Experimental investigations of process parameters on dimensional accuracy for FDM printed CF/PETG parts

Carbon fibre-reinforced polyethylene terephthalate-1,4-cyclohexanedimethanol ester (CF/PETG) material has found widespread applications in industries such as protective gear, lattice structures, and prosthesis manufacturing. Fused deposition modelling (FDM), a leading technology in additive manufacturing for fabricating complex geometrics, is widely employed in industrial production. However, improper selection of process parameters can result in reduced dimensional accuracy of components. Existing research primarily focuses on the dimensional accuracy of FDM-fabricated parts using conventional materials such as PLA and ABS, whereas CF/PETG composites remain relatively underexplored. This study investigates the influence of process parameters on the dimensional accuracy of CF/PETG components, with the objective of identifying optimised parameter settings to inform engineering applications. In this study, CF/PETG test specimens were fabricated using FDM technology to evaluate the effects of four critical processes, namely, parameters - nozzle temperature, heated bed temperature, layer thickness, and infill density, on dimensional accuracy. An L25 orthogonal experimental design was employed, incorporating dimensional measurements and error analysis of the test samples. Signal-to-noise ratio analysis was conducted to determine the relative influence of the primary and secondary order of the four factors' parameters in each XYZ direction, as well as to identify the optimal parameter combination of each direction. Additionally, grey relational analysis was employed to evaluate the overall dimensional accuracy, establishing the order of parameter influence as follows: heated bed temperature > infill density > layer thickness > nozzle temperature. The optimal set of process parameters was identified as a nozzle temperature of 245°C, heated bed temperature of 65°C, layer thickness of 0.16 mm, and infill density of 30%. A practical 3D printing case study involving an arm protective gear was carried out using optimised process parameters, and dimensional accuracy was assessed through reverse engineering analysis. The results validated that the optimised process parameters offer valuable reference data for enhancing the accuracy of CF/PETG components, thereby supporting practical applications in fields such as arm protective gear fabrication.