Stora Enso is a leading global provider of renewable solutions in packaging, biomaterials, wooden constructions and paper. They employ some 26,000 people in more than 30 countries. 1,300 work at the company’s Imatra mills.
The Imatra mills are located in Southern Finland. Stora Enso have two production units – Kaukopää and Tainionkoski – which produce chemical pulp and consumer board. Together, they are one of the largest consumer board producing entities in the world, exporting over 90% of their products to Europe and Southeast Asia. Their combined annual production is some 1,155,000 tons of consumer board, 1,020,000 tons of pulp, and 285,000 tons of plastic coating.
Meeting changing needs
In 2016, Imatra mills decided to increase their production capacity for extrusion-coated products and further enhance their position as a leading global supplier of premium paperboards. Stora Enso also made the decision to invest in a new automated roll warehouse alongside the new polyethylene (PE) coating plant.
Before this investment decision was made, Stora Enso’s Imatra mills had to utilize outside warehouses in the region to store their intermediate roll buffer. This was due to space limitations in the warehouse at the mills, which used the traditional clamp truck warehouse concept. There were multiple clamp truck handling phases between the base paper production, PE coating processes, and shipping. This decentralized process inventory was challenging to control, very labor-intensive to manage, and led to quality-associated costs.
All PE-coated rolls had to be fully wrapped twice before being shipped to the customer: once in order to tolerate the maneuvering by clamp trucks in the intermediate storage process, and again after the PE coating.
Storage tightly integrated into mill processes:
- Intermediate storage for production
- Shipment buffers for finished rolls
- Simplified, more efficient internal logistics
With the automated roll warehouse, the target was to integrate a sufficient intermediate roll buffer in the mill area between the production, converting, and shipping processes, as well as cut costs by simplifying and automating the internal logistics.
Delivering improved logistics efficiency
Pesmel’s TransRoll™ automated high-bay storage at Stora Enso is an ideal example of their Material Flow How® concept, representing the perfect union between storage and production. This automated storage operates both as an intermediate buffer for rolls going to PE extrusion coating, and as a shipping roll buffer for finished customer rolls. The defined volume was around 30,000 tons, with a wide range of roll dimensions and weights.
It is very important to analyze the total cost of ownership of each alternative when comparing different types of automated warehouse concepts. This not only means CapEx and OpEx costs related to the warehouse concept itself, but also the costs of the systems and structures needed to integrate it into the mill operations. These refer to the ability to integrate the automated warehouse into the center of the production process with a minimal number of conveyors, the civil engineering to feed the roll flow in, and then to distribute it for converting and shipping.
Here, system suppliers like Pesmel, who can offer the full scope including the conveyor system and all storage concepts, have the upper hand over part suppliers who concentrate only on their own core area. This advantage was obvious in the Stora Enso Imatra case where the automated storage was integrated with the production operations around it, using eight automated connections at different floor levels in a very limited amount of space.
Comparison of features between TransRoll™ high bay storage and traditional overhead crane warehousing
| TransRoll | Overhead crane warehouse | |
| Use of space/storage density | Footprint 1/3 | Footprint 3/3 |
| Handling capacity | 400 rolls per hour | 100 per hour |
| Simultaneous handling of different roll sizes | Yes | Not possible |
| Conveyor systems and storage connections | Simple conveyor systems, connects to the warehouse from wherever needed | Extensive conveyor systems, complicated to connect |
| Handling quality | Horizontal handling, no clamp handling | Lots of clamp handling |
| Safety (esp. fire safety) | Sprinklers in every roll channel. Rolls lie in the channel, with no danger of tipping | Sprinklers on store ceiling. Rolls are stacked, creating a tipping risk |
A smart and simple solution
Project Manager Tommi Myller, from Stora Enso Imatra mills says that “this new automated roll storage simplified our internal logistics a lot. Now we only need one operator to control the process of buffering and sorting the production between paper machines, PE coating, and shipping. This is a huge advantage over the previous decentralized operations, with multiple clamp truck drivers and supervisors to manage and handle the intermediate inventory.”
“This new automated roll storage simplified our internal logistics a lot.”
Tommi Myller, Project Manager, Stora Enso
For Stora Enso, where this new central distribution buffer required eight connection points, the solution was much simpler and less space-consuming to implement than any alternative method. An additional benefit is that it can be easily expanded in the future. If needed, the rack can simply be extended without disturbing the ongoing production process.