Robert Hofmann GmbH, Lichtenfels, Germany, has additively manufactured a fully functional aluminium cylinder block for a Volkswagen VR6 engine. Weighing around 25 kg, the AM cylinder block has undergone and passed a number of tests at Volkswagen, offering significant advantages compared with conventional prototypes.
The cylinder block is virtually the same as Volkswagen’s existing series VR6 cylinder block, except for being made from aluminium instead of a cast iron GJL-250 material. CAD data of the existing cast iron cylinder block was used for the prototype which took 300 hours to produce on a Concept Laser X 1000 R system. It was stated that Volkswagen wanted to investigate the potential of Additive Manufacturing technology and convinced the team at Hofmann to take on the project. “When Volkswagen approached us with the idea to build a complete cylinder block in a 3D-printer, we were a bit sceptical in the beginning,” stated Michael Dinkel who managed the project at Hofmann.
Following the initial build a number of post-processing operations were necessary, especially with the cleaning and removal of the necessary support structures. Aluminium powders loosely stuck to the cylinder block after the build had to be removed with close attention given to the difficult to access and narrow areas such as undercuts. Support structures had to be cut out with high precision, even in areas which were hard to reach.
Before the cylinder block could be fully tested at Volkswagen the cylinder liner was coated with an APS-lining.
Engineers at Volkswagen then carried out extensive metallurgical and geometric tests. For example, the tests included computer tomography to check internal geometries, such as the cooling jacket around the cylinder tubes, which showed that the AM cylinder block has low porosity and significantly smaller distortions and deviations from the desired geometry when compared to cast components. With the successful running of the motor, Robert Hofmann GmbH and Volkswagen proved that it is possible to produced functional cylinder blocks via Additive Manufacturing. This, they stated, could be an important milestone for the future of the car industry.
The cylinder block will on display at formnext, taking place in Frankfurt, Germany, November 15 – 18, hall 3.1, stand E30.