Real-time monitoring and control of the layer height in laser metal deposition with coaxial wire feeding using optical coherence tomography

Christian Bernauer, Sebastian Thiem, Pawel Garkusha, Christian Geiger, Michael F. Zaeh

Research output: Contribution to journalArticlepeer-review

Abstract

Laser metal deposition (LMD) with coaxial wire feeding is an additive manufacturing technology in which a metal wire is fed into a laser-induced melt pool. The repeated deposition of weld beads allows three-dimensional geometries to be created that can be used for manufacturing, repair, and modification of metal components. However, the process is highly sensitive to disturbances because the fed wire must always be fully melted, and no self-regulating effects as in powder-based LMD exist. The layer height is particularly important for process stability, as even small deviations accumulate over many layers and, ultimately, lead to the termination of the process. Therefore, monitoring and closed-loop control of the layer height during the deposition process are crucial. Due to process emissions, an interruption of the process is usually necessary for the accurate optical measurement of the layer height, which negatively affects the overall productivity. In order to overcome this drawback, an in-axis optical coherence tomography (OCT) sensor was employed in this work, which enabled real-time measurements of the layer height. It was found that positioning the OCT measurement spot as close as possible to the center of the wire provided the highest signal quality. Based on the real-time height data, a closed-loop layer height control was implemented, applying the wire feed rate as the manipulated variable. The experimental results showed that the proposed system was able to compensate for significant disturbances, ensuring dimensional accuracy and process stability.

Original languageEnglish
Article number042028
JournalJournal of Laser Applications
Volume36
Issue number4
DOIs
StatePublished - 1 Nov 2024

Keywords

  • additive manufacturing
  • annular laser beam
  • closed-loop control
  • coaxial wire feeding
  • directed energy deposition
  • height control
  • laser metal deposition
  • OCT

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