Quality and reliability

The lying down of levels of quality and reliability necessary to ensure product success and acceptability in a particular market is a cause for increasing concern. They are the most difficult aspects to quantify in absolute terms, although statistical data fi-om company product precedents are helpful here. There are expressions used such as mean time before failure (MTBF) and mean time to repair (MTTR) that are used with mechanical, hydraulic, pneumatic, electrical, and other products. Nonetheless, some quantitative expression must be made in respect of quality and reliability at the initial design specification stage. A Company must ensure adequate feedback of any failure analysis to the design team. 

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By applying this method, they demonstrated that the removal of insignificant variables increases the quality and reliability of the models despite the fact that the correlation coefficient, r, always decreases, although only shghtly. For example, the characteristics of a model with six orthogonalized descriptors were r = 0.99288, s = 0.9062, F = 127.4 and the quality of this model was sufficiently improved after removal of the two least significant descriptors, to r = 0.9925, s = 0.8553,... 

Introduction to quality and reliability engineering Cash flow... 

Next, we review the eosts of quality that typieally exist in a manufaeturing business, and how these are related to the way produets fail in serviee. The remainder of the ehapter diseusses the important elements of risk assessment as a basis for design. This puts in eontext the work on designing for quality and reliability, whieh are the main topies of the book. 

In order to quantify the sometimes intangible elements of variability associated with the product design and the safety aspects in service requires an understanding of risk . The assessment of risk in terms of general engineering practice will be discussed next. This will lead to a better understanding of designing for quality and reliability, which is the main focus of the book. 

Provides the designer with an understanding of the strueture of the system, and the faetors whieh influenee quality and reliability... 

It gives assuranee to management and/or eustomers that quality and reliability are being or have been properly addressed early in the projeet. 

Once the variability risks, and q, have been calculated, the link with the particular failure mode(s) from an FMEA for each critical characteristic is made. However, determining this link, if not already evident, can be the most subjective part of the analysis and should ideally be a team-based activity. There may be many component characteristics and failure modes in a product and the matrix must be used to methodically work through this part of the analysis. Past failure data on similar products may be useful in this respect, highlighting those areas of the product that are most affected by variation. Variation in fit, performance or service life is of particular interest since controlling these kinds of variation is most closely allied with quality and reliability (Nelson, 1996). 

Jeang, A. 1995 Economic Tolerance Design for Quality. Quality and Reliability Engineering International, 11, 113-121. 

Murty, A. S. R. and Naikan, V. N. A. 1997 Machinery Selection - process capability and product reliability dependence. International Journal of Quality and Reliability Management, 14(4), 381-390. 

Radovilsky, Z. D., Gotcher, J. W. and Slattsveen, S. 1996 Implementing Total Quality Management statistical analysis of survey results. International Journal of Quality and Reliability Management, 13(1), 10-23. 

To improve customer satisfaction and business competitiveness, companies need to reduce the levels of non-conformance and attendant failure costs associated with poor product design and development. Attention needs to be focused on the quality and reliability of the design as early as possible in the product development process. This can be achieved by understanding the potential for variability in design parameters and the likely failure consequences in order to reduce the overall risk. The effective use of tools and techniques for designing for quality and reliability can provide this necessary understanding to reduce failure costs. 

Quality and reliability are not free, but poor quality and reliability cost more than good quality (2]. Costs include excessive down time and asso-... 

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