CC BY
58LD-O-1
Optical Detection of Defects during Laser Metal Deposition: Simulations and Experiment
I.B. Gornushkin1, G. Pignatelli1, A. Straße1
'BAM Federal Institute for Materials Research and Testing, Richard-Willstätter-Strasse '', '2489 Berlin, Germany igor. gornushkin@bam. de
Laser metal deposition is a rapidly evolving method for additive manufacturing that combines high performance and simplified production routine [1]. Quality of production depends on instrumental design and operational parameters that require constant control during the process [2]. In this work, feasibility of using optical spectroscopy as a control method is studied via modeling and experimentally. A simplified thermal model is developed based on the time-dependent diffusion-conduction heat equation and geometrical light collection into detection optics. Intense light emitted by a laser-heated spot moving across a sample surface is collected and processed to yield the temperature and other temperature-related parameters. In a presence of surface defects the temperature field is distorted in a specific manner that depends on a shape and size of the defect. Optical signals produced by such the distorted temperature fields are simulated and verified experimentally using a 3D metal printer and a sample with artificially carved defects. Three quantities are tested as possible metrics for process monitoring: temperature, integral intensity, and correlation coefficient. The shapes of the simulated signals qualitatively agree with the experimental signals; this allows a cautious inference that optical spectroscopy is capable of detecting a defect and, possibly, predicting its character, e.g. inner or protruding.
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Figure 1. LMD-nozzle printer head and the optical head Figure 2. Temperature field around attached to it. Inset: the substrate with artificial defects. different defect types
[1] 1.I. Gibson, D. Rosen, B. Stucker, Additive Manufacturing Technologies, second ed., (Springer, 2015).
[2] H.L. Wei, T. Mukherjee, W. Zhang, J.S. Zuback, G.L. Knapp, A. De, T. DebRoy, Mechanistic models for additive manufacturing of metallic components, Progress in Materials Science 116, 100703 (2021).
