A key part of the solution are Pesmel’s advanced stacker cranes, which rely on ABB’s ACS880 variable speed drives with precise anti-pendulum function – to reduce swaying and speed up the goods handling.
In many industry companies that produce paper or steel rolls those products can weight from 6 tons up to 30 tons each. They are transported via their finished goods warehouse and placed on delivery trucks daily. These high-quality products are then delivered across to domestic or international markets.
When pulp and paper or metal companies are searching for the right solution to support their high-volume logistics flows, Pesmel, the Finnish supplier of automated high-bay storage and stacker crane solutions, offers a wide range of advanced solutions for such material flow logistics systems in numerous industries. These include pulp and paper, metals, and tire manufacturing. Pesmel delivers fully automated logistics solution, including stacker cranes, that are at the heart of the roll handling and logistics system.
Standing firmly behind Pesmel’s successful stacker crane solution is ABB, which supplies the versatile ACS880 industrial drives that are built into the advanced transport equipment. These drives that control the movement of the 100-ton cranes include a unique anti-pendulum function that helps precisely position the massive rolls rapidly in the storage bays. The anti-pendulum function built into the ABB variable speed drive (VSD) is especially valuable and useful, since it helps avoid any swaying of the rolls being handled at over 30 meters up in the air.
Timing is everything for industry customers
Many pulp and paper as well as metal industry manufacturers are known for their progressive and high efficiency operations that invests in top level equipment to make high-quality product grades. As business is growing and sales are progressively ramped up, they tend to want to increase the speed of loading and unloading of paper or metal rolls.
Some of the warehouse storage facilities, can be built side by side with the mill where the products come from. They can serve as a totally integrated automatic warehouse/distribution center – where fast timing and precise action is extremely important.
At the transportation loading dock of the mill, there can even be hundreds of trucks that are loaded each day with rolls to be delivered. Within 25 minutes from the time the ERP system has registered the truck arriving to the yard of the site and backing up the docking platform, the stacker cranes need to have placed all the rolls for that shipment on the dock platform. The rolls are then moved the final few meters by forklift into the cargo space on the truck.
Tricky physics with multi-ton rolls over 30 m height
It is a real challenge trying to safely handle and accurately position a massive product at over 30 meters up, and potentially very costly. Secure handling means avoiding damage to the valuable rolls, on which any damage to the outer layers of e.g. paper, such as scrapes or cuts, can cost thousands of Euros or more.
When the roll is lifted to those heights, there can normally be a slight residual swaying occurring which requires the crane to stop for a few seconds, before then finally moving the roll into its spot in the storage bay. Those few seconds are critical because on an average day the paper or metal mill, can have several stacker cranes that can do up to 100 tasks/hour. That can equal with e.g. four cranes to almost 9,600 tasks per 24-hour day. The anti-pendulum feature makes positioning faster and easier and is estimated to save about 20 minutes a day that would be lost work time, if the swaying was not controlled.
ABB drives solve the pendulum effect
Pesmel has designed several stacker cranes for various industry customers in the paper and metals mill business. They got in contact with ABB when they were looking for the best VSDs for the job. It needed a power range up to 400 kW and, of great importance, it had to have functions that would ensure smooth and stable crane operation to meet the needs of stacker crane operations.
Pesmel calculated that a combination of five motors in the crane – one for lifting and four for travelling – were required to lift and move the rolls with the highest precision. Precision positioning, high speed and reliable operation were the key focus areas for Pesmel and their customers. All five of the motors are being controlled in total by two ABB drives.
Perfect for this difficult task
The built-in anti-pendulum algorithms, combined with integrated functional safety features, in ABB’s ACS880 industrial drives made them perfectly suited to the application. The anti-pendulum control capability minimizes the swaying of the crane mast when in motion. This is made possible with the VSD controlling the positioning profile of the crane, to avoid an inverted-pendulum effect up high during movements of the load.
Thus, when the rolls are lifted and travelling at the same time towards their dedicated spots in the warehouse bays, there is no need to stop for a few seconds for the swaying to end. It is automatically minimized, thanks to the anti-pendulum function inside the ACS880 VSD, giving the pulp and paper or metal industry customer the capacity to do more roll-handling tasks in less time with the stacker cranes.
Regarding safety, the ACS880 has delivered additional major improvements, compared to previous drives used in stacker cranes. For example, it has integrated safety functionality, with Safe Torque Off (STO) built-in as standard. This enables the use of the optional FSO-21 safety functions module that integrates the Safely-Limited Speed (SLS) functionality into the drive and ensures safe and smooth operation when lowering the speed of crane movement.
Eero Anttila, Pesmel’s Manager of Material Flow Integration, explains the main benefits of the drive, including the anti-pendulum function:
The anti-pendulum function in the ABB drive is a key advantage in getting the rolls positioned quickly, and safely. The ability it gives to get controlled movement makes the whole logistics flow go faster and smoother. In addition, the energy regeneration function in the drive gives sustainability benefits, since 54% of the energy required is returned to the power grid via regeneration.
Another key sustainability advantage comes from the fact that instead of using many forklifts driven by operators, the Pesmel system is fully automated and runs on electricity. Thus, it is more efficient and produces lower CO2 emissions. It is also safer than human-operated forklifts and less prone to expensive damage for the valuable paper and metal rolls.
