Acoustic Emission Technique for Online Detection of Fusion Defects for Single Tracks During Metal Laser Powder Bed Fusion

One of the main drawbacks of laser based powder bed fusion, is lack of fusion between tracks due to non-optimal input process parameters, scanning and building strategies and/or inhomogeneity in the delivered powder layer. Unstable geometrical characteristics of single tracks and high roughness of the powder layer can cause porosity in 3 dimensional printed parts. In this study a non-destructive online monitoring technique, using acoustic emission was utilized to determine lack of fusion and balling effect of single tracks. This phenomenon was simulated by using an increased powder layer thickness. Short Time Fourier Transform was used as a tool for analysis of the acoustic behaviour of the system and it was compared with the acoustic emission (AE) recorded during processing of single tracks.