Optimisation of Fused Deposition Modelling Process Parameters for Structural Performance of Thermoplastic Polymer Parts using BoxBehnken Design and Grey Relational Analysis

Abstract

Fused Deposition Modelling (FDM) is the most widely deployed additive manufacturing technology for production of functional thermoplastic polymer components in engineering, medical, and consumer applications. The mechanical performance of FDM- produced parts is critically dependent upon process parameter selection, with layer thickness, infill density, print speed, nozzle temperature, and cooling fan speed collectively determining the microstructural characteristics and resultant mechanical properties of the printed component. This study presents a systematic multi- objective optimisation of FDM process parameters for five commercially relevant filament materials, PLA, ABS, PETG, TPU, and Nylon PA12, using a Box- Behnken Design (BBD) with 46 experimental runs and Grey Relational Analysis (GRA) for composite optimisation of three simultaneous response variables: ultimate tensile strength (UTS), flexural modulus, and surface roughness (Ra). ANOVA analysis identified layer thickness (31.4% contribution) and infill density (24.8%) as the most influential parameters for the composite Grey Relational Grade. The optimal FDM parameter set (layer thickness 0.15 mm, infill density 80%, print speed 45 mm/s, nozzle temperature 210 degrees C for PLA) achieved UTS of 52.4 MPa, flexural modulus of 2.84 GPa, and Ra of 3.2 micrometres, representing improvements of 28.6%, 22.4%, and 34.8% respectively over default process settings. Microstructural analysis using scanning electron microscopy (SEM) confirmed that layer adhesion quality and interlayer void fraction are the primary microstructural determinants of FDM mechanical performance. The study provides validated process parameter recommendations for each of the five filament materials investigated, supporting material- specific process qualification in industrial FDM deployment.