Manufacturing variability

In the next chapter, we introduce the concepts of component manufacturing capability and the relationships between tolerance, variability and cost. The Component Manufacturing Variability Risks Analysis is then introduced, the first stage of the CA methodology, from which process capability estimates can be determined at the design stage. The development of the knowledge and indices used in the analysis... 

Validation of the Component Manufacturing Variability Risks Analysis... 

Validation of the Component Manufacturing Variability Risk, is essential to CA in determining estimates for component characteristics at the design stage. Collecting component parts from various industrial sources with known statistical histories was central to this. The components were taken from a number... 

Figure 2.15(a) shows the relationship between and Cp for the component characteristics analysed. Note, there are six points at q = 9, Cp = 0. The correlation coefficient, r, between two sets of variables is a measure of the degree of (linear) association. A correlation coefficient of 1 indicates that the association is deterministic. A negative value indicates an inverse relationship. The data points have a correlation coefficient, r = —0.984. It is evident that the component manufacturing variability risks analysis is satisfactorily modelling the occurrence of manufacturing variability for the components tested. 

Component Manufacturing Variability Risks Analysis As mentioned previously, the first of the three key stages in CA is the Component Manufacturing Variability Risks Analysis. When detailing a design, certain characteristics can be considered... 

The CA methodology is useful in this respect. It is comprised of three sections the Component Manufacturing Variability Risks Analysis, the Component Assembly Variability Risks Analysis and the determination of the Effects of Non-conformance through the Conformability Map. 

The measures of dimensional variability from Conformability Analysis (CA) (as described in Chapters 2 and 3), specifically the Component Manufacturing Variability Risk, q, is useful in the allocation of tolerances and subsequent analysis of their distributions in probabilistic design. The value is determined from process capability maps for the manufacturing process and knowledge of the component s material and geometry compatibility with the process. In the specific case to the th component bilateral tolerance, it was shown in Chapter 3 that the standard deviation estimates were ... 

Looking at the process capability map for turning/boring in Figure 4.42 gives a risk value, A = 1.05, for a dimension of 012 mm. This value defaults to the component manufacturing variability risk, q, when there is no consideration of surface finish capability in an analysis. 

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