The influence of the robot's stiffness on roller hemming processes

Hemming is a widely used joining technology in car body manufacturing. It is mostly used to assemble the structured inner part and the outer part of car body hang on parts like doors, hoods and boot lids. A special hemming technology is roller hemming in which a standard industrial robot is used to join the assembly parts. The properties of the robot do have a significant influence on the process quality. The paper shows the influence of the robot's system stiffness on roller hemming processes. At first the influence of varying robot system stiffnesses on the hemming result is shown. After that a method to predict the stiffness behaviour of the robot is being introduced. The prediction method is validated and compared to real measurements in hemming experiments. Finally, the robots stiffness behaviour along a selected complex hemming path is shown and interpreted.