NSGA-II-Based Multi-Objective Optimization of Fused Filament Fabrication Process Parameters for TPU Parts with...

Area of Science:

• Materials Science and Engineering
• Additive Manufacturing
• Polymer Processing

Background:

• Fused filament fabrication (FFF) is a widely used additive manufacturing technique for thermoplastic polyurethane (TPU).
• Achieving optimal surface quality, dimensional accuracy, and mechanical properties simultaneously in FFF-processed TPU remains a challenge.
• Post-processing techniques like chemical smoothing can alter the surface characteristics and mechanical performance of 3D printed parts.

Purpose of the Study:

• To investigate the combined effects of extruder temperature, layer thickness, and printing speed on the surface roughness, dimensional deviation, and ultimate tensile strength of FFF-printed TPU.
• To evaluate the impact of Tetrahydrofuran (THF)-based chemical smoothing on the surface and mechanical properties of the printed parts.
• To perform multi-objective optimization of FFF process parameters for balanced surface quality, dimensional accuracy, and mechanical performance using a genetic algorithm.

Main Methods:

• Fabrication of TPU parts using FFF with a Box-Behnken experimental design, varying extruder temperature (210-230 °C), layer thickness (200-400 µm), and printing speed (30-50 mm/s).
• Post-processing of printed specimens via THF-based chemical smoothing.
• Characterization of surface roughness (Ra), dimensional deviation (DD), and ultimate tensile strength (UTS) before and after chemical smoothing.
• Multi-objective optimization using a non-dominated sorting genetic algorithm (NSGA-II) implemented in Python 3.11.

Main Results:

• Chemical smoothing significantly reduced surface roughness by 50-72% (from 13.17-15.87 µm to 4.01-7.35 µm).
• Dimensional deviation improved by 20-38% after post-processing (from 260-420 µm to 160-310 µm).
• Ultimate tensile strength increased by 10-24% following chemical smoothing (from 30.24-40.30 MPa to 33.97-47.94 MPa).

Conclusions:

• The study successfully demonstrated the significant improvements in surface quality, dimensional accuracy, and mechanical properties of FFF-printed TPU parts through optimized process parameters and chemical smoothing.
• The multi-objective optimization using NSGA-II identified optimal FFF parameter combinations for achieving a desirable balance between surface finish, dimensional precision, and strength.
• Chemical smoothing is an effective post-processing method for enhancing the overall performance of FFF-manufactured TPU components.