Development of combined tube drawing process for straight-type cowl cross bar of automobile

The cowl cross bar of an automobile is a frame component that is installed inside the cockpit module to provide a guide surface, to which functional components for electricity and air conditioning are attached. In the recent years, the geometries of cowl cross bars are getting more complex in order to meet the demands of a wide variety of embedded functional components and the reduced weight of frame parts with enhanced mechanical and noise/vibration characteristics. This paper seeks to develop an one-piece forming process which eliminates welding process for an automotive cowl cross bar in order to increase production efficiency and enhance the mechanical characteristics by applying the tube drawing process. However, it was predicted that a conventional tube drawing process cannot be applied to the current part since the area reduction ratio of the drawing reaches 51.7% which exceeds the general limiting value. In this study, therefore, a combined drawing process which adds a compressive force to a tensile force of the conventional drawing process was proposed and 2-stage drawing process sequence was designed by using CAE analyses. In addition, drawing experiments were carried out by using the manufactured combined drawing machine in order to verify the designed process.