Multi-Objective Optimization of FDM Dimensional Accuracy for PLA/TPU Blends Based on Entropy Weight-TOPSIS and Orthogonal Array Design

Fused deposition modeling (FDM) of polylactic acid (PLA) is plagued by dimensional inaccuracies—thermal shrinkage, warpage, and geometric distortion—that restrict its application in high-precision manufacturing. Blending thermoplastic polyurethane (TPU) with PLA enhances toughness, yet the coupled effects of blend ratio and printing parameters on dimensional accuracy remain unclear. This study establishes a multi-objective optimization framework integrating single-factor experiments, orthogonal design, ANOVA, and entropy weight–TOPSIS. Single-factor experiments combined with TOPSIS first identify the optimal PLA/TPU blend ratio, and orthogonal experiments are subsequently conducted on this optimal ratio to determine the best parameter combination. The 70:30 PLA/TPU blend delivers the optimal comprehensive performance (TOPSIS closeness: 0.680), attributed to favorable phase compatibility and robust interfacial adhesion as verified by XRD and SEM. Range analysis and ANOVA on the orthogonal results identify infill rate and layer height as the dominant factors governing dimensional accuracy (p < 0.05). Under the optimized parameter set (60 mm/s, 210 °C, 90% infill, 0.1 mm layer), the total dimensional deviation reaches only 0.256 mm, substantially lower than single-objective counterparts (0.321–0.418 mm). This work offers a validated strategy for precision control in FDM through synergistic optimization of blend formulation and processing parameters.