New improvement opportunities through applying topology optimization combined with 3D printing to the construction of gearbox housings

Abstract

The construction of gearbox housings is severely restricted by all the currently used machining processes. 3D metal printing opens up new possibilities in this area. However, a clear additional benefit compared to the standard cast housing must be given, in order to make additive manufacturing viable. The objective of the present project was to research both the potential and restrictions of additive manufacturing technologies regarding the design of gearbox housings. As a result of this investigation, a topology optimized lightweight gearbox housing with integrated oil channels and scraper was obtained. The topology optimization process of the new gearbox was carried out in two work steps. The first consisted of the determination and design of the primary load-bearing structure of the housing. Therefore, an iterative design process was needed in order to develop the final support structure, because the topology optimization only provides a design draft of the framework structure. Concerning the iteration, an FEM analysis was performed to check and improve the draft after each loop. During the evaluation, safety and weight were compared with the previous version. During the second step of the topology optimization, the structure of all the oil channels was developed, creating a morphological box. Finally, the new gearbox housing was generated by combining the topology optimization with the concepts from the morphological box. Selective Laser Melting (SLM) was chosen for manufacturing because it allows the printing of components of the desired dimension with the required accuracy. The developed gearbox prototype was printed using the aluminum alloy AlSi10Mg (A360). Due to the flexibility of the SLM technology, it was possible to fulfill all specific design criteria while also showing the typical topology-optimized structure too. Afterwards, the housing was machined to achieve precise dimensions and tolerances. Finally, the gearbox was assembled, and both its mechanical integrity and the functionality of the integrated oil systems were fully checked with short-term tests.