Neural Networks Applied to Thermal Damage Classification in Grinding Process

Abstract

Throughout the course of human progress from prehistoric times until now the technological world was characterized by the development and improvement of new methods to control the environment. One of the most obstacle to overcome in order to reach the complete automation of machining process within the integrated and flexible manufacturing systems is the development that can be named a non-human-assisted machining, that is, a process in which the moment for tool change, the tool change itself and the change of the grinding conditions no longer need the human being assistance. Thus, the development of monitoring and control systems in real time is of great importance. High temperatures in grinding process are the main source of thermal damages to the ground surface, which is a visible manifestation in steels known as grinding burn. Depending on the temperature reached in the grinding zone a burn degree on the part surface can be observed which is due to temper color from very thin oxide layers. One of the challenges found in the implementation of intelligent grinding process is the automatic detection of surface burn of the parts. Several systems of monitoring have been assessed by researchers in order to control the grinding process and guarantee the quality of the ground parts. However, monitoring techniques still fails in certain situations where the phenomenon changes are not completely obtained by the employed signals. Several monitoring systems which use force or power and acoustic emission sensors have been assessed by researchers to control surface burn in grinding (Aguiar et al.,2002; Aguiar et al., 1998; Kwak & Song, 2001; Wang et al., 2001; Kwak & Ha, 2004; Dotto et al., 2006; Aguiar et al., 2006a; Aguiar et al., 2006b). However, those techniques still need improvements where the phenomenon variations are not entirely acquired by the signals used. High temperatures in grinding are the main source of thermal damages to the ground surface. A visible manifestation of this damage in steels is grinding burn – a discoloration of the ground surface often visible directly to the naked eye or brought out by etching of the surface. Depending on the temperature reached in the grinding zone a burn degree on the part surface can be observed which is due to temper color from very thin oxide layers on the part surface. This layer of ferrous material is composed of Fe2O3, Fe3O4, and FeO membranes