Authors: Azam Moraditadi; Soroush Avakhdarestani
Addresses: Department of Industrial Engineering, Science and Research Branch, Islamic Azad University, Qazvin, Iran ' Faculty of Industrial and Mechanical Engineering, Qazvin Branch, Islamic Azad University, Qazvin, Iran
Abstract: Control charts are very effective tools which are used for detecting the assignable cause of variation. This paper investigated fuzzy individual x and moving range (IX-MR) control chart in the case of uncertainty for process parameters and data. In this paper, fuzzy mode method was employed to design fuzzy IX-MR control chart for triangular and trapezoidal fuzzy number fuzzy numbers coded by MATLAB software. Then unnatural patterns were studied in a fuzzy environment. To validate the model, an industrial example was utilised and then the results were verified. Results showed that the fuzzy one was more sensitive than the classic cases and more consistent with the actual situation. Also, fuzzy mode method was more sensitive for trapezoidal than triangular fuzzy numbers.
Keywords: fuzzy control charts; x-bar charts; moving range charts; fuzzy logic; statistical process control; SPC; unnatural patterns; uncertainty; trapezoidal fuzzy numbers; triangular fuzzy numbers.
International Journal of Productivity and Quality Management, 2016 Vol.17 No.1, pp.82 - 103
Received: 11 Feb 2014
Accepted: 29 Jun 2014
Published online: 30 Nov 2015 *