Collaborative Research: Modulating Powder Bed Cohesion to Reduce Defects in Binder Jetting

粘合剂喷射是一种3D打印方法，由于其多功能的材料选择（几乎任何粉状材料），高生产率和适度的设备成本越来越重要。这可以说是唯一的主流3D打印技术，同时适用于金属和陶瓷。它在能源、航空航天、化工和其他行业的应用越来越广泛。在粘合剂喷射过程中，3D零件逐层打印。在每一层上，粉末床被铺展，微观液滴沉积在粉末床上的选定位置。这些液滴渗透到床中，并将颗粒结合在一起。由于液滴的冲击速度较大，会对粉末床产生较大的扰动，导致3d打印零件产生气孔。这些孔隙会大大降低产品的强度和其他机械性能。该奖项支持基础研究，以了解粘合剂喷射中粘合剂与粉末的相互作用，并确定技术解决方案，以消除粘合剂喷射产品中形成的大孔隙。这将大大提高用粘合剂喷射工艺制造的零件的性能，并扩大其在各个行业的应用。通过允许为许多不同行业快速制造低成本定制组件，这将加强美国工业的制造能力和竞争力。本研究将探讨粘合剂喷射过程中粘合剂与粉末的相互作用。研究目的是验证部分饱和（预湿润）粉末会通过(i)加速粘合剂吸收和（ii）增加粉末床的凝聚力来抑制粉末飞溅和减少孔隙形成的假设。为了实现研究目标，将进行协同实验和数值研究。在实验方面，将建立定制的粘结剂喷射系统，实现粉末床的可控预湿，以及粘结剂喷射参数（如液滴大小、冲击速度等）的灵活调节。将进行参数研究，以确定粘结剂喷射参数和粘结剂/粉末材料特性对飞溅/孔隙形成的影响。现场高速x射线成像和非原位表征将用于观察粘合剂-粉末的动态相互作用。在建模方面，将采用计算流体力学和离散元方法相结合的多物理场模型来模拟粘结剂喷射过程中粘结剂-粉末和粉末-粉末的相互作用。实验和数值结果的结合将用于检验研究假设。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Binder jetting is a 3D printing method that is increasingly important due to its versatile material options (virtually any powdered material), high production rates, and modest equipment cost. It is arguably the only mainstream 3D printing technique that works for both metals and ceramics. It has found growing applications in energy, aerospace, chemical, and other industries. In the binder jetting process, the 3D parts are printed layer by layer. On each layer, the powder bed is spread and microscopic droplets are deposited on selected locations on the powder bed. These droplets penetrate into the bed and bind the particles together. Since the impacting speed of the droplet is rather high, it can significantly disturb the powder bed and cause pores in the 3D-printed parts. These pores can drastically reduce the strength and other mechanical properties of the products. This award supports fundamental research to understand the binder-powder interaction in binder jetting and identify technical solutions to eliminate the formation of large pores in the binder jetting products. This will significantly improve performance of parts fabricated with the binder jetting process and expand its applications in various industries. This will strengthen the manufacturing capability and competitiveness of U.S. industry by allowing for rapid fabrication of low-cost custom components for many different industries.This research will investigate the binder-powder interaction in the binder jetting process. The research objective is to test the hypothesis that partially saturating (pre-wetting) the powder will suppress powder spattering and reduce pore formation by (i) accelerating binder absorption and (ii) increasing the cohesion of the powder bed. A synergistic experimental and numerical investigation will be performed to achieve the research objectives. On the experimental side, a customized binder jetting system will be established to enable controlled pre-wetting of the powder bed as well as the flexible adjustment of binder jetting parameters (e.g., droplet size, impact velocity, etc.). Parametric studies will be performed to identify the effects of binder jetting parameters and binder/powder material properties on the spatter/pore formation. In-situ high-speed X-ray imaging and ex-situ characterization will be used to observe the dynamic binder-powder interaction. On the modeling side, a multi-physics model that integrates the computational fluid dynamics and discrete element method will be used to simulate the binder-powder and powder-powder interactions during the binder jetting process. The combination of experimental and numerical results will be used to test the research hypothesis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.