Process and property study of inkjet powder bed fusion technology

Inkjet powder bed fusion (PBF) is an advanced and relatively mature additive manufacturing (AM) technology developed to produce thermoplastic parts, consisting mainly of high-speed sintering (HSS) and multi jet fusion (MJF). In the process, the powders are partially melted and coalesced together by applying infrared light to sinter powders that have been selectively ink-jetted with radiation absorbing material (RAM). To date, the mechanism and material of infrared heating PBF have been researched, but there are still gaps yet to be filled, particularly with regard to the role of RAM on the powder bed and the development of composites. In response to the above, this work has focused mainly on the following study:
1. The characteristics of MJF manufactured polyamide 12 (PA12) parts were investigated to gain a comprehensive insight into inkjet PBF. The phenomenon of inhomogeneous pore distribution related to the dimensions of parts was identified by microcomputed tomography (micro-CT) and discussed with thermal properties of powders.
2. A series of numerical computational fluid dynamics (CFD) models were developed to assess the RAM ink infiltration depth in the powder bed during printing by COMSOL Multiphysics.
3. A cost-effective in-house-built HSS testbed was optimised and then used to produce PA12 parts for optimising part performance. By controlling ink jet times, powder bed temperature and heating power, the mechanical, thermal and microstructural properties of the parts were analysed. The maximum tensile strength achieved was 46 MPa.
4. Monolayer carbon fibre (CF) /PA12 composites were prepared through a stepped simulation experiment of HSS by control the weight precent of CF from 1% to 30%. The time-temperature curves during processing, thermal properties and microstructures of the composites were evaluated. The composites could be produced with dense microstructure at a low CF weight percent (1%). Increasing the CF weight percent would lead to a decrease in processing feasibility.
The research presented an increased understanding of inkjet PBF technology and helped to develop carbon-fibre composites within the field.