Carl Wänström

Impact of materials exposure on assembly workstation performance

This paper examines how the choice of materials exposure impacts workstation performance, in terms of non-value-adding work, space requirements and ergonomics. In a typical Swedish automotive setting, components are exposed in wooden pallets with frames beside the assembly line and supplied by forklift truck. In a case study, three workstations on an assembly line were studied and redesigned following the principles of lean production, using smaller plastic containers for the materials exposure. After the redesign, the space required for materials was reduced by 67%, non-value-adding work decreased by 20%, and walking distance was reduced by 52%. Furthermore, the ergonomics for the assembly operator improved greatly, with a 92% reduction of potentially harmful picking activities, thereby almost eliminating potentially harmful body movements. The theoretical contribution of this paper is firstly the development of an analysis model describing the impact of material exposure on workstation performance and secondly development of the existing categorisation of work operations to include different materials handling activities. The most important managerial implication is an increased understanding of the relationship between space, ergonomics, non-value-adding work and materials exposure. These findings have direct implications on workstation design in industry.

The impact of materials feeding design on assembly process performance

Purpose - The purpose of this paper is to provide an understanding of how the materials feeding design at a workstation impacts the assembly process performance, in terms of manufacturing flexibility, process support, materials planning and work task efficiency. Design/methodology/approach The empirical data are based on two embedded case studies performed in close corporation with two Swedish automotive companies; additional observations from more than 20 company visits in Japan, and small-scale case studies performed in Japanese companies. To fully assess the work measurement figures, video recordings, work instructions and layout drawings were used to plot the operatorswalking patterns, and it was then possible to map the whole work cycle for an operator. Industrial engineers, anagers, group leaders, team leaders and operators were interviewed. Based on the literature review and personal experience from the small-scale case studies carried out in Japan, the existing assembly systemscomponent racks were conceptually re-designed. This led to two hypothetical assembly systems, which could be used for understanding the impact of materials feeding design on assembly process performance. The design of the new component racks and the choice of packaging types were made together with practitioners. Findings The paper shows that the design of component racks and choice of packaging types have a major impact on the assembly process performance. Component racks with a large depth and small width and tailored packages create important advantages over traditional Swedish component racks designed for EUR-pallets. Line stocking is not always the best choice for materials feeding, but this paper shows that line stocking, especially in Swedish assembly systems, can be improved. Sequencing can thus be reduced, resulting in fewer problems when there are sequence breaks in the production flow. Component racks with small packages and large depth increase the work task efficiency, volume, mix, new products and modification flexibility. For example, free space is an important issue for these types of flexibilities. Component racks that are portable and easy to rearrange, together with free space, greatly facilitate handling of new product introductions or modifications of products. The new and old component can be displayed and fed to the same workstation, and if there is a larger change a whole segment of a component rack can easily be replaced by a new one between work shifts. Research limitations/implications - The scope of the study is limited to the conditions at workstations. Consequences for the materials flow upstream (i.e. internal materials handling, warehousing, transport, supplier processes, etc.) are not included, but must in further studies also be considered to avoid sub-optimisation. Originality/value - The paper highlights the fact that a shift in focus is necessary when designing workstations with component racks in Swedish companies, meaning that operators become the customers rather than the transport company or materials handler.

The impact of engineering change on materials planning

Purpose – The purpose of this paper is to increase the understanding of the impact of engineering changes on the materials planning process. Design/methodology/approach – This study is based on a conceptual discussion and empirical data from a case study of a supply chain in the automotive industry, including end producers (two OEM companies) and first, second and third tier suppliers. Findings – A framework comprising the situational dimensions of the engineering change was derived from the conceptual discussion and described in terms of product, supply, manufacturing, demand and materials planning characteristics. The empirical study shows the characteristics of the engineering change in the case company and how these have both positive and negative, as well as direct and indirect, influences on the materials scrap, administrative and transport/handling costs. The impact of the actual materials planning strategies is also shown. Another finding was that different engineering change situations exist within the same company. Thus, it is necessary to distinguish between them and to use different planning strategies for each situation. The paper discusses how such differentiated strategies could be developed in the case companies and in general. Research limitations/implications – The case study focused on a specific product and materials planning situation in the automotive supply chain. Other products and materials planning situations resulting from the same engineering change would have different characteristics and should, therefore, be planned and controlled accordingly. However, the developed framework is a general one. Practical implications – The appropriateness of a materials planning strategy differs between different engineering change situations. This calls for differentiated materials planning strategies based on the engineering change situation and materials planning characteristics. The framework developed in this paper describes the entire materials planning environment in engineering change situations in order to understand when and how to differentiate materials planning strategies. Originality/value – This paper fulfils a need for a framework that describes the impact on materials planning from an engineering change perspective. This framework is the first step in the designing of a normative guideline for differentiated materials planning strategies in an engineering change situation.

