Photodiode data collection and processing of molten pool of alumina parts produced through selective laser melting

Though SLM of ceramics is difficult, it is still attracting the attention of many researchers, because it is possible to fabricate high precision complex ceramics parts directly. As the molten pool behavior is the direct impact factor during SLM, monitoring and analysis of the molten pool behavior of ceramic will be beneficial to optimize SLM of ceramic. In this paper, an optimized molten pool data collection method called photodiode multi-detector divisional detection was designed to improve the precision of photodiode data during selective laser melting (SLM). Based on the system, the influence of laser power on the molten pool behavior of Al2O3 in single track was studied and relationships between molten pool data and several defects are analyzed. The experiment results shown that relative distances and incident angles between the molten pool and the photodiode had a great effect on the precision of photodiode data. The new data collection method can overcome this limitation to improve the precision of molten pool. Comparing the photodiode signal values at different laser powers (100 W, 180 W and 260 W), the higher of the laser power was, the bigger fluctuation range of the photodiode signal values was, the less stable of the molten pool became. The data cases shown that the delay of scanner, 'edge effect' and the unstable temperature field could be detected by comparing the photodiode data of the molten pool.