Influence of the feedstock-viscosity on photolithography-based metal manufacturing – predict printability threshold

In contrast to direct metal additive manufacturing techniques, the crucial component for photolithography-based metal manufacturing is the binder itself. In the end, complete removal of the binder is important to reach final part characteristics, and a low shrinkage pushes to high loadings. Additional to that, good green stability after printing and handling after debinding is often required. On top of that, the binder system itself regulates the viscosity of the feedstock which allows to stay under the printability threshold. All those requirements extend the development of feedstocks enormously. In this work, an approach to speed up the feedstock development with a low amount of material is presented. The main influences (temperature, particle size, loading) were analyzed and plate-plate rheology measurements were used to predict printing problems. Those printing problems affect the surface roughness of the green part, which was analyzed by digital microscope in fine depth composition mode. The comparison of the printing characteristics and rheology analysis helped to find the printability threshold. In this work, a viscosity level of 13 Pa s was registered as the printability threshold. The target value, the feedstock viscosity, can be used for other additive manufacturing processes that involve flow processes in the same manner.