3D Printers

Novel 3D printer uses ultrasound vibration to produce parts from recycled ABS with improved properties

Researchers at Universiti Teknikal Malaysia Melaka (UTeM) have developed a 3D printer that’s capable of producing more resilient parts from recycled ABS. 

By mounting two piezoelectric transducers to an ordinary gantry Fused Filament Fabrication (FFF) 3D printer, the engineers have managed to develop a means of reversing some of the reduction in strength often exhibited by recycled ABS.

Given the efficacy of their design, which is capable of improving the compression strength of parts made from reused material by 59%, the team say it could help minimize the amount of environmentally-damaging filament that goes to landfill. 

The researchers' ultrasound 3D printing setup. Photo via UTeP.
The researchers’ ultrasound 3D printing setup. Photo via UTeM.

Improving FFF’s material efficiency 

While 3D printing is often marketed as being more material-efficient than subtractive manufacturing technologies, it’s not without its own issues in this area. As any desktop 3D printer user will tell you, print errors can be expensive as well as time consuming, due to the amount of material they waste. Given that many of these plastics are wastefully disposed of, they’re also an environmental hazard. 

One way that makers and manufacturers have attempted to improve the efficiency of their systems is via the recycling of ABS, a material that’s already popular among the 3D printing community. However, as highlighted by the UTeM team in their paper, “the mechanical properties of recycled ABS are markedly degraded,” and reusing the material can reduce its final strength after printing by up to 49%. 

This weakening, which the researchers identified through their own recycled ABS testing, was found to be due to poor interlayer bonding. Such delamination can cause resulting materials internal damage, in a way that leads them to fail when 3D printed, thus making them an unappealing alternative to throwaway filaments. 

The scientists' tensile strength testing results. Image via UTeP.
The scientists’ flexural strength testing results. Image via UTeM.

Turning to ultrasound vibration 

Having developed their own recycled material, by granulating used ABS before extruding it into a 1.75 mm filament, the UTeM researchers then proceeded to 3D print it into samples with a prototype piezoelectric transducer-fitted FFF machine, designed to use ultrasound vibration as a means of improving its stability.

Although initial models produced at a nozzle temperature of 230°C were found to exhibit surface defects, the engineers went on to ascertain that raising this parameter to 270°C and reducing print speed rectified these issues. The team also discovered that exposing parts to ultrasound vibration at 20 kHz frequencies “greatly improved the adhesion of recycled layers.”

This proved the case when it came to improving the flexural strength and modulus of their printed objects, which were 43% and 53% higher than in unexposed parts respectively. The researchers’ results were later confirmed during tensile strength testing, in which materials treated at 20 kHz had a strength of 27.5 MPa, around 24% and 19% higher than those exposed to 10 kHz and those untreated entirely.

Following their initial study’s success, the researchers are planning to make their design open-source. In doing so, the team aims to make the addition of ultrasonic transducers to FFF 3D printers as easy as possible, and help drive the adoption of recycled ABS as a more viable alternative to conventional single-use materials. 

“Overall, [our] approach is a viable option for the better use of printed materials and, with the aid of ultrasound vibration, it improves the mechanical properties of recycled ABS,” conclude the team in their paper. “Therefore, this study shows tremendous potential for sustainable management of ABS waste through recycling, otherwise an increasing burden on resource and landfill sites.”

NC State's proof-of-concept 3D printed meniscus. Photo via NC State
A proof-of-concept meniscus produced using an ultrasonic 3D printing process. Photo via North Carolina State University.

Making waves in the 3D bioprinting sector 

The UTeM team may have identified a polymer 3D printing application of ultrasound waves, but the technology is more conventionally used within 3D bioprinting. In March 2021, scientists at the University of Bath and University of Bristol came up with an acoustic energy driven bioprinting process with tissue engineering potential.

The technology was reminiscent of that developed by researchers at North Carolina State University around two years earlier, which involved using ultrasound to arrange cells in 3D bioprinting gels. In their paper, the team suggested the technique could improve the fidelity of artificial tissues compared to their biological equivalents, in a way that enables them to address wound treatment applications. 

Elsewhere, Concordia University scientists have also uncovered a means of deploying ultrasound in polymer 3D printing. In essence, the team’s technology involves using sound waves to create sonochemical reactions in minuscule cavities and produce complex parts that can’t be achieved using existing techniques. 

The researchers’ findings are detailed in their paper titled “Investigation of Mechanical Properties of Recycled ABS Printed with Open Source FDM Printer Integrated with Ultrasound Vibration.” The study was co-authored by Maidin S, Ting K. H. and Sim Y. Y.

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Featured image shows the researchers’ experimental ultrasound 3D printing setup. Photo via UTeM.