Ss. Prabhu et al., A COMBINED ADAPTIVE SAMPLE-SIZE AND SAMPLING INTERVAL (X)OVER-BAR CONTROL SCHEME, Journal of quality technology, 26(3), 1994, pp. 164-176
Citations number
16
Categorie Soggetti
Operatione Research & Management Science","Engineering, Industrial
A conventional XBAR control chart works in an open loop manner. That i
s, the process control engineer waits until the control scheme signals
an out-of-control condition. This paper proposes a combined adaptive
XBAR chart that uses real-time, dynamic information available from the
process to make the control scheme pro-active. The procedure consists
of a simple method of varying the control chart design parameters (sa
mple size and sampling interval) between minimum and maximum values de
pending on the current state of the process. The proposed procedure is
compared with the standard Shewhart XBAR chart, a variable sample siz
e chart, and a variable sampling interval chart in terms of the averag
e time to signal an off-target process. Substantial improvement in the
performance over these schemes is demonstrated. Optimal values for th
e maximum sample size are also given. The advantages of using the comb
ined adaptive chart is illustrated by an example from a production pro
cess.