Robots work arm in arm

The high-tech gas cylinders from Alugas in Bad Sobernheim are up to 50 % lighter than conventional steel cylinders, making them ideal for mobile use.

The valve sleeves are an important element in gas cylinders. They fulfill key functions in terms of safety and connectivity. Alugas currently combines four sleeve models with three differently sized half-shells to offer a wide range of cylinders for all applications. Previously, the sleeves were welded onto the half-shells in a semi-automatic system. However, this had become outdated and no longer met the state of the art and the increased requirements. A new welding solution was therefore required. However, the aluminum used has special properties and behaviors, including very high thermal conductivity. This requires more specialized processes than the processing of other metals such as steel.

Tungsten inert gas cold wire welding is ideal for welding aluminum. It allows very precise control over the heat input and is ideal for applications where high precision and clean weld seams are important. However: "TIG cold wire welding is the supreme discipline in aluminum welding and requires precise temperature control of the workpieces," explains Dominik Sperling, project engineer at system builder Roland Ruegenberg. Alugas turned to him when looking for a partner to redesign and build its customized welding cell.

A compact system suitable for sea containers

In addition to the various half-shell and socket combinations, Alugas had other requirements: It had to be possible to expand the portfolio. And in order to be able to maintain the existing production processes, an autonomy time of 30 minutes had to be maintained. Equally important: the system had to be sea container-compatible. "There were two reasons for this: On the one hand, Alugas was planning a new site overseas, which was to have the same system as the main plant. On the other hand, the plant at the German site needed to be able to be relocated without major effort," says Sperling. Ruegenberg developed a very compact system. It contains two welding holders with a preheating function; the pre-process of laser marking the sockets and the downstream testing could also be integrated. Nevertheless, the system is designed in such a way that the individual modules can be easily separated and reassembled - and therefore fit easily into a sea container.

It is thanks to two Yaskawa Motoman industrial robots that all processes can be mapped on an area of just 3×5 m. These take care of component handling and the welding process: "All relevant handling processes are carried out in parallel with the individual welding processes. This means that the processes are optimally utilized," explains Sperling. The system is fed manually - the half shells, which weigh around 2 kg, are fed via roller conveyors, while the sockets are fed via a feed conveyor with a buffer. They are separated automatically, the sockets are then marked with a DMC code by an integrated laser and brought to the required preheating temperature on a temperature-controlled accumulation section. During the fully automatic welding process, a Yaskawa AR900 welding robot takes over the torch control. A Motoman GP12 handling robot then transfers the half-shell, now fitted with a socket, to a geometry inspection station. Here, the weld root and top layer are checked, and an AI supports pore detection. Finally, the finished welded and tested half shells are discharged via roller conveyors.

Two Motoman robots in use

For the design engineers at Ruegenberg, the Motoman GP12 was the ideal solution for the new system. Thanks to its slim arm design, it can also be used in confined spaces and has short acceleration and braking times. Its fast and highly dynamic servomotors from Yaskawa's Sigma 7 series are powerful and enable precise work at high cycle rates. "For us, robotics is an indispensable tool in automation," says Sperling.

The models in the AR series have been specially developed for the high demands of arc welding. They guarantee short process times with high path fidelity and stability. With its six axes, the robot at Alugas is able to weld the sockets onto the half shells all around without interruption. "The AR900 has an integrated interface to the welding power source of EWM welding machines. This allows us to control the parameters and programs according to the requirements and adjust the welding position individually. Creating individual programs for the respective welding application significantly reduces the set-up time," says Sperling.

Sperling was also impressed by the collaboration with Yaskawa: "In the search for robotics manufacturers who could turn our ideas into reality, Yaskawa proved to be a reliable and customer-oriented partner who is also on hand with advice and support." The new system also impressed Alugas' customers. The entire marking, welding and testing process in a modular and compact system is new. The fully automated welding process guarantees constant quality and utilization of the system. In addition, employee intervention is no longer necessary.

Hanover Fair, Hall 8, Stand D18