Critical components produced via additive manufacturing must be free of unwanted defects.
While defects may be detectable after deposition using nondestructive testing techniques,
detecting defects during the deposition process offers many benefits: it may enable users to
interrupt deposition to repair the part, or to abort deposition to minimize further loss of time and
material. Here, we present a method for real-time defect detection during directed-energy
additive manufacturing of metals. The method utilized optical emission spectroscopy and a
custom-built data acquisition and control infrastructure. It was implemented on a LENS MR-7
machine, and employed during manufacturing of Ti-6Al-4V components in which defects were
intentionally introduced. Emission spectra were correlated with defect locations, determined via
computed tomography and metallographic cross-sectioning. Preliminary results indicated that
defect formation was correlated with atomic titanium (Ti I) and Vanadium (V I) emissions and
that measurement of the line-to-continuum ratio for line emissions could be used for defect
detection. Based on these findings, sensing strategies for defect detection and, potentially, insitu-defect repair may be realizable.