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

混凝土是世界上应用最广泛的材料之一。多年来，传统工艺一直用于制造混凝土部件。然而，在过去的十年里，3D打印已经彻底改变了混凝土部件的制造方式。复杂的混凝土部件现在可以创建没有模板或模具工具。这很重要，因为它消除了与制造模具相关的时间和费用，但关键的是，它也提供了创造结构优化的零件的潜力，以保持较少的材料强度。这在成本方面带来了好处，但也代表了显著的环境效益，因为所需的材料更少，因此二氧化碳当量的排放量也减少了。然而，该工艺仍在开发中，目前的3D打印工艺导致几何形状和表面光洁度并不总是理想的，而且对于许多应用来说，零件精度太低。为了解决这个问题，3D打印过程可以立即通过减法过程进行，即铣削表面以修剪掉不需要的材料。这提高了精度和表面光洁度。通过使用两阶段的沉积和铣削工艺，可以制造出具有复杂特征和良好控制的表面光洁度的高质量零件。问题是，对于以这种方式制造的每个新零件，需要许多迭代过程开发试验来完善沉积和铣削策略。这既耗时又浪费，而且是采用该技术的障碍。First Time Concrete （FT-Concrete）项目将通过创建新的数字工艺和材料模型来解决这一问题，这些模型可用于帮助设计打印和铣削策略，而无需进行物理试验。为此，这些模型将在数字工作流程中耦合，从而可以同时优化材料沉积和铣削过程的工艺设计。因此，对于给定的零件，可以评估无缺陷制造的可行性，并且可以优化零件或工艺设计，以确保零件在第一时间打印正确。这将是一个双向过程，其中打印顺序，速度和几何形状将优化以适应铣削要求，反之亦然。为了实现这一目标，FT-Concrete项目将研究新的随时间变化的材料特性模型，该模型可以预测零件中每个位置的固化状态、最佳铣削窗口和铣削参数。这些必须考虑到混合、环境条件、打印顺序和打印部件形状的可变性。在“绿色”状态下研磨3D打印混凝土的新的互补过程模型也将被创建。这些必须能够处理固化混凝土所固有的高度可变的材料特性。最后，这些新模型将集成到一个数字设计系统中，这将减少或潜在地消除对物理原型部件的需求。我们设想的新的数字工艺和材料模型，以及数字耦合设计过程将具有重大的商业价值；因为它们有可能减少工艺开发时间、材料浪费和成本。我们相信，这将为3D混凝土打印带来广泛的新应用，促进该技术的普及。使目前无法生产的结构和几何形状成为可能。为了为这些模型的采用铺平道路，我们的目标是将它们集成到免费的、开源的3D打印设计软件中。此外，我们将与工业合作伙伴合作，通过工业驱动的案例研究来展示数字化方法的潜力。

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.