Controlling industrial measuring and monitoring equipment status through EWMA and I-MR charts

Abstract

Purpose – The main goal of this work was to develop a methodology to monitor the state of measuring and monitoring equipment (MME). The purpose of this method was to verify if a given MME remains fit for use and to ascertain the need to anticipate the next calibration or verification period, if any deviation happens. This method is based on the analysis of the stability of the instrument with regard to the measurement error and its ability to measure the target value. This article uses control charts, namely EWMA (Exponentially Weighted Moving Average) and I-MR (Individuals-Moving Range) charts. Design/methodology/approach – Verification data available from a company dedicated to the production of cork stoppers was used. Through a set of measuring instruments, which integrate the organization production process, these two types of control charts were built, for each significant verification point of these instruments. Findings – It was found that these charts combined bring important information about the measuring equipment status. The EWMA charts made it possible to understand if the equipment is measuring above or below the desire value. The I-MR charts allow to understand if, even though there is an increase in the measurement error, these errors are still far from exceeding the acceptance criterion (AC), verifications can be less frequent or, if the contrary, monitoring should be frequent due to the average error being close to the AC. Originality/value – The proposed approach allows taking decisions about the need to reduce or increase the interval between calibrations/verifications in order to reduce quality costs.