Thermoacoustic Curing Mechanism and Process Optimization in Non-Contact Ultrasonic 3D Printing.

Non-contact ultrasonic three-dimensional (3D) printing has emerged as a promising alternative to conventional energy-curing manufacturing techniques. However, an insufficient understanding of its underlying curing mechanisms still limits the precise regulation of solidification behavior and stable structural forming. In this context, this work develops a customized ultrasonic printing platform to investigate the thermoacoustic curing behavior of a modified PDMS-based material system. A multiphysics numerical model is established to characterize the focal acoustic pressure, concentrated energy distribution, and transient temperature evolution during printing. Simulated and experimental results collectively indicate that solidification behavior is governed by the balance between localized acoustic energy confinement and thermal diffusion. Systematic experiments are further conducted to quantify the effects of driving power, scanning speed, and line spacing on forming quality. The optimized parameter combination (17.5 W driving power, 0.4 mm/s scanning speed, and 0.2-0.25 mm line spacing) enables stable single-track morphology and favorable interlayer bonding. Additionally, reciprocating scanning trajectories are found to promote localized thermal accumulation, which may introduce dimensional deviations in printed structures. This study provides insights into ultrasonic thermoacoustic curing behavior and offers feasible process guidance for ultrasonic additive manufacturing under the specific material and experimental configurations adopted in this work.