Factors impacting manual picking on assembly lines: An experiment in the automotive industry

Manual picking on assembly lines is an important part of the assembly operators work. In the automotive industry, alternative material exposure strategies are continually evaluated in order to facilitate the assemblers work and minimise non-value-adding time, resulting in increased use of smaller bins or containers at workstations, instead of large pallets. The assembly operators retrieval of components from bins, containers or pallets is known as manual picking. Previous work in this area has focused on picking from pallets placed on the floor; therefore, there is a need to include other forms of material exposure. The purpose of this paper is to explain what material exposure factors have an impact on manual picking times on assembly lines. A full factorial experiment, testing seven factors in 128 experiments, was conducted in an automotive assembly line setting. The factors with the greatest impact on manual picking time were packaging type; angle of exposure; height of exposure; and part size. This study contributes by addressing the importance of six factors influencing manual picking times, enhancing knowledge derived from MTM and elsewhere. The results from this study can be useful for designing manual picking operations, not just at assembly lines but also other situations where discrete manual picking occurs such as at workstations or bench assembly. Managerial contributions are evident in the examination of factors important in designing new production systems, including materials supply processes and assembly processes. A further managerial application is the use of the results in managing assembly lines.

Manufacturing and supply chain flexibility - Towards a tool to analyse production network coordination at operational level

Purpose-The purpose of this paper is to explore how the manufacturing and supply chain flexibility impact on the ability to transfer production between the units, i.e. production network coordination. To take advantage of available opportunities for different actors and locations, companies need to effectively transfer production. Design/methodology/approach-The case studied was a transfer of production between The Netherlands and Sweden. The case was selected based on the opportunity it provided to perform a longitudinal study of an ongoing production transfer. Findings-Different flexibility dimensions have different importance depending on the receiver or sender. A production transfer can be divided into four parts: knowledge, physical, administrative and supply chain transfer. The manufacturing flexibility have a high impact on the physical and knowledge transfer, the new product development dimension also have a major impact on the administrative transfer in combination with the supply chain flexibility dimension IT. The supply chain transfer was impacted by the supply chain flexibility dimensions except IT. Practical implications-The paper presents a first step towards a tool for analysing the strength and weaknesses within units in relation to receiving/sending production. Furthermore, that the production transfer should be viewed as four parts with interdependencies help to identify the order of the transfer process. Originality/value-This paper widens the flexibility concept to a network level. Furthermore, it describes the link between the strategic decision of coordination in the network and the operational ability of the network to accomplish this change.

Assuring materials availability during the production transfer process – Critical characteristics of the materials planning environment

Purpose: The MP (materials planning) environment sets the prerequisites for the MP process. Before and during PTS (production transfer and start-up) supply chain uncertainty of the MP environment increases, as the company goes from a known to an unknown situation. The purpose of this paper is to describe the impact of the MP environment on the MP process before and during PTS. Design/methodology/approach: A conceptual framework describing the MP environment before and during PTS is developed and applied to one case of outsourcing from Sweden to China. The framework is based on a literature review and further evaluated by both researchers and managers. Findings: A conceptual framework describing the dynamic MP environment before and during PTS has been developed compared to previously static MP environments descriptions. In addition, this framework proved to be useful in analysing the importance of various characteristics of the MP environment before and during PTS. Practical implications: The study highlights the importance of a proactive approach to materials availability when transferring production. The conceptual framework developed here can be used as a checklist to identify the characteristics of the MP environment that are most important to ensuring materials availability. Originality/value: The paper highlights the PTS when outsourcing, a substantial time frame with a large impact on success. This is an important contribution, given the focus of previous outsourcing research on strategic issues. Further, the paper demonstrates the differences between static and dynamic MP environments.

A structured procedure for materials planning during production transfer

This paper explores materials planning procedures to ensure the materials’ availability during production transfers. The paper defines a production transfer as the preparation, physical transfer and start-up of relocated production. A structured procedure of materials planning during production transfer is developed based on theory, and then validated and refined based on the analysis of four case studies. The paper shows that there is a need for a structured procedure of materials planning during production transfers. It also explains the importance of activities that create prerequisites for the materials’ availability during production transfer, such as updating and adapting documentation, planning and control systems, and describes the activities that ensure the materials’ availability, such as preventive and corrective actions. A valid estimation of the time needed to reach a steady state and a combination of several preventive actions improves the ability to ensure that materials are available. The cases showed differences across company size, because large companies took more and farther-reaching preventive actions.

Creating a model to facilitate the allocation of materials planning resources in engineering change situations

Shortened product development times and more frequent product changes combined with product quality and timeliness of delivery are prerequisites of competitiveness. These have increased the workload and underscored the importance of effectively managing the materials planning process in engineering change situations. The purpose of this paper is to develop a procedure for creating a model to differentiate between items in order to facilitate the allocation of materials planning resources in change situations. It develops a procedure in the framework of the study and verifies it using the case study technique. Furthermore, the case study shows that there are many different engineering change situations that occur in the materials planning process. Many engineering change variables and materials planning variables have a major impact on the material scrap costs and material shortage costs, but only a few generate the different types of engineering change situations for the materials planning process. The case study shows that material scrap costs and material shortage costs decrease after the introduction of a tool to differentiate between items to facilitate the allocation of materials planning resources.