Design the control scheme with learning and forgetting effects consideration

A novel quality control scheme which considers the learning-forgetting curve is proposed. In the growth stage of a new product, the fraction of nonconforming (P) is often reduced rapidly due to the repetitive production and accumulation of experience. This phenomenon of diminishing the fraction of nonconforming has significant learning effect. In addition, along with some quality improvement projects which focus on reducing the fraction of nonconforming within a specific period, the learning effect of the fraction of nonconforming is more pronounced. In order to keep the monitoring effect of the control chart, the learning effect of the fraction of nonconforming should be considered in the p quality control chart. Meanwhile, there are possible interruptions between batches in the production system which generate forgetting. In this work, the proposed p quality control chart with the learning-forgetting effect of the fraction of nonconforming in the process has practical application value. Some p control charts can be used for comparison with and without consideration of the learning-forgetting effects.