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Thermocouple Process Monitoring for Additive Manufacturing

To understand the thermal history of parts manufactured in a laser powder bed fusion system, eight thermocouple sensors were imbedded at key locations with respect to the parts being built. The design comprised eight vertical cylinders 2.54 cm (1 in.) and 1.27 cm (0.5 in.) in diameter and four 2.54 cm (1 in.) horizontal cylinders. The temperature signature collected at the eight locations reveals the time intervals of depositing and melting each layer and the cooling trend associated with the stoppage required for filter cleaning. The temperature profile also reveals a fast rate of heat accumulation at the start of the process. As more layers are melted and the part becomes taller, the dissipation path for heat deposited by the laser increases prior to reaching the build plate. The heat accumulation, therefore, increases rapidly at first, then decreases, plateaus, and then drops slightly toward the end. Distortions due to residual stresses and resultant part separation from the build plate can be deduced from the thermal signature as detected by the thermocouple sensors. This allows the manufacturer to make adjustments or abort the process if necessary. Otherwise, these distortions that render the part a reject are discovered hours or days later upon completion of the additively manufactured part.



Abdul Aziz, M.S., T. Furumoto, K. Kuriyama, S. Tahago, S. Abe, A. Hosokawa, and T. Ueda, 2013, “Residual Stress and Deformation of Consolidated Structure Obtained by Layered Manufacturing Process,” Journal of Advanced Mechanical Design, Systems, and Manufacturing, Vol. 7, No. 2, pp. 244–256,

Bean, G.E., D.B Witkin, T.D. McLouth, D.N. Patel, and R.J. Zaldivar, 2018, “Effect of Laser Focus Shift on Surface Quality and Density of Inconel 718 Parts Produced via Selective Laser Melting,” Additive Manufacturing, Vol. 22, pp. 207–215,

Beshears, R., 2017, “Computed Tomography Inspection and Analysis for Additive Manufacturing Components,” ASNT Annual Conference, 2 November, Nashville, TN

Bilheux, H.Z., G. Song, K. An, J.-C. Bilheux, M.M. Kirka, R.R. Dehoff, L.J. Santodonato, S.B. Gorti, B. Radhakrishnan, and Q. Xie, 2016, “Advances in Neutron Radiography: Application to Additive Manufacturing Inconel 718,” Advanced Materials and Processes,

Brooks, A.J., G.L. Knapp, J. Yuan, C.G. Lowery, M. Pan, B.E. Cadigan, S. Guo, D.S. Hussey, and L.G. Butler, 2017, “Neutron Imaging of Laser Melted SS316 Test Objects with Spatially Resolved Small Angle Neutron Scattering,” Journal of Imaging, Vol. 3, No. 4,

Cerniglia, D., M. Scafidi, A. Pantano, and J. Rudlin, 2015, “Inspection of Additive-Manufactured Layered Components,” Ultrasonics, Vol. 62, pp. 292–298,

Edwards, R.S., B. Dutton, A.R. Clough, and M.H. Rosli, 2012, “Scanning Laser Source and Scanning Laser Detection Techniques for Different Surface Crack Geometries,” AIP Conference Proceedings, Vol. 1430,

Everton, S., P. Dickens, C. Tuckand, and B. Dutton, 2015, “Evaluation of Laser Ultrasonic Testing for Inspection of Metal Additive Manufacturing,” Proceedings Laser 3D Manufacturing II, Vol. 9353,

Griffith, M.L, M.E. Schlienger, L.D. Harwell, M.S. Oliver, M.D. Baldwin, M.T. Ensz, M. Essien, J. Brooks, C.V. Robino, J.E. Smugeresky, W.H. Hofmeister, M.J. Wert, and D.V. Nelson, 1999, “Understanding Thermal Behavior in the LENS Process,” Materials & Design, Vol. 20, No. 2–3, pp. 107–113,

Helvajian, H., A. Manzo, and S. Kenderian, 2016, “Application of Laser Ultrasonic Nondestructive Evaluation Technique to Additive Manufacturing,” ASNT Annual Conference, 26–27 October, Long Beach, CA

Klein, M., and J. Sears, 2004, “Laser Ultrasonic Inspection of Laser Cladded 316LSS and Ti-6-4,” Proceedings of the 23rd International Congress on Applications of Lasers and Electro-Optics, Laser Institute of America

Kube, C.M., 2016, “Attenuation of Laser Generated Ultrasound in Steel at High Temperatures: Comparison of Theory and Experimental Measurements,” Ultrasonics, Vol. 70, pp. 238–240,

Manzo, A.J., S. Kenderian, and H. Helvajian, 2016, “Application of Laser Ultrasonic Nondestructive Evaluation Technique to Additive Manufacturing,” Proceedings of SPIE, Vol. 9738,

Martinez-Anton, J.C., I. Serroukh, and E. Bernabeu, 1999, “Laser Diffraction Wire Diameter Measurements: Correction of Diffraction Models by Interferometric Calibration,” Proceedings, Optical Measurement Systems for Industrial Inspection, Vol. 3284,

McLouth, T.D., G.E. Bean, D.B. Witkin, S.D. Sitzman P.M. Adams, D.N. Patel, W. Park, J.-M. Yang, and R.J. Zaldivar, 2018, “The Effect of Laser Focus Shift on Microstructural Variation of Inconel 718 Produced by Selective Laser Melting,” Materials & Design, Vol. 149, pp. 205–213,

Rodriguez, E., F. Medina, D. Espalin, C. Terrazas, D. Muse, C. Henry, E. Macdonald, and R.B. Wicker, 2012, “Integration of a Thermal Imaging Feedback Control System in Electron Beam Melting,” Proceedings of 23rd Annual International Solid Freeform Fabrication Symposium, Austin, TX, pp. 945–961

Rodriguez, E., J. Mireles, C.A. Terrazas, D. Espalin, M.A. Perez, and R.B. Wicker, 2015, “Approximation of Absolute Surface Temperature Measurements of Powder Bed Fusion Additive Manufacturing Technology Using In Situ Infrared Thermography,” Additive Manufacturing, Vol. 5, pp. 31–39,

Slotwinski, J.A., and E.J. Garboczi, 2014, “Porosity of Additive Manufacturing Parts for Process Monitoring,” 40th Annual Review of Progress in Quantitative Nondestructive Evaluation, AIP Conference Proceedings, Vol. 1581, No. 1,

Smith, R.J., M. Hirsch, R. Patel, W. Li, A.T. Clare, and S.D. Sharples, 2016, “Spatially Resolved Acoustic Spectroscopy for Selective Laser Melting,” Journal of Materials Processing Technology, Vol. 236, pp. 93–102,

Thiede, T., 2018, “An Assessment of Bulk and Surface Residual Stress in Selective Laser Melted Inconel 718,” ECNDT 2018 Conference, 11–15 June, Gothenburg, Sweden

Watkins, T., H. Bilheux, K. An, A. Payzant, R. Dehoff, C. Duty, W. Peter, C. Blue, and C. Brice, 2013, “Neutron Characterization for Additive Manufacturing,” Advanced Materials and Processes, Vol. 171, No. 3, pp. 23–27

Zhou, X., D. Wang, X. Liu, D. Zhang, S. Qu, J. Ma, G. London, Z. Shen, and W. Liu, 2015, “3D-Imaging of Selective Laser Melting Defects in a Co–Cr–Mo Alloy by Synchrotron Radiation Micro-CT,” Acta Materialia, Vol. 98, pp. 1–16,


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