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To meet customer demands, printing paper suppliers must adapt to the large roll size requirements of the new generation of presses just coming online or on order in North American pressrooms. Now, paper producers must be flexible enough to produce well-structured large diameter rolls with widths up to 136 in., as well as serve customers who continue to need a wide variety of narrower widths. With an increasing variation in roll widths and diameters, the boundaries of winding and roll wrapping operations are being stretched.
St. Marys Paper Ltd., in Sault St. Marie, Ont., is positioned to meet the potential of this large roll market for SC grades after the April 1999 startup of a belt bed winder, an automated roll conveying system, and the first commercial installation of an indexed overlap wrapping line. Also, a new rewinder started up in August 1999. The mill, which produces 700 tpd of SCA and SCB grades on three paper machines, now has the capacity to produce well-structured rolls for the largest existing rotogravure presses in North America plus extra margin for anticipated new press requirements.
The new equipment can produce rolls from 610 mm to 1,524 mm (24 in. to 60 in.) in diameter, 406 mm to 3,708 mm (16 in. to 146 in.) in width, and weights up to 8,260 kg (18,200 lb). The winder can make rolls as narrow as 142 mm (5.5 in.). The new continuous heat seal wrapping process also provides them with tightly wrapped rolls with protection against shipping damage, resistance to moisture migration, and good roll appearance.
The $C25 million project also included a cull pulper with a roll splitter, a core storage area, a new electrical room, a trim handling system for two existing winders and the new rewinder, a new jumbo reel cart, and a new bridge crane in the winder room. Except for a small building extension for the cull pulper and core storage, the equipment was engineered to fit in the existing building.
St Mary's winder operator Terry Kirkpatrick, mill manager Norm Facey, and conversion superintendent Dan MacKay (l-to-r) display SC roll from the new No. 7 winder.
MARKET DRIVEN DECISION. Norm Facey, mill manager at St. Marys, explains the market-driven decision: “Our market research identified that the super-wide roll market was growing but was not being filled at the time.” Currently there are three 138.5-in.-wide rotogravure presses operating in North America. Rolls of 132 in. to 136 in. width at 50 in. diameter are now required. The mill expects that, within five years, new presses will stretch the limits to 144-in.-wide rolls at 55 in. diameter
Facey describes the evaluation process for selecting the equipment to meet the mill’s goals: “At St. Marys we have a philosophy and history of employee involvement, so we formed a cross functional group with the mandate to address this need for good quality, large rolls.” The team, comprised of production managers, operators, engineering, maintenance, and E&I staff, along with the project consultant NLK, set out to fully evaluate the best available technology from proven suppliers.
In addition to supplier factories, the team visited numerous reference sites that produced similar products or operated state-of-the-art winding, roll handling, or roll wrapping technology. The evaluation included operator-to-operator discussions, questioning maintenance experiences and conducting surveys of St Marys’ own customers. The technical evaluation and ROI analysis led to an innovative winding solution and the first commercial installation of an indexed overlap wrapping line.
St. Marys new No. 7 belt bed winder has a top speed of 7,500 fpm and provides SC rolls of 50 in. dia. and higher.
WINDING SOLUTION. The team established that the new winding solution must be proven to produce 50-in.-dia. to 60-in.-dia. rolls free of crepe wrinkles. It needed the capacity to handle all of the production from the No. 5 paper machine. Also, they needed to wind rolls on 3 in. and 6 in. cores. Initially, a single drum winder seemed to be the solution.
In the evaluation process, the team determined that, although the single drum design could handle a mixture of core sizes, the belt bed winder offered them some significant advantages. It would provide them with the capacity they needed and the ability to handle different roll diameters across a variety of grades. The team also agreed that the belt bed winder had a simpler design. Dan MacKay, conversion superintendent, says, “It is similar in operation to the two drum winders the operators were familiar with.”
