Diagonal needling drives press felt development; when "straight and true" won't do, papermakers turn to new needling technologies for felts that make a difference in the sheet.

Papermakers producing high value added grades need new ways to improve their products. Press felts that impart a more uniform and even surface to the paper web--particularly for high value printing and tissue grades--can deliver improved paper products.

Many advances in press felt technology focus on how the nonwoven "batt" that carries the paper web is attached under tension to the woven base fabric structure through a needling process.

That is the primary reason Weavexx, a machine clothing manufacturer based in Wake Forest, North Carolina, USA, invested US$12 million in a massive loom using new needling technology. The loom, built this year at the company's manufacturing plant in Starkville, Mississippi, uses Huyperpunch-D technology. Developed in Europe, Huyperpunch-D uses a combination of "curved bed" and elliptical needling technology to create a new breed of press fabrics. According to Weavexx, the loom represents its largest single investment in North America. Sister division Huyck Austria installed a similar loom in late 1998.

MULTIPLE ANGLES AND MOTIONS

"Huyperpunch-D needles press fabrics at multiple angles," said Ross Johnstone, development manager-press felts for Weavexx. "Conventional needling machines use a static, reciprocating motion where the needle is continuously punching at a 90[degrees] angle to the travel of the felt. Diagonal needling, takes the felt across a curved bed so the needle board enters the fabric at a range of angles starting at 90[degrees] and finishing at close to 45[degrees] (see Figure 1). Conventional needling creates larger holes in the weakest area of the batt and smaller holes elsewhere, Huyperpunch eliminates that problem." The patented diagonal needling process is available exclusively to Weavexx.

[FIGURE 1 OMITTED]

"The second innovation is an elliptical needle board motion we call Huyperpunch," Johnstone continued. "Non-woven manufacturers control microdrafting (a condition that distorts the batt) by changing the shape of the needle board motion from straight up to elliptical. In Huyperpunch, the needle board moves in synchrony with the fabric; it transports fibers while preventing microdrafting. Huyperpunch-D creates a more uniform, smoother surface with 40% more batt anchorage than traditional needling. That, in turn, increases sheet smoothness, improves two-sidedness and sheet dryness potential, reduces sheet breaks and sheet mark, and extends felt life."

Huyperpunch-D press fells have a more uniform pressing surface, which improves runnability in the press section, said Johnston. "For every 1% dryness increase in the press section, sheet strength improves by 12%. The more uniform and stronger surface means fewer breaks in the press section."

THIS LOOM REALLY LOOMS

The new Starksville Huyperpunch-D loom is enormous. The 12.6-meter working width machine weighs 1.5 million pounds and stands over two stories high. Construction began in early 2002 and included a 7000 sq. ft. building extension. The spring-mounted machine was shipped from Europe in 13 large pieces, constructed, and started up ahead of schedule in August 2002. An engineered concrete floor supporting the machine varies by less than one mm. The loom can produce felts for 98% of paper machines operating in North America (excepting machines below 47 inches wide.) Teams From several paper companies have already toured the facility.

Results for Huyperpunch-D press felts are promising, said Steve Cole, director-marketing for Weavexx. "We worked with a coated board manufacturer that could not meet the quality specifications of a particular customer on one of its board machines," he said. "They needed the quality to get premium pricing. After they ran Huyperpunch-D felts, they achieved that quality level. With no additional tonnage, they increased annual revenue by US$ 5 million." The customer has ordered the same felts for its other three board machines, said Cole. S!

Alan Rooks, Editorial Director