermoset polyurethane offers superior longevity through added cut resistance, abrasion resistance and load bearing capabilities

If you’re in an industry that uses rollers, you know that roller toughness and longevity really count. The Achilles heel for many applications is the roller surface, where challenges such as cut-resistance, abrasion resistance and load bearing capabilities can make a dramatic difference in the productivity of a plant.

Because roller changeover and resurfacing are both time-consuming and costly, many plants run theirs as long as possible in order to maximize production until replacement is mandatory.

“In many applications there is no in-between, the rollers are either operable or defective,” says Matt Menges, President of Menges Roller Company (Wauconda, IL). “But the toughness and impact-resistance of the surface covering can improve wear life by months or even years.”

For example, Menges says, in the steel coil industry, coils are stretched almost as tight as piano wire. Because the steel is very abrasive and usually has rough edges, cut-resistance is a major factor. As a result, standard rubber-coated rollers wear out relatively quickly, resulting in both maintenance, loss of product and downtime costs.

Flexible advantages of TPU

One of the solutions to greatly improving the wear life of roller coverings is the use of more advanced materials than can be tailored to an application. The use of thermoset polyurethane (TPU) plastic, for instance, provides the toughness and abrasion-resistance needed by most applications while at the same allowing the latitude to make the coating as hard or soft as the application requires.

Some of the properties available by various TPU formulations include: superior abrasion resistance, chemical resistance, cut resistance, impact resistance, high tear strength, flexibility and broad temperature operating range.

“Industries that can benefit from TPU-coated rollers include steel, aluminum, paper, roofing, converting, and others,” says Menges. To meet those needs his firm has developed a special line of TPU-coated rollers known as Tiger-Max. The new rollers are designed to outlast cast polyurethane, resulting in added uptime and reduced maintenance costs.

Longevity, savings and safety

A graphic demonstration of the powerful benefits of TPU-coated rollers may be found in the production of blown-film packaging at PPC Industries, Pleasant Prairie, WI. Because PPC runs its plants 24/7 for 365 days a year, the company’s engineering, production and maintenance people decided to investigate TPU-coated rollers to see how much additional longevity they could provide.

“The whole idea behind this was to get more life out of the rollers because they are expensive to replace and changeover requires a very big effort,” explains Tom Gussarson, PPC Purchasing Manager. “So, we’re hoping to get 2-3 times the service life out of these TPU-coated rollers as we do from a standard rubber roller, which is about a year.”
PPC initially installed TPU-coated nip rollers (one of Menges’ Tiger-Max models) on a blown film system about 18 months ago. Since then the bag machine nip roller and winder nip rollers have also been replaced with TPU models.
“We produce several different plastic bags with writing on them,” says Gussarson. “These bags are used for medical and food customers who require that messages be printed on the film. Any time you have printing on bags, that film must be treated through a corona system. The corona treatment causes added ozone, some of which lingers in the plant, especially in the area of the top nip roller, which is 60 feet in the air.”
Gussarson explains that the ozone exposure will deteriorate standard plastic- or rubber-coated rollers, causing them to dry out and become brittle and crack. This condition would normally accelerate the need for roller replacement.
“The TPU rollers hold up much better when exposed to ozone,” Gussarson says. “In fact, they are almost immune to the problem.”

In addition to productivity, another major goal with adopting the TPU-coated rollers was the avoidance of having to replace large, heavy rollers that are sometimes at considerable heights. For example, the rollers on our top nip section are 60 feet up, are 5 to 10 feet wide and can weigh between 4,000 and 6,000 lbs.

“That size makes the effort to change the rollers a major one,” says Gussarson. “Plus there is also a safety consideration. While we are very safety conscious, avoiding accidents requires reducing the exposure to incidents, so if we can reduce the frequency of changing those rollers, that is also a significant benefit.”
In addition to the TPU-coated rollers, Menges works with high quality compounds such as neoprene, nitrile, hypalon, EPDM, and Buna-N. The firm also works with specialty compounds like high-release silicone, Viton, natural rubber, EPDM/silicone blend, nitrile PVC and the proprietary Super ToughCoat rubber covering.
Menges Roller Company offers in new and replacement rubber-covered rollers for the printing, converting, metal processing, plastics, paper, and textile industries. The firm specializes in steel, tube, stainless steel, cast iron, carbon fiber composite and aluminum roll cores from 48 inches in diameter and 30 feet in length.