In addition, the team found that the belt bed winder was easier to maintain. Robin Smith, an operator on the evaluation team, reports that, because of the similarities to two drum winding, operators can transfer more easily from the older winders to the new winder, which is necessary during vacation periods. He also says that the set change times are very fast. The selected winder also occupied less floor space, an important consideration in older mills like St. Marys.
Ultimately, the recommended solution was a Valmet WinBelt winder as the main production winder—the No. 7—and another WinBelt as the No. 8 rewinder. The rewinder would rewind rolls onto different core sizes as required by their orders. The ROI calculations showed that the rewinder would be justified by salvaging reject rolls from the No. 4 and No. 5 paper machines. Facey reports that the evaluation team determined there was no difference in the quality of a rewound roll compared to an original wound roll.
The No. 7 winder is designed for a top speed of 7,500 fpm. The d.c. drives are supplied by General Electric. The windup section consists of a rear drum and a full width belt bed that supports the roll. The tightness of the surface layers and the roll’s hardness level are controlled by the so-called “winding force,” which is generated by the difference in force between the belt bed and the rear drum. In this tolerant winding process, the nip load is controlled during the roll building cycle by design of the winding angle.
The No. 7 winder is supplied with an integral computer automation system using Intouch Wonderware software. In addition to controlling the winding cycle, the automation system includes automated set changing, winding condition recipes for each grade, a historical database of winder operation conditions, and a diagnostic package. The latter function allows operators to quickly locate and correct an interlock condition if it is halting operation.
Short pitch slat conveyors and automated turntables transport rolls from the winders to the indexed overlap wrapping line.
INDEXED OVERLAP WRAPPER. The selection of the new wrap line was narrowed to two alternatives: a traditional glued wrapper line with multiple wrapper backstands or a new indexed overlap wrap line with a limited number of traversing wrapper cartridges and a continuous heat sealing process instead of gluing. Either alternative would have to fit into a restricted floor area with limited headroom. In any mill with a large range of roll widths, a traditional line might require up to 10 backstands. For instance, the 1970s vintage St. Marys line used eight wrapper backstands. The indexed overlap wrap line would definitely take up less real estate and provide the flexibility the mill needed to wrap the largest rolls along with a wide range of narrower widths. Also, the super wide wrap required for the traditional line was hard to find on the market.
Depending on roll size, the indexed overlap wrapping line uses one to three traversing cartridges to sequentially apply either one, two, or three overlapping, heat sealed wrappers.
The Valmet indexed overlap line called TopPack uses one to three traversing cartridges with standard width wrappers to sequentially apply either one, two, or three overlapping wraps. The backstand and heat sealing unit index into place for each wrapper feed cycle. By analyzing St Marys’ present roll width distribution and adding the expected super wide rolls, the most practical and economical solution was to use two cartridges with wrapper widths of 40 in. and 52 in. The wrapper size selection also included a margin for overlap and for optimized end crimping. The smallest rolls require one wrapper feed, medium sized rolls require two wrapper feeds, and the largest require three wrapper feeds. Since fewer large rolls are wrapped for the same tonnage, wrapping capacity is not sacrificed with the increased number of wrapping steps.
By limiting the number of wrapper widths, the ordering and control of wrapper inventory is simplified and more economical. There are no seldom-used widths to dry out in the warehouse or on the backstand. Joe Richichi, transportation manager says, “It gives us wrapping versatility with only two standard wrapper widths.”
The roll identification and wrapping application process is highly automated. Each roll is identified by its bar code and verified by its measured weight and length. The roll identification is cross-checked with the Proconex roll tracking system and an alarm is generated if there is a mismatch.
After identification, the TopPack control system then decides which cartridges to use in which order, automatically indexes them into place, and performs the wrapper application sequences. One person operates the wrapping operation compared to two persons on the previous line. During the transition phase, clamp trucks refilled the wrapper cartridges. A new platform permits roll-on refilling of the cartridges.
