Dual scan head approach for in-situ defect detection in laser powder bed fusion of metal

Laser powder bed fusion of metal has emerged as a key technology in additive manufacturing, enabling the production of intricate, high-performance metal components directly from digital designs. However, challenges such as dimensional inaccuracies and internal defects continue to hinder its broader industrial application. Addressing these limitations requires enhanced process monitoring and control strategies. This study introduces an innovative process monitoring system, designed to improve defect detection and process control. By employing a dual scan head configuration, enabling precise and independent path planning of the laser and the measurement field of an infrared camera, the Synchronized Path Infrared Thermography (SPIT) setup utilizes the principle of exploiting differences in cooling behavior to identify subsurface defects. Pre-printed samples with embedded cylindrical defects ranging from 300 to 1000 μm in diameter are used and an additional layer of powder is applied and fused within the experimental setup. The volumetric energy density and scanning speed are varied to analyze their influence on process monitoring reliability. The sensor scan head is synchronized with the laser scan head’s movements, while the infrared camera captures thermal radiation at 1904 fps. The results demonstrate the system’s capability to detect subsurface defects with a minimum size of 356 µm.