Smooth change

When Rockwell Automation helped paper supplier M-real redesign its plant to incorporate a new A4 cutting line, the project required installation of new hardware, PLCs, HMIs and software that had to be integrated into the existing converting control system. The throughput of pallets of all four lines also had to be optimized by major software modifications.

M-real’s new Thames Paper Mill in Kemsley, UK, produces office papers, converting reels of uncoated wood-free material into reams of A4 printer/copier paper.

“From our recycled fibre plant we produce around 100,000t of premium recycled fibre,” says conversion manager Alan Young. “This is used to produce a range of recycled products. The demand for these has been growing and with our capacity increase, we are now able to meet that demand.”

Paper reels are cut at high speed and accumulated into reams that are then wrapped and boxed. The boxes are then conveyed to palletizers. Full pallets are conveyed on two shuttle cars to one of two stretchwrappers, then labelled automatically and conveyed to shipping lanes ready for delivery.

The redesign project had to meet a tight schedule and agreed cost levels. Timing was vital to the development and integration of the fourth line, as its installation could only take place within a specific period. The project began in April 2006, and was fully implemented by that September. Implementation was carried out while other lines were still in production, and required the involvement of third party products and equipment.

Before engaging Rockwell Automation, M-real had a bottleneck where pallets from the three existing lines went through a single robot labeller. By adding a fourth line and a second labeller, increased throughput and productivity could be achieved and downtime reduced.

“When we installed the new cutter line, we also installed a new robot labelling line and all this had to be integrated into the Rockwell SLC6 controller on a third party network,” Alan Young explains. “This also required additions and modifications to the existing programs. Allen-Bradley PanelView HMI was already there for the first labeller, stretchwrappers and conveyor systems, but we modified it to control other conveyors and all the new equipment.

“The pallets come off the labellers and onto two turntables for conveying to the warehouse. This was all installed along with the robot labeller and had to be tied into the existing fieldbus. Because we had two existing SLC5 processors from a project going back to the year 2000, we already had a Rockwell Automation infrastructure.”

The system comprises two SLC5/05 processors with PanelView HMI terminals interfacing over a third party network using SST interface modules, with third party I/O installed throughout. A new Proface HMI was also installed on the new line.

The two labellers now provide more capacity and flexibility. With these and all four lines running, production can be maximized. If one robot requires maintenance, production of all four lines can carry on through the other wrapper at reduced rates.

When a reel needs changing on a stretchwrapper, the operator opens the safety gate, an interlock shuts the machine and sends a signal to the Rockwell controller. The program then changes the way the two shuttles run and collect pallets for wrapping, until the controller gets another signal saying the wrapper is available again.

The new line now gives M-real the capacity to produce 190,000t/year of cutsize product. Although the four lines are laid out differently, they all have the same elements in the same order and the process is the same. The first stage in each is where five reels of paper, each weighing about 2.5t, are drawn into a cutting section that converts the paper into A4 sheets before finally being collated into 500 sheet reams. Each ream is then wrapped in protective paper and stacked into boxes.

The boxes are then strapped to secure the lids and placed on a pallet. The pallets from all four lines are placed on one of two shuttles and routed through one of the stretchwrappers, labelled automatically and transferred by conveyor to a warehouse holding up to 26,000 pallets.

“The work was mainly integration into the existing system, although there were some new programs for the new equipment,” adds Alan Young. “Because of floorspace constraints, we built a platform above the new machine to house the control cabins containing the Rockwell equipment. By using spiral conveyors, we raised the new cutter line above ground level, so it occupies much less floor area than the other lines.

“Building the line took us less than nine months, and then another three to get it fully commissioned and the operators trained. On January 2, 2007, it was in full production. In early April, the 1,000t/week project target was achieved on Number 6 cutter.”