Purpose

The purpose of this study is to propose a novel simulation framework and show that it captures the main effects of the deposition process, such as droplet shape, volume and speed.

Design/methodology/approach

In the framework, the time-dependent flow and the fluid-structure interaction between the suspension, the moving piston and the deflection of the jetting head is simulated. The system is modelled as a two-phase system with the surrounding air being one phase and the dense suspension the other. The non-Newtonian suspension is modelled as a mixed single phase with properties determined from material testing. The simulations were performed with two coupled in-house solvers developed at Fraunhofer-Chalmers Centre; IBOFlow, a multiphase flow solver; and LaStFEM, a large strain FEM solver. Experimental deposition was performed with a commercial jet printer and quantitative measurements were made with optical profilometry.

Findings

Jetting behaviour was shown to be affected by not only piston motion, fluid rheology and head deformation but also the viscous energy loss in the jetting head nozzle. The simulation results were compared to experimental data obtained from an industrial jetting head and found to match characteristic lengths, speed and volume within ca 10%.

Research limitations/implications

The simulations are based on a rheological description using the Carreau model that does not include a time-dependent relaxation of the fluid. This modelling approach limits the descriptive nature of the deposit after impact on the substrate. The simulation also adopts a continuum approach to the suspension, which will not accurately model the break-off of the droplet filament under the characteristic diameter of the particles in the suspension.

Practical implications

The ability to accurately simulate the deposition of functional materials will enable the efficient development of novel product designs with a minimum of used resources and minimised product development duration.

Social implications

The ability to accurately simulate the deposition of functional materials will enable the efficient development of novel product designs with a minimum of used resources and therefore an improvement from a sustainability perspective. The ability to plan deposition strategies virtually will also enable a decrease in consumables at manufacturers which will in turn decrease their carbon foot print.

Originality/value

While basic fluid dynamic simulations have been performed to simulate flow through nozzles, the ability to include both fluid-structure interaction and multiphase capability together with a more accurate rheological description of the suspension and with a substrate for surface mount applications has not been published to the knowledge of the authors.

中文翻译：

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用于表面贴装技术的焊膏喷射印刷模拟

目的

本研究的目的是提出一种新颖的模拟框架，并表明它可以捕捉沉积过程的主要影响，例如液滴形状、体积和速度。

设计/方法/方法

在该框架中，模拟了悬浮液、移动活塞和喷射头偏转之间的瞬态流动和流固耦合。该系统被建模为两相系统，其中周围的空气为一相，而稠密的悬浮液为另一相。非牛顿悬浮液被建模为混合单相，其特性由材料测试确定。模拟是使用两个在 Fraunhofer-Chalmers 中心开发的耦合内部求解器进行的；IBOFlow，多相流求解器；和 LaStFEM，一种大应变 FEM 求解器。实验沉积是用商业喷射打印机进行的，定量测量是用光学轮廓测定法进行的。

发现

表明喷射行为不仅受活塞运动、流体流变学和头部变形的影响，还受喷射头喷嘴中的粘性能量损失的影响。将模拟结果与从工业喷射头获得的实验数据进行比较，发现与特征长度、速度和体积的匹配度在约 10% 以内。

研究限制/影响

模拟基于使用 Carreau 模型的流变学描述，该模型不包括流体的时间相关松弛。这种建模方法限制了沉积物在基材上撞击后的描述性质。模拟还对悬浮液采用连续方法，这将无法准确模拟悬浮液中颗粒特征直径下液滴丝的断裂。

实际影响

准确模拟功能材料沉积的能力将能够以最少的资源和最短的产品开发时间有效开发新颖的产品设计。

社会影响

准确模拟功能材料沉积的能力将能够以最少的资源有效开发新颖的产品设计，从而从可持续性的角度进行改进。虚拟地规划沉积策略的能力还可以减少制造商的消耗品，从而减少他们的碳足迹。

原创性/价值

虽然已经进行了基本的流体动力学模拟来模拟通过喷嘴的流动，但包括流固相互作用和多相能力以及更准确的悬浮液流变描述和用于表面贴装应用的基板的能力尚未公布给作者的知识。