- May 01, 1996, Walker, Juliana M.
Nashua Graphic Products eliminates dust problems on a slitting line and improves slit width tolerance with a Dienes Laser Positioning System.
In order to be more cost-effective and competitive, Nashua Graphic Products, Merrimack, NH, was eager to improve its #2 makeready slitting line. The ISO-9002 certified company provides other Nashua facilities as well as outside customers with adhesive label papers for retail and pharmaceutical applications, specialty coated papers for unique applications, thermal papers for variable bar code information, carbonless papers for business forms, and ticket and tag papers for the entertainment industry and retail stores. Finished products include domestic and international-sized fax paper, photocopier paper, and laser printing paper.
Nashua found that, while it was meeting its customers, requirements and delivery schedules, setups were not productive. Setups were changed numerous times a day, with operators making as many as 20 cuts from the coated roll of paper. This was being done by manually adjusting each male and female knife set. The slitter operator used a steel rule to measure each slit width across the web, a process that was tedious and time-consuming. Newer operators often had to make additional adjustments after short test runs showed some of the slit widths out of tolerance, They also had trouble setting the correct male/female knife relationships, such as side pressure, toe-in, etc., to achieve clean cuts across the web.
In order to keep dust to a level that permitted customers to do their printing and other follow-up operations, top male knives would be changed weekly and bottom female knives about every six weeks. Because Nashua maintains its own in-house knife sharpening operation, turnaround time wasn't a problem. Knife life, however, definitely was a problem.
As part of the companys corporate-wide quality program to upgrade its manufacturing equipment and capabilities, a team consisting of management and production personnel looked at various systems in an effort to streamline the #2 line. They chose the Dienes, Module IIL Laser Positioning System.
Nashua process engineer Allen R. Steele explains, lt was the only system that could meet the requirement to slit as narrow as 11 5/16 in., and Dienes, modular PSG-Narrow shear-cut knife-holders offered the stability and added capabilities that we desired. Laser accuracy has improved slit width tolerance from [+ or -] 1/32 to [+ or -] .004 in. The system also meant fewer modifications to the 30-year old slitter."
Becoming a Believer
Steele admits the system sounded almost too good to be true at first. "When Dienes" local representative showed us the Module IIL Laser Positioning System, I had no qualms regarding its accuracy and faster setup, but I was somewhat skeptical about the claims regarding its almost dustless operation.
"Today I'm a believer. We can run more than ten times longer with our top male knives and still be below the dust level we used to drink was acceptable. And we didn't need to buy special knives. We use the same male knives that we've always used, so we know the difference is due to the laser system and the holders, not the knives. And I'll probably be retired before we resharpen those, because they haven't shown signs of wear!"
Steele adds that not only has training for new operators been reduced to a single demonstration, but the system is so easy to learn that their setup times are almost as good as those of the more experienced operators. "They can set up 20 cuts across the web with precision and accuracy just as fast as they can move the laser from position to position. New operators also spend less time in cleanup and have less downtime, because they don't have to change knives as often."
Butch Nichols, day-shift operator and slitter set-up trainer, reports, "I used to have to show them over and over how to properly set the side pressure to obtain a clean cut. Today, it's done automatically and precisely. We no longer have 20 different side pressures when we're slitting. We get the same high quality cuts across the web."
Nichols, a 23-year employee, was one of the team members who evaluated the various systems under consideration. "I can't think of one reason that I would go back to the old system. The multidigit linear scale read-out in conjunction with the set of indicator fights, quickly and accurately tells me when the bottom female knife is exactly positioned for the slit width I want on each cut right down to three decimal points.
"Then all I do is slide the top male knife holder over until it locks in place, and I know I've obtained the correct alignment with the bottom knife. You're done the first time."
Another benefit of the system, says Steele, is that the laser can be used to check the squareness of the bottom knives without removing the knives from the shaft. "The knifeholders also feature a quick-change cartridge that lets us remove the used male knives and put on sharpened knives without removing the holders from the mounting rail or using any tools."
Nashua has made other moves in upgrading its quality. A beta gauge measuring system was added to a coating line to measure the thickness and moisture content across the web. It also allows the operator to change the process as needed to achieve a uniform coating throughout the entire length and width of the roll.
This system provides a flatter, smoother surface that enhances the customers, printing and other follow-up operations and allows operators to run at a faster speed, thus increasing productivity.
The beta gauge system and the Dienes laser positioning system are key elements in Nashua's improvement program, helping the company provide its customers around the world with higher quality, more cost-efficient product.