Simulations of Online Non-Destructive Acoustic Diagnosis of 3D-Printed Parts Using Air-Coupled Ultrasonic Transducers

Abstract

Abstract The open-loop process by which 3D printers operate often leads to significant time and material losses due to print failures. A challenge in Additive Manufacturing (AM) is assessing 3D-printed parts mid-print for the dimensional stability of the internal structures and their microstructure and material properties. These internal features are typically opaque to visual inspections after print and can only be accessed for property characterization if the part is cut open. An assessment of methods for evaluating parts in situ using air-coupled ultrasonic transducers in this paper. The purpose is to determine the microstructure and limited effective properties (density and modulus) of internal structures during the print process using acoustic methods. We examine the effectiveness of acoustic wave reflection, absorption and propagation through the infill channels, which make up a part on a fused deposition modeling printer to obtain dimensional measurements while the part is on the print bed. We simulated the acoustic wave response for common frequencies of commercially-available air-coupled transducers (25–300 kHz) placed near simulated 3D-printed parts. We compared the return signals using the k-Wave Acoustics Toolbox, a time-domain model for acoustic wave propagation, and validated these simulations with physical readings. The results showed the behavior of the peak amplitude of the received signals for various materials and infill channel lengths. Simulations and physical experiments were conducted for both through-transmission and pulse-echo approaches. The simulations optimize parameters for a maximized peak received signal strength. The results will limit the scope of computationally expensive methods of observing obfuscated structural deficiencies and deformations in a 3D-printed part in situ using air-coupled ultrasonic transducers and similar ultrasonic NDE technologies.