Contributions to increasing the accuracy and reducing the forming forces of robot-based two-point incremental forming

¹ Fraunhofer Institute for Machine Tools and Forming Technology IWU, Reichenhainer Straße 88, Chemnitz, 09126, Germany
² University of Bremen, Bremen Institute for Metrology, Automation and Quality Science, Linzer Straße 13, Bremen, 28359, Germany
³ Chemnitz University of Technology, Straße der Nationen 62, 09111 Chemnitz, Germany

^* Corresponding author: dieter.weise@iwu.fraunhofer.de

Abstract

This article presents the latest research results on the enhancement of robot-based incremental sheet metal forming performance in detail and comprehensively. Since the low robot stiffness leads to deformations of the robot and thus deviations of the final part, the presented contributions aim for increasing the part accuracy. The article demonstrates how an advanced sensor network, analogous to a µGPS, can be established for tracking the tool pose utilizing innovative shadow imaging sensor technology. Static experiments show that a measurement uncertainty below of 50 µm is achievable after the correction of systematic errors. Additional experiments demonstrated the applicability of the sensor network for measuring the tool position on a moving robot. Based on the measurement, a robot position correction will be enabled to achieve a reduction of machine-dependent component tolerances. A further approach to reduce the geometric deviations due to robot deformation is reducing the forming forces in robot-based two-point incremental forming. This is achieved by a modular vibration unit that has been specially developed for this purpose. The introduction of ultrasonic vibrations into the forming process has been shown to reduce the forces in the sheet metal plane by 70%. As a result, the sensor network and the introduction of ultrasonic vibrations provide a robust foundation for the advancement of higher accuracy classes with cost-effective robot technology, which is becoming increasingly crucial in the industry.