Economic Design of Attribute Control Charts for Multiple Assignable Causes

Abstract

Two production models are presented for maintaining current control of an industrial process subject to a multiplicity of assignable causes. The formulated cost function includes the cost of inspection, charting, downtime, search for assignable cause, repair, and defective items. Two models are formulated. The first model allows for shutting down the process during the search for the assignable cause. The second assumes that the process is allowed to continue in operation during the search for the assignable cause. Computer search procedures were used to find the optimal sample size, acceptance number, and intersample interval that minimize the formulated cost functions. The article shows that the complex multiple cause model can be well approximated by a “matched” single cause model. Ten numerical examples show how the formulated models can be applied.

• Cost Function
• Economic Design
• np Control Charts
• Process Control Optimization

Additional information

Notes on contributors

Isaac N. Gibra

Dr. Gibra is Professor of Operations Research and Management Science and a Senior Member of ASQC.