Metal AM Making metal parts 'sing': Acoustic quality control for 3D printing

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Penn State researchers are making metal 3D-printed parts sing — literally. Backed by a 1 million dollar Darpa grant, their groundbreaking acoustic technique could revolutionize defect detection during printing, speeding up production for critical defense applications.

A multidisciplinary research team led by Penn State has been awarded a 1 million dollars, two-year grant to transform quality control in metal additive manufacturing, also known as 3D printing. Funded by the Defense Advanced Research Projects Agency’s (Darpa) Structures Uniquely Resolved to Guarantee Performance (Surge) program, the project aims to detect and address defects in metal parts during the printing process itself, rather than afterward.

The team includes Christopher Kube, associate professor of engineering science and mechanics at Penn State; Allison Beese, professor of materials science and engineering and of mechanical engineering at Penn State; Andrea Argüelles, associate professor of engineering science and mechanics and of acoustics and affiliate of the Materials Research Institute at Penn State; and Tao Sun, associate professor of mechanical engineering at Northwestern University.

Additive manufacturing has greatly increased the speed and uniformity of producing metal parts. However, the process often introduces defects such as tiny pores that can compromise structural integrity. Traditionally, advanced X-ray computed tomography is used to detect such defects after production — a method that is both costly and time-consuming.

Instead, Kube’s team proposes an innovative in-process approach. They will develop acoustic sensors and ultrasonic microphones built into the printing platform to detect and measure pores as the parts are being printed.

“In laser-based metal 3D printing, a laser beam selectively melts metal powder in succession and layer-by-layer to create a 3D-printed part. Defects such as pores manifest from micron-sized bubbles formed in the laser melting process and get deposited into the solid part when the liquid melt pool solidifies,” said Kube.

“Our team recognized that the melt pools emit characteristic acoustic tones related to bubble formation in the liquid, which is a precursor to a pore. Our technique is based on stimulating the melt pools with short duration ultrasonic waves such that the bubbles ‘sing’ to the acoustic microphones installed within the build chamber.”

A key part of the research involves collaboration with Sun and the Advanced Photon Source (APS) at Argonne National Laboratory. At APS, high-speed X-ray imaging will allow the team to directly observe the formation of bubbles and pores, providing critical data to train their acoustic detection models.

“Our acoustic technique will be developed at APS, where direct high-speed X-ray images of bubbles and pores will provide the training data that will allow us to interpret the acoustic signatures when measurements are performed in printers at Penn State,”Kube explained.

The project promises significant improvements in manufacturing efficiency, quality control, and reliability.

“There are currently no in-process sensing techniques that can reliably measure 25-micron subsurface pores and locate them to within 125 microns. Achieving these metrics enables downstream modeling of microstructure and mechanical properties like part strength to become accurate and viable,” said Kube.

“Coupled sensing and modeling is a paradigm shift from the current quality-control practice. In the future, we could have print farms producing thousands of parts one day and installed into defense systems the next day. It is exciting to be part of a program that has the potential to impact supply chains, enable superior performance and make systems more sustainable.”

The technique will be developed and tested at Penn State and the Advanced Photon Source.

“In late 2026, we will demonstrate the ability to detect, measure and locate pores in an actual print in a laser powder bed fusion 3D printer at Penn State,” Kube said.

If successful, the project could dramatically reshape how high-performance metal components are manufactured and deployed across a range of critical industries, especially defense.

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