Selective laser sintering of HDPE: Impact of process parameters on mechanical properties, microstructure, and dimensional accuracy

High-Density Polyethylene (HDPE), a dominant polyolefin in global plastic production, presents significant challenges in additive manufacturing due to its pronounced warping and shrinkage, inherent to its semi-crystalline nature. Overcoming these limitations is essential to harness HDPE's potential for fabricating robust, functional end-use parts with high design flexibility. This study systematically investigates the influence of key Selective Laser Sintering (SLS) parameters bed temperature, laser energy density, and print orientation on the printing performance of HDPE. The findings demonstrate that bed temperature is the critical factor governing bed adhesion and mitigating warpage, with suboptimal conditions severely compromising mechanical integrity. Laser energy density was directly correlated with the degree of particle coalescence and ultimate tensile strength (UTS), with a maximum UTS of 26.3 MPa achieved at an optimal energy density of 7.37 J m⁻¹. Scanning Electron Microscopy (SEM) and quantitative image analysis confirmed that this optimum promotes complete sintering and a homogeneous microstructure with minimal porosity (1.7 %). Beyond this point, excessive energy density induced over-melting and void formation, reducing strength. Print orientation significantly influenced tensile properties, with flat-oriented specimens exhibiting superior performance. Furthermore, dimensional analysis revealed high geometric fidelity, with minimal average deviations of 0.0285 mm and 0.0243 mm in the Z direction. This work provides a comprehensive processing-structure-property relationship for SLS-fabricated HDPE, delivering critical insights for optimizing mechanical performance, dimensional accuracy, and practical applicability in advanced manufacturing.