Choon Yong QuekNg Hue Thung CalistaJing Yee ChaiZhen Ye LeeMing Yee Khaw0000-0003-2276-6632chen hunt ting0000-0003-2884-6027Koay Seong ChunMing Yeng Chan2026-10-122026-10-122025-12-0210.21315/jps2025.36.3.1https://dspace-cris.utar.edu.my/handle/123456789/11694The recycled high-density polyethylene (rHDPE) has the potential to be used as a sustainable printing material for fused filament fabrication (FFF). The main challenges producing 3D printable filament from recycled plastic include maintaining a consistent filament-like diameter and ovality, ensuring the printability of the material and achieving adequate mechanical strength in the printed part. This study compares the printability, filament geometry, melt flow index (MFI) and tensile properties of printed specimens using rHDPE and commercial HDPE filaments. The research successfully produced 3D printing filament from rHDPE at 220°C, which was compatible with FFF printing. However, rHDPE filament exhibited significantly higher diameter deviations and filament ovality compared to commercial HDPE filament. During printing, both rHDPE and commercial HDPE specimens experienced warping at the bottom layers, a common challenge in 3D printing high-crystalline thermoplastic materials. rHDPE had a lower MFI value than commercial HDPE, allowing it to be printed at a lower temperature. For optimal tensile strength and modulus, both materials performed best when printed at 230°C. However, printed specimens made from rHDPE showed lower tensile strength and modulus than those made from commercial HDPE filament. This study highlights the feasibility of using rHDPE as a feedstock for FFF printing while addressing the challenges related to filament geometry, warpage and mechanical properties. © Penerbit Universiti Sains Malaysia, 2025. This work is licensed under the terms of the Creative Commons Attribution (CC BY) (http://creativecommons.org/licenses/by/4.0/).en-US3D printingcommercial HDPEfuse filament fabricationrecycled HDPEFabricationPlastic filamentsPlastic recyclingStrength of materials3-D printing3D-printingCommercial HDPEFuse filament fabricationHigh-density polyethylenesMechanicalMelt-flow indexOvalityPropertyRecycled HDPETensile strengthtext::journal::journal article::research article