(378d) Novel Device for the SLA Printing of Solid-Suspension Composite Materials and Filled Polymers.

Additive manufacturing continues its growth as an important production process, with new applications and methodologies developed almost as quickly as they can be imagined. Part of this rapid growth is driven by continuous development of new materials that can be printed. These new materials often have enhanced or novel properties such as higher strength, electrical conductivity, and environmental responsiveness. Often the new materials are based on composite systems. This approach is commonly used in Fused Filament Fabrication, also called Fused Deposition Modeling, where composite filaments are created from standard printing polymers and reinforcing materials. These reinforcements can improve mechanical properties without requiring major changes in the printing process and without significant impact on print quality. Translating this approach to vat-photopolymerization printing methods, Dynamic Light Printing and Stereolithography, has proven more challenging. Often, differences in the binder and filler densities result in separation during the printing process. This separation can occur on the order of several minutes or hours, a similar time frame as for many vat-photopolymerization printing processes, and often results in inhomogeneity of the printed material. These problems have been addressed in the past using methods such as adding other components to change the viscosity of the binding resin, adding surfactants or similar materials to increase the adhesion between the binder and filler, or performing surface modification of the filler material. Each of these processes requires fundamental alterations to the composition of the composite, which can affect the final properties, and often involves a significant amount of time and effort. These processes also tend to have limited compatibility and can require a whole new process and new printing parameters to be developed for each binder and filler combination. As a novel solution for this problem, this study presents a device for conducting continuous active mixing of the printing resin during the vat-photopolymerization printing process. This solution allows for maintaining filler distribution without the need for changes in composition or additional post processing. In this talk, we will discuss the limits of this approach in regards to filler loading percentage, filler particle diameter, and mixing speed as they relate to print quality and filler distribution uniformity. Specific focus will be given to filler loadings between 0.1-30.0wt%, particle diameters of less than 100µm, and non-miscible fillers composed of inorganic materials.