Expert’s-Based New Tolerance Allocation Methods

According to the American Society of Mechanical Engineers [1], tolerance is the total amount by which a specific dimension is permitted to vary from its nominal value. Tolerance allocation, also called tolerance synthesis, is carried out at the process planning stage in order to distribute the component’s design-specified tolerances, also called blue print (BP) tolerances, among the various operations required for the production of that component. These operational tolerances represent the limits that each process should comply with such that the final product is produced within design specifications. Every tolerance allocation model in the process planning stage should fulfill the requirements of the BP tolerances. One or multiple operational tolerances may stack up to a one BP tolerance. Tolerance stack-up is handled by the identification of the tolerance chains. The tolerance chain identification relates to the recognition of the relationship between the operations based on their sequence and the determination of the effect of each operation on the dimension of the produced component.