Satbir Khanuja

Three-Dimensional Printing: The Physics and Implications of Additive Manufacturing

Abstract Three Dimensional Printing is a process for creating parts directly from a computer model. 3D Printing builds parts in layers by spreading a layer of powder and then selectively joining the powder in the layer by ink-jet printing of a binder material. After all layers are printed, the layer loose of powder is removed to reveal the finished part. Application areas include ceramic molds for metal castings, directly printed parts for end-use and for use as tooling, ceramic preforms for metal matrix composites, structural ceramic parts, and others. 3D Printing is a member of a group of layer manufacturing techniques which have the primary distinguishing feature of creating parts by the controlled addition (rather than subtraction) of material. The primitive building element in 3D Printing is a spherical ensemble of powder particles held together by one droplet of binder. Ballistic effects are important in the formation of primitives due to kinetic energy associated with the incoming droplet. Stitching together of droplets forms surfaces and hence determines surface finish. Vertical dimensional control is determined in pan by the compression of powder layers by subsequently applied powder. These physical mechanisms help to determine the dimensional control and surface finish of 3D Printed parts.

Structural Ceramic Components by 3D Printing

The Three Dimensional Printing (3DP) Process hasbe~nadapted for processing of fine ceramic powders to •• prepare structllraLceramic components. Our preliminary study was designed to reveal those aspects ofthe.3DPprocesswhichmust be modified for use with fine ceramic powders. The basic elements of the modified process are to spread submicron alumina powder and printJatex binder. Several methods were used to spread thin layers of submicron powders. Gre.enparts are isostaticaUypressed followed by thermal decomposition prior to sintering to remove the polymer. The fired alumina components are greater than 99.2% dense and have·average flexural strength of324 MPa. This is lower than the best conventionally prepared alumina, but we believe that the strength results will improve as we learn more about the relationship between strength limiting flaws and the 3DP build process.