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Integrating Lean in a process has become increasingly popular over the last decades. Lean as a concept has spread through industry into other sectors such as service, healthcare, and administration. The overwhelming experience from this spread is that Lean is difficult to integrate successfully. It takes a long time and requires large resources in the integration,

as it permeates all aspects of a process. Lean is a system depending on both tools and methods as well as human effort and behavior. There is therefore a need to understand the integration process itself. As many companies have worked with the integration of Lean, there should be a great deal of accumulated knowledge.

The overall intent of this research is therefore to examine how a current state of a Lean integration can be established, that takes into account the dualism of Lean regarding the technical components of Lean, as well as the humanistic components of Lean. Both issues must be addressed if the integration process of Lean is to be efficient. 

Through a literature review, eight views of Lean are established. Taking into consideration historical, foundational, and evolutionary tools and methods, systems, philosophical, cultural, and management views, a comprehensive model of Lean at a group level in a process is proposed. Through two multiple-case studies, the experiences of actual Lean integrations are compared with Lean theory to establish a current state of a Lean integration. There were large similarities in the experiences but also differences due to context and the complexity of Lean as a system. The current state is described in:

• 9 instances of strongly positive findings. They are often simple tools and methods.
• 11 instances of weakly positive findings. They are often of a system nature in the dependencies between the Lean methods.
• 3 instances with vague findings. Seems to be due to lack of focus on the intent of integrating Lean.
• 3 instances of mixed findings. Can often be connected to personal commitment and the creation of efficient islands.
• 3 instances of conflicting findings. Seem to be connected to contextual factors.
• 3 instances of insufficient data. The indications are too few to draw any conclusions. 

Accurately establishing the current state of the Lean integration process is seen as a necessary first step of a Lean integration of Lean.

Flexible assembly systems have emerged in response to changing markets and increased variety in form of demands of new products and manufacturer’s need for differentiation. Assembly systems play a critical role in handling great variety and adapting to dynamic changes at the same time as securing product quality and productivity. Therefore, assembly systems should be designed to be able to handle changes. However, the design of flexible assembly systems is a challenge because it involves several subjects such as the configuration of the flow, the material handling and the flexibility to handle future changes and adjustment. In addition, time-to-market and time-to-volume are important which means that faster assembly systems designs are required.

The design process of assembly systems concerns the procedures that guide the design work to achieve an assembly system proposal. The design process is divided into a number of stages/phases describing the activities that should be done and when they should be performed as well as the expected result after each phase supporting the decision-making process. Research argues that working in a systematic and structured way is important in order to achieve better assembly systems in shorter time.

However, even though there is extensive research work in regard to flexibility, knowledge is limited concerning the design process of assembly systems. Therefore, the objective of this thesis has been to increase the knowledge about the design of flexible assembly systems by investigating the relation between the assembly system design process and flexibility. The characteristics of flexible assembly systems and how flexibility is considered during the design process have also been studied in this thesis.

Literature reviews were conducted as well as three case studies and one exploratory survey in the manufacturing industry of heavy vehicles. Study I concerns the results of having studied an industrial international project of the design process of a flexible assembly system during two years. In study II, flexibility needs, enablers and challenges in assembly systems were identified. In study III, the mechanism used to achieve flexibility in the assembly systems of two companies were investigated. The exploratory survey study IV, was a pilot study to investigate the relationship between the design process of assembly systems and flexibility based on the association of different variables involved in the design process of flexible assembly systems.

From the holistic perspective adopted in this thesis, the results showed that flexibility should be considered in a comprehensive way during all the design process. The design process of flexible assembly systems is iterative, circumscribed by different conditions, and requires support as well as the participation of different roles and functions to achieve a solution. The increased knowledge generated in the research is expected to lead to future development of working procedures that better can support the design process of flexible assembly systems.

Designing is becoming increasingly complex. Manufacturers strive achieving flexible assembly systems that can easily accommodate diverse product offerings while transitioning towards new (radical) products, integrating new manufacturing technologies and providing specific customer solutions. However, designing flexibility is a challenge. There are several flexibility dimensions and perspectives as well as a need for design support to achieve it in a long term.

 A design process concerns the way of working (how) to generate an assembly system solution before its realisation. Thus, it is crucial to establish preconditions for the development of assembly systems. A single design process does not fit all the design problems, so already during the design process, changes in assembly systems by means of flexibility should be further investigated. The purpose of the research is to increase knowledge on how to achieve flexible assembly systems through design processes with the objective to contribute to the development of working procedures to support design processes of flexible assembly systems.

 Factors involved in the design process of flexible assembly systems and their influence in the design process to achieve flexible assembly systems have been studied based on literature reviews and five case studies conducted in the manufacturing industry of heavy vehicles. The thesis is based on six appended papers.

 A framework has been developed which integrates the findings of the research. It highlights the need of working in early phases of technology development to address timely changes and adaptations in both products and assembly systems designs. Thus, showing the importance of involving different processes as well as roles and functions within an organisation. Furthermore, it shed lights on activities that could facilitate the design process of flexible assembly systems in a long term. These working procedures are meant to support those involved in the design process of flexible assembly systems.