Tailorable and Adaptive Connected Digital Additive Manufacturing

TACDAM项目将消除在汽车应用中采用增材制造的最后障碍。虽然增材制造（AM）中产品成本的最大单一贡献者过去一直是构建时间，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部件中去除多余的粉末。在粉末床融合方法AM中，连续的粉末层（例如，金属粉末）被放置在制造床上，并且使用高功率激光将粉末一起烧结在构建的适当区域中。在该过程结束时，这会留下残留在部件内部的多余粉末，这些粉末必须被去除。这通常通过多种机制来实现，包括以高频振动部件以使粉末流化，从而允许其在重力下流出。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。对于该研究团队中的组织正在开发的复杂组件，例如HiETA开发的紧凑型热交换器，这一点尤为重要;热交换器中数千根管道内的任何残留粉末都会大大降低性能。同时，所开发的复杂几何形状意味着流化粉末的流动不是直接的。我们对整个项目的贡献的目标是开发一种方法来模拟部件内残留粉末的流动，以便能够识别粉末去除中的问题，并优化粉末去除策略。我们将首先回顾流化粉末流动的现有技术水平。这通常不适用于这类问题，因此我们将确定物理建模可能需要进一步开发的领域，以科普这类问题的具体情况。在此基础上，我们将开发一个非牛顿公式的流化粉末的流动，实现这到OpenFOAM CFD代码库。当粉末流出部件时，会产生空气空隙，因此我们需要在自由表面流动模型中制定流化粉末流;这将使用OpenFOAM中实现的标准流体体积公式来完成，并根据文献和项目其他部分（ASDEC）的实验结果进行验证。建模还需要考虑到部件的振动模式，可能通过固体部件的耦合建模，这将作为一项单独的任务进行研究。具体的特征几何形状将被确定为使用新的建模进行调查，这些将是几何形状，如成角度的弯曲，歧管和收缩，经常发生在AM或表现出特殊的问题与粉末去除。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，访问他们对AM的一般知识）中获取特定的输入。我们将模拟这些几何形状，以识别流动问题，特别是诸如粉末未被去除的死点等问题;并尝试将其与粉末去除的经验知识相关联。最后，我们将研究可能的方式，这种建模可以更广泛地使用，例如通过嵌入到一个专家系统的AM制造。

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.