Numerical and experimental investigations of dimensionless material parameters in laser additive manufacturing of polymers for accelerated material development and process optimization – Phase 2: Expansion of the application field optimization

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Compared to other manufacturing processes for plastic components, there are only few materials available for laser-based powder bed fusion (PBF/LB). The overall goal of the priority programme is to overcome this limitation. Numerous research groups are currently working on developing new powder feedstock materials and manufacturing methods. The complexity and material requirements of PBF/LB make the development of new powders difficult. To accelerate powder development, a better understanding of the process is necessary. In particular, the influence of material properties on processing behaviour is of interest. This enables optimizations in the development of polymeric feedstocks. The increased understanding of material-process relations allows to manufacture components reproducibly with improved mechanical properties.The main objective of the project is to develop dimensionless characteristic numbers (DCN) that can realistically represent the PBF/LB process and allow the definition of stable process windows depending on the material. In the first funding period, theoretical considerations and numerical simulations led to an increased understanding of material-process relationships. However, further investigations are necessary to take into account material parameters that have been neglected so far. In addition, effects that occur during multi-layer application are to be investigated in greater depth.The first sub-objective is to investigate the correlation of further intrinsic and extrinsic material parameters with the process. As extrinsic material parameters, the influences of the shape and size of the polymer particles on, in particular, the coalescence behaviour in the PBF/LB process are to be investigated. Intrinsic material parameters whose influence will be investigated are viscoelastic properties and crystallisation kinetics. In addition, the laser attenuation coefficient in different polymers or polymer blends is to be analysed in depth. Since there are no established measurement methods for this yet, an analysis method is to be developed. Numerical simulations will be used to investigate the influence of all the material parameters mentioned and to determine their respective relevance for processability.The second sub-objective is to validate the process windows derived from the DCN with further materials. Novel powders from cooperating groups are to be used for this purpose. In addition to validation, newly developed powders can thus be investigated regarding their processability.The third sub-objective focuses on the influence of the application of several successive layers. The steady-state melting and coalescence behaviour of ten layers will be investigated, which presumably depends on the time interval between the application of the layers.