Evaluating Temperature Influence on Low-Cost Microphone Response for 3D Printing Process Monitoring †

Abstract

The 3D printing process deals with the manufacture of parts by adding layers of material onto a heated printing bed. Electret microphones are widely used as low-cost and precise measuring devices. However, its response was negatively affected by higher temperatures due to the field effect transistor utilized in its construction. The Pencil Lead Break (PLB) method is a standardized artificial acoustic emission source utilized for the evaluation of sensors response. The present work aimed to study the electret microphone response for 3D printing monitoring and to evaluate the efficiency of a proposed housing to reduce the printing bed temperature’s influence on the electret microphone’s response. The microphone housing was 3D-printed utilizing ABS filament; its geometry was designed with the purpose of separating the sensor from the heated bed and creating an acoustic shell. Then, PLB tests were performed, and the raw signal was collected from housed and non-housed microphones at 5 MHz sampling frequency. The sensors were tested under three temperatures of the printer bed: at 25 °C (ambient), at 65 °C (operating temperature), and, finally, after the temperature of the table was naturally stabilized from 65 °C to 25 °C. The signals were investigated in the time and frequency domain. The results showed that the housing impacts the microphone’s response positively when operating at 25 °C, where the signals presented higher amplitudes in both domains. However, the response obtained by the housed sensor was considerably attenuated at 65 °C. Furthermore, the signals collected at 25 °C after exposing the housed microphone to heat demonstrated a “greenhouse effect”, keeping the sensor at higher temperatures for an extended period. It can be concluded that the proposed housing failed in reducing the temperature effects in the sensor’s response. However, these effects were shown to be significant and the need for an alternative method to attenuate them was reinforced.