Determining the process tolerances based on the manufacturing process capability

An efficient approach has been developed for determining the process tolerances. This approach simplifies the traditional procedures of tolerance chart balancing and takes into account the capability of the process producing the workpiece. A mathematical model, based on the modified rooted tree chart, has been established. By using the model, the process tolerance can be obtained effectively and accurately without the effort of finding the additional tolerances. The work done previously by Ngoi is examined and several drawbacks are identified. A comparison between the results generated by the proposed method and by Ngoi is also made.Notation d_i additional tolerance to be added - f_j jth functional relationship betweent_i andd_i - m the number of blueprint specifications - n the number of operations - r_i the failure rate - estimated standard deviation ofith operation - T_i initial tolerance - TB_j blueprint tolerance - TP_i upper limit of process tolerance - _i process tolerance for operationi - x_i standardised process tolerance - w_i weighting value - Z the minimum value amongx_i