The design tolerances and material defects are frequently inevitable in the real manufacturing process, where unexpected additional cogging torque might be caused as a result. An approach fast estimating the design performances under manufacturing uncertainties is highly expected. In this paper, the previously proposed worst-uncertain-combination-analysis (WUCA) approach is further modified, where the influences of rotor geometries could be taken into account. A 10-pole-12-slot (10P12S) permanent magnet (PM) machine with non-uniform air-gap considering the rotor uncertainties is taken as an example. The cogging torque robustness for designs with different air-gap saliency ratios are discussed and compared. A medium value of air-gap saliency is suggested to achieve a balance between the ideal and worst-scenario performance under rotor uncertainties. Three prototypes with different air-gap saliency ratios are manufactured, where the possibly worst-case under uncertainties are imitated with a special PM assembling sequence. The deduction is then verified by the experimental results of the prototypes.INDEX TERMS cogging torque robustness, robust design, non-uniform air-gap rotor, worst-uncertaincombination-analysis approach.