The construction and testing of an IR absorption metric for high speed sintering

High Speed Sintering (HSS) is a new and innovative Rapid Manufacturing (RM) process that enables the manufacture of complex 3D geometries from polymer powders. The process utilises an ink jet print-head, which selectively deposits a Radiation Absorbing Material (RAM) onto a preheated bed of Duraform Polyamide (PA) powder, thus creating regions of increased emissivity. These printed regions are then sintered using a short burst of thermal energy from an Infra-Red (IR) lamp; conversely, due to the difference in emissivity, unprinted regions remain as powders. The work presented within this thesis expands the knowledge surrounding the HSS process; wherein its main contribution is a validated procedure which tests the suitability of new RAMs for HSS through the analysis of their spectral emissivity. In developing the procedure for selecting new RAMs, it was first identified that for efficient energy transmission from one surface to another, the spectral emissivity of the transmitting surface must be well matched with that of the absorbing surface. This finding was applied to HSS, and consequently, it was suggested that for sintering to occur, the spectral emissivity of the IR lamp must be well matched with the spectral emissivity of the RAM and not the polymer powder. In order to investigate this, the spectral characteristics of the HSS IR lamp and a selection of RAMs were then determined, and an Energy Absorption Value (EAV), a value which quantified how well the spectra overlapped, was defined. The EAV was then validated through the manufacture of a series of tensile test specimens using each RAM, which were then tested for their mechanical properties and Degree of Particle Melt (DPM). Strong correlations were found between the EAV, DPM and each mechanical property. These results consequently validated the effectiveness of the EAV and its potential use to select new RAMs for HSS.