EHTC 2009

Cost Minimization for the planet carrier by topology optimization

Torsten Bunge, Flender

The objective of the work was to minimize by means of topology optimization the costs for the planet carrier in the main gear stage for a planetary gear unit being presently developed.

In this case, the starting point was a reduction in weight. To this end, the already existing draft was analyzed first. The boundary conditions to be taken into consideration were determined. Then, a calculation method for the optimization of the topology was made up and the optimum determined by means of different parameters. On the basis of the results, three planet carrier variants were developed and compared with the existing draft. An evaluation scheme was worked out to assess the evaluation criteria according to their relevance.

Because of the technical demands on a planet carrier and the small space available, it is not possible to reduce the costs by material savings. If a functional and manufacturing-oriented planet carrier is designed, it becomes heavier than the reference model. But it was possible to derive constructional rules from the optimization which can be easily realized without great design expenditure and amount of time required.

Although in this concrete case topology optimization did not lead us to our goal it is nevertheless correct and purposeful to use this tool for the task of cost reduction. As the calculation results show, the design engineer gets clear indications of what the design of the component should look like in the ideal case to satisfy the determined boundary conditions. It may, however, not excite the impression that this technology would make designing unnecessary. Although manufacturing restrictions such as the direction of extraction in the foundry or the necessity of a repetitive pattern have been implemented to a small extent, a design proposal achieved by optimization cannot be taken on without expensive and time consuming rework. It can serve for orientation only.

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