October 2020

32 n MACHINE BUILDING October 2020 www.drivesncontrols.com Linear guides solve problems with huge robotic train-welder A German train manufacturer was experiencing recurring problems with a huge – 30m long and 10m wide – robotic welding machine that it uses to weld aluminium assemblies up to 28m long to wagon shells. The system was broken down more often than it was in operation, and it was giving the company a considerable headache. “The problems we faced with the Duo machine were multi-faceted,” recalls Günter Becker, deputy branch manager at Spie, the German engineering services company that was responsible for repairing, maintaining and refurbishing the train-maker’s machinery. “We had to visit the customer almost every week, with two men working two or three shifts to maintain the welding machine. This was not economically viable for us and it was a huge problem for our customer as these failures meant the machine was often at a standstill, with a knock-on impact on other plant processes.” The welding system is enormous. Four robots are mounted on each of the two welding machines – two on a lower level, and two on an upper level. In a slow, constant movement, the robots weld aluminium assemblies to the train shells. They are mounted to motorised rack-driven carriages that run on two guide rails. “The key difficulty was that the existing welding system from the 1990s had been built with inadequate drive and guidance systems,” Becker explains. “They were not suitable for heavy loads or such a dirty working environment. The existing rail systems had also been mounted on milled surfaces that were not perfectly flat. “In addition,” he continues, “the guide rails were heavily worn due to the loads they had seen. This caused not only the drive motors to fail regularly, but also meant that the seams were not neat. In addition, dirt particles made their way into the recirculating ball bearings in the guide blocks for each welding robot – a common issue in this type of environment. This accelerated wear and also contributed to the frequent blocking of the motors. “The question arose of how to obtain a smooth-running and reliable system without having to change the entire machine,” Becker adds “This would incur high costs – probably in the region of €2m – and extended production downtime. A linear guidance system was required that could operate in a very dirty environment, under extreme and constant load, with a long rail length, minimal maintenance, and that could be installed on the existing machine without interrupting production – a particular challenge.” Becker turned to HepcoMotion for help. He was familiar with the British linear systems specialist from a previous job he had at a machine-builder. “To my knowledge, they are the only company that offer the flexibility to adapt to different sizes and lengths whilst coping with mechanical stresses and loads of the welding robots. “Our plan was to swap the existing guides one-by-one with a more appropriate system,” Becker explains. He worked on the project for more than four months to ensure that everything functioned correctly, so that he could convince his manager and customer of the feasibility and profitability of his proposals. Spie specified rails, carriages and bearings from HepcoMotion's GV3 system. Around 500m of single-edge slides were needed. The upper slides for each assembly were A 30m-long robotic welding system operated by a German train-maker was breaking down repeatedly, disrupting production. The engineering services company brought in to solve the problems turned to UK-made linear guides. The 30m-long and 10m-wide train welding system consists of four robots mounted on each of the two welding machines