Retrofitting without line downtime
Success story Bosch Homburg
Competent engineering for an individual solution
That’s impossible! Or isn’t it? It took only one weekend and hardly any modifications to integrate the two robots into the line – during ongoing operations. The experience in the Bosch facility in Homburg/Saar shows that this really is possible. Since June 2017, the two APAS assistants are working in the production of Diesel injection systems for utility vehicles. They have taken over the previously manual tasks of joining and aligning magnetic cores and tubes, and of inserting the aligned components into a welding laser. The two robots complement a shielded laser welding station and increase the productivity of the entire line. Moreover, they relieve employees of a monotonous job at an ergonomically challenging workplace.
A line with a history
The line is used to assemble and weld magnetic cores and tubes for Common Rail injectors for utility vehicles. Since the year 2000, a conventional shielded laser welding station was used for joining and welding. A growing demand made it necessary to extend the line with a manual welding laser. This manual workstation, however, was not very popular among employees. In a confined space, like in a passport photo booth, the employee on duty sat in front of the welding laser, jammed in between measuring device and infeed belt, and had to align and join the magnetic cores and tubes, insert them into the laser before removing them again and inserting them into the measuring device. With a steadily increasing demand, the capacity of the line was no longer sufficient and expansion potentials were discussed at the end of 2016. Another important point was to relieve the employees of their unpopular manual workstation. The biggest challenge consisted in the lack of space, which led to the decision for an automation solution, which could be realized within the given space and enabled a safe cooperation with humans.
Space-saving expansion thanks to sensor skin
The plan was to automate the manual workstation. However, employees would still be working in the immediate vicinity, and should of course not be endangered. “The automated production assistants are ideally suited to upgrade existing lines,” says Stefan Betz, group manager mechanical design in Homburg, who initiated the project. Thanks to the sensor skin, which encloses the robot arm, a space-consuming safety enclosure is not necessary. Spatial conditions often limit the expansion possibilities of existing lines. The same is true for Homburg: a second conventional shielded welding system was out of the question. The APAS assistant with its sensor skin was the ideal solution.
Two APAS assistants complement magnet assembly line in Homburg
It took half a year from the first request in Stuttgart to start-up in Homburg. After analyzing the process steps and requirements, it was quickly clear that one APAS would not be enough. The tasks were simply too complex. So the jointly developed concept involved two APAS assistants to share the work. One robot removes the magnetic core and the tube from the washing frames, aligns them with the pin holes and assembles the aligned workpieces. The other robot inserts the assembly units into the laser welding station, removes them after welding and inserts them into the measuring device. After measuring is completed, the production assistant places the good parts on the transport belts, while the faulty parts are rejected. Double grippers, especially developed for these processes, imitate human hands. The initial idea of positioning the two APAS assistants behind the welding laser was quickly discarded by the project team.
A preliminary CAD analysis showed that it would be difficult to realize the material supply due to space constraints. In the new concept, the first APAS assistant, which is responsible for joining and aligning, is installed on a “feeder table” and integrated into the station via transfer belt. The Bosch software Control plus made it possible to easily integrate the belt into the control concept of the line. After joining, the first APAS assistant places the workpieces on the feeding belt, which transports the parts to the second APAS assistant. An operator delivers new parts to the robot on the feeder table every half hour to ensure consistent operations. The APAS can continue working, however with reduced speed. If the operator comes too close, the robot will automatically stop its movements. This way humans and robots can work together without any danger for the employees.
Short reaction times and straightforward implementation
Thanks to the safety concept of the APAS assistant, the existing line only had to be altered slightly. The magnet assembly line could continue production during the entire modification. A single weekend was sufficient for both modification and start-up. Implementing a conventional robot with safety fence would have required significant modifications, leading to downtimes of about four weeks. Not to mention the resulting production loss. Demands for high quantities did not allow for such a scenario. “A short realization time combined with the easy implementation into the line without production downtime are some of the many advantages of the APAS solution,” says Betz. This way it was possible to keep the very tight schedule.