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Performance of eddy currents for the in-situ detection of defects during PBF-LB metal AM In this joint study by Carl Zeiss AG, AMiquam SA, and EOS GmbH, the performance of eddy currents as a tool for the in-situ detection of defects in Laser Beam Powder Bed Fusion (PBF-LB) has been assessed. Process variations, including lack of fusion and keyhole formation could be detected in-situ, as well as individual defects as small as 0.3 mm post-build and post-polishing. Here, Jonatan Wicht, Harald Krauss, Frank Widulle, Julian Schulz, and Edson Costa Santos, Alain Berthoud, and Bernard Revaz present their latest findings.
Near-surface and sub-surface defects are one of the main factors currently hindering the growth of metal Additive Manufacturing applications. This is because they reduce the performance of the produced parts and lead to significant production, qualification, and certification costs. It is therefore desirable to accelerate the development of a technique enabling early detection of these defects – ideally during the process. Only a few physical principles are available to achieve this goal: eddy currents, ultrasound, thermography, and X-ray. These detection technologies are based on the physical changes in the material caused by the defects (difference in electrical conductivity, acoustic properties, heat-transfer, x-ray absorption, etc.). They can, however, only be used in-situ if they meet certain detection requirements (accuracy, defect types) within the constraints of the Additive Manufacturing process (speed, surface roughness, machine environment) and machine integrability [1, 2].
In this study by Carl Zeiss AG, AMiquam, and EOS, the performance of eddy currents was assessed in this context. In-situ measurements were taken using the AMiquam Eddy Current W1 to document potential industry use cases and assess the actual performance of the product. The eddy current measurements have
been achieved by instrumenting the machine recoater with shielded absolute coils (5.8 mm outer diameter (OD) and 200 kHz interrogating frequency, resulting in a theoretical electromagnetic penetration depth of 0.95 mm in the Inconel 718 material from which the components are made).
Fig. 1 An EOS M290 Laser Beam Powder Bed Fusion machine fitted with the AMiquam Eddy Current W1 device (Courtesy AMiquam)
Vol. 10 No. 2 © 2024 Inovar Communications Ltd
Metal Additive Manufacturing | Summer 2024
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Eddy currents for in-situ defect detection
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