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. (C) 2002 Kluwer Academic Publishers.