Electroplated zinc alloys can provide increased corrosion protection for automotive body panels compared with zinc coatings of similar thickness. As a result, their use is becoming widespread. In particular, outstanding results have been reported in the literature for the corrosion resistance of zinc-manganese, and the alloys are said to offer good paintability, weldability and formability. However, the production of zinc-manganese coatings is restricted by the instability of the sulphate-citrate bath from which the alloy is usually deposited. The solution deteriorates rapidly and precipitates appear in the bath. The aim of this research was to investigate both the process of alloy deposition from the sulphate-citrate bath and the solution instability. The electrodeposition of zinc-manganese was assessed in terms of the polarisation behaviour of the system, in order to determine the role of the bath components and the operating parameters in the deposition process. The coatings were analysed using scanning electron microscopy, and the efficiency of metal deposition was established. The sodium citrate complexant was not found to significantly move the deposition potentials of zinc and manganese together. Instead, its action as a buffer can be used to explain metal deposition and the polarisation behaviour of the system. The sodium citrate suppresses the hydrogen evolution reaction, such that manganese can be deposited from the electrolyte. The bath deterioration with time and the resulting precipitate were examined using a variety of chemical techniques including spectroscopic methods, namely ultraviolet and visible, atomic absorption and infrared. Bath discolouration and precipitation were found to be two separate phenomena. The precipitate was determined to be a citrate of known composition with a ratio of Mn2+ ions to Zn2+ ions of 2:1. The formation took several days, and it was precipitated once the solubility limit in the bath was exceeded. Solution discolouration resulted from reactions occurring after the oxidation of Mn2+ ions and could be delayed by the use of antioxidants.

Next generation manufacturing companies have to become highly responsive in order to succeed in an ever more rapidly changing global market. The ability to effectively develop and adapt their assembly facilities (systems) to changing requirements on demand plays a crucial role in achieving high responsiveness since the assembly process has to deal with the full inherent complexity of increasingly mass-customised products. This work was motivated by the current lack of a holistic assembly system design theory that would enable design environments to address the need for rapid system development and adaptation. The challenge is to create a common environment where domain experts can effectively collaborate while taking advantage of the best practices of their diverse domains. This thesis investigates how a domain ontology can help to overcome those challenges. The approach is taking advantage of the higher levels of standardisation inherent in the modular assembly system paradigm which is considered to be one of the fundamental enabling factors to achieve a high level of adaptation. A new ontology framework has been developed to support the design and adaptation of modular assembly systems (ONTOMAS). The ONTOMAS framework is based on engineering ontology principles structuring the domain using formalisms for aggregation, topology, taxonomies, and system theory principles. A number of design patterns have been identified and formalised to support key design decision-making tasks during the design of modular assembly systems. Furthermore, the function-behaviour-structure paradigm has been applied to capture the characteristics of modular assembly equipment at different levels of abstraction that reflect the specific needs of the engineering design process. The proposed ONTOMAS framework provides a sound foundation for computer based support tools to reduce the assembly system design effort and time while maintaining a high level of quality. An integrated design framework for the requirements driven specification of assembly processes and configuration of modular assembly system has been developed. The design approach applies the new formalisms of ONTOMAS to support the design decision-making activities. The developed ONTOMAS framework has been applied in several industrial and synthetic use cases to verify its applicability and appropriateness. Furthermore, the new ontology and design framework have been used as foundation for the development of a prototype collaborative design environment which allows different domain experts to participate in the design of modular assembly systems.

