Research of on-line monitoring technology and control strategy for laser-directed energy deposition: a review

As an advanced metal additive manufacturing technology, laser-directed energy deposition (DED-LB) has attracted a lot of attention in recent years, and is increasingly used in aerospace, automotive, marine, and biomedical applications. However, as industry application standards continue to improve, the challenges of part quality, process stability, and molding efficiency faced by DED-LB are becoming more and more prominent. On-line monitoring and real-time quality regulation can effectively avoid quality defects in processing, which is an effective measure to solve the problem. This paper summarizes the current research status of on-line monitoring means and closed-loop quality regulation technology for DED-LB. The on-line monitoring signals and related sensing devices mainly based on image signals, temperature signals, spectral signals, acoustic emission signals, and X-ray imaging, as well as the closed-loop control strategies and intelligent optimization methods in the process are discussed. Finally, a view on the future direction of on-line monitoring-control system for DED-LB is presented.