Design and simulation of nozzle head for 3-D printing with cement

Abstract

Concrete 3-D printing (3DCP) is a revolutionary technology that is extensively used in industry as it provides automation in manufacturing. Such technology is classified as a key area in the fourth industrial revolution, also known as Industry 4.0. Research on 3DCP mainly involves experimental work and limited work has been done on Computational Fluid Dynamic (CFD) simulation of concrete flow. As such, this research project focuses on using CFD simulation to predict the strength performance at the interface between concrete layers. In addition, using this methodology as a tool, numerous novel designs of the nozzle head are introduced. A good design of the nozzle is one that will be able to enhance the strength of the printed structure by reducing the notch effect as well as improving the bond strength at the layer interface. To analyse the tensile strength of the printed structure, CFD simulation model was setup. The model involves simulations of both the two-phase and single-phase concrete flow. Through CFD simulation of the two-phase flow, the shape of concrete flow can be captured. However, the shape of the flow does not fully capture the boundary layer effect due to the presence of air at the wall boundary. This requires the simulation of the single-phase flow to be carried out. Contour plots of the interface pressure, shear stress and shear strain rate obtained will then be analysed to understand the interface strength of the printed structure. Simulations have been done to understand how factors governing the nozzle design will affect the flow of concrete mixture, leading to varying tensile strength in the printed structures. An example of such factors is the inclusion of the vertical side trowels in the nozzle design, which efficiently reduces the notch effect and increases the extent of the interface area of concrete flow subjected to shear strain rate as well as pressure. Good interface shear strain rate and interface pressure behaviours will lead to high tensile strength within the printed concrete structure.