Monitoring two-stage processes with a profile at the second stage

ABSTRACT

In the multistage processes, quality of a process or a product at each stage is related to the previous stage(s). This property is referred to as a cascade property. Sometimes, quality of a process is characterized by a profile. In this paper, we consider a two-stage process with a normal quality characteristic in the first stage and a simple linear regression profile in the second stage. Then we propose two methods to monitor quality characteristics in both stages. The performance of the proposed two methods is evaluated through a numerical example in terms of average run length criterion.

KEYWORDS:

• Cause selecting control chart
• Phase II
• Profile
• Statistical process control
• Two-stage processes.

MATHEMATICS SUBJECT CLASSIFICATION:

• Primary 62J05
• Secondary 62J20

Acknowledgment

The authors are grateful to the anonymous referee for precious comments which led to improvements in the paper.