First Time Concrete: Integrated digital models for right-first-time 3D concrete printing and milling

Concrete is one of the most widely used materials in the world. For many years traditional processes have been used to make concrete parts. However, over the last decade, 3D printing has revolutionised the way concrete parts are made. Complex concrete parts can now be created with no formwork or mould tooling. This is important as it removes the time and expense associated with making the moulds, but critically it also offers the potential to create parts that are structurally optimised to maintain strength with less material. This brings benefits in terms of cost but also it represents a significant environmental benefit as less material is needed, so carbon dioxide equivalent emissions are also reduced.

The process is still in development though, and current 3D printing processes result in geometric forms and surface finishes that are not always desirable, and part accuracy that is too low for many applications. To address this, the 3D printing process can be followed immediately by a subtractive process that mills the surface to trim off unwanted material. This improves both accuracy and surface finish. By using a two-stage process of deposition followed by milling, it is possible to create high-quality parts, with intricate features and well-controlled surface finishes. The problem is that for each new part manufactured in this way, many iterative process development trials are required to perfect the deposition and milling strategy. This is time-consuming and wasteful, and it is a barrier to the uptake of the technology.

The First Time Concrete (FT-Concrete) project will address this problem by creating new digital process and material models that can be used to help design printing and milling strategies without the need for physical trials. To do this, these models will be coupled within a digital workflow that enables optimised process design of both the material deposition and the milling process together. So, for a given part the feasibility of defect free manufacturing can be assessed, and the part or process design can be optimised, to ensure parts are printed right first time. This will be a two-way process, where printing sequence, speed and geometry will be optimised to suit milling requirements and vice versa.

To achieve this the FT-Concrete project will investigate new time-dependent material properties models that can predict the curing state and optimal milling window and milling parameters for every position in a part. These must account for the variability of the mix, ambient conditions, printing sequence and the shape of the printed parts. New complementary process models for milling 3D printed concrete in a 'green' state will also be created. These must be able to cope with the highly variable material properties inherent to curing concrete. Finally, these new models will be integrated within a digital design system that will reduce, or potentially remove, the need for physical prototype parts.

The new digital process and material models that we envisage, together with a digitally coupled design process will have significant commercial value; as they have the potentially to reduce process development time, material waste, and cost. We believe this could unlock 3D concrete printing to a wide range of new applications, boosting the uptake of the technology. Enabling structures and geometries that are currently impossible to produce. To pave the way for the uptake of these models, our aim is to integrate them within freely available, opensource, 3D printing design software. In addition, we will work with industrial partners to demonstrate the potential of the digital approach through industrially driven case studies.