Temperature Measurements During Robotized Additive Manufacturing of Metals

Abstract: Additive Manufacturing has brought about substantial benefits to the manufacturing industry due to the numerous advantages it provides, at the same time there are factors that can be improved upon. Temperature control is an important parameter during the build process as it affects build quality. The main objective of this thesis project was to investigate what sensors could be used for monitoring the temperature during the additive manufacturing processand to compare and evaluate their performance. This involved implementing two 2-color pyrometers and a short-wave infrared camera to monitor the temperature of the area behind the melt pool and then visualizing the respective data. Initial issues arose during test runs in the form of noise in the pyrometer data, this was solved by implementing a smoothing filter to the signal. Multiple runs were conducted to capture the required data as images produced by the camera were overexposed and out of focus during initial runs. This was solved by changing the camera position and exposure settings. Reading the temperature values from the images involved interpreting the Average Dark Units (ADU) values of the region of interest and then comparing those values to a reference chart. The data gathered with the help of LabVIEW software and the proprietary imaging software of the camera showed that the selected sensors were in fact suitable for the intended task and could be used in conjunction with each other. This data could then be used to create a closed-loop system in the future (not in the scope of this thesis work) and thus enable the increase in the level of automation for Robotized Laser Wire Additive Manufacturing.