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26.03.2020
Author: Schmitt Matthias, Group Manager Additive Manufacturing, Fraunhofer IGCV
The Fraunhofer IGCV has extensive cross-industry experience in the field of additive manufacturing. Together with the Institute for Machine Tools and Industrial Management at the Technical University of Munich (iwb), the Fraunhofer IGCV operates the AMLab, one of the largest laboratories for additive manufacturing in Europe.
Description of the component:
The "pinion shaft" is a combination of gear wheel and associated shaft. These were combined into one component during the development process at the Fraunhofer IGCV. The component was manufactured from 16MnCr5 case-hardening steel using laser beam melting. The component is used in highly stressed gearboxes.
Challenges:
When it comes to meeting the requirements of gearbox construction, conventional processes and materials reach their limits. Additive manufacturing processes are suitable for extending the application limits and increasing resource efficiency. They are particularly suitable for reducing component mass or for integrating functions. Within the pinion shaft, there was limited installation space in the gearbox that needed to be utilized as effectively as possible. High demands were also placed on the temperature and lubrication behavior of the gear pairing.
Solution:
In order to meet the high demands, the Fraunhofer IGCV redesigned the component. First, the two components, gear wheel and shaft, were combined into one component (component integration). An internal cooling lubricant channel was then developed, which runs helically from the shaft into the tooth head. This makes it possible to ensure the best possible lubrication and reduce the tooth flank temperature. The helical geometry creates a self-feeding of the lubricant. A computer-aided lightweight design optimization (topology optimization) was carried out around these cooling channels. Here, areas subject to low loads are removed, while areas subject to high loads are retained. This made it possible to create a force flow-optimized geometry that reduces the component mass by 70 percent compared to the conventional combination of shaft and gear wheel. To enable production using laser beam melting, the researchers involved developed a self-supporting support structure for the tooth flanks. This consists of branched branches and was constructed using bionic development methods. In order to achieve the required material properties, the Fraunhofer IGCV made it possible to process the material 16MnCr5 for laser beam melting. The case-hardening steel 16MnCr5 has a carbon content of 0.16 percent by mass and therefore requires suitable process parameters to guarantee crack- and pore-free processing. Finally, the pinion shaft with self-supporting support was manufactured from 16MnCr5 at the Fraunhofer IGCV.
Conclusion:
Additive manufacturing was the only way to best meet the requirements of small installation space and high performance in one component. The field of application and the experience gained can be used in the automotive, aerospace and general mechanical engineering sectors. Additive manufacturing increases performance and improves resource efficiency.