https://www.mdu.se/

Increasing customer demands for product variety in conjunction with the short lifecycle of products has caused manufacturing companies to introduce a wide range of products by accommodating flexibility. An assembly system is an essential part of the manufacturing system from both cost and time perspectives. Hence, the shift towards flexibility in manufacturing companies highlights the significance of establishing flexible assembly systems and designing products that are closely aligned with them. Despite its significance, however, the flexible assembly system concept and its requirements for product design have not been clearly defined in research and from a practical point of view. Most research on flexible assembly systems has mainly approached either the design or the balancing and scheduling issues of these systems, whereas only a few studies have briefly defined the flexible assembly system they focused on, without further specifying the characteristics of a flexible assembly system and its requirements for product design.

Taking that into account, the objective of this work is to provide a framework to contribute to the understanding of the concept of flexibility in an assembly system and its requirements for product design. In order to fulfil the objective, four empirical studies combined with literature reviews have been conducted. The empirical studies, a multiple case study and three single case studies, investigate the definition of flexibility in an assembly system as well as the requirements that a flexible assembly system imposes on product design.

Through its findings, this research provides a definition of flexibility in assembly systems that mainly revolves around volume, mix and new product flexibility. In addition, six constituents of a flexible assembly system have been identified: adaptable material supply, versatile workforce, increased commonality, standardised work content, integrated product properties and strategic planning. Furthermore, three requirements of a flexible assembly system for product design are defined, which, if fulfilled, reduce the complexity created by product variety and consequently support flexibility in the assembly system. Accordingly, to increase the understanding of the concept of flexibility in an assembly system and its requirements for product design, a four-staged framework is suggested. The proposed framework deals with the activities related to the concept and the development of a flexible assembly system and is expected to be received by assembly practitioners as a link between assembly and product design teams in the product realisation process. Future research can further validate the framework in practice.

Growing customer demands for product variety, new and rapid technological developments, and the short life cycle of products characterise the current volatile market. To maintain a competitive edge in the market, manufacturing companies need to accommodate flexibility in their assembly systems that are essential parts of the manufacturing systems with respect to cost, time, and creating product variety. Given the importance of establishing flexible assembly systems, the complexity raised by increasing product variety and the value of appropriate product designs to assembly systems highlight the pivotal role of product design in a flexible assembly system. Despite its significance to theory and practice, however, the characteristics of flexibility in an assembly system and its links to product design are still ambiguous and unexplored.

The objective of this thesis is to expand the current knowledge of flexibility in assembly systems and using product design to support its achievement. To accomplish the objective and by adopting an interactive research approach, five case studies were conducted in the heavy machinery manufacturing industry. A literature review underpins all the case studies comprising one multiple and four single case studies.

Through its findings, this research defines flexibility in an assembly system, identifies its dimensions, and pinpoints its enablers. Additionally, three requirements of a flexible assembly system for product design are identified: a common assembly sequence, similar assembly interfaces, and common parts. These requirements, if fulfilled in product design across distinct product families, reduce the perceived complexity and support various flexibility dimensions in the assembly system. Moreover, the development of a common assembly sequence and similar assembly interfaces, as the two key requirements of a flexible assembly system for product design, is described.

Further, based upon developing understanding and knowledge about a flexible assembly system and its requirements for product design, a model and a framework are proposed. The model addresses the role of product design in achieving flexibility in an assembly system. To support the alignment of product design with the key requirements of a flexible assembly system during the product design process, the assembly-oriented framework details the development of these requirements. Through its outcomes, this thesis contributes to the research area of flexible assembly systems and sheds light on its interface with the engineering design field. Moreover, the proposed model and framework aim to assist assembly practitioners and product designers in establishing a flexible assembly system and aligning product design with its key requirements.