The flowability and spreadability of three different polymer powders for selective laser sintering were investigated by analysing the powder at different temperatures. These measurements were performed using both the Revolution Powder Analyzer and the Schulze Ring Shear Tester. The latter device was modified with a self-developed heating system to allow testing at temperatures up to 170 °C. Overall, the results of both tests showed that the powders' flowability decreases as the temperature increases, with the largest decrease observed near the materials' melting point. Afterwards, recoating tests were conducted on an EOS P395 machine, which utilized a self-built AI monitoring system to detect and evaluate the severity of defects in the powder bed. The tests revealed that the number and severity of defects also increases with temperature. When approaching the sintering window, the number and severity of defects greatly decreases, and the powder bed becomes stronger and more resistant to defects.