Application of printing technique for manufacturing MPC-based products

Abstract

Three dimensional printing (3D printing), also known as additive manufacturing, are now being widely studied and developed, as well as in the constructional domain, where the 3D printing is beginning to move from an architect's modelling tool to delivering full-scale architectural components and elements of buildings such as walls and facades. 3D printing process is an additive manufacturing method from one dimensional dot/line to a two dimensional plane, then to a three dimensional object. In this study, magnesium phosphate cement (MPC), which has properties as fast setting, early strength, is introduced to one of the 3D printing techniques, powder based 3D printing. This study is focused on the designing of a 3D printer, the study of raw material print-ability, and the properties of the printed result. A final 3D printer has been built and MPC samples have been successfully printed. The printed result, which is sandwich-like structure, are acceptable with compression strength at 19.4MPa, direct tensile strength at 10.6KPa, and flexural strength at 6.5MPa, maximum in three dimensions. Many other properties can also be derived from this new printing method due to this sandwich structure of the printed result. The major contributions of the study are: 1. Introducing magnesium phosphate cement into the 3D printing technique. The printing material is the key factor to the development of the 3D printing. An acceptable work procedure of magnesium phosphate cement mix is found and applied in this 3D printing research. The raw material is separated to solid and liquid parts, while the particle size of the solid powder mix should be less than 300 micro meter, and both of the solid and liquid could be controlled automatically. 2. A printing strategy is invented to adapt the printing material and the selected printing nozzle. Horizontal scanning is the best choice for this liquid-jetting printing technique. The printing nozzle is a standard needle, with which the liquid is jetted out under a specified pressure. 3. The key parameters of this powder printing technique are found: liquid / solid ratio, and the designed layer thickness. The liquid / solid ratio, as the water /cement ratio in this study, should remain relatively low (around 0.05) to accomplish the printing request. The mechanical properties of the printed results are mainly determined by the designed layer thickness and the degree of the combination between the printing components. 4. A prototype printer has been installed, and designed product is successfully printed out of the magnesium phosphate cement material. The basic properties of the printed result have been tested and studied.

Date of Award	2017
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology