The Stereolithography (SL) process has developed into an accurate method of replicating 3D CAD images into tactile objects used for functions such as product evaluation, preproduction testing or as patterns around which tool cavities can be formed. One of the main limitations with the SL process is the surface roughness of parts resulting from the layer manufacturing process. To-date surface roughness has only been reduced using techniques such as additive coating or abrasive finishing. Research has shown however, that these techniques are both detrimental to the accuracy of parts and can prove to increase the cost of SL parts to the end user. The object of this research is to assess the fundamental cause of surface roughness in layer manufacturing and develop techniques that can be used during the build process to produce SL parts with lower surface deviation. To do this a comparison of the most common commercial RP systems was undertaken to identify the attributes causing surface deviation. From these attributes a mathematical model of layer manufactured surface roughness was developed. Parts manufactured using different SL machines were compared to the mathematical model showing a variety of causes in surface deviation not considered in earlier research, such as layer composition, layer profile and the affects of over curing or print-through on surface deviation. The layer edge profile caused by the shape of the scanning laser also has a significant effect on roughness deviation. However, by using a combination of part orientation and optimal shaped meniscus smoothing, the surface deviation of SL parts was found to be reduced by up to 400% on at least 90- degrees of continuous surfaces. A better understanding of layer manufactured surface roughness has now been achieved and a new smooth build algorithm has been developed.

The potential advantages of Cellular Manufacturing Systems (CMS) are very well known in industry. However it is also shown that their performance is very sensitive to changing production requirements. The detrimental effects of changing production requirements on the performance of CMS can be alleviated by "implementing better manufacturing cell designs", "employing effective part loading strategies" and "reconfiguration". This thesis proposes a decision support framework that provides solution strategies for manufacturing cell design, cell loading and reconfiguration problems. There are three main modules in the proposed framework, named as cell formation, loading and reconfiguration. Each module can handle multiple objectives and integrates several planning and design functions, by considering the capabilities of manufacturing resources. Reconfiguration decisions are made explicitly in the proposed framework by answering the questions "when to reconfigure?" and "how to reconfigure?”. In order to answer these questions, the modules of the proposed framework are interconnected. The cell formation module creates the initial set of cells. The loading module makes the 'part to cell assignment' and the scheduling in each production period. The reconfiguration module regenerates manufacturing cells, if the loading module can not find a satisfactory solution. The cell formation module solves the part-machine cell formation problem by simultaneously considering multiple objectives and constraints. Overlapping machine capabilities and generic part process plans are taken into account in the model formulation. A new approach for the evaluation of machine capacities is also presented. Results of the comparative study show that the proposed cell formation method gives better results than several other cell-formation procedures. The manufacturing cells are formed with improved capacity utilisation levels and reduced extra machine requirements. The method is also more likely to produce independent manufacturing cells with higher flexibility. The loading module solves the 'part to cell assignment' and 'cell scheduling' problems simultaneously for cellular manufacturing applications. Alternative parts to cell and machine assignments are considered by making use of generic part process plans in the model formulation. A parametric simulation model is developed to determine cell schedules for a given part assignment scenario. The proposed loading system can assess performance of the CMS in each production period. Therefore a decision can be made about its reconfiguration. It is also shown that the efficiency of CMSs facing changing production requirements can be improved and/or sustained by using the proposed loading strategy. The reconfiguration module takes the existing cell configuration as the current solution and generates a new solution from it, to enhance its performance. The model is objective driven and considers multiple objectives and constraints within a goal programming framework. The virtual cell concept is applied as the reconfiguration strategy. In the virtual cell approach the physical locations of machines are not changed, only cell memberships of machines are updated after reconfiguration. The results of the test studies showed that it is possible to improve the performance of CMS by reconfiguring it using virtual cells. The cell formation, loading and reconfiguration problems issues discussed in this thesis are combinatorially complex multiple objective optimisation problems. Additionally simulation is used to evaluate several of the objective functions used in the modelling of loading and reconfiguration problems. Classical optimisation algorithms have various limitations in solving such problems. Therefore Tabu Search (TS) based multiple objective optimisation algorithms are developed. The proposed TS algorithms are general-purpose and can also be used to solve other multiple objective optimisation problems. The results obtained from several test problems show the proposed TS algorithms to be very effective in solving multiple objective optimisation problems. More than 500/0 improvement in solution quality is obtained in some test problems.

