SPH analysis of inkjet droplet impact dynamics

This paper presents a novel Smoothed Particle Hydrodynamics (SPH) framework for analysis of droplet impact dynamics in a 3D inkjet printing process. Results obtained are validated against experimentally derived high-speed imaging data. The numerical framework is based on the Smoothed Particle Hydrodynamics approach of Monaghan et al [1] which has been proven to be efficient and effective for analysis of dynamic fluid flow problems involving free surface interfaces. The SPH approach has been augmented through addition of the kernel gradient correction scheme proposed by Belytschko et al [2] and stabilization terms of Marrone et el [3]. This correction provides a more accurate approximation of the boundary forces including surface tension which dominate at typical inkjet droplet lengthscales (<100 µm). Analysis is expedited through adoption of the OpenACC programming paradigm to enable GPU based computation. Numerical analyses have been validated against analytical solutions, reference macroscale problems and through comparison with experimental high speed imaging data of the inkjet printing process. The experimental setup consisted of a Fuji Dimatix SL-128 inkjet printhead jetting an acrylate based 3D printing build material onto a glass substrate. Images of a single inkjet droplet impacting onto the glass slide were captured at a rate of 100,000 frames per second, with droplet diameter assessed using a weight test approach. Qualitative comparison of the numerical and experimental results showed a good agreement, indicating that the implemented framework is effective for analysis of the fluidic aspects of the printing process. The model is able to assist in tackling manufacturing issues that can detrimentally influence the quality of manufactured parts through provision of insight into the process.