This thesis presents two computer packages to simulate the rotary forging process, by means of a mathematical model. The results are displayed in a graphical and numerical manner, showing the tool movement and the tool / workpiece interaction. The first package, PATH, is shown to be capable of simulating the motions of all known rotary forging systems. Its results show the rotary forging tool path throughout a chosen process. The motions of any rotary forging system can be programed by a simple set of instructions displayed on the screen, and the results displayed quickly and graphically. The widely used motions of rocking - die rotary forging machines were investigated. From these investigations, formulae were put forward, which were shown to be capable of predicting the tool motion of any rocking - die rotary forging situation. The second package, PROFS, presents a meshed representation of the tools and workpieces used in rotary forging systems. The rotary forging tool is represented as a conic wire frame mesh, on which no forces or loads are considered to act. The workpiece is represented as a cylinder constructed from a number of hexahedral elements. The elements are treated in either a non - constant volume or a constant volume manner. The non - constant volume model workpiece is one which is simply cut away by the action of the tool on it. This model is similar to a process of 'rotary cutting'. Using the model, a technique of investigation into the progression of the contact geometries created during a real rotary forging, was developed. It enabled the progression and size of the contact geometry to be followed from start to finish of the forging cycle. No consideration of the loads or forces occurring during the process was taken into account. The constant model workpiece requires that its volume remains fixed during the simulation. This is achieved by a radial expansion of the elements of the workpiece as it is being 'deformed' by the tool. Again no consideration of the loads or forces occurring in rotary forging was taken into account. Investigations, using the model, enabled the instantaneous contact geometries, contact areas, and displaced volumes of material to be predicted during two real rotary forging processes. Results revealed the potential of PROFS, to determine areas of workpiece instability in the early stages of forging, and reveal ares of insufficient die fill. The potential of data from the simulations, to control a rotary forging machine, is discussed, and is seen as the first step towards the design and manufacture of rotary forging parts and dies by a C.A.D. - C.A.M. route. Contact areas produced during the rotary forging process are essential for any calculations of the forces and stresses occurring in the die and workpiece. The possibility of PROFS to be used as a die / design tool and in pre production trials for new parts is discussed. A physical simulation of a non - constant volume model workpiece was carried out using a 'short lead milling' technique to cut away a solid workpiece. This revealed the instantaneous contact geometries and areas of the workpiece, which were shown to be accurately predicted by PROFS using the non - constant volume. The results confirmed the accuracy and validity of the simulated instantaneous geometries, allowing a large degree of confidence to be assumed in the accuracy of the package. A data base of radial, circumferential, and custom die profiles has been built up and incorporated into PROFS. From the data base a chosen profile can be used to generate a conic meshed representation of a rotary forging die. Investigations, using a die generated from a custom profile, revealed areas of possible workpiece instability. The two packages put forward in this thesis have been shown to be capable of simulating the motions and contact geometries of the rotary forging process, and confirmed using physical and real rotary forging comparisons.

The study reported on in this thesis was an empirical investigation into the implementation and use of, Statistical Process Control (SPC) techniques and tools in a product development environment. The data used originated from four different business units in the European flavour division of a large International company, belonging to the Flavour and Fragrance industry. The study highlights many of the problems related to the use of real data, and working with individuals throughout an organisation. The data distributions were positively skewed, and a comparison of the effectiveness of various methods for calculating the position of both the center line and the process control limits, on individual measurements control charts was made. The author was able to show empirically that SPC is a useful project management tool. Additionally, the author demonstrated that the use of either the median or trimmed mean approaches, were more effective in use when dealing with these types of skewed data distributions. Additionally, it was possible to define the relationship between the numbers of outside out-of-control signals and the numbers of run out-of-control signals. The study also provided some interesting insights into possible barriers to the transfer of the techniques, from the manufacturing floor into more traditional management areas. It also highlighted some areas for improvement in the product development laboratories of the company and potentially the industry.

Discrete event simulation is now a well established modelling and experimental technique for the analysis of manufacturing systems. Since it was first employed as a technique, much of the research and commercial developments in the field have been concerned with improving the considerable task of model specification in order to improve productivity and reduce the level of modelling and programming expertise required. The main areas of research have been the development of modelling structures to bring modularity in program development, incorporating such structures in simulation software systems which would alleviate some of the programming burden, and the use of automatic programming systems to develop interfaces that would raise the model specification to a higher level of abstraction. A more recent development in the field has been the advent of a new generation of software, often referred to as manufacturing simulators, which have incorporated extensive manufacturing system domain knowledge in the model specification interface. Many manufacturing simulators are now commercially available, but their development has not been based on any common standard. This is evident in the differences that exist between their interfaces, internal data representation methods and modelling capabilities. The lack of a standard makes it impossible to reuse any part of a model when a user finds it necessary to move from one simulator to another. In such cases, not only a new modelling language has to be learnt but also the complete model has to be developed again requiring considerable time and effort. The motivation for the research was the need for the development of a standard that is necessary to improve reusability of models and is the first step towards interchangability of such models. A standard framework for manufacturing simulators has been developed. It consists of a data model that is independent of any simulator, and a translation module for converting model specification data into the internal data representation of manufacturing simulators; the translators are application specific, but the methodology is common and illustrated for three popular simulators. The data model provides for a minimum common model data specification which is based on an extensive analysis of existing simulators. It uses dialogues for interface and the frame knowledge representation method for modular storage of data. The translation methodology uses production rules for data mapping.

