Riassunto analitico
In today's technologically advanced age, where products can be manufactured with surgical precision and a policy of maximising efficiency is being pursued, measurement and the evaluation of errors are becoming increasingly important. In general, "measurement" refers to the numerical expression of the dimensions of an object relative to a fixed reference used as a unit of measurement. The misclassification of defective products as finished products generates complaints from customers and a loss of prestige and credibility for the company. In other words, it is essential to implement a "Measurement Control System", a system in which all members of an organization involved in the production process perform correct measurements at every stage of the production process itself. The basic prerequisite is that everyone involved in the production is an expert and knows how to handle and use measuring instruments correctly. The problem of measurement and its correct handling is therefore vast, complex and extremely important. The aim of this thesis, therefore, is to formulate a model for assessing the impact of measurement errors on production processes. In order to achieve this aim, a careful and accurate analysis was carried out which, starting from the definition of the concept of error, created the necessary basis for structuring a complete and effective model. In fact, Chapter 1 deals with the theory of error and uncertainty. Starting from the measurement of error and the concepts defined by the GUM Standard (ISO/IEC Guide 98-3) and VIM (ISO/IEC Guide 99), the types of error, the concept of uncertainty and the main factors that influence it are introduced, as well as the mathematical-statistical tools which are at the base of the generalised laws that regulate error propagation. In Chapter 2, attention is focused on the instrumentation, which represents the means by which measurements are made and errors are determined. The concepts of sensors and transducers, transmission systems, characterisation methods for measuring instruments, the concepts of traceability and calibration, Error Management Tools, Quality Management Systems and general standards for metrological systems are defined. In Chapter 3, risk evaluation techniques related to industrial measurements are introduced: analysis related to reliability, availability, maintainability and safety are part of the large field of RAMS analysis (Reliability, Availability, Maintainability and Safety) and have the task of defining with the greatest possible accuracy the possible failure scenarios of the various components that could lead to the loss of functionality of an entire system. To carry out this type of analysis, various application methodologies are available, which allow both qualitative and quantitative safety and reliability studies to be carried out, such as the Fault Tree Analysis or the Failure Mode and Effect Analysis. Thanks to the concepts analysed in Chapter 4, a model was developed for evaluating the impact of measurement errors on production processes, which allows the best techniques presented in the previous sections to be implemented in an organic, systematic and effective manner. The last two chapters, Chapter 5 and Chapter 6, consist of the validation of the elaborated model, as it is applied to the case of Federal Mogul, a company whose main production process is the assembly of ignition coils for the automotive sector. In the Conclusions, final reflections are given which, by briefly reviewing what has been reported in the previous chapters, try to draw conclusions on the entire activity carried out.
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