Tailorable and Adaptive Connected Digital Additive Manufacturing

TACDAM项目将消除增材制造在汽车应用中的最后障碍。虽然在过去，增材制造（AM）产品成本的最大单一贡献者是制造时间，但与预处理和后处理相关的成本现在变得相对重要得多。其中，后处理中的一个重要问题是从组件中去除多余的粉末。在粉末床融合增材制造方法中，连续的粉末层(例如：金属粉末)放置在制造床上，并使用高功率激光器将粉末在构建的适当区域烧结在一起。在这个过程的最后，剩余的粉末被困在组件的内部，必须被清除。这通常是通过许多机制来实现的，包括在高频振动组件以使粉末流化，使其在重力作用下流出。这个过程很少被详细分析，但它是整个制造过程的一个重要方面。这对于该研究团队内部组织开发的复杂组件尤其重要，例如HiETA开发的紧凑型热交换器；热交换器中数千根管子内的任何残留粉末都会大大降低性能。同时，复杂的几何形状意味着流化粉末的流动不是直截了当的。我们对整个项目的贡献将是开发一种方法来模拟组件内残余粉末的流动，以便能够识别粉末去除中的问题，并优化粉末去除策略。我们将首先回顾流体化粉末流动的现有状态。这通常没有应用于这类问题，所以我们将确定物理模型可能需要进一步发展的领域，以应对这一问题的具体情况。在此基础上，我们将为流化粉末的流动开发一个非牛顿公式，并将其实现到OpenFOAM CFD代码库中。当粉末从组件中流出时，会产生空气空洞，因此我们需要在自由表面流动模型中制定流化的粉末流动；这将使用OpenFOAM中实施的标准流体体积配方来完成，并根据文献和项目其他部分（ASDEC）的实验结果进行验证。建模还需要考虑组件的振动模式，可能通过实体组件的耦合建模，这将作为一个单独的任务进行研究。将确定具体的特征几何形状，以便使用新模型进行研究；这些将是几何形状，如角度弯曲，歧管和收缩，要么在增材制造中经常发生，要么在粉末去除方面表现出特殊问题。在确定这些几何形状时，我们将从合作中的工业合作伙伴（特别是HiETA，获取他们对增材制造的一般知识）那里获得特别的输入。我们将模拟这些几何形状，以确定流动的问题，特别是诸如粉末未被清除的死点等问题；并尝试将其与去除粉末的经验知识联系起来。最后，我们将研究这种建模可以更广泛使用的可能方法，例如通过嵌入到AM制造的专家系统中。

The TACDAM project will remove the the final hurdles for the adoption of additive manufacturing in automotive applications. Although the biggest single contributor to product cost in Additive Manufacturing (AM) has in the past been build time, costs associated to pre- and post-processing are now becoming relatively much more significant. Of these, one significant issue in post-processing is the removal of surplus powder from the component. In Powder Bed Fusion approaches to AM, successive layers of powder (eg. metal powder) are laid out on the manufacturing bed and a high powered laser is used to sinter the powder together in the appropriate regions of the build. At the end of the process, this leaves surplus powder trapped in the interior of the component which has to be removed. This is typically achieved by a number of mechanisms, including vibrating the component at high frequency to fluidise the powder allowing it to flow out under gravity. This process has rarely been analysed in any detail, but is a vital aspect of the manufacturing process as a whole. It is particularly critical with the complex components being developed by organisations within this research team, such as the compact heat exchangers developed by HiETA; any residual powder within the thousands of tubes in the heat exchanger will substantially degrade performance. At the same time the complex geometries developed mean that the flow of the fluidised powder is not straightforward. The objective of our contribution to the overall project will be to develop a methodology to model the flow of the residual powder within the component in order to be able to identify problems in the powder removal, and optimise powder removal strategies.We will start by reviewing the existing state of the art in fluidised powder flow. This has not typically been applied to this type of problem so we will identify areas where the physical modelling may need further development to cope with the specifics of this problem. Based on this we will develop a non-Newtonian formulation for the flow of the fluidised powder, implementing this into the OpenFOAM CFD code library. As the powder flows out of a component, air voids will develop, so we will need to formulate the fluidised powder flow within a free surface flow model; this will be accomplished using the standard Volume of Fluid formulation as implemented within OpenFOAM, and validated against experimental results from the literature and from other parts of the project (ASDEC). The modelling will also need to account for the vibrational modes of the component, possibly through coupled modelling of the solid component, which will be investigated as a separate task. Specific characteristic geometries will be identified for investigation using the new modelling; these will be geometries such as angled bends, manifolds and constrictions which either occur frequently in AM or exhibit particular problems with powder removal. In identifying these geometries we will take particular input from the industrial partners in the collaboration (particularly HiETA, accessing their general knowledge of AM). We will simulate these geometries to identify problems with the flow, particularly issues such as dead spots where powder is not being removed; and attempt to correlate this with empirical knowledge of powder removal. Finally, we will examine possible ways in which this modelling could be made more widely used, for example through embedding into an expert system for AM manufacturing.