Method of manufacturing a vehicle body and frame assembly including hydroformed side rails

Abstract

A method is disclosed for manufacturing a vehicle body and frame assembly including a pair of side rails, each of which is formed from a single closed channel structural member that extends the entire length of the vehicle body and frame assembly and is deformed into a desired shape by hydroforming. The first step in the process is to provide a length of stock material, preferably a tubular metallic workpiece, having a predetermined length. The tubular workpiece is then typically pre-bent by a conventional tube bending apparatus to have some or all of the bends in the side rails to be formed. The bends initially formed in the workpiece during this pre-bending step usually do not have the exact angles and shapes which result in the final product. Rather, this initial pre-bending operation is performed to facilitate the insertion of the workpiece within a die cavity defined by cooperating die sections of a hydroforming die. The next step in the method involves hydroforming the pre-bent workpiece to a desired shape. The hydroforming die may be configured to include whatever shapes, including recesses, protuberances, openings, and the like, as are necessary to form the desired fmal shape for the side rails to be formed. In the fmal step of the method, the two hydroformed side rails are connected together by cross members to complete the vehicle frame assembly.