Surprising component solutions are not unusual in the world of manufacturing. But the extent to which they are changing our previous view of manufacturing is reflected in a small 3D metal printed part from Bosch in Bamberg. In the assembly of common rail injectors (CRI), a conventionally machined part has been replaced by a metal printed part. The object is a new oil header that wets a thread with oil in order to optimize the subsequent fitting of two components.
Conventional versus AM – “Win on points” for the new vision of design could be the motto for the story of a 3D oil header. Two employees from the common rail injector production line told us this unusual story. Why was the decision taken to abandon the path of a conventional metal solution and switch to AM? Wolfgang Schliebitz, production planner, and Dr.-Ing. Anna Ebert, process expert at Bosch in Bamberg, had the courage to embrace the adventure of AM. Once the 3D oil header had convinced people at Bosch at the lead plant for CRI production in Bamberg, the component was then also introduced at the other four plants in Korea, Turkey, Germany and France.
For newer generations of injectors, with different surface properties, it has become increasingly important to lubricate the outside diameter of the thread as well in order to prevent friction during the process. This might sound simple at first but is in fact a tricky task in relation to friction and placement. If the torque expands out of the tolerance window during the process, the injector is discarded. Dr.-Ing. Anna Ebert examined the oil process on the CRI assembly line in precise detail. The diagnosis was that the thread was only wet with oil on the upper thread geometry, but not on the bottom side. So there were blind spots for lubrication. An oil header with improved lubrication resulted, in the first design, in a machined component with three or four parts. This approach was too complex due to the excessive outlay.
In the Bosch network, at the Nuremberg plant, there is already a 3D printer from Concept Laser, an M2 cusing. However, the rather small oil header required a smaller machine. This is how the company came to approach the manufacturer in Lichtenfels directly and asked it for a redesign and the fabrication of a fairly small number of oil headers. Working with the design and manufacturing experts at Concept Laser, Wolfgang Schliebitz and Dr.-Ing. Anna Ebert sought a production-ready solution from the 3D printer. This then resulted in a combination of a new geometry for the oil channels, a new material and a laser melting machine with the correct parameters – and as usual this was all delivered with the one-shot technology that laser melting offers.
The material for the new oil header was to be high-strength and of course non-corrosive. Concept Laser opted for CoCr as the material along with a small Mlab cusing as the production machine, which is regularly used to produce very delicate parts with a 100W laser. What was then particularly exciting was the redesign of the oil channels to optimize the wetting of the thread. The AM specialists are familiar with such functional integrations primarily from working with transport channels for coolants. The conventional component underwent an assessment at Concept Laser. This was followed by reengineering - the analysis and creation of a design to suit the process. After a very short space of time, Concept Laser delivered a new oil header to Bosch in Bamberg.
Wolfgang Schliebitz: “The new oil header looked different. Smaller and more compact. But what was really surprising was the effect on our process during trials.” Dr.-Ing. Anna Ebert: “The process fluctuations were visibly smoothed out. The 3D oil header was much better at delivering the right amount of oil to the right place. The optimized oil channels were the crucial factor behind this. They guaranteed that wetting with oil took place not just at the top of the thread, as was previously the case, but also at the bottom. The blind spots for lubrication that we had previously been accustomed to no longer existed with the AM part.”