Adapting flexible system in trim-recovery operations.

Published: August 01, 1995, By Simonsis, Yolanda

Product output improves after James Rivers' Flexible Packaging Group installs a new air handling system for trim recovery and reprocessing on a cast extrusion line.

The original intent of installing a more powerful trim-recovery system at James River's New Castle, DE, plant was to increase line speed and recover more trim for reprocessing on Line 42, a 175-in. Egan five-layer coextruder. As an unexpected bonus, other benefits accrued, including more efficient in-line processing, product savings and various operator conveniences.

As part of the Packaging Business in the approximately $5-billion family of businesses owned by paper giant James River Corp., based in Richmond, VA, the New Castle facility accounts for a healthy segment of the 25% of sales generated by this division. (The other two divisions are the Communications Paper Business and the Consumer Products Business.)

With the installation of new equipment from Convair Systems, Elmwood Park, NJ, trim recovery effectively doubled while the lb./day produced has averaged 15% to 20% higher than before.

A new Convair eductor-type trim-handling system was selected based on performance specifications provided by plant management, along with the complete installation of ancillary venting equipment for trim-removal operations. At present, it is the only one of three extrusion lines equipped with such capabilities.

Flexibility a Necessity

Line 42 makes polyethylene film used for bags and overwraps for bread, toilet tissue, paper towels and related paper products. Since it runs anything from fractional gauges to 5-mil thicknesses, technical management feels it is important to have a flexible system with excellent reliability. Line 42 Business Leader Chris Daly notes, "Overall production setup is always geared to providing customers with the most desirable film characteristics possible as dictated by their changing product wrap needs."

Most of the PE film processed at the plant is slit in-line and wound onto a fiber board core. The rollstock is sent for printing and converting into bread bags at the company's Greensburg, IN, plant. Master rolls of film can also be diverted for other uses and slit off-line into smaller-width increments on a new 62-in. Kampf center-wind, razor-supported slitter at the New Castle plant (also with a Convair unit) or on one of several Dusenbery slitters.

The other fiber-core-wound film is designated for towel and tissue over-wrap that's printed at the New Castle plant on any one of seven six-color flexographic presses from Paper Converting Machine Co. (PCMC) or Windmoeller & Hoelscher (W&H).

The 175-in.-wide line typically slits the film down to between three and six rolls, so, essentially, a lot of waste can be generated if one considers that the plant runs around the clock 365 days a year. "We effectively doubled our trim-recovery capability with the new air handling system in place," explains Daly. "Now we're capable of getting back up to 30 inches of trim - about double what we were getting before."

Daly adds, "The job of increasing line-speed capacity and recovering more of the trim generated on Line 42 was completed successfully with the addition of two 25-horsepower blowers for edge trim along with a 10-horsepower blower for the center trim. This power increase gave us the extra air thrust that enables the line to accept a wider trim. While it's difficult to put a fixed percentage on the savings achieved by weight alone, I'd estimate that we are able to recover up to 40% more trim without having to slow the line down or run a trim roll."

The former trim-removal system simply could not keep up with the changes in production requirements. "The word 'flexible' you see on the sign on our front lawn as part of 'Flexible Packaging Group' says it all," Daly says.

"The old system meant taking a roll of trim, cutting it, then manually feeding it into a chopper for recycling. This entire process not only led to delays, it also required extra bodies to complete. It could also give the line operator problems as he had to take trim at two different locations at opposite ends of the line."

Originally, the trim on Line 42 was taken at two locations. Because the trim system did not have enough capacity, trim was first removed immediately after the die to eliminate the edge bead. The remainder was taken at the winder section. If there were frequent production changes to accommodate different customers, the problem became more acute. Varying trim widths made it difficult to spread the proper suction evenly across the web via the manifold at each trim point.

Line Can Now Run to Specification

Another negative aspect of the old system was its inability to allow the extruder to achieve its design speed of 1,800 fpm. This speed is now possible. In addition, with the Convair system, instead of taking trim at both the extruder and winder sections, all of the power is supplied at the winder.

The technical specifications for the new air handling installation from Convair Systems include an eductor unit specially designed to handle two 12-in.-wide edge trims and 6 1/2-in.-wide center trims. For 1.25-mil PE film, the system will run at 1,800 fpm, and for 3 to 5 mils, it's 700 fpm. The lb./day that have been recovered average about 15% to 20% higher than before.

On installation, the James River and Convair engineers encountered very tight space restrictions in attempting to position the eductor piping above the line, then on through a wall to an air separator unit located over a grinder positioned behind the wall.

With ingenuity, the engineering team successfully completed the project. Essentially, the air separator divides the trim material from the conveying air and deposits the trim into the grinder. It is then chopped into small pieces for reuse in the extrusion process.

This air separator unit also required special consideration in design since there was limited space in which to separate a high volume of material from the conveying air that deposited the material into the existing grinder. The unit was built to process continuous trim from plastic film while overcoming static and plugging, both of which can occur when an extruder runs continuously.

The new system has eliminated the need to collect 15-in.-wide trim rolls (or smaller, with the attending tracking problems these sizes cause) for manual feeding to the chopper. The new system requires no winding or subsequent feeding of trim rolls to the chopper at all - and it involves no manual labor.

"This new equipment is much more efficient," reports Daly. "We're also finding fewer problems at the winder section, even at the speeds we're now running.

"When Line 42 was originally set up, it was the world's largest nonoriented cast film line. Nowadays, there might be wider lines around, but I don't believe any of them can pump out more pounds of good product outside of stretch wrap applications."

Daly emphasizes, "'Flexibility' is the name of the game around here. The new Convair trim-recovery system is only part of the production picture, but the more product we ship out the door, the more money we make. Obviously, reliable processing systems contribute significantly in keeping the line running 24 hours a day."