Economic design of X control charts : evaluation and implementation in manufacturing
Dausman, Christopher R.
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Over the past forty years, many models have been introduced to study the problem of economic design of control charts. However, difficulty in understanding and implementation have prevented their widespread use. This study examines an existing model for the economic design of an X statistical quality control chart to determine if it can be implemented in a manufacturing environment. This involves finding values for the sample size, sample frequency, and control limit width in order to minimize the expected cost per hour for the process. A review of the history of economic design in control charts and model development concludes with the model selection for the thesis. An in-depth examination of the model parameter requirements results in the estimates necessary to successfully implement the model. It also introduces a model modification in the estimation of the model parameter p based on observation for the value of ARL2. The model is tested over several hundred parameter settings and the optimal levels for the parameters’ sample size, sample frequency, and control limit width are found. A sensitivity analysis is conducted to determine how sensitive the expected cost per hour is to changes in the model parameters.