Aplicação do controle estatístico do processo por meio de gráficos de controle no processo de usinagem por mandrilamento

Abstract

This work focuses on the application of control charts in the boring machining process, with the objective of evaluating the state of statistical control and dimensional variability in cast iron parts. The research was conducted through a descriptive study, with a qualitative approach, using data obtained from primary sources, from measurements performed with three-dimensional equipment, and from secondary sources, such as the technical literature on Statistical Process Control (SPC). Thirty-three parts machined in a single batch were analyzed, using cutting parameters used in the daily production of this item. The control charts applied in Phase I, together with the Anderson-Darling normality tests and histograms, allowed the investigation of the statistical behavior of the characteristics of interest, top and bottom bearing diameters. The results indicated that the process operates out of statistical control, with the presence of special causes of variation. This conclusion was based on the detection of points outside the control limits in the moving range graphs and the non-random distribution of data around the center line. In addition, the histograms presented smoothed curves, with low concentration around the mean, which reinforces the observed instability. The integrated analysis of the statistical tools demonstrates the importance of controlling the variability in boring, since its instability directly compromises the quality of the product.