New vacuum tech slashes porosity by 75 percent in large-scale 3D prints

Large-format additive manufacturing (LFAM) – a bigger-picture take on 3D printing that enables the direct printing of meter-scale components – is used to create large, complex parts for various industries.

Even though these materials provide excellent stiffness and low thermal expansion, their widespread use has long been held back by internal porosity, or voids, that compromise the printed parts’ strength and reliability.

Now, thanks to the new vacuum-assisted technique, the researchers have managed to remove the gases trapped during printing, thus significantly reducing the voids and making the parts stronger and more consistent.

Understanding porosity defects

Vipin Kumar, PhD, a composites and fiber manufacturing expert at ORNL, explained that even though 3D-printed materials provide excellent stiffness and low thermal expansion, their potential is greatly limited by persistent intrabead porosity.

Porosity in 3D printing refers to tiny voids or defects within the printed material, often caused by trapped gas or incomplete fusion during the printing process.

These weak spots can act like small chips in glass, spreading under stress and ultimately compromising the strength, durability, and reliability of critical components such as medical implants or aerospace parts.

To tackle the issue, the researchers integrated a vacuum hopper – a device used to remove air, moisture, and trapped gases from materials in manufacturing – directly to the extrusion process, where heated material is pushed through a nozzle to form the printed part.

To their surprise, the initial results greatly highlighted the method’s effectiveness, as it reduced the porosity by up to 75 percent, even in parts with varying fiber content – a major factor in large-scale manufacturing where material consistency can be difficult to maintain.

Furthermore, in some cases, the internal void rate dropped below two percent, which Kumar described as a significant advancement compared to conventional methods.

Reinventing polymer printing

“Using this innovative technique, we are not only addressing the critical issue of porosity in large-scale polymer prints but also paving the way for stronger composites,” Kumar explained in a press release.

The team suggested that the vacuum-assisted method could be seamlessly integrated into existing LFAM workflows, helping streamline production and improve part quality across sectors like aerospace, automotive, and defense.

“This is a significant leap forward for the LFAM industry,” Kumar concluded, explaining how the design effectively pre-degasses the material, ensuring a cleaner and denser output.

Since the system is currently designed for batch based processing, the team is now actively working to expand its capabilities for continuous, scalable, and industrial-grade applications.

They revealed they have already developed a patent pending concept to integrate the vacuum extrusion method into continuous deposition systems, in a step that could move the technology into mainstream, real-time manufacturing environments.