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At a time when the paper industry is rapidly consolidating into large global corporations, Mohawk Paper Mills - with two relatively small mills located a few miles from each other along the Hudson River valley in New York - remains a tightly held, family-owned company. With some smaller, older mills in the Northeast shutting down, Mohawk's two mills, which originally date from 1878 and 1917, have been driven to develop new products that tap into emerging market segments.
One of these new segments is digital papers - stocks intended for use with digital printers and presses. From basic desktop units to commercial digital-to-plate systems, the number of digital printers is growing, as is the demand for papers designed to meet the unique characteristics of digital printing. Mohawk was one of the first companies to address this segment, coining the term "digital papers" when they introduced patented stocks specifically formulated to provide better laser, toner, and inkjet printing characteristics.
Mohawk president and COO Tom O'Connor admits that the company "produces less coated paper than some big machines spill." So, how is Mohawk, with its aging mills, able to remain competitive? O'Connor now refers to Mohawk as "a technology company - not a paper company," since strategy is focused on investing in technologies that provide advantages in quality and customer responsiveness for the company's specialty digital paper markets.
For example, more than $80 million was spent on rebuilding the single paper machine at Cohoes, N.Y. This mill has also been among the first in North America to adopt innovations like new dryer drive and air pickup technologies. However, despite such upgrades, a bottleneck situation in converting was impacting the company's ability to meet customer orders.
Unlike rolls and conventional printing and writing sheets, digital papers must be cut in a range of unusual sizes - such as 9 in. x 14 in., 12 3/8 in. x 18 1/8 in., or even square sheets - to fit into printers. Like most mills, the in-house converting, wrapping, and transport capabilities at Mohawk were geared towards traditional cut and ream sizes. "We were trying to make conventional machinery do things it wasn't designed to do," describes Bob Scammell, Cohoes' manager of manufacturing.
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These vertical slitters can be positioned for a wider variety of cuts than any other system in North America.
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There were setup and running problems, including high waste rates, when running the odd sizes. Each changeover was a time-consuming, manual process that involved, among other things, removal and replacement of gear sets. This was a particular problem for Cohoes, since the converting room handled frequent grade changes and short runs. Running odd digital sizes also taxed the wrapping and packaging lines, which were also geared toward conventional cut sizes, ream sizes, and wrappings.
As a result, the entire Cohoes mill was converting limited. Some sheets even had to be cut and packaged manually, causing both time and quality control issues. Other orders had to be shipped to outside converters, which also created problems with quality assurance and delivery times.
By early 2000, order backlogs were growing, and Mohawk management felt its ability to succeed in carefully chosen niche markets was being compromised. "Converting capacity issues not only limited our ability to meet existing customer requirements," says Craig Slemp, Mohawk's senior vice president for marketing and business planning. "It was also challenging our ability to meet new opportunities."
UNIQUE CONVERTING REQUIREMENTS. In early 2000, a Mohawk team began looking for a solution the company "could grow with in capacity and capabilities," according to O'Connor. The team that was tasked with researching and selecting the new converting technology included everyone from converting machine operators to executives like O'Connor and Kevin Richard, Mohawk's executive vice president of operations. The team soon found that they were looking for machinery that did not exist yet, because the requirements for the new converting system were so specific.
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The six pocket sorter and its control station.
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First of all, the system had to meet a broader range of cut size requirements, with easy changeover capabilities for each size. Wrappers, conveyors, and transport systems would also be automated, yet designed to avoid marking the sensitive coated sheets. This was especially challenging, since transition points could have a serious effect on marking. Fully automated quality control systems were specified to check cut quality, ream size, and paper quality at every stage - kicking out any substandard paper or ream.
In addition, wrapping capabilities had to accommodate all specified cut sizes and operate with various different wrapping materials and wrapping configurations. Automated quality control (QC) was needed to remove reject reams. Finally, every ream would be identified with an automated bar coding and label printing system, whose inspection capabilities would remove any poorly labeled or coded ream. A further requirement called for the system to integrate seamlessly with an already existing cartonizer line.
According to O'Connor, several prospective suppliers expressed interest in the project, but no converting manufacturer had an existing system that could accommodate all the functions and capabilities - especially the unusual cut sizes - that the team felt was essential. However, bielomatik was eventually able to assure Mohawk that it could create a line capable of meeting the requirements.
