Master of Philosophy (Mechatronic Engineering)
School of Mechanical, Materials and Mechatronic Engineering
Taylor, Adam Christopher, System and process development for a coaxial extrusion nozzle for fused deposition modelling, Master of Philosophy (Mechatronic Engineering) thesis, School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, 2015. http://ro.uow.edu.au/theses/4508
Additive fabrication, commonly referred to as 3D printing, creates three-dimensional objects by depositing successive layers of a desired shape. While a number of additive processes currently exist, there is insufficient completed work regarding implementation of co-axial fabrication through any technique. Although initial progress has been made in this field, areas for potential improvement have been identified. This thesis has developed one of the first documented systems and associated processes to enable co-axial additive fabrication as a reliable printing method. This will expand the potential uses for these technologies and hence increase their appeal.
The developed integrated system allows two materials to be printed coaxially through the basis of fused deposition modelling (FDM). To do this, the printer must have simultaneous and independent control of two extruders. This feature, coupled with individual temperature control of up to 275°C for each heat chamber, allows for the device to facilitate a wide range of potential materials for extrusion. The materials extruded from this device form a fibre and sheath configuration with an outside diameter of approximately 900μm and an inside diameter of 400μm. This system produces fibres with a coaxial concentricity significantly lower than previous literature, reaching offsets as low as 2.89%.
In addition to this, a supplementary coaxial extrusion tip has been developed to allow for the creation of a coaxial coating process. This system facilitates the inclusion of pre-formed materials into the typical FDM process, allowing for the production of novel structures of increased complexity. The core material (a pre-formed material) is extruded passively by process of entrainment from the sheath material (typically a thermoplastic) and deposited in a layer-by-layer fashion. This has enabled the printing of conductive pathways using a variety of pre-formed materials with differing diameters (65μm iron and 190μm copper). A single thermoplastic coupled conductive pathway exhibits outside diameters of approximately 900μm and produces coaxial concentricity values which vary with core material diameter.
The outcomes of this research provide an opportunity to alter the paradigm of biofabrication by introducing a new level of versatility to the construction of biofabricated structures.