A detailed statistical process control implementation for density in MDF manufacture through PCA, Shewhart and EWMA charts

Abstract

Density is one of the major decision-making criteria of medium-density fiberboard (MDF) in terms of product quality. It is therefore very important to keep this key quality characteristic of the MDF in control. This research presents an industrial implementation of Shewhart’\(\:\stackrel{-}{\text{x}}-\text{s}\) control charts, which are generally constructed to catch large shifts, and exponentially weighted moving average (EWMA) control chart, which is mostly used to uncover small and moderately shifts, to monitor the density in the MDF manufacture in a forest products enterprise. Besides, a process capability analysis (PCA) was used to evaluate whether or not the measured outputs of density fall inside the specification limits. As a result; it was detected that the process was not in control for both \(\:\stackrel{-}{\text{x}}-\text{s}\) and EWMA, which demonstrate the changes in the density. The PCA also revealed that the process did not have sufficient capability in meeting the specifications of the density. Ultimately, such studies will allow both engineers and quality control officers to monitor a large number of measurements of quality characteristics in manufacturing processes. This can make a major contribution to detecting whether quality-related issues exist in processes and thus guide practitioners in improving or maintaining the quality level. Furthermore, in light of the current study, the efforts to be carried out to identify and eliminate factors that cause the process to deviate from specifications as well as factors that cause signal generation are expected to contribute to both reducing the amount of non-conforming products and achieving a more stable process.