In today's business environment, firms increasingly think in the context of a supply chain rather than a single factory and operate globally rather than in a single nation. At the same time, we have also witnessed increasing breadth in product ranges and accelerating rates of new product introduction in the marketplace. While there are potentially strong interrelationships between product variety and international supply chain management, the issues have been addressed separately in the research literature. Owing to this shortfall, this study investigates the issue of product variety in the context of international supply networks. More specifically, the study seeks to gain insights on different types of co-ordination and configuration of international supply network and to more deeply understand the impact of, and the interrelationships between, product variety, supply lead-time and demand uncertainty on the performance of an international supply chain. Empirical and simulation studies have been conducted to fulfil the above objectives. The empirical study involves eleven manufacturing companies in Indonesia, belonging to both Multinational Corporations (MNC) and contract manufacturers, and one company in the UK operating internationally that owns manufacturing units as well as contracting out. The empirical study generated findings on configuration structures, co-ordination policies, and product variety impact and management. Based on their configuration and coordination strategies, MNC supply networks involved in the empirical study can be classified as supply networks that have regional autonomous subsidiaries, regional clusters of subsidiaries and purely global supply network. Contract manufacturers' configurations may change from one selling period to another. More co-ordination efforts are found to be necessary in MNC supply networks compared to contract manufacturer supply networks. Although companies face different challenges with respect to product variety and uncertainties in demand and supply, the evidence shows that product variety principally affects the procurement of materials, as various products require different materials and parts. Product variety also affects production due to the need to conduct set-up activities. To obtain a deeper understanding of the impacts of product variety, supply lead time and demand uncertainty on supply chain performance, a simulation study has been conducted. A simulation model was developed based on the insights obtained from the empirical study. The model represents a three-stage MNC supply network producing consumer goods in discrete manufacturing processes. Product variety is represented in the model by the use of different types of material required at different stages of the production process. An extensive set of simulation experiments concentrated on flow time and inventory performance. Results from the simulation experiments show that increases in product variety extend the average flow time due to the need to conduct set-up activities. The impact of product variety on flow time depends on the severity of set-up and the stage at which variety occurs in the production processes. Variety occurring early in the production process and generating long set-up times has a more pernicious impact on average flow time compared to variety occurring later and requiring shorter set-ups. Supply and demand uncertainty may affect the supply chain performance as it may delay the manufacturing processes. When supply lead-time is subject to uncertainty, materials may not be available at the right time for production. Similarly, demand uncertainty may lead to a situation where the available materials may not be adequate to meet the production requirements. The simulation results show that producing high variety when material delivery time is subject to uncertainty has a damaging impact on the two supply chain performance metrics - flow time and inventory level. The supply chain performance worsens with increasing level of supply uncertainty. Producing high variety when either aggregate-level or product-level demand is subject to uncertainty results in a higher level of inventory and longer average flow time. The worst performance in terms of average flow time and average inventory is evident when the supply chain produces maximum variety and both supply and demand are subject to uncertainty. The simulation study provides a guide to the magnitude of the impact in each case. Findings from the empirical and simulation study are synthesised into a framework for understanding and managing product variety in international supply chains. The framework can be used to understand interrelationships between key factors in managing product variety in international supply networks and to identify potential strategies to mitigate the negative impact of those factors on performance.

An experimental study has been made of the behaviour of "very thin" torispherical ends subjected to internal pressure. The seventeen ends tested were full-size production ends made from stainless steel, with thickness to diameter ratios (te/Di) varying from 0.002 to 0.001. At each value of te/Di the knuckle radius (ri) and crown radius (Ri) were varied to cover the range of ends frequently used. Each end was stain gauged on both inner and outer surfaces and then pressurised until buckling occurred in the knuckle region. The strain gauges were monitored throughout each test thus giving a detailed coverage of the strain distribution. High compressive hoop strains, shown to exist on both surfaces of the knuckle, are responsible for the buckling mode of failure. A shape/thickness survey was performed on each end prior to pressure testing. The effects of thickness reductions and deviations of curvature from the nominal are discussed. Residual strain measurements were made on three ends and were shown to be significantly large in the pressed and spun manufactured ends. A study of the effect of work hardening on the properties of the material from which the ends were made is also presented. It is shown that the proof stress and Vickers hardness number increases rapidly when the material is work hardened. The dependence of the elastic stress indices, limit pressures and first buckling pressures on wall thickness, knuckle radius and crown radius has been examined. The design implications of the study are discussed and a method for predicting the first buckling pressure of production ends given.

