Multi-scale simulation of molding materials for inorganic binders using binder-jet-3d-printing

近年来，3D打印已经发展成为一种用于生产铸造操作的砂芯的技术，特别是用于快速原型和小批量铸造应用。然而，这种工艺的分层结构与传统的芯吹有很大的不同，特别是在实现的密度水平方面。该项目的目标是了解砂芯的3D打印过程，以确定过程变量对最终产品的影响。这将确保打印砂芯的高质量，同时最大限度地减少所需的测量工作以及对专业知识和经验的依赖。以下几个方面是要更详细地调查：1。印刷部件通常具有比常规生产的部件低得多的密度。此外，这种密度在3D打印机的安装空间上是不均匀的和部分随机分布的。此外，可以观察到不同性质的各向异性。2.在构建过程中，可以观察到已经印刷的层的卷曲到一定程度，它们被重涂器撞击，这导致整个构建过程受到干扰。3.构建作业的逐层结构增加了已打印区域的负载。这导致非线性构造误差，其表现为有缺陷的层或组件的未对准。4.如果涂层速度太高，则构造中的组件将在构造体积中移动其位置。实践经验表明，除了粉末成分、大气条件和涂层工艺本身的控制之外，基材是否已经印刷是最重要的。为了实现上述目标，申请的项目旨在创建一个数字模型-密切伴随着相关的实验研究-它描绘了3D打印中砂芯层的分层结构。基于工业用砂的计算机断层扫描图像，分析在粘合剂的影响下，在已经印刷的层上的砂粒的再涂覆。随后，计划对打印砂芯的机械、热和气体渗透性能进行模拟和实验评估。前身项目µ-Core由DFG资助，涉及经典吹芯工艺的微机械建模，将作为起点并将大幅扩展。对砂芯3D打印所涉及的微观过程的更深入了解将成为进一步开发环境方面的材料和优化打印过程本身的基础。

In recent years, 3D printing has been developed as a technology for producing sand cores for casting operations, especially for rapid prototyping and low-volume foundry applications. However, the layered structure of this process differs greatly from traditional core blowing, especially in terms of the density levels achieved. The goal of the proposed project is to understand the 3D printing process of sand cores in order to identify the influence of process variables on the final product. This should ensure the high quality of the printed sand cores in an application-specific manner, while minimizing the measurement effort required and the dependence on expert knowledge and experience. The following aspects are to be investigated in more detail: 1. Printed components generally have a much lower density than conventionally produced ones. In addition, this density is inhomogeneously and partially stochastically distributed over the installation space of a 3D printer. In addition, an anisotropy of different properties can be observed. 2. During the building process, a curling of already printed layers can be observed to an extent, that they are hit by the recoater and this causes the entire building process to be disturbed. 3. The building job's layer-by-layer structure increases the load on already printed areas. This leads to non-linear construction errors, which manifest themselves in defective layers or misalignment of the component. 4. If the coating speed is too high, components under construction are shifting their position in the build volume. Practical experience has shown that in addition to the powder composition, atmospheric conditions and the control of the coating process per se, the fact whether the substrate has already been printed or not is of utmost importance. In order to achieve the above-mentioned objectives, the project applied for is intended to create a digital model - closely accompanied by relevant experimental investigations - which depicts the layered structure of the sand core layers in 3D printing. Based on microcomputer tomography images of industrially used sands, the recoating of the sand grains under the influence of the binder on already printed layers is to be analyzed. Subsequently, a simulative and experimental evaluation of the mechanical, thermal and gas permeability properties of the printed sand cores is planned. The predecessor project µ-Core, which was financed by the DFG and dealt with the micromechanical modeling of the classical core blowing process, will serve as a starting point and will be substantially extended. A deeper understanding of the microscopic processes involved in the 3D printing of sand cores will serve as a basis for the further development of materials under environmental aspects and for optimizing the printing process itself.