Quality control and cost are considerations when adding more robots into a manufacturing process. A prime example of this is the robot line set up to make the latest version of Mercedes G-Class chassis ladder fames at Magna Presstec’s plant in Lebring, Austria. This was a specially commissioned installation from technology supplier Kuka and replaced what had previously been mainly manual procedures implemented elsewhere.

“There was no previous ladder frame production in Lebring, so it was also a new and exciting project for Magna,” notes Dominik Pfeiffer, Kuka’s project manager for the installation.

Nevertheless, though the production technology and the ladder frame configuration (specifically its slightly larger size) were new, all the operations had to be shoehorned into a less than ideal space. “The difficulty was a long-stretched area, which was severely limited by adjacent walls,” explains Pfeiffer. “In addition, the area between the installation and component supply had to be divided. That is why we had to make the installation as compact as possible.”

What this meant in practice, Pfeiffer continues, is that “process-stable production involved two central challenges.” These were the confined available space of less than 2,000 sq.m and the enlarged size of the workpiece of 4.3x1.2 metres – 53mm and 121mm greater than before, respectively. Each workpiece has 145 individual parts to be processed – a total weight of 230kg – requiring 80m of welding seams and more than 200 spot welds. Two frame types are involved, he reports, “one derivative for the European market and one for the US market”.

More automation on the line

Magna’s incentive for commissioning the installation was not the larger dimensions of the workpiece. “Magna wanted a highly automated production line to manufacture the ladder frame and obtain the required quality at the best possible cost,” says Pfeiffer. These demands are satisfied by an installation involving 40 of Kuka’s KR30 six-axis robots to carry out the actual welding, plus a further number of the company’s KR240 and KR500 machines for handling tasks, stud welding, in-line measurement and spot welding.