Effectively managing and measuring the product development process is widely seen as a means of ensuring business survival through reduced time to market, increased quality and reduced costs. This thesis explores the research question of "How do companies know that they are making effective use of their product design and development function?". A review of the literature in this area revealed that there is a distinct lack of detail available on how measurement of product development should be approached. Where articles do exist, it was found that most report on isolated projects or jump from problem solving straight through to results, without explaining the methodology used. Additionally, both in the literature and in practice, many applications of performance measures to date have been incomplete - without due consideration being given to monitoring and controlling the whole design and development process. For example one tool or technique has been introduced in isolation or schemes have been introduced without evidence of the benefits gained. This thesis documents the development of an implementation framework and a tool (usable in the form of a workbook) to enable a Project Manager, Concurrent Engineering or Process Improvement Champion to use performance measures to improve decision-making during the product development process. The investigative part of the research was carried out by following a longitudinal case study approach with sustained participation in the organisation. This was supplemented by a series of follow-up cases, together with results from surveys to academics and industrialists both in the UK and overseas. Through interpreting the literature and triangulating the results from the data collection and analysis, a number of principles surrounding performance measurement in this area were identified. These were then grouped into system-related and metrics-related principles. Opinions of European managers were gained throughout to ensure direct applicability. The resulting Performance Measurement for Product Development (PMPD) Methodology, consisting of an implementation framework and accompanying practical paper-based workbook (with software extensions), was tested in two companies to determine its usability. These testbeds yielded encouraging results and provided opportunities for further refinement and improvement. The next step will be further testing and refinement in a wider range of applications. It is believed that the research outputs of the international survey results, generic PMPD Implementation Framework, Workbook and Training Guidelines have together made a positive contribution to understanding and measuring the product development process in manufacturing organisations.

A dented pipe fails either through being punctured or by fatigue damage accumulation due to internal pressure fluctuation. Increasing the wall thickness may prevent these failures but is impractical. As a pipe is punctured, transmission services must be cut off and repair processes have to be made immediately. However, when a dent depth is not large enough to puncture the pipe, the pipe can safely continue in service for a long time until a fatigue crack initiation occurs. Therefore, the fatigue life assessment has attracted much attention in the pipe industries for economic and safety reasons. The severe tensile residual stress concentration and the large plastic strain deformation in the dented region are the main causes of the pipe failure due to fatigue damage. Accurate calculation and prediction of the residual stress and variations resulting from internal pressure fluctuation can lead to safety assessments and prediction of the remaining life of the dented pipe. Due to the complex nature of the contact process, the deformed pipe geometry and the elastic-plasticity, analytical approaches are incapable of obtaining stress solutions. Therefore, FE modelling is employed in the present work. Experimental tests are employed to investigate the indenter force-dent depth behaviour which can be compared with the FE solutions to confirm and validate the FE models. The rigid perfect elastic-plastic limit load method and an energy-based method are also used to analytically calculate the limit load and the indenter force/deflection relationship of indented rings to predict damage. Two dimensional FE modelling is performed to calculate the contact and residual stress and strain distributions on the outer, inner surfaces and through the wall thickness. These FE solutions show that high stress concentrations occur in the indented region, which give the potential for fatigue damage. As the 2D FE modelling requires only limited resources, the indenter size and indentation position can be changed to analyse their effects on stress and strain distributions in the indented region. This forms the foundation of later 3D FE modelling. Stress sensitivity and the validation of shell models are investigated and confirmed through the 2D and 3D FE modelling and by comparing experimental test data with the FE solutions. Based on this work, the decision is made to use shell element modelling to perform the residual stress and stress range calculations in a 3D pipe. Semi-empirical formulations are developed to predict stress and stress range values if the residual dent depth, the pipe and indenter geometries, material property, internal pressure and pressure range are known. These FE solutions and semi-empirical formulae can be used to calculate the stress range and mean stress.

The difficulties that faced many manufacturing firms were attributed by Skinner (1969) to the inadequate attention given by top managers to the manufacturing function. He proposed a holistic framework of manufacturing strategy development that link manufacturing with corporate strategy. This work of Skinner is the first of three stages in the progression of thinking with respect to the strategic role of manufacturing as pointed out by Hum and Leow (1993). The other two stages being the demand of manufacturing to support and be consistent with corporate strategy (Wheelwright, 1978), and the present thinking that manufacturing can lead other functional areas in its contribution to the development of corporate strategy. This research is concerned with the current understanding of the strategic role of manufacturing which was provided by Wheelwright and Hayes (1985). They suggested that even though strategic manufacturing effectiveness is developed along a continuum, there are four identifiable stages that can indicate a firm's position. Furthermore, they suggested that strategic manufacturing effectiveness can be operationalised through the emphasis that firms place on manufacturing choices and decisions; there are factors that affect strategic manufacturing effectiveness; and the higher the level of strategic manufacturing effectiveness, the better the firm's performance. With respect to the factors affecting manufacturing effectiveness, Wheelwright and Hayes (1985) perceived five such dimensions. They are the attitude of top managers towards manufacturing, the involvement of manufacturing managers in setting the strategic direction of the firm, the emphasis on formulating manufacturing strategy, manufacturing proactiveness, and the co-ordination between manufacturing and other functions. The framework of Wheelwright and Hayes (1985) is a diagnostic tool that is used to appraise manufacturing's role within a firm. However, the relationships among its constituents have not been examined in detail before. This research develops a model that clearly identifies such dimensions and how they influence manufacturing effectiveness. Also, the notion that there are four identifiable stages is investigated. Moreover, mediating effects of the types of industry, the sizes of firms, and the types of production process on manufacturing effectiveness are also examined. The results from hypotheses testing indicated the significance of the attitude of top managers towards manufacturing and the involvement of manufacturing managers in setting the strategic direction of the firm as being the key factors that influence the process of acquiring strategic manufacturing effectiveness.

