Again the data is collected regarding the
number of castings produced and number of
casings rejected because of casting defects and
machining defects
P – chart was drawn as shown using the
data as shown in table. It shows that some sample
points are close to process average, P̅
The capability P̅ = 0.0462
= 4.62 %
It is concluded that process capabilities are
improved by decreasing the rejection rate from
6.52% (before SPC) to 4.62% (after SPC). It is
shown in Table 7 to Table 9 and further illustrated
graphically. It is shown in Fig 9.
A pareto analysis for comparative results reveals
that there exists reduction in wastage of units
produced. It is shown in Table 10 and Fig 10.