Development of a robot-based die-less incremental sheet metal forming process

对于原型和小批量的成本效益生产，当前的研究项目正在开发增量金属板成形工艺，其使用具有小的甚至没有工件依赖性的工具。最终的板材几何形状是通过用简单的半球形工具重复局部成形来实现的。为了提高几何精度，可以在板的背面支撑板。已经开发了不同的成形方法，其使用工件相关或独立的支撑工具。第一个范围从简单的垫板到复杂的全模具。后者要么根本不使用支撑件，要么使用运动学控制的工件独立支撑工具。机器人成形属于最后一组，这是最灵活和最具成本效益的，只需要CAD模型。Roboforming是LPS开发的一种方法，其中两个协作的工业机器人使用成形和支撑工具逐步形成板材。它目前提供两种成形策略：周向作用支撑工具和局部支撑工具。由于运动控制的成形工艺，特别是与成形元件的后续成形相结合，Roboforming能够以高灵活性形成大范围的零件。然而，对于工业应用，需要非常高水平的几何复杂性和几何精度。目前，特别是后续变形的结果，不同形状的元素的相互作用，导致几何偏差，这是限制了部分范围的增加。因此，该项目的目的是增加几何复杂性和增加的几何精度在运动控制的增量金属板成形在所谓的Roboforming。这应通过创建一个程序来实现，该程序用于优化Roboforming中每个成形步骤、其顺序及其成形策略的设计。在规划过程中，考虑到零件的方位，每个形状元素都必须根据其稳定或随后的变形效果进行分析。此外，必须进行研究，以确定在成形过程中的哪个点，每个元件应该直接或随后成形，以获得具有非常好的精度的复杂零件。这需要对元素的直接和随后形成进行详细分析。后者允许显著增加拉伸角，并通过使用防止其变形的周边支撑工具来支撑相邻区域。应通过优化成形策略并结合和调整每个零件来充分利用两种移动工具的潜力。如在渐进式金属板成形中所要求的，必须发展一种方法来优化设计各个成形步骤及其顺序，这是一个特殊的挑战。

For a cost efficient production of prototypes and small batch sizes, current research projects are developing incremental sheet metal forming processes, which use tools with a small or even no work piece dependency. The final sheet geometry is achieved by repeated localized forming with a simple hemispherical tool. To increase the geometrical accuracy, the sheet can be supported on its backside. Different forming methods have been developed which use work piece dependent or independent supporting tools. The first range from simple backing plates to complex full dies. The latter either use no support at all or a kinematically controlled work piece independent supporting tool. Roboforming belongs to the last group, which is the most flexible and cost efficient, only requiring a CAD model. Roboforming is a method developed at the LPS, where two cooperating industrial robots incrementally form a sheet with a forming and a supporting tool. It currently offers two forming strategies: a circumferentially acting supporting tool and a local supporting tool. Due to the kinematically controlled forming process particularly in combination with subsequent forming of shaped elements Roboforming is able to form a large part scope with a high flexibility. For the industrial application, however, a very high level of geometrical complexity and geometrical accuracy is necessary. Currently, especially the subsequent deformation as a consequence of the interaction of differently shaped elements causes geometrical deviations, which are limiting the increase of the part scope.Thus the project aims for an increased geometrical complexity and increased geometrical accuracy in kinematically controlled incremental sheet metal forming in the so called Roboforming. This shall be achieved by creating a procedure for an optimal design of each forming step, their sequence and their forming strategies in Roboforming. During the course of planning, taking into account the part orientation every shaped element must be analyzed according to its stabilizing or subsequently deforming effect. Additionally research has to be done in order to determine at which point in the forming process each element should be directly or subsequently formed in order to get complex parts with a very good accuracy. This requires a detailed analysis of the direct and subsequent forming of elements. The latter allows a significant increase of the draw angle and supports the adjacent areas by using the peripheral supporting tool which prevents their deformation. The full potential of the two moving tools shall be used by optimizing the forming strategies and by combining and tuning them for each part. The necessary development of an approach to optimal design of individual forming steps and their sequence, as is required in the incremental sheet metal forming, represents a particular challenge.