Automated assembly technology may be the key to sustaining manufacturing industry in more developed countries. Currently this comprises dedicated systems that can assemble single products at high volumes and flexible systems to assemble a wide variety of products in low volumes. However, competitive forces demand a compromise between the two and Reconfigurable Assembly Systems are an avenue for achieving high volume and high variety production. Although this technology is coming to the fore, there is a distinct lack of tools and methods that make the prospect attractive to key decision makers in organisations. Reconfigurable solutions, which may be profitable in the long term, are rejected in favour of short term solutions, which prove to be more expensive over time. The benefits of requirements engineering have been exploited in software engineering and this work demonstrates how these can be adapted to an assembly environment to form a new basis for communication between the system vendors, who supply assembly system solutions, and system users, who use them. Knowledge Engineering has become a key aspect in industry due to the challenges of retaining personnel and their knowledge within organisations. This is because employees take their knowledge of the organisation with them when they leave. The retention of this knowledge would help to maintain the continuity within organisations. This thesis reports on research that aims to provide a means to integrate these three aspects to form a basis for sustaining competitive manufacture in more developed countries. Moreover, Knowledge Based Requirements Specification for Reconfigurable Assembly Systems will provide a vital medium for promoting Reconfigurable Assembly Systems and encourage their implementation by providing a knowledge-based platform for the specification of Reconfigurable Assembly Systems.

Rapid prototyping (RP) provides a means of producing physical models directly from computer aided design (CAD) data. The aim of this research was to determine the most effective method of integrating RP into the design process. A review of the links between design and RP was undertaken. This revealed that RP is a technology which can benefit several key areas of engineering design. Many computer tools were identified which supported the designer's use of RP but most of these relied on using CAD geometry alone. Using this incomplete set of design information hindered the integration of RP into the design process. A hypothesis was formulated which stated that a feature-based product modelling methodology was needed to enable RP to become an integrated part of the design process. To demonstrate the validity of the methodology, it was embodied in a design support system (DSS) for rapid prototyping. The DSS requirements were determined through a survey of designers using RP, and a full specification for the system was defined. A demonstration version was implemented using a relational database coupled with a CAD system. The demonstration DSS enabled feature-based geometry and non-geometric information to be integrated within a single product model. An application program was developed which used the product model data to optimise the orientation of an RP model in order to meet the differing surface finish requirements for each feature in a component. This example use of the system illustrated the benefit of using a feature-based product model to optimise the designer's use of RP. Future work needed to improve the DSS to a state where it would be ready for development into a commercial package was identified. Finally, conclusions were drawn as to how all the objectives were met and summarising the original contribution to knowledge made by the research.

Several techniques are applicable to the modelling of production and inventory control systems. In this thesis discrete linear control theory is examined as a method of modelling multi-product, multi-level systems. These systems are categorised and a general discrete linear control model is used to determine system stability and to predict system responses to specific patterns of input information. The response of the system to random variability in input or other system variable is also shown to be predictable. A library of sub-system models is provided and the method is illustrated by examples and a case study. Alternative modelling techniques rely upon sequential simulation, either directly or in solving equations representing the system. The need to include forecasting, inventory and production decision-making procedures makes such models large and their sequential nature imposes the need for complete remodelling for each system modification and for each input pattern. Where random effects are modelled, protracted runs are necessary to achieve statistically acceptable results. In contrast, discrete linear control theory provides a nonsequential model, thereby alleviating these problems. Thus it is possible both to reduce computing expense and increase the range of systems susceptible to manual analysis. The method is limited by the restriction of linearity, but, in many practical situations this restriction poses no insuperable difficulty in the interpretation of results.