Optimal Tolerance Allocation for Multi-body Mechanical Systems

Tolerance allocation is a key process for multi-body mechanical system design and assembly. It plays a significant role in linking design features together including design requirements, product quality, manufacturing costs and system perfoiinance. An innovative CPT (cost-precision-time) approach along with a comprehensive computer program is presented in this paper to meet the aforementioned multi-objective design needs. The CPT is a systematic design procedure comprising a Monte Carlo method for tolerance allocation, and genetic algorithms / factorial design for comprehensive cost consideration. Two different production models including a Fortini's clutch and a SCARA robot, are employed to verify the overall quality and reliability of the CPT method. The design results show that the CPT method is capable of 3D tolerance design for static structures, dynamic systems and robotic models. The tolerance models thus obtained by using CPT approach are sufficiently accurate and more economic as compared to those obtained by using other methods that are presented in literature. The CPT method and associated design procedure presented here is thus proved to be systematic, economic and accurate for comprehensive tolerance design of given industrial production systems.