RapidSheet

Economic manufacturing of customized sheet metal parts in small lot sizes is a challenge in industrial production. As conventional deep drawing requires expensive tools, incremental sheet metal forming (ISF) is a suitable alternative. Thereby, a forming stylus forms the sheet metal over a counter die. Instead of a counter die milled with a separate machine tool, the project RapidSheet proposes to combine an additive manufacturing of the counter die with the ISF process in a single machine tool. To increase not only the speed but also the accuracy of ISF, the geometrical deviation due to the deflection of the forming stylus must be corrected. For this purpose, an in-process tool deflection measurement is investigated.

To measure the tool deflection optically with a low uncertainty in a large machining volume, a novel multi-sensor-system is created, where each sensor consists of a camera chip and a mask. An LED attached to the tool tip casts a shadow on the camera so that the tool tip position is evaluated from the image of the shadow. Experimental results show that a lateral position measurement uncertainty of a single sensor of less than 15 µm in an angle-of-view of ±4,3° and a distance range between 100 mm and 500 mm is achievable. This already meets the sensing requirements. However, the measurement uncertainty of the axial position component with a single sensor is proven to be insufficient for the tool deflection measurement. Therefore, the axial component must be determined by triangulation with data from the neighbouring sensors.

Now, the multi-sensor-system will be realized with the goal of a three-dimensional position measurement with a sufficient uncertainty in the entire machining volume. Furthermore, a commercial acceleration sensor will be included which measures the high-frequency deflections. Finally, the combined measurement system will be validated during an in-situ measurement of the tool deflection in ISF.