The Line Formation with Alumina Powders in Drop on Demand Three Dimensional Printing

Three Dimensional Printing (3DP) is a Droplet-Based Manufacturing (DBM) process, in which powdered materials are deposited in layers and selectively joined with binder from an ink-jet style printhead. Unbound powder is removed upon process completion, leaving a three dimensional part. With this technology, functional parts or moulds (rapid tooling) can be created directly from a CAD file. Drop on Demand (DoD) is an emerging inkjet technology in 3DP, but it seems that the interaction between drops and powder grains cannot be explained with the available Continuous Jet (CJ) models. In this paper, an experimental theory describing the main physical phenomena involved is proposed. The role of the powder mobility is stressed and documented by pictures and observations coming from a systematic experimentation exploring a multidimensional variable space. A simple mathematical model to predict the line size and density is also proposed.