Freeform fabrication by controlled droplet deposition of powder filled melts

A method of directly delivering highly filled hot-melt particulate suspensions using piezoelectric droplet generators is presented. Highly fluid suspensions of alumina in a mixture of long and short chain n-alkanes containing up to 40% by volume solids have been prepared. These fluids were subsequently used to deposit ceramic objects using a commercial ink-jet printer. These objects were then successfully sintered to near full density. The deposition mechanism is controlled by the propagation of acoustic waves in a droplet generating chamber. We have observed the change in resonance of this chamber with the introduction of particles into a fluid. A simple model is developed to explain these observations in terms of changes in the speed of sound of the fluid on the addition of solid particles in suspension.