Manufacturing of combined convex-concave form elements by using active-medium support in incremental sheet forming

板料渐进成形（ISF）是一种柔性高、适合小批量生产的制造工艺。然而，在坯件下方没有固体支撑（例如通过模具或配对工具）的情况下，不能形成具有良好几何精度的复杂几何形状。第一个资助期的研究项目的增量板成形与活性介质（IFAM）满足了这一挑战，提供了一个软支持，通过液体或气体介质的坯料的底面。刀具路径和压力水平的组合使得能够制造凸形元件和凹形元件以及组合的凸形-凹形部件。第一个供资期的一个方面是通过分析、实验和数值方法分析凸形膨胀行为。为了准确地实现目标几何形状，必须考虑工艺参数和零件形状之间的复杂相关性，并导致与机器学习领域的跨学科合作。训练神经网络，预测所需的压力，在线闭环控制的几何性能。与恒定压力的制造过程相比，通过使用动态调节的压力水平，几何精度显著提高。除了这种控制概念的巨大潜力之外，它还具有局限于一种特定材料和一种预定几何形状的缺点。第二个资助期的动机是解决这个问题，并将控制概念的适用性扩展到任何任意材料和几何形状。扩展的控制概念是基于研究假设，即目标形状、成形能量和切向成形力之间存在很强的关系，并且可以用数学方程表示。分析模型，其中包括上述数学方程，证明了数值结果作为本项目建议书的初步工作。在这种方法中，介质的压力水平作为一个关键的校正变量被取代的切向力，因此需要进一步调查的过程参数之间的相互关系。为了确保扩展的控制概念包括所有的依赖关系，与机器学习领域的多学科合作是必要的。此次合作的基本目标是开发一种在线闭环控制，以实现可靠和可重复的制造过程。控制成形过程将通过设计指南来完成，其中包括CAD文件的处理和通过调整组合凹凸零件的制造顺序和刀具路径来补偿几何偏差。

Incremental sheet forming (ISF) is a manufacturing process, which has a high flexibility and is suitable for producing small lot sizes. However, without solid support beneath the blank, for example through a die or a counter tool, complex geometries with a good geometrical accuracy cannot be formed. The first funding period of the research project on incremental sheet forming with active medium (IFAM) met this challenge by providing a soft support through a liquid or gaseous medium on the blank’s underside. The combination of tool path and pressure level enabled both the manufacturing of convex and concave elements as well as combined convex-concave parts. One aspect of the first funding period was analysing the convex bulging behaviour by including analytical, experimental and numerical methods. To achieve a target geometry accurately, the intricate correlations between the process parameters and the part shape had to be considered and led to an interdisciplinary collaboration with the field of machine learning. A neural network was trained to predict the required pressure in an online closed-loop control of the geometrical properties. Compared to the manufacturing process with constant pressure, the geometrical accuracy was significantly improved by using a dynamically adjusted pressure level. Beside the great potential of this controlling concept, it has the disadvantage of being restricted to one specific material and one predetermined geometry. The motivation behind the second funding period is to solve this problem and extend the applicability of the controlling concept to any arbitrary material and geometry. The extended controlling concept is based on the research hypothesis that a strong relationship between target shape, forming energy and tangential forming forces exists and can be expressed by a mathematical equation. The analytical model, which includes the aforementioned mathematical equation, was proven by numerical results as preliminary work to this project proposal. In this approach, the pressure level of the medium as a pivotal correcting variable was replaced by the tangential forces and thus requires further investigation of the interrelation between the process parameters. To ensure that the extended controlling concept includes all dependencies, the multidisciplinary cooperation with the field of machine learning is necessary. The underlying goal of this cooperation is to develop an online closed-loop control for a reliable and a reproducible manufacturing process. The controlled forming process will be completed by design guidelines, which include the processing of CAD-files and the compensation of geometric deviations through adapting manufacturing sequences of combined convex-concave parts and tool paths.