Development of a model for performance measurement in just-in-time enabled manufacturing environments

In this era of globalisation and fierce competition amongst businesses, there is a need to improve advanced operations management philosophies such as just-in-time (JIT) manufacturing to enhance business performance. Literature review shows that there is no mechanism so far to identify key JIT drivers relevant to a given organisation and its production processes, and their impact on enterprise performance. The research carried out here therefore involved the development of a generic performance measurement model to identify and capture the influence of JIT practices on enterprise performance. A conceptual performance measurement model, which was designed based on comprehensive literature review and informal interviews/discussions with both academic researchers and industry practitioners describes the link between JIT drivers (Xi) and measurable performance (Y). This mathematically determined model is aimed at assisting managers in the systematic identification of the influence of key JIT drivers on enterprise performance using a multidimensional tool such as the extended balanced scorecard. The case study approach was selected as the most suitable methodology for testing and validating the conceptual model in JIT enabled production plant and was applied to the production process of Denso Manufacturing (UK) Ltd., a global automotive component manufacturer. A novel eight-step implementation procedure was designed to collect data, which were analysed and validated by design of experiments, linear mathematical modelling, computer based dynamic simulation and analytic hierarchy process tool. The performance measurement model was then successfully applied to a non-automotive component production plant (Risane Ltd.). In conclusion, the performance measurement model can now be suitably applied to JIT enabled manufacturing environments using relevant organisation specific JIT drivers and key performance indicators to optimise system performance. The contribution to knowledge is an innovative, user friendly, robust and multidimensional performance measurement model enabling industry practitioners to optimise JIT processes with substantial performance enhancement. The model could also be applied by future researchers to other operations management philosophies and industries, and at a higher level could be developed into a self-optimising software package, which will enable rapid determination of the key control parameters needed to optimise process performance just in time.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A review of interconnection technologies for improved crystalline silicon solar cell photovoltaic module assembly

The identification, adoption and utilisation of reliable interconnection technology to assembly crystalline silicon solar cells in photovoltaic (PV) module are critical to ensure that the device performs continually up to 20 years of its design life span. With report that 40.7% of this type of PV module fails at interconnection coupled with recent reports of increase in such failure in the tropics, the review of interconnection technologies employed in crystalline silicon solar cells manufacture has become imperative. Such review is capable of providing information that can improve the reliability of the system when adopted which in turn will increase silicon PV module production share more than the current value of 90.956%. This review presents the characteristics of interconnect contacts in conventional cells and other unconventional crystalline silicon cells. It compares series resistance, shadowing losses and the induced thermo-mechanical stress in the interconnection for each interconnection technique employed. The paper also reviews interconnection technologies in these assemblies and presents a comparison of their concept, cell type, joint type, manufacturing techniques and production status. Moreover, the study reviews and discusses the material and technological reliability challenges of silicon solar cells interconnection. The review identifies laser soldering technology as one which has the potential of making interconnection with higher reliability when compared with conventional soldering technology. It was found that this technology supports the current design trend of thinner, wider and cheaper crystalline silicon solar cells significantly whilst producing interconnection that experience relatively lower induced thermo-mechanical stress. The authors recommend that wider acceptance and usage of laser soldering technology could improve the performance and consequently extend the mean-time-to-failure (MTTF) of photovoltaic modules in general and particularly the ones which operates in the tropics. This will enable improvement in the reliability of PV modules for sustainable energy generation

Effect of intermetallic compounds on thermo-mechanical reliability of lead-free solder joints in solar cell assembly

The solder joints in crystalline silicon solar cell assembly undergo thermo-mechanical degradation during the device lifetime. The degradation is accelerated by the formation and growth of intermetallic compound, IMC, in a solder joint which contains copper and tin as alloying elements of the solder. This investigation quantifies the contribution of the presence of IMC in the joints on the reliability of the assembly. The study employs finite element modelling (FEM) to simulate the nonlinear deformation of SnAgCu solder joints in two models of crystalline silicon solar cell assembly. One of the models contains IMC in the interface joints between solder and copper ribbon while the other, which is the control, does not contain IMC in the joints. The degradation of the solder material is simulated using Garofalo-Arrhenius creep model. The geometric models were subjected to accelerated thermal cycling utilising IEC 61215 standard for photovoltaic panels. Analysis of the results of the creep strain profiles of the two models indicate that the deformation amplitude in the solder joint containing IMC is higher than that in the solder joint containing solder only. Similarly, it can be observed from the plot of strain energy density against load step that the solder joint containing solder+IMC have considerable higher strain energy density compared to solder only joint. This infers that the presence of IMC significantly impacts the thermomechanical reliability of the assembly joints. The results also demonstrate that IMC decreases the mean-time-to failure (MTTF) of the assembly joints