Interlayer adhesion optimisation of fused deposition modelling 3D printed PEEK

Abstract

Fused deposition modelling (FDM) has become the preferred 3D printing method for hightemperature polymeric materials. This is mainly due to FDM’s wide availability and comparatively minimal cost of entry. Poly-ether-ether-ketone (PEEK) is one such high-temperature, highperformance polymer with several potential uses in various industries and applications. However, its use hinges upon whether the required geometry may be successfully 3D printed in such a way that its high-performance characteristics and properties are retained in the produced part. This project, developed in collaboration with the University of Malta and Trelleborg Sealing Solutions Malta, aims to develop an optimised printing profile which results in strong interlayer adhesion of successive layers of the printed geometry, as printed in the Z-axis, vertical build orientation. Towards this aim, this project considered the effects of four quantitative printing parameters, namely: Layer Height, Nozzle Temperature, Printing Speed, and Extrusion Multiplication over two levels (or parameter values), on the tensile strengths and flexure strengths of a set of standard testing geometry. The selection of these four factors and their levels was based on a review of the available literature, and on observations made by the researcher during a series of familiarisation experiments with the printer being utilised. A Design of Experiment (DoE) technique, the associated theory, and several statistical tools were utilised in the design, analysis, and interpretation of the results obtained. The best performing tensile test specimen was specimen 16, with optimised parameter values of LH = 0.2mm, NT = 430˚C, Speed = 1800mm/min, and EM = 0.8. This specimen had an observed ultimate tensile strength of around 19MPa. This value was considerably below the 100MPa tensile strength observed in moulded PEEK specimens. The best performing flexural test specimen meanwhile was specimen 6, with optimised parameter values of LH = 0.1mm, NT = 430˚C, Speed = 900mm/min, and EM = 0.8. This specimen had an observed flexural strength of 116.4MPa, which was comparable to the flexural strength observed in moulded PEEK specimen which had a value of 164MPa.