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The present work investigates, by both mathematical modelling and experiment, the contribution of bonding between the filaments to the strength of the parts manufactured by fused deposition modelling (FDM). A mathematical model for neck growth between cylindrical filaments is derived based on viscous sintering for cylindrical filaments. Theoretical ultimate tensile load is determined from the layer thickness information and predicted average final neck size between filaments. The experimental ultimate tensile load is obtained by conducting a simple tension test with two different build directions. Agreement between theoretical and experimental ultimate tensile load and scanning electron microscope (SEM) photomicrographs of the fracture surface indicate that the strength of the FDM part is primarily due to intra-layer bonding, inter-layer bonding and neck growth between filaments. It also indicates that the total time and heat available to the filaments are just sufficient to grow necks but not enough to fully coalesce. [ABSTRACT FROM AUTHOR]

In the present work, the relationships between two important quality objectives, namely, strength and volumetric shrinkage of fused deposition modelling (FDM) parts and selected process parameters, namely the build interior, the horizontal build direction and the vertical build have been determined through a minimum number of experiments based on face centred central composite design. Specimens have been manufactured on an FDM machine and tests have been conducted to evaluate strength and volumetric shrinkage. The relationship for each of these two response variables in terms of the three process parameters has been constructed using analysis of variance. The resulting two objective functions are optimised simultaneously using the non-dominated sorting genetic algorithm. In order to validate the Pareto optimal solution, three randomly chosen experimental runs at intermediate parameter values (other than design of experiments levels) were repeated and good correlation was found between these results and the Pareto optimal. [ABSTRACT FROM PUBLISHER]