Hartmann Christoph, van den Bosch Lucas, Spiegel Johannes, Rumschöttel Dominik, Günther Daniel
Fraunhofer Institute for Casting, Composite and Processing Technology IGCV, Lichtenbergstr. 15, 85748 Garching, Germany.
Materials (Basel). 2022 May 26;15(11):3798. doi: 10.3390/ma15113798.
Binder jetting is a layer-based additive manufacturing process for three-dimensional parts in which a print head selectively deposits binder onto a thin layer of powder. After the deposition of the binder, a new layer of powder is applied. This process repeats to create three-dimensional parts. The binder jetting principle can be adapted to many different materials. Its advantages are the high productivity and the high degree of freedom of design without the need for support structures. In this work, the combination of binder jetting and casting is utilized to fabricate metal parts. However, the achieved properties of binder jetting parts limit the potential of this technology, specifically regarding surface quality. The most apparent surface phenomenon is the so-called stair-step effect. It is considered an inherent feature of the process and only treatable by post-processing. This paper presents a method to remove the stair-step effect entirely in a binder jetting process. The result is achieved by controlling the binder saturation of the individual voxel volumes by either over or underfilling them. The saturation is controlled by droplet size variation as well as dithering, creating a controlled migration of the binder between powder particles. This work applies the approach to silica sand particle material with an organic binder for casting molds and cores. The results prove the effectiveness of this approach and outline a field of research not identified previously.
粘结剂喷射是一种用于制造三维零件的基于层的增材制造工艺，在该工艺中，打印头将粘结剂选择性地沉积到一薄层粉末上。粘结剂沉积后，再施加一层新的粉末。重复此过程以制造三维零件。粘结剂喷射原理可适用于许多不同的材料。其优点是生产率高且设计自由度高，无需支撑结构。在这项工作中，粘结剂喷射与铸造相结合用于制造金属零件。然而，粘结剂喷射零件所达到的性能限制了该技术的潜力，特别是在表面质量方面。最明显的表面现象是所谓的阶梯效应。它被认为是该工艺的固有特征，只能通过后处理来解决。本文提出了一种在粘结剂喷射工艺中完全消除阶梯效应的方法。通过对单个体素体积进行过度填充或填充不足来控制粘结剂饱和度，从而实现这一结果。饱和度通过液滴尺寸变化以及抖动来控制，从而在粉末颗粒之间产生粘结剂的可控迁移。这项工作将该方法应用于带有有机粘结剂的硅砂颗粒材料，用于制造铸模和型芯。结果证明了该方法的有效性，并概述了一个以前未被识别的研究领域。
