Accurate Determination of Laser Spot Position during Laser Powder Bed Fusion Process Thermography
Ivan Zhirnov, Sergey Mekhontsev, Brandon M. Lane, Steven E. Grantham
Thermography and high-speed imaging are useful tools for researching the additive manufacturing laser powder bed fusion (LPBF) process by providing transient, spatial, and thermal information in and around the melt pool. However, it is not directly possible to ascertain the position of the laser spot with respect to the imaged melt pool, which could provide key information regarding how laser energy is distributed and absorbed. In this paper, we demonstrate a procedure for registering the laser spot position with the melt pool using a bright illumination source co-axially aligned with the laser to project a sharp spot on the build plane. This spot fixed to the laser position and used as a reference frame for registering the laser spot with the melt pool radiance temperature distribution. Measurement results demonstrate the effect of varying process parameters (laser power and scan speed) on the melt pool thermal field and respective position of the laser spot.