CONTINUOUS HEAT SEALED WRAPPING. The indexed overlap line also features a new innovation to North America—continuous heat-sealed wrapping using an electric infrared heater just before the wrapper is applied to the roll. This process avoids the mess, contamination, and costs of hot melt adhesives.
With continuous heat-sealed wrapping, the heating unit activates a polyethylene coating on the wrapper so that it adheres to the outer paper layer of the roll in a continuous process. The inner heads are manually inserted before the wrapping process begins. Wrapping and crimping occur simultaneously, resulting in a less bulky crimp. The second wrap then adheres to the first wrap, providing a tight seal. The number of wraps is adjustable and is currently set up for 2 1/2 wraps. Richichi reports, “It’s like on-line laminating. It provides an air tight package so that rolls are less susceptible to changes in humidity.” The package is completed with the application of heat sealed outer heads. The wrap line is driven with variable frequency drives instead of servo motor drives, reducing the field wiring installation cost.
Since continuous wrapper heat sealing is new to North America, the mill needed to develop sources of supply other than from Europe. They looked at four companies in North America, two of which currently supply the wrapper line. The one side coated wrappers from North America were first checked on the Valmet pilot line in Finland. European suppliers were used only for the startup in April 1999. Currently, the mill is evaluating different basestock basis weights and strength qualities. The cost savings associated with heat sealed wrapping have been in line with projections, according to Richichi.
There are two standard wrapper widths on the St. Marys wrapping line. Using bar code information, the line's control system decides which cartridge to use on each roll.
HANDS-FREE ROLL HANDLING. After the winder deck, the transportation of the rolls is totally hands free, avoiding unnecessary rolling. Previous roll kickers and cushions were eliminated. Compact short pitch slat conveyors gently “walk” the rolls on to a series of four automated turntables that redirect the rolls past the No. 5 and No. 6 winders, past the rewinder, and to the wrap line. A lifting scoop elevates the rolls to the wrap line level, and a final turntable orients the roll for wrapping. After wrapping, the roll is manually labeled and proceeds to an upender and a flat top conveyor where the rolls are removed by clamp trucks.
MINIMIZING RISKS. The project, which started in January 1998, was complicated by many challenges. The new equipment had to be “shoe horned” into an operating mill, some parts of which were more than 100 years old. Civil engineering skills were tested and there were some surprises. For instance, the loading docks needed to be reinforced for the new heavy rolls and heavier clamp trucks. This required multiple concrete pours to reinforce the foundation while the loading dock was in use.
In addition, the new equipment and its high level of automation were unfamiliar to many E&I, engineering, and operations staff. The roll tracking system was being upgraded during the process, and the new TopPack indexed overlap line was a first for the mill and for the world. Above all, during the transition period in early 1999, production levels could not be compromised. Aside from supplier guarantees, the project implementation risks had to be managed.
Training and involvement were key ingredients. A lead operator and an E&I technician who were on the selection team and had visited many other mills became the experts who supported and trained others. They were involved in all aspects of the installation and startup. The lead operator and four winder operators were trained at the machine vendor’s Appleton, Wis., facility. In turn, these operators trained the crews.
The wrap line was an extremely new technology. To ensure a workable system arrived at the mill, the complete wrap line and roll conveyor systems were tested at the machine vendor’s shop in Finland. The mill’s choice of PLCs and other equipment were shipped to Finland and the system was tested according to St. Marys’ production requirements. After delivery, mill personnel were actively involved with the machinery installers. Just in case, the old wrapping system was kept operational during the transition period.
“During the transition period operators were transporting rolls on hand-operated lifts,” Facey explains. “But, since they knew the end result, everyone worked together to make the mill better.” In fact, the mill set new production records during the transition.
The mill is looking to continue to improve roll quality and productivity by upgrading the existing No. 5 and No. 6 winders with “compliant” drum coatings, pivoting core chucks, new lowering cradles, and a new drive system on one winder. With these upgrades and other improvements St. Marys is well positioned to address the expanding market for high quality SC papers.
Mark Williamson is a freelance writer located in Thornhill, Ont
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