Redesigning an oil header to help Bosch eliminate lubrication blind spots
GE Additive has been working closely with an automotive parts team at Bosch in Bamberg, Germany to redesign an integral engine component using additive manufacturing to improve process and operational efficiencies.
With conventional diesel injection systems, fuel pressure has to be generated individually for each injection. With the common rail system, however, pressure generation and injection are separate, meaning that the fuel is constantly available at the required pressure for injection.
For newer generations of common rail injectors (CRI) - with different surface properties - it has become increasingly important to lubricate the outside diameter of the thread, in order to prevent friction. This might seem simple, but in fact is a tricky task in relation to friction and placement. If the torque spirals out of the tolerance window during the process, the injector is discarded.
Dr. Anna Ebert responsible for Bosch’s CRI assembly in Bamberg examined the oil process and discovered blind spots for lubrication. The thread was only wet with oil on the upper thread geometry, but not on the bottom side. The team decided to use conventional machined processes to design an oil header component in three or four parts to improve lubrication. However, due to the excessive outlay this approach was deemed too complex.
Dr. Ebert and her colleague Wolfgang Schliebitz began to consider using additive manufacturing as potential solution to the challenge with the oil header.
The Bosch team required a production-ready solution. A redesign of the component was achieved after working closely with the design and manufacturing experts at Concept Laser, using a combination of a new geometry for the oil channels, a new material and opting for a laser melting machine with the correct parameters.
The Bosch team already had access to a Concept Laser M2 cusing machine in its plant in Nuremburg, but given the size and the delicate nature of the oil header, a smaller machine was required.
The Mlab cusing with its 100W laser is well-suited to producing intricate parts and was selected as the production machine. And given the new oil header needed to be high-strength and non-corrosive, the team opted for CoCr as the most appropriate material.
The redesign of the oil channels to optimize the wetting of the thread was a particularly exciting phase. The conventional component underwent assessment at Concept Laser, followed by reengineering, analysis and creation of a new design to suit the process. After a very short space of time, the new metal printed oil header was delivered to Bosch in Bamberg.
“The process fluctuations were visibly smoothed out. The 3D printed oil header was much better at delivering the right amount of oil to the right place,” according to Dr Ebert.
The optimized oil channels were the crucial factor and guaranteed that wetting with oil took place not just at the top of the thread, as before, but importantly also at the bottom. The blind spots for lubrication that had previously been accustomed no longer existed with the additive manufactured part.
“The new oil header looked different - smaller and more compact. But what was really surprising was the effect on our process during trials,” added Wolfgang Schliebitz.
With great results and a positive impact on manufacturing and operating efficiencies, the component has since been introduced to four other plants in Korea, Turkey, Germany and France.