Hidden in a picturesque landscape between lakes and surrounded by forests, is the southern Swedish town of Olofström – approximately two hours from the international air traffic hub of Copenhagen. Here, away from the industrial centers of Stockholm, Gothenburg and Malmö lies the most important bodywork plant of the Volvo group, a factory which is steeped in tradition. In the 18th and 19th centuries, the factory – at that time not yet under the name of Volvo – manufactured in particular wrought iron and semi-finished products such as steel pipes and iron plates. Since 1927, the Olofström factory has been producing bodywork parts for all Volvo models.
Today, five trains with 280 containers full of bodywork parts leave Olofström every day, heading for the Volvo assembly plants in Gothenburg and Ghent, Belgium, where they are assembled to form complete bodies. This amounts to 50 million bodywork components annually.
"Most of what you can see of a Volvo comes from Olofström," explains Leif Winberg, the plant engineer in charge of resistance welding in the Volvo Olofström factory. This includes load-bearing components like the A, B and C columns, the bumper reinforcement, the front side members, the side impact beams, the cross beams and the roof arch and roof rail, together with doors and frames. All these components are produced in different versions for the various Volvo models, ranging from the compact V40 through to the S60 saloons and the large SUV, the XC90.
A key element in bodywork production is resistance welding, since correctly welded sheet metal components play a crucial role in the passive safety of a vehicle. Within the welding process, there is great potential for increased productivity in the milling of electrodes. Welding gun electrodes become blunter as they are being used and have to be milled after approximately 150 spot welds to ensure the spot welding is perfectly accurate. "Electrode milling operates on the same principle as the sharpening of a blunt pencil," explains welding expert Winberg.
Mobile tip dressers are not necessary for the welding guns on the ABB articulated-arm robots. These robots can feed their electrodes to the electrode milling device themselves after 150 spot welds. This freedom of movement of the welding guns opens completely new horizons. In a first step, the articulated-arm robot brings the welding gun to the tip dresser. This then mills the electrodes. In the next step, the robot swings its electrodes in front of the lens of the Festo SBO… - Q vision system. "The system produces an image which supplies the robot system with all the data necessary in order to position the electrodes correctly to weld the next sheet metal components," says Winberg. "The vision system is also easy to integrate and simple to commission via parameterization." The system includes not only the sensor system for the acquisition of image data but also a complete electronic evaluation unit and the interfaces (Ethernet/CAN) required for communication with primary PLC controllers. The vision system itself is accommodated in a housing which is no bigger than a one-liter carton of milk.
Olofström, Sweden
Key activity: Vehicle manufacturing
Västerås, Sweden
Key activities: Energy technology, factory and process automation