Shape Evolution of Droplet Impingement Dynamics in Ink-Jet Manufacturing

Ink-jet printing enables more efficient, economic, scalable manufacturing for a wide variety of materials than other traditional additive techniques. The impact of droplets onto a substrate is critical for accuracy control and optimization of the droplet deposition process. However, most previous research about droplet impact focused on the spreading radius of the droplet, which does not provide enough information for manufacturing purposes. This paper presents new methods to model and characterize droplet shape change during impact so that the droplet deposition process can be optimized to build desired geometries. A validated numerical model is used to study the shape change of the droplet impingement on a solid surface. A dimensional analysis is conducted to reduce the number of parameters of the impact conditions by matching Reynolds, Weber, and Froude numbers as well as possible. In addition, a new method of characterizing droplet shape is presented that measures its similarity to a desired shape. The shape evolution of a wide range of impact conditions is simulated with the validated numerical model using both physical and dimensionless quantities. The effects of the dimensionless numbers on the shape evolution are examined and analyzed. Successive multiple droplets impact is also simulated.