Technical enhancements of the rotary-draw-bending to a semi-kinematic process with reduced tool surfaces

根据DIN 8586，旋转拉伸弯曲是一种广泛使用的型材弯曲方法。该工艺的应用范围可扩展到具有恒定弯曲半径的大量几何形状。这些产品可用于广泛的工业和私人应用。旋转拉伸弯曲是一种工具约束成形工艺，其中工具表面由横截面和弯曲几何形状（弯曲半径）决定。半成品几何形状（例如圆周或壁厚）或弯曲几何形状（弯曲半径）的改变需要调整和/或补充成形工具。除了恒定半径的弯曲之外，自由形式弯曲工艺（例如三辊推弯）的优点是无需改变工具几何形状就能产生自由弯曲轮廓，因为它们基于动态弯曲。该项目的最高目标是通过简化几何形状和附加刀具轴的刀具，将受刀具约束的旋转拉伸弯曲工艺扩展到部分运动弯曲工艺。这就有机会满足未来对提高成形工艺灵活性和经济地生产少量个性化产品的需求。目前还不知道一种减少工具表面的系统方法。在该项目中，一种基于局部和时间变化的工具接触减少的工具表面的方法进行了研究和测试。刀具接触分析与有限元模拟，以检查的影响，刀具的接触表面减少。生成的曲面元素用作简化的刀具曲面。将该方法分别应用于回转式拉弯工具的弯曲模、压力模、夹紧模和刮水模。在减少工具的表面后，将研究与传统工具相比，在这种方法中生成的工具对成形结果的影响程度。当考虑成形过程中接触正应力的发展时，也可以推导出运动学概念，其中表面只具有临时成形效果。主要结果是实现了旋转拉弯过程的柔性化。利用基于部分运动弯曲的工具配置，可以通过所建议的方法弯曲不同的弯曲半径和不同的管尺寸。

Rotary draw bending is a widely used method for bending profiles according to DIN 8586. The application spectrum of the process extends over a large number of geometries with a constant bending radius. These products can be used in a wide range of industrial and private applications. The rotary draw bending is a tool-bound forming process, in which the tool surfaces are determined by the cross section and the bending geometry (bending radius). A change of the semi-finished geometry (e.g. circumference respectively wall thickness) or the bending geometry (bending radius) require an adaptation and/or supplement of forming tools.In addition to bending of constant radii, free-form bending processes (e.g. the three-roll-push-bending) have the advantage to produce free bending contours without need of changing the tool geometries as they base on kinematic bending. The project has the superordinate goal to extend the tool-bound rotary draw bending process to a partial kinematic bending process, by tools with simplified geometries and additional tool axes. This gives the opportunity to serve future demands for enhanced flexibility of forming processes and the economic production of smaller quantities towards individualized products.A method for a systematic approach to reduce tool surfaces is not yet known. In the project, a method based on local and temporal variations of tool contacts for the reduction of the tool surfaces is investigated and tested. The tool contact is analyzed with FE simulations to examine the effects of the tools’ contact surfaces reductions. The generated surface elements are used as reduced tool surfaces. This method is applied to the rotary draw bending tools bending die, pressure die, clamp die and wiper die, respectively. After reducing the tools’ surfaces, it will be investigated to what extent the tools generated in this method influence the forming results compared to conventional tools.When considering contact normal stress development over the process time of forming, kinematic concepts could also be derived in which surfaces only have a temporary shaping effect.The main result is achieving a flexibilization of the rotary draw bending process. With a tool configuration based on a partly kinematic bending, it is possible to bend both, different bending radii and different tube dimensions by the suggested method.