Development of P-3DP (Powder-based 3D Printing) process for the realization of cement-based or generally inorganic materials

Powder-bed binder jet 3D printing (BJ3DP) is a viable method for producing cement-based products to digitalize the construction industry. The geometry in the deposited powder bed is generated by applying organic/inorganic binder materials to solid voxels, layer by layer. There are numerous advantages to this process over other additive manufacturing technologies, including its ability to create objects with more than one material, a lower cost, no support hinges, and the ability to print a variety of materials, such as ceramics, from centimeters to meters in size. Despite the significant potential of BJ3DP for producing free-form cement-based components, the adoption of this technology in the construction industry has been slower compared to other sectors (e.g., medial and foundry). The main reason for this could be the lack of qualitative relationships between manufacturing parameters and the final quality of printed parts because of a lack of adequate understanding of the fundamentals of the technology. The current BJ technology for concrete printing relies on trial and error. Alternatively, the design of experiment (DOE) is a methodological approach to acquire a comprehensive understanding of the process by collecting the required data and providing quantitative/mathematical models for the quality of the product as it emerges from the printing process. This research project develops the BJ3DP process for the fabrication of cement-based or inorganic materials. For this purpose, through literature review, all printing parameters were systematically categorized and those are applicable on the available 3D printer set-up were studied. Details of the 3D printer setup were explored prior to running experimental activities. To narrow down the number of experiments and keep the focus on the printer, a recipe for magnesium oxychloride cement — as a quick reactant cement and suitable for AM technologies — was developed and kept constant to exclude material-related factors. As part of this step, details related to powder feedstock, binder, and powder binder interactions were investigated, including powder bed density, binder rheology, droplet formation mechanism, and granule formation mechanism. By crater formation, inter-voxel and interlayer bonds are formed in the powder bed via the flow of binder liquid under high pressure. For the binder jetting process, the amount of binder, or water-to-cement ratio in traditional concrete casting, was defined. The effect of six key manufacturing factors on the modulus of rupture of MOC cement-based components was studied using an analysis of variance. The parametric analysis revealed that the strength is strongly influenced by three process inputs: particle size, amount of binder and layer thickness. A quadratic regression model was introduced which can assist the operator in selecting a combination of binder jet process inputs for pre-determined final material performance. An in-depth understanding of manufacturing processes was also gained by studying the effects of printing strategies on mechanical properties and finishing surfaces. The interfaces of SCA-printed concrete are anisotropic, unlike traditional concrete castings. In AM technologies, such as binder jetting, process parameters are based on physical principles. Unfortunately, current binder jetting operations rely on low-fidelity data transmission between the powder–binder interaction and the computer numerical control machine. The flow rate of the binder has a significant effect on the quality of the printed objects. As a result, a new configuration of the 3D printer is proposed in which the flow rate can be controlled by the CAM system and automatically adjusted. This will allow for a more accurate DoD dispensing unit, and the 3D printer will be more capable of printing materials with the desired mechanical properties.