Proceedings of the Institution of Mechanical Engineers,Part B: Journal of Engineering Manufacture

This paper studies an intentional force increase during the process of resistance spot welding (RSW). Known for decades, the forging force as a way of influencing weld quality has rarely been applied in the automotive industry. There has been little research in this area. In this paper, the effects of varying forging force are investigated using both experimental and analytical approaches. Through the analysis of dynamic electrical resistance, the mechanism of the forging effects is explored. This study achieves a better understanding of forging force application and shows the benefits of the forging force on weld quality.

Porosity in the die casting process causes costly scrap loss and limits the use of die-cast parts in critical high-strength applications. The amount of porosity is closely related to the die casting process parameters. Consequently, the mechanisms of porosity formation in relation to die casting parameters have to be studied in detail. A considerable reduction in porosity formation can be obtained by Taguchi technique implementation in the die casting process. Through simple multifactorial experiments in the foundry, controllable factors can be isolated to provide centring and variance control for a process variable. The primary objective of this paper is to investigate the effects of process parameters on porosity formation in the pressure die casting process to improve casting quality. Examples of the off-line technique used in a Greek aluminium die casting company are given for the purpose of illustrating the practicality and ease of use by industry engineers and managers.

There is growing interest in additive and subtractive shaping theories that are synthesized to integrate the layered manufacturing process and material removal process. Recently, layer-based machining has emerged as a promising method for integrated additive and subtractive shaping theory. In this paper, major layer-based machining systems are reviewed and compared according to characteristics of stock layers, numerical control machining configurations, stacking operations, input format and raw materials. Support structure, a major issue in machining-based systems which has seldom been addressed in previous research, will be investigated in this paper with considerations of four situations: floating overhang, cantilever, vaulted overhang and ceiling. Except for the floating overhang where a support structure should not be overlooked, the necessity for support structures for the other three situations is determined by stress and deflection analysis. This will be demonstrated by the machining of a large castle model.

This paper presents experimental evidence for the existence of non-Euclidean contact geometry at the tool-chip interface in the machining of aluminium alloy, which challenges conventional assumptions. The geometry of contact at the tool rake face is modelled using fractals and a dimension is computed for its description. The variation in the fractal dimension with the cutting speed is explored.

This research paper presents a prototype object-oriented and rule-based system for product cost modelling and design for automation at an early design stage. The developed system comprises a computer aided design (CAD) solid modelling system, a material selection module, a knowledge-based system (KBS), a process optimization module, a design for assembly module, a cost estimation module and a user interface. The system development process has passed through four major steps: constructing the knowledge-based and process optimization system; developing a design for assembly module; integrating the KBS with both a material selection database and the CAD system; developing and implementing a fuzzy logic approach to generate reliable estimation of cost and to handle the uncertainty in the cost estimation model that cannot be addressed by traditional analytical methods. Two manufacturing processes, namely machining and injection moulding processes, were considered in the developed system.

The main function of the system, besides estimating the product cost, is to generate initial process planning, including the generation and selection of machining processes, their sequence and their machining parameters, and to recommend the most economical assembly technique for a product and provide design improvement suggestions based on a design feasibility technique. In addition, a feature-by-feature cost estimation report is generated using the proposed system to highlight the features of high manufacturing cost. Two case studies were used to validate the developed system.

This paper describes an intelligent fuzzy decision support system for real-time scheduling and dispatching of parts in a flexible manufacturing system (FMS), with alternative routing possibilities for all parts. A fuzzy logic approach is developed to improve the system performance by considering multiple performance measures and at multiple decision points. The characteristics of the system status, instead of parts, are fed back to assign priority to the parts waiting to be processed. A simulation model is developed and it is shown that the proposed intelligent fuzzy decision support system keeps all performance measures at a good level. The proposed intelligent system is a promising tool for dealing with scheduling FMSs, in contrast to traditional rules.

This paper is concerned with the evaluation of combined dispatching and routeing strategies on the performance of a flexible manufacturing system. Three routeing policies: no alternative routeings, alternative routeings dynamic and alternative routeings planned are considered with four dispatching rules with finite buffer capacity. In addition, the effect of changing part mix ratios is also discussed. The performance measures considered are makespan, average machine utilization, average flow time and average delay at local input buffers. Simulation results indicate that the alternative routeings dynamic policy gives the best results in three performance measures except for average delay at local input buffers. Further, the effect of changing part mix ratios is not significant.

An innovative approach to the manufacture of impulse turbine blades using rapid prototyping, fused decomposition modelling (FDM), is presented in this paper. These blades were designed and manufactured by the Wave Energy Research Team (WERT) at the University of Limerick for the experimental analysis of a 0.6m impulse turbine with fixed guide vanes for wave energy power conversion. The computer aided design/manufacture (CAD/CAM) package Pro-Engineer 2000i was used for three-dimensional solid modelling of the individual blades. A detailed finite element analysis (FEA) of the blades under centrifugal loads was performed using Pro-Mechanica. Based on this analysis and FDM machine capabilities, blades were redesigned. Finally, Pro-E data were transferred to an FDM machine for the manufacture of turbine blades. The objective of this paper is to present the innovative method used to design, modify and manufacture blades in a time and cost effective manner using a concurrent engineering approach.

This paper provides a methodology for managing safety and strategic stocks in materials requirements planning (MRP) environments to face uncertainty in market demand. A set of recommended guidelines suggest where to position, how to dimension and when to replenish both safety and strategic stocks. Trade-offs between stock positioning and dimensioning and between stock positioning and replenishment order triggering are outlined. The study reveals also that most of the decisions are system specific, so that they should be evaluated in a quantitative manner through simulation. A case study is reported, where the benefits from adopting the new proposed methodology lie in achieving the target service level even under peak demand conditions, with the value of safety stocks as a whole growing only by about 20 per cent.

A three-dimensional numerical simulation using the boundary element method is proposed, which can predict the cavity temperature distributions in the cooling stage of injection moulding. Then, choosing the radii and positions of cooling lines as design variables, the boundary integral sensitivity formulations are deduced. For the optimum design of cooling lines, the squared difference between the objective temperature and the temperature of the cavity is taken as the objective function. Based on the optimization techniques with design sensitivity analysis, an iterative algorithm to reach the minimum value of the objective function is introduced, which leads to the optimum design of cooling lines at the same time.

Numerical simulation is a flexible, practical tool for efficiently investigating machine vision hardware/software configurations for myriad industrial applications and can significantly reduce the engineering time necessary to design and implement a system. In this paper, physically accurate image synthesis is used to investigate the ability of diffuse angle images to detect topographical defects reliably in smooth, highly specular coatings; a specular-plus-diffuse reflectance model provides the scientific underpinning for this hypothesis. The specific results presented in this study show that diffuse images of topographical defects yield high-contrast grey-scale images compared with diffuse images of similar coatings without topographical defects, facilitating effective defect detection and providing a foundation for characterizing the severity of defects present in a given region.