Online Monitoring Technology of Metal Powder Bed Fusion Processes: A Review

Abstract

Metal powder bed fusion (PBF) is an advanced metal additive manufacturing (AM) technology. Compared with traditional manufacturing techniques, PBF has a higher degree of design freedom. Currently, although PBF has received extensive attention in fields with high–quality standards such as aerospace and automotive, there are some disadvantages, namely poor process quality and insufficient stability, which make it difficult to apply the technology to the manufacture of critical components. In order to surmount these limitations, it is necessary to monitor the process. Online monitoring technology can detect defects in time and provide certain feedback control, so it can greatly enhance the stability of the process, thereby ensuring its quality of the process. This paper presents the current status of online monitoring technology of the metal PBF process from the aspects of powder recoating monitoring, powder bed inspection, building process monitoring, and melt layer detection. Some of the current limitations and future trends are then highlighted. The combination of these four–part monitoring methods can make the quality of PBF parts highly assured. We unanimously believe that this article can be helpful for future research on PBF process monitoring.

Measuring the Cooling Behavior of Melt Pools in L-PBF by Pyrometry

“…McCann et al [ 2 ], Everton et al [ 6 ], Hou et al [ 7 ] as well as Yang et al [ 8 ] provide an overview of L-PBF process monitoring technologies and their challenges. Here, McCann et al [ 2 ] point out the main problem of pyrometry: Without knowledge about the emissivity of the regarded material, only qualitative statements can be made.…”

“…The literature describes pyrometry as a promising, affordable and robust candidate for melt pool recording as well as process monitoring in L-PBF (e.g., see McCann et al [ 2 ], Everton et al [ 6 ], Yang et al [ 8 ], Gutknecht et al [ 11 ] or Hooper [ 13 ]). Since most studies focus on the potential of using pyrometry for processing and quality monitoring (e.g., see [ 7 , 18 , 19 , 20 ]), the obtained signals are mainly interpreted as arbitrary units. Measuring temperatures instead of arbitrary units remains challenging due to the dependency of the emissivity from unknown factors such as temperature, surface condition and aggregate state.…”

Emerging Materials for Additive Manufacturing

“…In total, two reviews and thirteen original research articles are included. In their review article, Minasyan and Hussainova discussed the recent developments of ceramic particulate-reinforced aluminium alloys produced by laser powder bed fusion [14], while Hou et al elaborated the use of monitoring systems for powder bed fusion processes with a focus on metals in their comprehensive review [15]. For original research, Gatões et al studied the fabrication of different stainless steels using selective laser melting, a type of laser powder bed fusion technique [16].…”