During the assembly process of planetary gears, the pinion shaft is initially pressed in to the planetary carrier and then staking is performed to fix the pinion shaft to the carrier. The main purpose of the staking process is to prevent the movement of the pinion shaft during transmission operation. During assembly there should be minimal distortion of the assembly. The press-in process, pinion shaft and carrier are subjected to extremely high frictional loading due to the interference fit. The staking process permanently deforms the pinion shaft top and bottom ends, forming a protrusion that holds the shaft in position. The pinion shaft needs to sustain operational loads exerted by helical planetary gears, which tend to push the carrier flange out of position during operation. Staking length, staking force and interference between shaft and carrier hole are the critical parameters, which determine the maximum axial force that the pinion shaft can withstand.
Finite element (FE) analysis is commonly used to evaluate the necessary force requirement for press-in, staking, and to find the residual stresses around the press fit region. The simulation is correlated with the results obtained from transmission assembly plants for validation of the FE model and its assumptions. In this study, the pressing and staking force data acquired from the assembly process were correlated against the FE results. Multiple cases were investigated using FE analysis, to account for maximum and minimum tolerances allowed for pinion and carrier hole in dimensions as well as axial positioning of the shaft. Good correlation was observed between the measured data and FE results.