Vision Based Temperature Input in PID-Controlled 3D-Printer Applications : Viability of IR-thermometer thermography for use in 3D printer applications

Abstract: In 3D-printers, accurate control of temperature is important and most often a thermistor is used to regulate it. However, while thermistors are cheap, they tend to be quite inaccurate at the wide temperature range of 3D-printers. And since they need to be in contact with the object they are measuring, they have to withstand the temperature that the object operates in. This work explores the possibility and viability of using a contactless solution for temperature feedback for the PID-regulator in 3D-printers instead of thermistors. Originally this work was supposed to use a thermal camera but because of unforeseen shipping problems, the thermal camera did not arrive in time, instead an IR-thermometer was used. The work was done by modifying the software of the 3D-printer to receive temperature from an external source, two available pins on the motherboard of the 3D printer were connected to a Raspberry Pi and with a custom made communication protocol and modified firmware, temperature data could be transferred between them. An IR-thermometer was mounted on the extruder of the 3D-printer, measuring the temperature of the heating block, it was also connected to the Raspberry Pi and its reported temperature was sent to the 3D-printer. To measure the performance of the different solutions, important data was logged and a visual inspection of printed parts were conducted. The results of the work showed that it was possible to replace the thermistor with a contactless IR-thermometer with a print quality that was on par with the original solution. It was also found that the IR-thermometer had a faster response-time to changes in temperature compared to the thermistor. The IR-thermometer should also have a wider object temperature-range than the thermistor but because this work was delimited to one specific thermoplastic material with one temperature-range, this was not tested. In conclusion the contactless solution had a result better than expected and is a promising proof of concept. The price of the contactless solution is magnitudes higher than that of the thermistor but with its promising accuracy and response time to changes in temperature it could be a viable solution for industrial applications.