Scientists develop vacuum-assisted technique dramatically reducing porosity in large-scale 3D printing.

Breakthrough in Large-Format Printing

Researchers at Oak Ridge National Laboratory (ORNL) in Tennessee have developed a new vacuum-assisted extrusion process capable of slashing internal porosity in 3D printed polymer parts in commercial production by an unprecedented 75%.

The novel method overcomes a major barrier in large-format additive manufacturing (LFAM) and has the potential to revolutionize the way parts are produced in a variety of industries, particularly aerospace and automobile.

LFAM enables the direct printing of meter-scale components but has been limited by internal voids that compromise strength and reliability. The new vacuum-assisted approach effectively removes trapped gases during printing, creating stronger and more consistent parts.

Solving the Porosity Problem

“Although 3D-printed parts demonstrate very good mechanical properties due to their quality of fabrication in the intralayer, the quality of the interlayer has not been as good, which has limited their potential, especially in tension,” said Vipin Kumar, PhD, a composites expert at ORNL.

“These weak spots work like little chips in glass,” spreading when placed under stress and ultimately degrading the performance and reliability of such critical parts, said Kumar.

The scientists incorporated a vacuum hopper directly into the extrusion system and preliminary trials appeared effective. It decreased the porosity of parts by as much as 75 percent, even in regions of parts that had different fiber compositions, a big challenge in industrial processes, where it is hard to control consistency.

In some of them, the internal void rate was below two per cent, which was nearly three-times better than is typical.

“This solution will help solve the vital problem of porosity in large scale polymer prints and opens up new processing windows for stronger, more useful composite materials,” Kumar said in a statement.

The group proposed the vacuum assisted approach could be implemented with ease into the current LFAM process and assist with the production efficiency and part quality in a variety of industries.

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While it is designed for batch applications, the team is engaged in ongoing efforts to extend the capability for continuous, scalable, and industrial implementation.