During the spring of 2000, Mohawk and its supplier refined the design for the new converting line. By early summer, preacceptance testing of the completed system was underway at the supplier's facility in Germany, where Mohawk machine operators were involved in assembling and operating the equipment developed for the new Specialty Converting Center. This center would be located in a facility near the paper machine.
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Every stage of the converting line is controlled, including unwinding.
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The new line was installed in an off-site facility for two reasons. For one, since the system would also have excess capacity for the mill's needs, the plan was to establish a separate business unit - Mohawk Specialty Converting Services - to market the excess converting capability to other papermakers and converters. Also, the mill owned a suitable building adjacent to the Cohoes mill that fit well into overall logistics requirements.
THE COHOES CONVERTING LINE. The final converting line design was based on bielomatik's P26-02 sheeter, which is a direct drive cut-size machine, and its CSW100 wrapper. The converting line begins with four floor pick-up unwind backstands, each with 60-in. roll capacity. These backstands are equipped with regenerative brakes mounted at right angles to the roll chuck to save space and to provide better access to the unwind stands.
The four backstands feed a 56-in. web, which is kept centered by an optical edge guiding system from bielomatik. This system uses a photo cell to detect the web edge position. If the web edge is out of alignment, a photo cell sends a signal to a PLC, which moves the backstand arms with the roll in increments to a position that brings the web edge back to alignment.
After unwinding, the sheet first travels through a "waterfall" decurler section equipped with stationary and rotary decurlers that remove curl in order to facilitate proper slitting and cutting. The de-curler is computer controlled and dives automatically into the web, depending on roll diameter. Also, Luraflex spreader bars smooth the sheet directly prior to slitting, to further ensure accurate cuts. Guide rolls advance the paper into a second spreader roll position where the web is ironed before slitting.
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An overhead view of a ream prior to wrapping.
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Next, the paper is cut, passing through rotary knife slitters and a horizontal cutter. The slitters are equipped with a patented quick release and mounting of the bottom slitter shaft. The top knives can be set by hand-wheel according to a digital read out. Total changeover time is around two minutes. To keep the air clear and machinery clean, a bielomatik slitter dust collection system, including a separate high volume blower and filter system along with suction shoes and hosing, was installed to eliminate any contamination from worn slitter blades and anvils.
After cutting, the paper is gathered and sorted by a six-pocket collector and separator. Sheet count is changed electronically via keyboard and feedback from the edge guiding station. A gripperless collection station was required to make sure that sheet marking did not occur. Gripperless operation is accomplished by positioning pre-collecting fingers underneath the completed reams in the collecting station as full reams are lowered onto specially controlled crossbars. These cross bars are actuated by a proprietary drive system that allows non-destructive acceleration of the transport system. This is especially significant when running small ream counts, such as 100 sheets. It is also necessary to prevent skewing of coated reams at high discharge speeds.
In addition, automated sheet and ream inspection systems use photo cells to detect anomalies such as undersized reams and ripped or wrinkled top sheets, kicking the substandard reams out of the process line before they reach the wrapping station.
Like the sheeter, the wrapping section is designed for operational flexibility. The system can be set to wrap reams in a variety of different configurations, using paper, plastic, or other specialized wrapping materials.
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Sensors at this automated station calibrate and trim the wrapping paper for any ream size up to 12 3/8 x 18 1/8 in.
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A Pago automated bar code and labeling system with a thermo transfer printer downloads labels from the label design system, printing labels on demand and adhering them to freshly-wrapped reams. These reams are subjected to one last stage of automated QC via bar code reader or CCD camera. Defect reams are rejected automatically to a roller conveyor to be reworked and introduced into the process again. During this process, blasts of air are directed at the wrapper seams, since a loose seam will flap and be detected by photo cells, causing the automated system to reject that ream. Finally, finished reams coming off of the line move on to an automated cartonizer (originally used with the previous converting line) for boxing.
FAST INSTALLATION. While design of the system was still underway, Mohawk and its supplier planned the installation strategy. The existing converting line was scheduled for removal in early August 2000. The team gave themselves a timetable of two and a half weeks since converting backorders were growing. As installation approached, worries were that even this accelerated timetable would not bring the new system online quickly enough.
