Roller hemming: A new simulation model for the automotive industry

Hemming is used in the automotive industry to join two sheet metal panels by bending the flange of the outer panel over the inner one. In roller hemming process, a robot guides a small roller across the flange to fold a sheet onto itself or onto another sheet. The process is oriented to low volume automotive applications, providing a distinct advantage in manufacturing closures and subassemblies with developed flanges. The most important benefit of the roller hemming process is the flexibility to handle multiple product variations. Robotic roller hemming can be used to replace some flanging operation reducing overall investment costs. Robot roller hemming is a relatively new process, so nowadays there is no much fundamental process know-how available. The trial-And-error process is the most common way to achieve and maintain the right quality. To make a finite element analysis of the process can avoid this cost and time method. The work described in the paper is a development of a FE-simulation technique; which can accurately predict the geometry of the part before hemming, and also the required forces for the hemming operation. A complete 3D model was developed, considering the robot stiffness as well as the rotary of the roller, and the results were compared with experimental measurements for simple pieces (straight, convex and concave parts) showing a very good agreement.