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Comparison of the Different Tolerance Designs

<img src="/ueditor/php/upload/image/20260131/1769820231162100.png" title="1769820231162100.png" alt="1.png"/>The variants determined by MOPSO on the Pareto-Front were weighted for two exemplary cases. As an example, Figure 12 compares two design points that emerged as the best solution for the different weightings. For the optimization point with fF = 90 percent and fA = 10 percent, a tolerance design was identified that is pF = 7.5 percent cheaper to manufacture on the basis of the C-T cost model used compared to the reference. Based on the tolerance position of the geometric features in Figure 12, left, it can be seen that the tolerances of the gear have been increased compared to the reference tolerance design. To achieve the qualities of the gear, the algorithm suggests using finish hobbing instead of a honing process (estimation of quality loss due to heat treatment pinion shaft: -2.07 quality classes, gear: -1.55 quality classes), as this is the most cost-effective for the reduced tolerance requirements of the gear.The tolerances for the pinion are also extended in order to reduce costs. One exception is the tolerance for the profile angle deviation, where a restriction is made to A 3.6, which corresponds to a virtual interpolated intermediate class. In particular, the stricter tolerancing of the geometric features on the housing is evident, which is carried out in return for the tolerance extension on the gears. In particular, the bearing seats of the pinion shaft require a reduction from the former quality class A 7 to A 4.4 in some cases. This is a plausible behavior, as the smaller bearing distance to gear on the shorter pinion shaft means that the effects of fitting deviations and bearing clearances have a much greater influence on axial position deviations than on the wheel shaft, which is longer. In the acoustic assessment, however, the design falls behind by around pA = +3.2 percent, which is still within the acceptable rating of gA = 5.2 < gA,max = 6. The plausibility of each favored design must be checked in detail to ensure its validity.A tolerance design aimed at stricter compliance with the acoustic limit values can be seen in Figure 12 on the right. Here, an improvement in the acoustic behavior and the manufacturing cost score is achieved by limiting the tolerance of most of the features on the housing while at the same time increasing the gear and roller bearing tolerances, but while retaining the reference process chain. The comparison with the reference quality classes on the pinion shows, with the exception of the quality requirement for the flank form deviation ffβ, a possibility for extending the tolerances, which results in potential cost savings for the overall gearbox.The percentage cost changes shown in Figure 12 relate to the reference costs determined by the stored cost model. It can be seen that for both compared designs, the main savings are made in the gearing of the pinion shaft and wheel. Due to the higher absolute cost shares of the gear geometry compared to, for example, dowel pin bores or bearing seats, cost savings can be achieved in total. The percentage savings for the pinion gearing can correspond to more than p > | 50 percent|, whereas the geometry-determining production steps for inserting precisely fitting bearing seats in the housing can sometimes be more expensive by p > |+150 percent|. This reciprocal exchange of tolerance specifications enables the excitation quality to be maintained, although the overall costs can be reduced. However, it can be stated that especially housing tolerances such as of the bearing seats or the positioning pins are relatively cheap features which should be manufactured in good quality. This is especially relevant if the distance of gear to the bearing seat is smaller.

28 Jan,2026

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