Abstract
Acceptance sampling plans are practical tools for quality management applications and provide the producer and consumer a general rule for lot sentencing and reduce the cost. As the rapid advancement of manufacturing technology, suppliers required their products to be of high quality with very low fraction of defectives often measured in Parts Per Million（PPM）. Process capability indices are convenient and powerful tools for measuring process performance and it is widely used in Acceptance sampling plans. This paper attempts to develop a Variables Quick Switching Sampling System（VQSS System）based on the Cpk index. The VQSS System consists of two inspection plan along with a set of switching rules between them. The first sampling plan, called normal inspection plan, is applied for periods with good quality. The second sampling plan, called tightened inspection plan, is applied for use during problems encountered periods. The probabilities of acceptance under normal inspection and tightened inspection are derived, and the proposed VQSS System is also developed based on the exact sampling distribution rather than approximation approach. Three types of the proposed plan parameters are determined by solving a non-linear optimization problem with two-point conditions on the OC curve. The behavior and performance of the proposed sampling system is discussed and also compared with the conventional variables sampling plans. Finally, tables of the plan parameters for various selected quality levels and risks are provided for practical applications.