Recycled HDPE Sandwich Composite Materials for Casting Using FDM 3D Printing

In ‘Recycled HDPE reinforced Al₂O₃ and SiC three dimensional printed patterns for sandwich composite material,’ authors Narinder Singh, Rupinder Singh, Ranvijay Kumar, and IPS Ahuja explore new ways to create sacrificial patterns for investment casting using FDM 3D printing and recycled materials.

While recycling is a major concern overall, worldwide, increasing use of thermoplastics raises even more questions in terms of waste disposal. Because of the challenge in separating sub-parts, researchers have been seeking other ways to recycle—expressly, without separation.

“Commercially various waste materials are created by service, manufacturing industries and municipal solid wastes,” state the researchers. “The expanding awareness about the Earth has contributed to the concerns related with transfer of the disposal of the wastes. One of the major concerns especially in developing nations like India is solid waste management.”

Flow chart of industrial recycling process cycle.

Previous research has been performed regarding recycled HDPE for wood composite, and WPC has been studied as well, although the authors inform us that bioplastics are usually cost-prohibitive for use. In most cases, however, polymers do include fillers meant to strengthen thermal and mechanical properties.

Investment casting usually requires a mold and ceramic shells to create prototypes, with separation lines and inserts built into the molds. Structures are then finished, assembled, and filled with liquid wax, after which, the contents of the mold are broken out.

“In conventional IC process, substantial investments are focused on model or generation of tooling advancement,” state the researchers. “The committed resources increment significantly with mold intricacy or low volume fabrication.

“All things considered, a tool maker needs to assess individual mold configurations before focusing to manufacturing since design errors or iterations are typically costly and tedious to alter.”

New technology has been responsible, however, for better accuracy and strength in final products created through rapid prototyping.

RIC process.

In this research, the scientists used feed stock filament wire made of HDPE and reinforced with Al₂O₃/SiC (of average diameter 50 μm). Patterns were then fabricated on an open-source FDM 3D printer. Traditionally, such production would take up to three months just to make one part, costing up to $500. With FDM 3D printing, the process took only eight hours at the most.

With die stone powder, the team was able to create a reliable sandwich composite material, offering shell stability, and temperature resistance up to around 1100 °C. Along with Al, other metals and alloys can be used too, with the end results presenting suitable surface hardness and porosity levels for prototyping.

“These SCM can be used as two phase material, reinforcing elements for cement composites with fractal architecture, shape optimization of the force networks of masonry structures for civil engineering applications, tensegrity architecture, meta-material printing. The proposed route for recycling of plastic solid waste is in line with the application domain discussed by other investigators via 3D printing,” concluded the researchers.

Composite materials are becoming increasingly popular in the world of 3D printing and additive manufacturing as researchers continue to find new ways to produce better prototypes and parts, whether in using wood composites, continuous carbon fiber, metal polymers, or other polymer composites.

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Steps followed for preparation of SCM.