Recent computer developments have allowed a new dimension to the scientific inventory control. An example is the multi-item inventory model described in Johnston (1980) which represents the departure from the traditional optimization towards decision aid models which the manager can use interactively in the examination of the trade-offs which could improve his current policy. The Johnston model has however limitations. The scope of this thesis is to overcome some of these limitations, namely, the treatment of the non-captive demand, the determination of the reorder frequency and the extension to a two level inventory system, together with a critical examination of the variables involved, in order to improve the decision making. In relation to non-captive demand, the problem can become relevant when more than one order overlaps. Then, service levels and average stocks are normally higher than the predictions from formulas derived for captive demand. The main result now achieved is the introduction of the notional control level which relates to the conventional reorder or top up levels and to the lost demand. The notional level allows the extension of established formulations, including the Johnston model, from non-captive to captive demand. Johnston leaves the reorder frequency to be decided on a practical basis. Here, the same criteria adopted by Johnston have been used to derive consistent expressions for the number of orders. Empirical functions have been incorporated to reach formulas ready for use. The two level system comprises one main warehouse and its satellites. The analysis covers, basically, the rules to decide the allocations, the theoretical prediction of service levels and the extension of the initial Johnston formulation to this system. The allocation rule derived says that quantities should be allocated so as to have the same probability of depletion. For the prediction of service levels, the depletion time distribution rather than the demand distribution has been used in the formulations, because the conventional approach, based on the latter, does not produce the desired results. Implementable formulas are given for situations in which satellites are of the same order of magnitude. The results in the three areas mentioned above are accompianied by considerations about the economic meaning of the variables and a method is suggested to cross-check the consistency of the decisions. They are new contributions for the inventory control and constitute an important complement to the initial Johnston model.

Few significant changes in Programmable Logic Controller (PLC) software design techniques have taken place since PLC's were first introduced in the 1960's. Programs written in the traditional language used in PLC's, ladder logic, are generally thought to be difficult to maintain and modify, and thus ill suited to the support of modem flexible manufacturing processes. This work demonstrates that the choice of PLC software structure used in a project has an impact on process flexibility with an appropriate choice providing significant cost savings in development time. An overview of work on formalised programming tools conducted in academia is provided together with a report on the PLC software structures used in industry. The factors influencing the choice of PLC and software structure are identified. Familiarity was found to be a major factor influencing selection. A method for comparing code structures, which allows the results to be expressed as a time saving (and consequently a cost) has been created. Implementation of this approach was used to show that the formalised programming tool under test provides a 33% increase in "right first time" rate together with an 80% time saving over traditional contact based ladder logic. Among experienced practitioners, performance with step-based ladder logic was found to be a close match to the formalised tool, demonstrating that the commonly perceived limitations are the result of the structure in which the language is used rather than a function of the programming tool itself. Further investigation of participant preferences among skilled PLC users showed a mismatch between their performance with a tool and their preference, with at least 25% selecting a tool based on their prior knowledge rather than performance. This highlights the need for the use of objective measures when conducting evaluations between products and technologies. With the information provided in this work, automation end users are provided with a mechanism for ensuring the selection of automation tools best suited to their business needs, whilst at the same time providing automation vendors with the ability to best demonstrate the strengths of the products.

