Variation analysis and assembly success rate computation for clearance fit under constraint of location priority

Analysis of variation between assembly features is fundamental to analysis of assembly variation. Orienting to affection of location sequence on clearance fits between assembly features of two parts, an analytical model for fit variation and a computation method for assembly success rate are proposed. A mathematical model for multi-datum assembly is established to analyze variation of assembly features with relative to nominal position before mating. Then, based on contact relationship between parallel planes or cylinders or cones or spheres, constraint conditions on variation of assembly features after mating are obtained. The algorithm to compute fitting variation between assembly features is proposed and the method to obtain assembly success rate between two parts is presented as well. Afterward, through simulating variation of assembly features randomly based on given constraint conditions, fit variation and assembly success rate can be derived. A measurement instrument is illustrated as example to prove feasibility of the proposed model and method.