STATISTICAL REPRESENTATION AND COMPUTATION OF TOLERANCE AND CLEARANCEFOR ASSEMBLABILITY EVALUATION

The design of tolerances should take the functionality, manufacturabil ity, assemblability and cost effectiveness of a product into considera tion. This paper presents a method of analyzing and evaluating the ass emblability of a product under given tolerance specifications in order to provide a tool to aide for tolerance design. Introduced is the ran ge of feasible displacement of a part of an assembly as a result of th e accumulation of clearances between mating parts along the serial as well as parallel chain of assembly, which can play a role of compensat ing for the pose error of the corresponding part due to the accumulati on of tolerances. Assemblability is determined by the probability that all the parallel as well as serial chains of the assembly can be form ed successfully under given statistical properties of tolerances. This requires to numerically compute the probability that a pair of mating parts forming a parallel chain can align themselves within the error margin defined by their mating clearance, accounting for the possible compensation of the ranges of pose errors associated with the mating p arts due to tolerance accumulations by the ranges of feasible displace ments of the mating parts due to clearance accumulations. Simulation r esults are shown.