Effects of Jetting Parameters and Sodium Silicate-Based Binder on Droplet Formation

Abstract

Binder jetting additive manufacturing is one of the 3D printing technologies currently used to manufacture 3D geometries. In this process, a liquid binder agent is ejected to a desired position of a substrate. The binder’s properties and the jetting condition used for form droplets can affect the formability of the geometries. Herein, we optimized the solid content and jetting condition of a sodium silicate-based inorganic binder, for 3D printing. To observe the range of single droplet formation, the behavior of the discharged droplets was analyzed by Z value, which is the inverse of the Ohnesorge number. As the solid content increased, a higher driving voltage was required to form the droplets to overcome viscous dissipation. For 40S(Z = 4.33) with a content of 40 wt%, the droplet tail from the nozzle was stretched further. The droplets of 25S(Z = 15.09) with a content of 25 wt% were accompanied by satellite droplets. The jetting condition was optimized for 25S, which was capable of ejection at various driving voltages. Stable single droplets were formed at a driving voltage of 20 V and a dwell time of 4 μs. In addition, when ethylene glycol and glycerol were added into 25S as a humectant, stable droplets were formed under the optimum jetting condition, and each droplets was in the range of 2.70 < Z < 15.09.