Automatic Dewiring Improves Safety at Sonoco Board Mill

In Finland, paper mills often have long histories, and the newly-updated Sonoco Alcore Karhula core board mill is no different. The mill site dates back to the late 19th century, when the mill was developed to manufacture cardboard, and it has been running ever since. Today the mill has approximately 70 workers and its 65-meter long, 3-meter-wide core board line produces roughly 80,000 metric tpy of OCC-based core board for core manufacturing.

Sonoco acquired the mill in 2006 and has proactively developed and invested in it to become one of Finland´s top board manufacturers for the paper core business. The Sonoco Alcore Karhula board mill produces core board mainly for Sonoco’s own core manufacturing needs and the material is transported worldwide to different Sonoco mill and factory locations.

Factory Operations Manager Janne Ruoti sees that the future for the mill is brighter than ever with its newly updated automatic bale dewiring and pulper line. He has been working in the mill for several decades and knows how the operations have changed during the different stages of the mill´s lifecycle.

At the Sonoco Alcore Karhula board mill, the core board manufacturing line starts by dewiring the incoming OCC bales. The bales are buffer stored outside and then loaded to an angled conveyor that runs up to the Cross Wrap Dewiring machine. This feeding conveyor and the dewiring machine are automatically paced to run with the pulpers. The feeding conveyor is quite long to make room for a good quantity of bales. This gives time for the operator to load the line with a steady pace and to unload arriving trucks at the same time.

The Cross Wrap Dewiring machine safely removes the bale wires by cutting and spooling them automatically.

The Cross Wrap Dewiring machine removes the bale wires by grabbing them on both sides of the bale with patented grippers; then the machine’s front cutter cuts the wires. The material is then conveyed forward, and the bale wires are coiled automatically into a tight bundle. This separates the metal from the material stream. The Sonoco Alcore Karhula board mill can sell the coiled bale wires for recycling and the wire separation also cuts back on maintenance costs for the pulper.

“Before, we needed to pay to get rid of the uncoiled bale wires and the pulper emptying was very labor-intensive,” explains Ruoti. “Today, we get money back from the wire recycling, plus the pulper maintenance work load and costs have decreased significantly.”

After dewiring, the raw material is conveyed up to the large first stage pulper and then the material is run through a second pulping stage. Plastic and metal particles are separated during and after these processes and pushed out of the material stream. This reject material is compressed to get rid of excess moisture, and then it is transported to a biomass power plant. The power plant is located just next door to the mill, where the reject is burned for energy and steam to run the mill and to provide heat and energy for the city of Kotka.

From the pulping stages the OCC pulp runs through chemical treatment and then ends up at the beginning of the 65 meter-long core board mill and drying line. The line ends with a state-of-the-art stacking line. The final products are transported to Sonoco core factories around the world.

As its main raw material, the Karhula board mill uses baled OCC collected mainly from Finnish recycling operators. The bales stored outside in the mill yard must be constantly replenished to feed the mill’s hungry system. Fast-changing raw material inventory helps to save space and prevents the bales from degrading, keeping the material in somewhat good condition.

“On the negative side, the Finnish climate does have impact on the bales in the winter, when the moist and freezing sea breeze coming from the Gulf of Finland can make the bales ice up,” says Ruoti.

These conditions, the mill’s running targets, and the varying bale size created the template for the selection of dewiring machinery. The co-operation possibilities between the machinery providers and the mill were also important to consider as the project team debated on its machinery acquisitions.

“For the latest revision to the core board line, we studied a lot of different bale handling and raw material pulping solutions and saw the benefits in automatic bale wire removal,” Ruoti explains. “Now that we finally have the machinery running steadily, we can see the differences when comparing the new system to the older one. Today we need to clean the pulper much less often, which is good for the operation flow.”

The dewiring machine differs from the traditional bale breaking or bale opening by removing the bale wires from the material stream. The Cross Wrap Dewiring machine cuts, separates, and coils the metal wires so that they are easy to recycle. This means that the core board producing line is no longer getting a steady stream of metal wires to roll around in the pulper. Less metal wire going to the pulper means less pulper blade wear and pulper run downs.

Says Ruoti, “This dewiring has two kinds of benefit for us. On one hand, we need some amount of metal wires going to the pulper, where they help to separate the plastic and metal material from the OCC; but on the other hand, the automatic wire removal creates less need for pulper cleaning and maintenance. Now that the machinery has been running for a while, we can see that the bale quality fluctuations make it possible to run the machinery so just enough wire goes through to the pulper.”

The Sonoco Alcore Karhula board mill’s main target when updating the bale handling line was to improve safety. The safety improvements were possible due to the Cross Wrap Dewiring machine’s automation and its safety equipment, such as safety fences, remote control, laser and sonar sensoring, and safety key operation.

“Today the operation runs smoothly, and we need only one operator to feed the line with OCC bales. This work is easy and unrushed because of our long feeding conveyor, which gives room for actions such as unloading the trucks and piling up bales to the storage area. The steady working pace is also a key factor that improves safety,” Ruoti explains.

The Cross Wrap Dewiring machine also gets positive comments from the loading operator, Markku Piiroinen, who notes that the machine has been very easy to use and operate. He thanks the Cross Wrap design and engineering team, which has been guiding and helping the machine keep up its pace at the board mill.

Improving and updating the Sonoco Alcore Karhula board mill’s bale dewiring and handling operation was a true pilot project. The Cross Wrap Dewiring machine has been through several evolutions during the incorporation period when the mill machinery was being updated. The steep learning curve between these different evolutions gave important know-how to Cross Wrap and to Sonoco Alcore Karhula board mill personnel.

“Good cooperation has been an important part of this uncharted way of finding the best possible solution,” Ruoti states. “Cross Wrap personnel have been very helpful and keen on improving the machine to work the best way possible in our operations.”

Getting the most out of the chosen machinery is a learning process, during which mill personnel need to be in close contact with the machinery provider. Sonoco Alcore Karhula board mill Electrician Joni Sven appreciates the way engineers at Cross Wrap were able to listen, teach, and customize aspects of the dewiring machine.

“There are some things, such as the cold weather and the bale quality fluctuations, that create challenges for bale dewiring, but the Cross Wrap machine has proven itself during the different evolutions and updates,” Sven says. “The fact that the machine has dewired more than 248,500 bales and is continuously running strong shows a textbook example of proper engineering.”

Sven also credits the whole Cross Wrap design team and Cross Wrap engineer Henry Blom, who was at the site doing all-around machine inspection during the interviews for this article.

The Karhula board mill’s daily capacity is roughly 250 metric tpd, and the production line runs 24/7. All the line improvements aim to create more stable material flow, lower maintenance costs, and improved safety. These improvements are necessary to keep up with changing world challenges. The Cross Wrap Bale Dewiring machine is a good example of a machine that is born from the user’s need to keep capacity high and running costs low, and to advance safety.

As Ruoti sums up, “OCC material costs seem to be quite stable, though we have seen price changes during the years. The tightening Asian paper import regulations may have some effect on pricing in the future, but right now the market prices have stayed steady. Luckily, we have a smoothly running mill operation to back it up.”

The Sonoco Alcore Karhula board mill has been constantly aiming for more modern operations and has been through multiple machinery updates and revisions. While the mill walls still tell a long story, everything inside is new and high-tech. Janne Ruoti sees Sonoco as a good owner because of the constant improvement and steady business strategy. There are all the building blocks for tackling the future.

Panu Kantosalo is marketing manager, Cross Wrap Ltd. To learn more about the Sonoco Alcore Karhula mill, visit For more information about Cross Wrap, visit