Hydroforming is a special type of cold-forming that uses a high pressure liquid stream to hydraulically mould a tube at room temperature.
The process involves pre-bending a metal tube and placing the preformed tube into a mould of the desired shape and applying pressure. Under the pressure of the tubes in the mould, the tubes can be perforated at the same time, thereby avoiding secondary operations in most cases. Hydroforming can form complex concave shapes, which cannot be achieved with standard stamping.
Hydroforming is considered a cost-saving process for shaping lightweight metal forming. One of the advantages of this process is that it can create at three dimensional tube, while cold-stamping can only weld two shells. This ability to retrofit thick materials is used in the chassis business.