A contribution to the monitoring of ceramic surface quality using a low-cost piezoelectric transducer in the grinding operation

The grinding process is usually one of the last stages in the manufacturing process chain since it can provide superior surface finish and closer dimensional tolerances. However, due to peculiarities of the grinding process, workpiece material is susceptible to many problems, what demands a reliable real-time monitoring system. Some grinding monitoring systems have been proposed by means of sensors. However, literature is still scarce in terms of employing time-frequency analysis techniques during grinding of ceramics. Thus, this paper proposes an application of the low-cost piezoelectric transducer (PZT - lead zirconate titanate) in the analysis of the surface quality of ceramic workpieces during grinding process by means of frequency-time domain technique along with the ratio of power parameter (ROP). An integrated high-cost commonly used acoustic emission (AE) sensor was employed in order to compare the results with the low-cost PZT transducer. Tests were performed using a peripheral surface grinding machine. Three values of depth of cut were selected in order to represent slight, moderate and severe grinding conditions. Piezoelectric signals were collected at 2 MHz. The short-time Fourier transform (STFT) was studied in order to obtain the frequency variations over time. An analysis of the ratio of power (ROP) values was performed in order to establish a correlation with the surface roughness. The ROP values are highly desirable for setting a threshold to detect the workpiece surface quality and implementing into a monitoring system. The results of the PZT transducer had a great similarity to those of the AE sensor.