Robot-based incremental sheet forming - compensating for disturbances caused by a local heating and the inaccuracy of the metal forming device

增量板成形（ISF）是一种灵活的、与工件无关的工艺，用于小批量生产钣金件。ISF工艺的主要缺点之一是其几何精度低，这限制了它们的广泛工业应用，特别是在形成非对称零件时。这些研究项目已经在生产系统主席（LPS）上成功推进，证明了基于机器人的ISF具有很高的工业潜力，特别是在原型制作方面。已经有可能大大减少几何偏差，特别是在高温下进行成形过程的结果。因此，该项目的目的是利用热成形迄今为止取得的积极成果，并对目前由成形装置不精确和高温成形引起的偏差作出反应。为此，研究重点应放在以下几个方面：(1)补偿成形装置的顺应性；(2)提高成形装置的定位精度；(3)补偿局部加热造成的收缩行为。为了实现补偿策略，第一个目标是开发一个过程控制系统，该系统可以集中监控成形设备的状态信息并影响实时成形过程。随后，该项目将在LPS成形机器人上成功实现的刚度模型集成到实现的实时环境中。该刚度模型得到增强，包括成形和支撑机器人的联合操作，以增加整个成形装置的刚度。此外，本项目旨在开发两种成形工具的协调力控制，并将其集成到控制系统中，以提高成形装置的定位精度。此外，该项目还旨在分析局部加热引起的几何误差。统计实验计划有助于彻底研究热成形板的收缩行为。为了确定收缩行为的特征，有必要确定不同工艺和几何参数以及由此产生的部件收缩的因果关系。在此基础上，我们的项目开发了一个模型，根据实际工艺和几何参数计算优化的刀具路径，以防止板材的收缩。最后将已开发的补偿策略整合到过程控制中。本项目为成功实现薄板原型和小批量系列生产工艺奠定了必要的基础；它的目的是提高精度，在集中监测和控制成形过程，以及研究收缩行为的热增量成形板。

Incremental sheet forming (ISF) is a flexible, workpiece-independent procedure to manufacture sheet metal parts in small lot sizes. One of the major drawbacks of ISF processes is their low geometrical accuracy, which limits a widespread industrial application of these especially when it comes to forming asymmetric parts. The research Projects, which have been successfully advanced at the Chair of Production Systems (LPS), prove that robot-based ISF has high industrial potentials especially for prototyping. It has been possible to considerably reduce the geometrical deviations especially as a result of performing the forming processes at elevated temperatures. Therefore, the aim of this project is to use the positive results of hot forming achieved so far and react on the current causes of deviations resulting from inaccuracies of the forming device and from forming at elevated temperatures. To achieve this, the research focus shall be placed on the following:(1) compensating for the compliance of the forming device,(2) increasing the positioning accuracy of the forming device,(3) compensating for the shrinkage behavior as a result of local heating.To implement the compensation strategies, the first objective is to develop a process control system which makes it possible to centrally monitor the state information of the forming device and to influence the real-time forming process. Afterwards, the project integrates the stiffness model, which has successfully been implemented on the forming robot at the LPS, into the implemented real-time environment. This stiffness model is enhanced to include a combined operation of the forming and supporting robot to increase the stiffness of the entire forming device. In addition, the project is designed to develop a coordinated force control of both forming tools and to integrate it into the control system to increase the positioning accuracy of the forming device.Moreover, the project has the aim to analyze the geometric inaccuracies caused by local heating. A statistical experimental planning serves to thoroughly investigate the shrinking behavior of a hot formed sheet. To identify the characteristic of the shrinking behavior, it is necessary to determine the cause-effect relationships of varying process and geometry parameters and the resulting component shrinkage. Based on this, our project develops a model to calculate an optimized tool path in dependence of the actual process and geometry parameters in order to work against the shrinkage of the sheet. The developed compensation strategies are finally brought together in the process control.Our project lays the necessary basis for a successful realization of a procedure to manufacture sheet prototypes and small batch series; it aims at increasing the accuracy, at centrally monitoring and controlling the forming process as well as investigating the shrinking behavior of hot incrementally formed sheets.