A Single-Level Continuous Sampling Plan for High Quality Production Line

Abstract

This paper presents a plan SKIP-CSP-1 for inspection of a high quality continuous production line.  The plan is defined by 3 parameters  (the number of consecutive non-defective units that must be produced during a 100% inspection of the line), a fraction f (the specified sampling frequency during a fractional inspection of the line) and k (the number of units for skipping over in an inspection). SKIP-CSP-1 computes 3 performance measures, average fraction inspected (AFI), average outgoing quality (AOQ) and average outgoing quality limit (AOQL), for given values of the parameters and incoming fraction of defective units on the line (p). The validity of the performance measure formulas have been tested by extensive simulations. The formulas of performance measures,  AFI and AOQ are valid for all the sets of  p, i, k, r (r = 1/f) values.  The SKIP-CSP-1 plan has been compared with CSP-1 and CSP-2 plans. On comparing AFI and AOQ, we have found that SKIP-CSP-1 does not give an appreciable difference in the number of units inspected and output quality for low level of  p (0.001, 0.003, 0.005) and for all the sets of i, k, r. Further, for higher levels of p , but low levels of k , it also does not give different results.  However, compared with CSP-1, we have found that SKIP-CSP-1 gives lower number of units inspected and output quality than CSP-1, whereas compared with CSP-2, SKIP-CSP-1 gives higher number of units inspected and output quality than CSP-2.