Prediction of the penetration depth of particle-loaded inks in binder jetting

Abstract

Particle-loaded inks in binder jetting have proven to increase the packing density of the powder bed, to improve the sintering properties, and to selectively change the material composition in the part. However, particles also change the rheological properties and thus the penetration behavior of the ink in the powder bed. The penetration behavior influences the reliability of the binder jetting process. To ensure adequate accuracy and sufficient strength of the green part, an effective connection between the layers is crucial. Insufficient penetration leads to a weak bonding of the layers, while excessive penetration reduces the geometrical accuracy. The prediction of the penetration behavior can be beneficial to set the process parameters for new material systems and to control the distribution of particles in the green part. This study presents a modeling approach for the determination of the penetration depth of particle-loaded inks in the binder jetting process on the basis of the sessile drop method. An additional process model was established that allowed the integration of the process parameters of the binder jetting procedure. The validation was performed by measuring the penetration depth of three inks with particle loads of 1 m%, 5 m%, and 10 m% into a spherical aluminum oxide powder. The comparison of the experimentally determined with the predicted penetration depths showed a good agreement for low particle loads. With higher particle loads, the deviations from the experimental data increased due to an accumulation of the particles on the top of the particle-loaded layer.