Superior Part Quality Based on Position-synchronous Laser Power Control

Laser powder bed fusion is on the way to being a standard production technology for metal parts. It offers a very high degree of flexibility concerning final part geometry. However, the printing process parameters must be very sophisticated to reach the highest part quality. Thin-walled geometries need special attention since the heat dissipation can be very different compared to massive parts. The lower the heat dissipation, the higher the risk for excessive heat in the process zone. With excessive heat the melt pool gets bigger, which can cause edge bulging – an unwanted geometry deviation of the part to be printed. High-speed process videos show that enlarged melt pools occur especially in sections with short vectors.

The researchers of Fraunhofer ILT have shown that this root cause of edge bulging can be suppressed by geometry-adapted process control. The build processor software classifies the vectors by their length and adapts power ramps at the beginning and end of the vector. The required database was created with standard experiments with varied wall thicknesses. Execution required very precise position-synchronous power control, which can be reached with modern scan technology called SCANmotionControl. The success of the suppression strategy is shown with high-speed videos and topography measurements.