Total control over paperboard production in Skoghall

Skoghall Mill belongs to the Stora Enso Group and manufactures paperboard, primarily for the food industry; milk and juice cartons are frequently the end-product. The mill has two board machines, BM7 and BM8; both operate continuously day and night, all year round. BM8 is the world’s largest board machine for liquid packaging board.

• Production during a 24-hour period corresponds to 100 million 1-liter packages
• Annual production of the paperboard could circle the earth 10 times 
  

The ABB Web Imaging System (WIS) was installed on BM8 in 2006 and was updated in 2012. The first version was installed on BM7 in 2008 and was updated in 2015. 

Through an updated camera model and specially designed algorithms, every square millimeter of the paperboard web is now inspected at speeds of up to 800 meters a minute. The most recent upgrades that were performed also allow for the detection of shearing defects in the paperboard. 

“Shearing defects are tiny millimeter-sized shifts in the paperboard’s structure, which, in the worst-case scenario, can lead to cracks when the paperboard is folded into packaging. The cracks can then cause leakage when the cartons are filled with liquid,” says Björn Wikström, Maintenance Technician at Stora Enso in Skoghall. 

Correcting shearing defects is time-consuming and can result in major production losses. Using camera beams at BM8 and now at BM7, Stora Enso can correct the process in 2–3 minutes, thanks to continuously updated information that reaches the operator stations within seconds. 
 
“Shearing arises very sporadically. The cameras have to be able to detect tens of thousands of defects in just a few minutes. At the same time, the defects have to be analyzed and visualized so that they can be rectified quickly. The operator now has a tool at his or her disposal that visualizes the shearing defects of various sizes as color-coded markings on a chart,” says Håkan Österholm, product manager at ABB.  

“This is a very user-friendly tool that benefits everyone, from machine operators to winder and re-reeler operators, and naturally also our quality and development engineers. We have designed the interface so that it suits the unique needs of all user groups,” adds Wikström. 

With ABB’s Web Imaging System, the mill has full control over the production, which in the long run means less rejected paperboard and further enables the mill to save large amounts of energy. Every meter of paperboard that cannot be delivered to customers results in unnecessary consumption of energy and raw materials.  

Karlsson also emphasizes another advantage of ABB‘s WIS – It is now easier to specifically address customer concerns and pinpoint the exact location of product defects. 

“The system has not only improved quality and the work environment for operators, our sales organization also greatly benefits from it. We were previously often forced to take back the entire order if a customer discovered defects in some of the delivered rolls. Today we can trace exactly which rolls are concerned through our database where all of the images are stored for at least two years. The difference in complaint-related costs is enormous,” said Karlsson.  

The massive memory storage capacity within the Web Imaging System is the secret. One year of production at Stora Enso in Skoghall corresponds to a paperboard web that circles the earth 10 times – every square millimeter is inspected, and all defects are traced in photos that can be easily accessed when required. This is truly big data; the tens of thousands of gigabytes enable valuable and easily accessible information to be created. 

The Web Imaging System detects, photographs, visualizes and traces all defects that are larger than one square millimeter in the paperboard web. The detection process takes place throughout the entire production line – from board machine, via the coater, to the winder and re-reeler. The system inspects the top, the bottom and even the inside of the paperboard.  

The configuration on BM8 is based on six inspection stations, and it contains 100 digital cameras, while the configuration on BM7 has four inspection stations and 65 digital cameras. 

ABB's Web Imaging System notifies the operators in each processing segment of all defects that need to be rectified, so that production can be continuously optimized. Skoghall’s salespeople can also log into the system’s database, and thus together with their customer, more specifically trace which paperboard roll caused a potential complaint.