Abstract
One of the fundamental issues in the Fused Filament Fabrication (FFF) additive manufacturing process lies in the mechanical property anisotropy where the strength of the FFF-3D printed part in the build-direction can be significantly lower than that in other directions. The physical phenomenon that governs this issue is the coupled effect of macroscopic thermal mechanical issues associated with the thermal history of the interface, and the microscopic effect of the polymer microstructure and mass transfer across interfaces. In this study it was found that the use of 34.4 kHz ultrasonic vibrations during FFF-3D printing results in an increase of up to 10% in the interlayer adhesion in Acrylonitrile Butadiene Styrene (ABS), comparing the printing in identical thermal conditions to that in conventional FFF printing. This increase in the interlayer adhesion strength is attributed to the increase in polymer reptation due to ultrasonic vibration-induced relaxation of the polymer chains from secondary interactions in the interface regions.
Highlights
Fused Filament Fabrication (FFF) technology represents a capable, flexible, and cost-effective option in the additive manufacturing industry
Currently a widely adopted prototyping tool in production of engineering products, for the FFF process to advance into a manufacturing tool, its process and material characteristics, such as tolerance and accuracy, surface finish, as well as material property uniformity, need to reach a high level of maturity
Unlike the strength in directions normal to the build direction which can be optimized by infill and raster strategy, the inter-layer strength of the FFF part is governed by the thermal history-dependent mass transfer across layers as well as the rheology-dependent microstructures of the printed tracks [13,15,16,17]
Summary
Fused Filament Fabrication (FFF) technology represents a capable, flexible, and cost-effective option in the additive manufacturing industry. It is evident that reducing the radius of gyration of polymer chains could result in similar improvement in inter-layer strength This can be achieved by promoting relaxation of the stretched polymer chains in the printed tracks. The work reported here describes, for the first time, a technique of using ultrasonic vibrations as an in-process method to reduce the chain–chain secondary interaction and allow more relaxation and diffusion of the polymer in the interface region to result in an improvement in interfacial adhesion strength. This effective technique has the potential to produce FFF-printed parts with isotropic mechanical properties
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