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

与塑料部件的其他制造工艺相比，只有少数材料可用于基于激光的粉末床熔融（PBF/LB）。优先方案的总目标是克服这一限制。许多研究小组目前正在开发新的粉末原料材料和制造方法。PBF/LB的复杂性和对材料的要求给新粉体的开发带来了困难。为了加速粉末的发展，有必要更好地了解这一过程。特别是，材料性能对加工行为的影响是令人感兴趣的。这可以优化聚合物原料的开发。对材料-工艺关系的进一步了解使制造具有改进机械性能的可重复部件成为可能。该项目的主要目标是开发能够真实地表示PBF/LB过程的无量纲特征数（DCN），并允许根据材料定义稳定的过程窗口。在第一个资助期，理论考虑和数值模拟导致对材料-过程关系的理解增加。然而，考虑到迄今为止被忽视的材料参数，还需要进一步的研究。此外，在多层应用过程中发生的影响将进行更深入的研究。第一个次要目标是研究进一步的内在和外在材料参数与过程的相关性。作为外在的材料参数，聚合物颗粒的形状和尺寸对PBF/LB过程中的聚结行为的影响将被研究。本征材料参数的影响将研究粘弹性性能和结晶动力学。此外，还对不同聚合物或聚合物共混物中的激光衰减系数进行了深入分析。由于目前还没有确定的测量方法，因此需要开发一种分析方法。数值模拟将用于研究所提到的所有材料参数的影响，并确定它们各自与可加工性的相关性。第二个子目标是用进一步的材料验证从DCN派生的过程窗口。为此目的将使用合作小组生产的新型粉末。除了验证之外，新开发的粉末还可以对其可加工性进行研究。第三个子目标侧重于几个连续层的应用的影响。将研究十层的稳态熔化和聚结行为，这可能取决于各层应用之间的时间间隔。

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.