Process Monitoring using Modified Successive Sampling

The presence of variation cannot be avoided in different kinds of manufacturing and non-manufacturing processes. A better understanding of the causes of variability in any process is necessary to improve the process. Control chart is a very frequently used tool for checking whether the process parameters are stable or not. The current study devises a sampling technique, named as modified successive sampling scheme, that is not only cost effective but also efficient as compared to the simple random sampling scheme. A number of Shewharts type control chart will be proposed based on the said sampling scheme and the performance of the proposed charts will be evaluated using average run length as a performance indicator. In terms of average run length values, the proposed charts will be compared with existing Shewhart control chart for both positive and negative shifts in the process. Finally, the new proposals will be applied for a real dataset where the variable of interest is inside diameter measurements of forged automobile engine piston rings.