Rationale for the Use of Subassemblies in Production Systems: a Comparative Look at Sequential and Arborescent Systems

In designing a production system for the fabrication of a product, a manufacturing engineer usually has some control over the extent of the use of subassemblies. He/she may have the freedom to decide whether or not parts or groups of parts should be assembled together before being added to the main assembly. In this thesis, we study the pros and cons associated with that choice. We present a list of qualitative advantages and disadvantages of subassembly use, based on a broad literature search that covered the conventional manufacturing and assembly literature, as well as the literature in areas that exhibit subassembly-like entities such as modules or subroutines. We also develop a simulation to compare the output rate of the production system configurations which display the most extreme use of subassemblies: the sequential and arborescent configurations. Specifically, we compare the output rate of non-synchronous arborescent and sequential production systems with reliable stations with stochastic processing times for different buffer allocation schemes. This part of the thesis is meant to mark the beginning of a comprehensive study of the quantitative impact of subassembly use in assembly and production systems. To facilitate such a study, we present algorithms to determine the most arborescent and most sequential assembly sequences possible for a product, based on the algorithmic liaison sequence generation method of De Fazio and Whitney (1986).