Additive manufacturing process monitoring and control by non-destructive testing techniques: challenges and in-process monitoring

This paper examines on the obstacles specific to the implementation of non-destructive testing (NDT) techniques in additive manufacturing (AM). The general challenges impeding the adoption of AM for volume production of parts, and the use of NDT techniques to ameliorate some of these challenges are studied. These challenges include the lack of understanding of AM materials, and insufficient standards for the mechanical testing and NDT of additively manufactured parts. An overview on the principle of operation for in-process inspection NDT methods is presented. The techniques include thermography, and acoustic emission testing. The applications of these NDT techniques in AM and their suitability for defects detection of additively manufactured parts are reviewed. The sensitivity, and the advantages and disadvantages of each technique are evaluated. The types of defects, and the detectability of these defects by NDT techniques are assessed.