Berretta, Silvia, Ghita, Oana, Evans, Ken, and Anderson, Andy
Laser sintering (LS) is an additive manufacturing technique that allows production of prototypes and fully functional components characterised by the highest level of freedom of design currently achievable. High customisation, multi-functional integration, design optimisation and the potential for reducing cost and production time of a single item are the most outstanding characteristics of the LS process. However, the small number of polymers at present available constitutes a significant drawback for many engineering applications, especially in the automotive and aerospace industrial sectors where seemingly only one commercial high temperature grade, Poly Ether Ketone (PEK) HP3, can meet the high material performance required. With the aim to expand the choice of materials for LS and especially High Temperature Laser Sintering (HT-LS) manufacturing, this research project has focused on the investigation and implementation into LS of a new high temperature polymer, Poly Ether Ether Ketone (PEEK). This study has examined some of the key requirements needed for the successful development of new materials in LS processes at experimental and theoretical levels. Two generic PEEK grades 150PF and 450PF have been quantitatively investigated in parallel with well-established LS polymers in terms of particle size, particle morphology and flow behaviour. A calculation of the inter-particle interactions has been evaluated for all the materials proposed. These analyses, coupled with two strategies for the improvement of powder flowability, have formed a systematic and fundamental approach for studying powders in LS. The PEEK 450PF grade has been selected for optimisation into the HT-LS system, EOSINT P 800. The HT-LS processing parameters and their effect on the mechanical characteristics of the laser sintered units have been investigated and optimised, and new insights into the HT-LS mechanisms and functionalities of the EOSINT P 800 system are presented. A basic technique for the prediction of one of the HT-LS processing temperatures is proposed. A formula for linking material properties to processing parameters has also been assessed. Lastly, the medical equivalent grade of PEEK 450PF, PEEK-OPTIMA® LT1, has been utilised for the manufacture and test of two medical components.