INFLUENCING THE MECHANICAL PROPERTIES OF FUSED FILAMENT FABRICATION PARTS BY NON-PLANAR MATERIAL EXTRUSION
- Publisher:
- American Society of Mechanical Engineers
- Publication Type:
- Conference Proceeding
- Citation:
- ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE), 2021, 2A-2021
- Issue Date:
- 2021-01-01
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| Filename | Description | Size | |||
|---|---|---|---|---|---|
| v02at02a007-imece2021-70144.pdf | Published version | 3.5 MB |
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Current applications of Fused Filament Fabrication in additive manufacturing tend to produce heavily anisotropic parts. This is largely due to the discretisation of heterogeneous planar layers, resulting in surface artefacts, stress concentrations and weak thermal fusion bonding that fundamentally limit the strength of end-use parts. In an effort to improve the mechanical properties of parts produced by Fused Filament Fabrication, this work developed a novel method by which to implement non-planar toolpath generation for a conventional three-axis machine. Utilising Boolean-based mesh approaches, arbitrary sinusoidal surfaces were used to generate non-planar toolpaths for the test specimens. To do so, a point cloud representing a non-planar surface was triangulated to form a surface mesh. A Boolean intersection between this non-planar surface mesh and the specimen mesh was then used to return the non-planar surface bounded by the geometry of the specimen; an edge traversal technique was then employed to obtain three-dimensional toolpaths. The frequency and amplitude of the non-planar sinusoidal surfaces were incrementally increased from the planar case until the geometric limits of the print-head were reached. Test specimens were then manufactured on a conventional three-axis machine and subject to a three-point bending test. There was a strong negative correlation between the flexural moduli of the specimens and the frequency and maximum tangential angle of their non-planar surfaces, while there was a strong positive correlation between the toughness of the specimens and the frequency of their non-planar surfaces. Non-planar specimens also exhibited more prominent yield points, and were better able to dissipate energy and resist crack propagation. A key finding was the significant increase in plastic strain exhibited by the non-planar samples; certain specimen types were able to withstand an average of 250% more strain in the plastic region, when compared to the planar samples, before significant progression of fracture. This is demonstrative of a notable improvement in ductility and reduction of brittleness. Non-planar samples also saw improvements in fracture toughness of up to 60%; however, this is perhaps not as significant as it could be, as greater tangential angles rotated the fibres away from their ideal colinearity with the normal stresses induced by bending. This work serves as a proof of concept for the feasibility of non-planar implementations of Fused Filament Fabrication, and provides a framework for future work aimed at non-planar alignment of material extrusion with stress tensors. It is anticipated that stress-vector fields will be used to generate non-planar surfaces, aligning material extrusion directions with principal stresses.
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