Automated ladder frame production with MAG robots at automotive supplier

Automated welding of ladder frames: no problem at MAGNA Presstec in the Austrian town of Lebring, near Graz, thanks to a KUKA production line. The frames for the Mercedes G-Class have been manufactured here fully automatically since 2017.

Welding large parts with a KUKA body-in-white line for process stability

The G-Class has been an integral part of the Mercedes-Benz product portfolio since 1979. The robust and durable off-road vehicle enjoys iconic status. This also remains true of the latest update. The main focus was placed explicitly on the engineering and the recognition value – two features that have characterized the G-Class right from the outset. Particular attention was paid to the reworking of the ladder frame, which provides the required stability of the vehicle body, enabling the vehicle to make its way safely over mud, gravel and rough terrain with its additional 53 millimeters in length and 121 millimeters in width.

The launch of the new G-Class also marked the beginning of a new era in production: whereas the welding of many large parts had previously still been done manually, this work is now carried out at MAGNA Presstec by a production line from KUKA that can weld the ladder frames automatically.

Experienced partner for automation with MAG robots

“Above all, process-stable production involved two central challenges,” says Dominik Pfeiffer, project manager at KUKA. One was the restricted space available. Not all of the production and logistics area measuring 2,000 square meters could be used for the production system. Furthermore, the production shop was long and narrow. “The other challenge was that the size of the workpiece had to be taken into consideration: with a length of 4.30 meters and a width of 1.20 meters, the ladder frame weighs more than 230 kilograms.” Some 145 individual parts are processed in the system. Seams with a total length of around 80 meters are welded and more than 200 spot welds are applied.

KUKA MAG robots weld the longitudinal and cross members to the front end and rear end.
“The solution: 45 robots, particularly of type KR 30 L16 as MAG robots and KR 240 as handling robots, that join the numerous parts and automatically weld the ladder frame,” says Dominik Pfeiffer. The left-hand side of the production shop serves as a utility aisle for wire drums or robot equipment, while the individual parts are placed in component racks during the production process. System and process control are performed using KUKA’s own miKUKA control standard. This transparently displays information about the machine status and simplifies operator control by means of standardized functions.
The KUKA MAG robot system produces 20,000 ladder frames annually.

Automated welding of 20,000 ladder frames each year

20,000 ladder frames are produced annually on the KUKA body-in-white system. The parts, some of which are very large, are welded together in various stations. The lines for the two main assemblies – the front end and rear end – have the same structure, but a mirror-inverted layout. Major components of the solution are the two squeezing stations. The parts are then welded with minimum distortion and stress using a sophisticated welding procedure.
Welding large parts: Magna Presstec uses the KUKA production line to manufacture 20,000 ladder frames a year.

Even any disruptive factors that arose could always be satisfactorily resolved. We were thus jointly able to bring the project to a successful conclusion.

Dominik Pfeiffer, project manager at KUKA.
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