STABILITY ANALYSIS OF THE TECHNOLOGICAL PROCESS OF MECHANICAL WOOD PROCESSING USING CONTROL CHARTS

Abstract

This paper presents a quality control tool, that is, a quality control method, which in this case concernsthe mechanical processing of wood, but in general, it can be implemented in any form of production (mechanicalengineering, traffic, food technology...). The goal of the research is to show the way of applying the control chartmethod, that is, to determine the stability of the technological process of mechanical wood processing in order to beable to define appropriate corrective measures in order to improve that part of the production process. The controlchart that was created in this paper is a graph consisting of a horizontal (abscissa) and a vertical axis (ordinate). Theorder of observations is plotted on the abscissa, and the corresponding values on the ordinate. Apart from theprecise creation of control charts, their correct interpretation is also of great importance. It is easiest to interpretcontrol charts where the process is "outside statistical control", that is, the process where the values of individualmeasurements are outside the control limits. This means that some special cause of variation is present in the processand an adjustment needs to be made. However, placing all points within the control limits, that is, obtaining acontrol map on which the process is "within statistical control", does not necessarily mean that such a process isacceptable by statisticians. On the basis of the results, that is, on the basis of the graph that has the shape of a brokenline, we observe whether the control limits have been exceeded, and we draw certain conclusions about the stabilityof the process. If the graph is between the control limits, we can conclude that our process is stable and undercontrol, that is, that our quality variation is within normal limits. If there are any jumps, ie. if some value in someobservation is out of bounds (above the upper control limit or below the lower control limit), then we conclude thatour process is not stable, not under control and that our quality variation is not within normal limits. In that case,certain corrective measures were proposed, which should improve the technological process of mechanical woodprocessing and bring it under control.Control charts, as an engineering-mathematical tool, are a very suitable tool for achieving the goals of statisticalcontrol. Optimal application of control charts ensures constant monitoring of the process, direction towards thedesired flow and undertaking of possible corrective measures. Also, their application ensures the fulfillment of thedesigned or required quality characteristics, that is, the fulfillment of the requirements of a certain standard. Withtheir simplicity of application and reliability, they provide users with convenience in work and relevant processindicators, and provide process controllers with valid data about the process flow. As such, they represent a tool thatkeeps the entire process within the given limits.