India: Researchers Investigate Validity of Multi-Material 3D Printing for Structural Applications

While it is obvious the impact of 3D printing is going to continue to be enormous for industries around the world, there are still challenges—and skeptics. Despite a multitude of new materials (with a focus on metal for many different industrial companies) available for printers of all sizes today, questions continue regarding the strength and durability of 3D printed objects. Researchers Ranvijay Kumar, Rupinder Singh, and Ilenia Farina, all from India, explore some of the problems—and solutions—for 3D printing in their recent paper, ‘On the 3D printing of recycled ABS, PLA and HIPS thermoplastics for structural applications.’

As the researchers point out, there are a variety of different ways to 3D print today, including:

• Fused deposition modeling (FDM)
• Stereolithography (SLA)
• Inkjet printing
• Selective laser sintering (SLS)
• Digital light manufacturing (DLP)
• Selective laser melting (SLM)
• Electronic beam melting (EBM)
• Laminated object manufacturing (LOM)

The team explores the use of multiple materials and their reusability, focusing on Acrylonitrile Butadiene Styrene (ABS), Polylactic Acid (PLA), and High Impact Polystyrene (HIPS).

“ABS is amorphous in nature and having high impact resistance. Low thermal conductivity, heat resistance and toughness, bio-degradability and bio-compatibilities are the key advantages of PLA, whereas HIPS is a low strength structural polymer which has better machinability and fabrication characteristics with low cost,” state the researchers in their paper.

Steps involved in multi-material printing

During testing, PLA exhibited the ‘anticipated’ results, showing the ultimate in break elongation, as well as load and break strength—while HIPS resulted in the opposite. As testing went on further, the researchers examined:

• MFI characterization – flowability of the material
• DSC – determination of melting points
• TSE – extrusion processes
• FDM – multi-material 3D printing with four layers
• Thermal features

“Break load of ABS was 116.55 Kg, PLA was 156.34 Kg and HIPS of 87.84 Kg, multi-material component at experiment no. six resulted in 92.24 Kg which was smaller value than ABS and PLA but greater than HIPS,” reported the researchers during testing. “Similar results were observed for the break strength where at experiment number 6, the break strength was smaller than ABS and PLA but greater than HIPS.”

Schematic configuration of MFI indexer

They also found that in pull-out testing, both strength and elongation could be better manipulated at predicted settings:

“It was noted that break elongation of multi-material component was observed smaller as compared to ABS and PLA. At the same time, break load and break strength has been observed greater than HIPS in case of pull out tests.”

Multi-material printing also reflected better flexural strength than HIPS, but less than PLA or ABS.

“The literature survey reveals that multi-material component comprised of advantages of all the material combined together and can be potentially applied in the area of civil engineering fields especially in structural application,” stated the team.

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Commercial FDM setup

Thermal testing