A Framework for Analyzing the Operative Performance of Sequential Module Flows

Doctoral thesis, 2002

This thesis deals with sequential module flows (SMFs) and their operative performance. In brief, an SMF denotes the preassembly of components into product modules, which are delivered to a final assembly line in the same sequence as product variants are assembled. Following previous research, SMFs strongly enhance the efficiency and lead-time with which product variants can be delivered to customers. A company with many product variants can thus greatly benefit from using an SMF, which also implies an integrated assembly system. From the perspective of a final assembly line, SMFs must therefore be carefully analyzed and managed. Research on operative aspects of sequential module flows is scarce, however, and the purpose of this thesis is to develop a framework for analyzing the operative performance of sequential module flows. The framework is based on literature studies within the fields of Operations Management, Organization Theory, and Performance Evaluation. It is also based on four case studies conducted at Volvo Car Corporation, Toyota (Burnaston, UK), and Saab Automobile AB respectively. The first case study included studies of 21 sequential module flows during the production start-up of the Volvo S80. A second case study at Volvo involved four of these flows, concerning the cockpit, powerpack, exhaust systems, and headliner modules. Two case studies focused Toyota and Saab's respective sequential cockpit flows. Altogether, the cases give a deep understanding for the characteristics of sequential module flows and their operative performance. The conclusions are formed into a framework for analyzing operative performance of SMFs. The framework prescribes that an SMF's output performance, i.e. the module characteristics and the terms for their delivery, should be analyzed at its interface to the final assembly line through the criteria Module quality, Delivery precision, and Module cost. Module quality also needs to be analyzed when complete products are tested while Delivery precision also concerns the SMF's influence on production plans. Moreover, the SMF's influence on the design and operation of the final assembly line and parallel SMFs should also be analyzed through the criteria of quality, delivery and cost. The framework also prescribes the use of processual and structural criteria. These reflect the processual and structural characteristics of the SMF and its environment, of which the important parts are the line, parallel SMFs, component suppliers, and other assembly systems. These criteria can be used for analyzing the factors influencing an SMF's output. The framework differentiates the factors and the corresponding processual and structural criteria with regard to their influence on the output performance. In total, using the framework constitutes a relatively complex analysis task. The conclusions therefore outline what parts of the framework are relevant to use dependent on the aim of the analysis. In addition to the framework and its use, the findings also deepen our understanding for four vital characteristics of modular assembly systems as a whole.