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Computerized controls allow changeovers in minutes instead of hours.
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Meanwhile, the 50-year-old building that would serve as Mohawk's new Specialty Converting Center was undergoing refurbishment. The structure was gutted and received new electricity, lighting, and compressed air systems.
On August 5, 2000, the first loaded container arrived on site, and, by August 9, the converting line was running, and the first test cuts were being made. Since site preparation had already occurred, the around-the-clock installation beat its target date by 12 days. Startup went smoothly, especially considering the speed of installation and the broadened scope of operations that saw the converting staff working with new sizes and stocks. "There were problems here and there," recalls Henry Weatherwax, who was the first Mohawk operator to run the machine. "But, by the first Saturday, we were getting good quality."
ELIMINATING PRODUCTION LIMITATIONS. Once running, the Mohawk Specialty Converting Center provided more than a 400% increase in converting capacity over the previous converting line. While the old six-pocket sheeter barely averaged 15,000 lb per shift, the new bielomatik six-pocket system can do 60,000 to 70,000 lb per shift, according to Joseph Gerwin, Mohawk's production planning and product distribution manager.
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Each ream’s label is automatically checked for accuracy and position. If there is any irregularity…
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This increase was achieved through complete automation of changeover procedures wherever possible. On the old line, three to four grade or size changes per shift were not uncommon. By the time gears were removed and replaced and each slitter knife was repositioned by hand, a change could take as much as half a shift. By contrast, changeovers on the new system are accomplished in minutes by pressing buttons on a control console.
Once changed over, the horizontal cutter performance is much more precise and consistent, since the new system is engineered to produce a broad range of cuts. Runnability is also improved, according to Weatherwax. "We were constantly fighting sheet squareness on the old machine," he explains. "We could spend an hour just getting the sheet square. Curling and jamming were constant problems, too. But with the curler/decurler, we don't get folded corners anymore."
Automation of other processes, such as wrapping, further minimizes handwork and downtime. The addition of a fully automated palletizer from Columbia at the end of the converting line in the spring of 2001 eliminated the last manual process in the converting center. Maintenance has also been reduced. Where the old system required monthly knife changes, the new system has run from startup with the same set of slitter knives.
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…the ream is rejected before it reaches the cartonizer.
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As for quality issues, the new slitters are able to deliver a consistent level of replicable precision - from the beginning of a run to the end and from one run to another - that the previous manually-controlled slitting system could not. By automating the wrapping process, the potential for errors and inconsistency are minimized even further.
If any errors do occur, quality checks located all along the converting line identify everything from sheets with splices to poorly sealed wrappers to reams with incorrect labels. One quality check occurs with the splice detector located in front of the slitting station, while control for unwrapped reams occurs via photos cells and a reject gate in front of the ream wrapping machine. Also, wrapped ream control occurs after wrapping via air blasts, photo cells, and a reject gate, while label control utilizes photo cells. "I've often tried to fool the QC system, by tearing a paper edge, for instance," says Paul Graver. "But every time so far, the system's caught me."
CREATING NEW OPPORTUNITIES. With the new converting line, lead and delivery times have reduced. According to Gerwin, "there are times when we can literally make it, sheet it, and ship it in the same day." The ability to produce a broader range of higher quality sheets and packaged reams in about one quarter the time has also had positive impacts for the Mohawk salesforce by improving customer responsiveness.
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The new converting line has increased capacity by more than 400%.
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"Mohawk's appeal is in large part focused on our ability to respond quickly, and we now feel much more qualified to approach new business," says Christopher Harrold, manager of Mohawk Digital Papers. "It not only gives us a solid foundation to build on in our current markets, it's also opened up a lot of non-traditional Mohawk markets to us."
This level of productivity and flexibility has also greatly reduced inventory requirements. Mohawk has been able to safely reduce some 8 in. x 11in. stocks to half their previous inventory levels. At the same time, out of stock problems have been almost eliminated. Where thirty or forty items would be out of stock at any one time a few years ago, now all but a few stocks are available at all times.
With its new converting capabilities, Mohawk can compete for a larger number of orders, based on their rapid delivery times. Mohawk claims it can deliver any in-stock order to anywhere in the U.S. within three days. The mill has even been able to guarantee faster delivery times to West Coast customers than some West Coast mills can offer.
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