Investigation and Characterization of Clay Mixture Feedstock for Extrusion-Based Additive Manufacturing

The 4th industrial revolution facilitates a broad range of applications for sustainable, reliable, printable, and functional materials to consistently meet industrial requirements. Additive manufacturing (AM) is a promising manufacturing methodology since it enables the user to create bespoke designs with various geometric and material specifications. Extrusion-based AM technique has been recently employed for rapid and efficient ceramic components fabrication. The extrusion technique enables users to deposit clay or concrete in addition to plastics. Extrusion offers scalability and cost efficiency make it a good candidate for implementation and investigation. 

This paper investigates aspects of the extrusion technique to print ceramic materials. Specifically we assess the formulations (composition of water and ethanol-based clay mixtures) and mixing processes that can achieve the easiest and most applicable formulation, where an optimized process recipe to be developed. This work aims to formulate water and ethanol-based clay mixtures, using clay supplied from Wasproject, without additional additives, to achieve optimized range of viscosity of the clay feedstock.  We experiment with different clay pastes by varying clay, water, ethanol ratios, as well as mixing parameters (rotation speed and mixing time). We measure the viscosity of clay pastes using DV3T Rheometer. Afterward, the produced clay pastes are used as a feedstock for WASP Delta 60100 3D printer and undergo a computer-controlled extrusion deposition process. Clay models are designed using Fusion360 software. 

The quality of the printed clay depends on printer parameters, such as the nozzle diameter, pump pressure, and pumping rate. Different approaches will be used to evaluate the quality of the clay pastes for: (i) pumpability, which indicates how easy the material is moved through the delivery system; (ii) printability, which indicates how easy and reliable is the deposition of the material on a printing bed through the deposition nozzle; and (iii) buildability, which indicates the resistance of deposited wet material to deformation under load.  We monitor the pressure and flow rate to assess the pumpability. We also monitor if the nozzle is able to extrude material continuously to assess the printability. Lastly, we monitor the maximum number of layers-without-collapse to assess the buildability. Finally, clay specimens require special thermal treatment post printing, where the temperature of the heating furnace along with the heating duration is controlled and investigated. This study assesses the full production cycle of ceramic printing and correlates the mixture composition and process parameters, to the viscosity of the mixture, and thermal treatment to ensure successful 3d printing and quality control.