An Investigation of The Effect of Rheo-Printing Technology on Big Area Additive Manufacturing

Abstract

A novel processing innovation named Rheo-printing technology was introduced that could impact the field of the Big Area Additive Manufacturing (BAAM). The Rheo-printing technology applies a controlled circumferential and axial shear rate to the polymer melt before depositing the polymer through the printing nozzle. The rheological polymer properties modify due to the applied shear rate, and the ultimate goal is to enhance the product's properties. The application of the circumferential shear rate on the polymer melt is accomplished through a rotational printing nozzle. Adjusting the rotational speed of the printing nozzle controls the shear rate applied to the polymer melt, providing control over the rheology of the polymer melt. This research employs an extrusion-based AM machine that uses polymer pellets as a feedstock to investigate the impact of Rheo-printing technology on BAAM. The effect of Rheo-printing technology was investigated theoretically and numerically to examine the shear rate impact on the material's viscosity. Different shear-thinning polymers were included in the investigation; the viscosity influence of each polymer has been studied through a range of rotational speeds, and statistical analysis has been applied to the obtained results for a comprehensive understanding. The investigation compared the influence of Rheo-printing technology on two different nozzle sizes. For small additive manufacturing or desktop 3D printers, a 0.6 mm nozzle diameter was utilized, while a 2 mm nozzle diameter was employed for BAAM. Overall results showed that the effect of Rheo-printing technology appeared more significant with a bigger nozzle diameter. Also, there is a favorable correlation between nozzle rotation and viscosity for all polymers, regardless of nozzle diameter. Specifically, this correlation manifests as a decrease in viscosity as the nozzle is rotated, with the magnitude of this reduction becoming more pronounced at higher rotational speeds and near in the outermost region of the extruded polymer road. Two different numerical simulations were included to study the impact of the temperature on the printing process. The first numerical simulation was to study the effect of printing speed on the temperature evolution of each layer during the printing process. Results showed that the temperature fluctuation as each layer's heating and cooling during the printing process decreased with increasing the printing speed. The second numerical simulation was to study the platform temperature's impact on each layer's temperature evolution during printing. The effect of increasing the platform temperature was shown clearly on the cooling interval of each layer. Increasing platform temperature reduces the heat losses in the printed layer during the cooling interval. An experimental investigation also employed conventional printing and Rheo-printing technology to investigate the temperature evolution during printing and compare the obtained results. This investigation was performed by printing two samples using conventional and Rheo-printing technology and monitoring the temperature evolution during printing. The anisotropy and porosity of BAAM products were investigated, and the enhancement of Rheo-printing technology on product properties was validated numerically and experimentally. Three groups of different layer-building times were designed, and twenty-four samples were printed using conventional and Rheo-printing technology, investigating the impact of Rheo-printing technology on interlayer adhesion strength. Also, three configurations were designed, and eighteen samples were printed using conventional and Rheo-printing technology, investigating the effect of Rheo-printing technology on void formation. The enhancement of the Rheo-printing technology on mechanical properties of BAAM samples was validated where the anisotropy and porosity percentage were reduced.