EVALUATION OF THE TEMPERATURE EFFECT ON A LOW-COST MICROPHONE RESPONSE FOR FFF PROCESS MONITORING

The evaluation of the response of sensors fixed to the print bed in the Fused Filament Fabrication (FFF) process has been the subject of recent studies, due to the increasing use of the FFF process in manufacturing industries. Many of these studies focus on topics related to monitoring the FFF process through the signals collected by sensors, as the response of such sensors is affected by the temperature on the print bed used in the FFF manufacturing process. Thus, this work presents the study of the response of a low-cost electret microphone fixed to the print bed under temperature values within the range for printing with Polylactic Acid (PLA) material, in order to determine the temperature value at which the sensor's response begins to undergo significant changes and whether this influence on the sensor's response is limited to a specific frequency band. To achieve this, tests using the graphite breakage method (PLB) were conducted on the heated print bed at temperature values ranging from 25°C to 65°C. The acoustic waves generated by the tests were captured by the electret microphone attached near the breakage point using the PLB method, and the signals were sampled using an oscilloscope at a frequency of 2 MHz. The signals were processed in the time and frequency domains, followed by comparative analyses between the signals obtained at different temperature values. The results showed that it was not possible to determine a single temperature value at which the response of the electret microphone starts to undergo significant changes, but rather that this value is located close to the extremes of the recommended temperature range for FFF manufacturing with PLA. Furthermore, the results showed that the temperature influence occurs in different frequency bands of the electret microphone's response.