Hybrid manufacture of Precision 3D ceramic components

Advanced ceramic materials and ceramic thick-film electronics are used across a diverse range of industries including aerospace, automotive, medical and power generation. Digitally driven fabrication techniques such as Additive Manufacturing (AM) present an alternative way to manufacture parts from advanced ceramic materials. However, standalone ceramic AM has a number of shortcomings that limit its use within commercial and end-user applications. This thesis presents the development of a new digitally driven manufacturing process, which combines high viscosity paste extrusion, sacrificial support extrusion and micromachining in a hybrid manufacturing platform. This was achieved using a commercial feedstock formulation composed of 96wt% alumina, using existing material formulation and post-processing operations. The resultant process was implemented using a 3-axis CNC, benchtop platform, using a positive displacement pumping system, machining spindle with an automatic tool changer and Fused Filament Fabrication (FFF) sacrificial support extruder. The fabrication of 3D ceramic component featuring spanning, overhanging and conformal geometries with densities of up to 99.93% and shrinkages of 15-19%. The synergistic use of AM and subtractive processing resulted in the reduction of surface roughness from Ra 34.3 µm (Rq 42.4 µm) down to 0.5 µm (Rq 0.6 µm). Flexural testing of the fabricated samples demonstrated an average strength of 221 MPa, but as high as 252 MPa. Functionalisation of these parts was achieved with a ceramic thick-film process depositing a Low-Temperature Co-fire Ceramic (LTCC) silver conductor using Direct Ink Writing (DIW). The deposited tracks had a measured resistivity of 8.4937× 10-08 - 1.1383×10-07 Ωm. The production of a functional 555-timer circuit on planar and 3D ceramic alumina substrates that were made using the hybrid manufacturing platform demonstrate the feasibility of this approach. The production of co-fireable ceramic electronics was also demonstrated with the extrusion of LTCC dielectric and conductor materials that were subsequently co-fired. This presents an alternative approach for the fabrication of multilayer ceramic electronics for harsh environment applications.