Predicting and Controlling Resolution and Surface Finish of Ceramic Objects Produced by Stereodeposition Processes

Stereodeposition techniques are well suited for the Solid Freeform Fabrication of dense ceramic components. As opposed to forming a pattern in a particle bed or polymer bath, stereodeposition processes deposit material directly onto the previously created layer. The key to stereodeposition is a material's ability to be dispensed as a fluid, yet rapidly stiffen to hold the shape of the object. This is accomplished by either solidification of a thermoplastic binder upon cooling from a melt (Fused Deposition) or by polymerization of a binder (Reactive Stereodeposition). We are developing both techniques for the production of functional ceramic and engineering polymer objects. A key issue in developing a successful stereodeposition system is controlling the rate of bead transformation from liquid to solid. Control is critical to achieving high resolution and low surface roughness of the finished product, but is made complex by the large number of parameters involved. These include binder parameters (surface tension, gelling characteristics), slurry parameters (viscosity, particle loading and size distribution), and process parameters (deposition rate, temperature). Current efforts at the University of Arizona are focused on modeling and controlling the deposition and transformation of ceramic slurries used in the Reactive Stereodeposition process.