Assembly system design is an important task for a manufacturing company regardless of the nature of its existing assembly activities. However, unlike the product development process, the process of designing assembly systems has not been emphasised.

The research presented in this thesis aims at identifying and structuring the performance of assembly systems and their design processes, and proposing a framework for identifying important relationships between the results of specific design projects and influencing factors in the field of the design process. These objectives have been accomplished through theoretical and empirical studies. The empirical studies were carried out in the form of an interview study at 15 companies and three case studies at Swedish manufacturing companies both aimed at describing and analysing companies' assembly systems as well as their assembly system design processes.

A number of characteristics of successful assembly systems have been identified and classified according to the system theory. They have then been structured in a model where the mentioned characteristics have been classified into nine groups indicating the performance of the assembly system. Assembly system performance is represented from a higher level of abstraction by assembly strategy, to a lower level of abstraction by quality, lead time and delivery precision, flexibility, cost and productivity of the assembly system.

The assembly system design processes have also been investigated and analysed empirically, showing that structured methods are seldom used in the assembly system design process, but mainly experience and knowledge of system designers is utilised. Although larger companies worked more systematically, no specific method for the design of assembly system has been found. The performance of the assembly system design process has been identified and presented in a model with nine performance indicators into three levels, from a higher level of abstraction (design process strategy) to a lower level of abs traction (quality, lead time and delivery precision, flexibility, cost and productivity).

From the two performance models, an approach to a matrix linking design factors to the design project results has been developed. Examples of the design factors have been given based on research studies in the field of product development, and on the theoretical and empirical studies presented in this thesis. The matrix described is an approach to a tool for the support of production managers and system designers in order to design successful assembly systems.