Determinação do tempo ótimo de dressagem utilizando séries temporais no Controle Estatístico de Processos – CEP

Abstract

Aiming the improvement of the performance of industrial processes, the manufacturing companies are used the Statistical Process Control -SPC to control the variability ofthe process. Thus, it is possible to intervene in the special causes that are acting, in the process, improving continuously the product quality. In the manufacture rods ofshock absorbers, the rugosity is an important characteristic of the quality, which is determined by engineering specifications. The used equipment to take care of these specifications is called dressing machines "centreless". The operation of the process, break off this machines demanding, therefore, an intervention of the operator called dressing process. To proceed the adjustment from the grinding machines, the operator must determine the period of time that must command the interventions, so thatthey donothave normore interventions ofthat the necessary number, nor less. Currently, this time is established in 45 minutes. In this work, the behavior of data origined from the operations system of the company TECNO of the Lavras/MG was analyzed, with the objective to determine, scientifically, the optimum time of dressing process of such machines. Initially, a simple solution was presenteei, getting a time ofapproximately 52 minutes to effect the dressing process. As the data are correlated inthe time, there wasthe necessity to usea more adequate methodology for attainment ofmore trustworthy results. Forthis, it was used the methodology of times series. In this case, the optimum time of dressing process were ofapproximately 73 minutes. It is observed that making use of a more adjusted methodology, there was an addition of 28 minutes in the time currently used, implying in the reduetion of the number of interventions. This fact generates a significam reduetion ofthe time wastefulness, effòrts ofthe operator and, additionally, the solution of a pendency in the auditorships of norms of the quality management.