Evaluation of Different Tools of Precision Finishing for Sun Gear with Inner-Outer Tooth Shapes

Aiming at the technical difficulty of poor teeth accuracy of the extruded sun gears, an innovative precision finishing approach was developed as the subsequent process of producing high-quality sun gears, and three finishing tools were designed, namely mandrel with gap, mandrel without gap and interference mandrel. A finite element prediction method was proposed by using the post-processing toolbox of DEFORM software to study the distribution laws of outer and inner teeth deviations of the reshaped sun gear. Moreover, the effects of various precision finishing tools on the formability of sun gear (such as tooth deformation, tool stress and tooth accuracy) were investigated. The results show that the tooth accuracy class of the reshaped outer teeth in profile and helix were seventh and eighth, respectively, and the total M-value error of the inner teeth was decreased to 72.3 μm and the reduction ratio was 73.8% by adopting the interference mandrel, which indicates that the finishing effect of the interference mandrel was better than that of mandrels for both with gap and without gap, and the forming accuracy of the finished teeth could be considerably improved. Therefore, the interference mandrel can be recommended as the optimum finishing tool in the manufacture of precision sun gears. The simulated results were in good agreement with experimental ones within a maximum error of 14.4%, which proves the practicability of the sizing approach and the dependability of the finite element prediction method.