Fig 1.
The CRL value represents the number of inspected samples between two consecutive non-conforming samples in the CRL chart. The conforming and non-conforming samples are represented by the hollow and solid dots on the CRL chart, respectively.
Fig 2.
The VSI chart is illustrated when two sampling intervals are considered in a process. These sampling intervals are known as the short and long sampling intervals.
Fig 3.
A graphical illustration of the VSI synthetic chart.
The VSI synthetic chart consists of the
sub-chart and the CRL sub-chart. The short and long sampling intervals are used in the
sub-chart and the CRL sub-chart.
Table 1.
Optimal parameters (L1,L2,k,w,d4) and the corresponding ATS1(δopt) for VSI synthetic chart, for sample sizes, n = 3, 5, 7 and 9, and ATS0 = 370 when d1, d2 and d3 are set as 0.5, 1.5 and 0.5, respectively.
Table 2.
Optimal parameters for synthetic , VSI
and EWMA
charts to minimize ATS1(δopt) when n = 3, 5, 7 and 9, and ATS0 = 370.
Table 3.
ATS1(δopt) for the , EWMA
, VSI
, synthetic
and VSI synthetic
charts when n = 3, 5, 7 and 9, and ATS0 = 370.
Table 4.
Flow width measurements (μm) for the hard-bake process.
Fig 4.
The VSI synthetic chart for the flow width measurements.
This chart is used to monitor the flow width measurements (in micrometres, μm) for the hard-bake process. The chart signals an out-of-control at the 15th sample which corresponds to the 17th hour from the start of the process.