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Unformatted text preview: C HAPTER 1 Introduction 1 This introductory chapter provides an overview of quality and reliability engineering techniques, the relationship between reliability and cost, and reliability, design, and assess- ment. This chapter also presents the scope and organization of the book. 1.1 INTRODUCTION Design involves innovation and requires knowledge from the science and engineering fields. It includes the selection of materials, parts, and tentative parameter values in the product design stage and the selection of production equipment and tentative values for process factors in the process design stage. The term quality has been defined in different ways by various authors. Crosby (1979) defines quality as, quality is conformance to requirements or specifications. Juran (1974) proposes the definition for quality as quality is fitness for use. A more general definition for quality is given as follows: the quality of a product or service is the fitness of that product or service for meeting or exceeding its intended use as required by the customer. The term quality implies different levels of expectations for different groups of consumers or customers. Quality should be designed into a product. There are three aspects generally associated with the definition of quality. They are: ( a ) quality of design ( b ) quality of conformance ( c ) quality of performance Quality of Design: Quality of design focuses on the stringent conditions that the product must minimally possess to satisfy the requirements of a customer. In other words, the product must be designed to meet at least the minimal needs of the customer. Quality of design is generally influenced by factors including the type of product, cost, profit policy or criteria, product demand, materials and parts availability, and product safety. In general, the effect of an increase in the designed quality level will increase the cost at an exponential rate. On the other hand, the value of the product increases at a decreasing rate. The rate of increase approaches zero beyond a certain designed quality level. Quality of Conformance: Quality of conformance requires that the manufactured product must meet the standards selected in the design phase. This would involve defect prevention, defect finding, and defect analysis and rectification. Defect prevention is accomplished using statistical process control techniques. Defects are usually located using inspection, test, and statistical analysis of data from the process. Once the sources or causes for the presence of defects are determined, then corrective measures or actions are taken accordingly. 2 PRODUCT AND PROCESS DESIGN FOR QUALITY, ECONOMY AND RELIABILITY Quality of Performance: Quality of performance focuses on how well the product performs when put to use. Quality of performance is a function of both quality of design and the quality of conformance. If a product does not meet the specified expectations, then adjustments are to be made in the design or conformance phase.be made in the design or conformance phase....
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This note was uploaded on 02/03/2012 for the course ENGR 202 taught by Professor Hi during the Spring '11 term at UCLA.
- Spring '11