This research aimed to study real-time shop floor control problem in a manufacturing environment with dual resource (machine and labour), under impact of machine breakdowns. In this study, a multiperspective (order and resource perspectives) control strategy is proposed to improve effectiveness of dispatching procedure for promoting shop floor stability. In this control strategy, both order and resource related factors have been taken into account according to information on direct upstream and succeeding workcentres. A simulated manufacturing environment has been developed as a platform for testing and analysing performances of the proposed control strategy. A series of experiments have been carried out in a variety of system settings and conditions in the simulated manufacturing environment. The experiments have shown that the proposed control strategy outperformed the ODD (Earliest Operation Due Date) rule in hostile environments, which have been described by high level of shop load and/or high intensity of machine breakdowns. In hostile environments, the proposed control strategy has given best performance when overtime was not used, and given promising results in reduction of overtime cost when overtime was used to compensate for capacity loss. Further direction of research is also suggested.

Concerns about changes in the quality of the maturing British spruce resource (principally stiffness) have raised doubts about maintaining strength grading pass-rates. Acoustic (or stress wave) instruments provide a non-destructive measurement of stiffness and are increasingly used to classify/segregate forests, trees and logs. A fundamental assumption in the use of acoustic instruments is that of constant density, yet there is little understanding of density variation within the British spruce resource. Understanding this variation is essential for understanding the accuracy of acoustic instruments, which can affect how and when they should be used. The extent of variation in density was determined experimentally from a range of sites with contrasting silviculture and environments, and trees within-site were chosen to reflect the extremes of growth rate. Variation within tree (important for log resonance measurement) was found to depend both on dominance class (i.e. relative diameter) and height within the tree. The density in the outer part of a tree (important for standing tree time of flight measurement) was found to vary with dominance class, distance in from the bark and season. Mean green density profiles of the outer part of the tree show that density ceases to be constant between dominance classes after 10 mm in from the bark. The effect of this variation could not be quantified because the propagation behaviour of the stress wave within a tree is not fully understood. An examination of wave propagation showed that it did not conform to behaviour as described in the literature and interaction with both density variation within the tree and with the tree's boundaries is likely to affect the accuracy of this technique. The utilisation of these instruments was also examined within a sawmill simulation study, to provide an alternative to simply diverting low stiffness logs to lower value, non-structural products. Exploiting the predictable within-tree stiffness variation and adjusting cutting patterns to avoid the lower stiffness core of lower stiffness logs allowed production of consistently higher stiffness battens. A reduction in twist and knot severity was also observed, but not at significant levels until the juvenile zone (first ten years) was completely excluded. All batten properties improved with increasing cambial age (number of growth rings from the pith). Alternative cutting patterns had no effect on the recoverable batten volume from within a log and showed considerable potential to improve value to sawmills.

Printing has a long and illustrious history as a craft industry. This study explores the effects of technological change on skilled workers in the Edinburgh general printing industry. Three, initially distinct, areas of sociological theory concerning technological change shaped the research questions. These were, firstly, to establish the nature of recent technological change, and what drives it; secondly, to explore managers' decision-making in relation to such changes; and thirdly, to understand how workers' experiences of work, and their relationships at work, have changed with these changes in technology. My findings are based on three waves of investigations carried out over fifteen years, using responses from both managerial and shop-floor staff in five selected companies. This was done initially through questionnaires and later through semi-structured interviews. At Wave One (1991-92), most companies had made initial changes towards sophisticated computerisation, which had become embedded by Wave Two (1996-97). By Wave Three (2005-06) there was an ongoing programme of continual updating of these established systems constrained by the need to maintain compatibility with the computer systems used by customers due to the global hegemony of computer manufacturers. However, the effects upon workers were unexpected. Computerised typesetting programs inevitably brought deskilling, but original skills, learnt and used by workers over many years of rapidly changing technology, did remain relevant, and the acquisition of new skills associated with computerisation was regarded favourably. The most significant change for workers was the increased pressure resulting from a close relationship with customers, with vastly reduced time allowed for each job, and some erosion of workers' capacity (and managers') to produce work which satisfied their own standards of quality. The three, originally separate, themes converged to show that the particular nature of computerised technology used in this sector of the printing industry has led to a change in the traditional capitalist production relationship. These workers were not alienated, their skills had not been entirely lost, as neo-Marxist labour process theory would suggest. Rather, relationships between managers and these skilled shop-floor workers were characterised by mutual respect and understanding of the need for collaboration, not conflict, in the face of external hostile pressures.