Assembly Synthesis for Optimal In-process Dimensional Adjustability Based on a Joint Library

Achieving the dimensional integrity for a complex structural assembly is a demanding work due to the manufacturing variations of parts and the tolerance relationship between them. One way to resolve this problem is fabricating all the parts with tight tolerances, which is not an economical way. Another way, which is preferred, is taking advantage of small motions that joints allow such that critical dimensions can be adjusted during assembly operations. This paper addresses this problem by providing a systematic method that decomposes the product geometry at the early stage of design, configures joints and generates subassembly partitioning in such a way that the critical dimensions can be adjusted in assembly processes. The method employs Genetic Algorithm (GA) which generates synthesized assemblies based on a specific joint library for the application. Each synthesized assembly given by the GA undergoes subsidiary optimization routine where the subassembly partitioning is decided for the optimal in-process adjustability by recursively applying a partitioning policy, which is transformed to the well-known minimum cut problem. In order to prove the effectiveness, the method is applied to a three-dimensional automotive space frame example with the accompanying joint library.