The early history of tube hydroforforming(high pressure forming) can be used in a series of US patents, although in this period, Europe and Japan have similar inventions.

I. Development of high pressure forming of pipes in the period from 1900 to 1980:

The use of fluid pressure to form tubular metal parts dates back to the early 20th century. One patent (Park 1903) describes a device for constructing a serpentine hollow body of a steam boiler, the serpentine member being constructed of a small tube. A heated straight tube is first placed between the mold and the mold filled with molten lead and pressurized to expand into a closed mold cavity shape. This patent defines the basic principle of using fluid pressure as a forming medium. Mold closure, fluid sealing and pressurization are achieved through hydraulic operation. In 1917, a process to improve curved copper tubes for musical instruments was patented (Foster 1917). According to this patent, the main elements of the in-tube high pressure forming process are determined, showing the preformed electrically conductive metal tube and fluid sealing method placed in the lower tool cavity. The patent "Reducing Hand Machining and Scrap, Improving the Uniformity of Shape and Size" defines the advantages of this process. A similar technique is currently used to make plumbing equipment, another interesting patent (Davies 1932), which describes the process of making prostheses (arms and legs) from aluminum tubes. The tube is first rotationally formed on the mandrel to achieve the desired edge section perimeter. The blank is then preformed so that it is in the tool. The text of this patent explains: "The curved spindle is then extended to the center shape of the limb using a pressure of 2000 psi, which is satisfactory." The 1940 patent (Gray 1940) describes a device for making a forged metal T-shaped fitting. It details the axial feed of the material at a lower pressure and then increases the pressure to the maximum value of the final shape. This method of pushing the material from the tube end makes it possible to manufacture the branch assembly, and the same technique is also applicable to the expanded shaped part used in the exhaust system. A 1950 patent (Kearns 1950) was used to produce hollow metal aircraft propeller blades. The variable cross section of the blade core is formed by expanding the tube blank using high fluid pressure. The hydroformed structural approach increases stiffness while reducing blade weight. The invention of a method of making a camshaft from a hollow steel tube is described in the 1959 patent (Garvin 1959), in which cam lobes are formed on one shaft, in turn by axially feeding material from the end of the tube. In the 1960s, Japan Expansion Industry Corporation also developed various processing technologies that utilized fluid pressure. The 1970 patent (Fuchs 1970) describes a method of forming and forming articles. The methods and apparatus encompassed by this patent illustrate swaging (reduced end diameter reduction) by high pressure, axially expanded axial feed, slotted perforations, and in-mold end shearing.

Second, the development of high pressure forming of pipes in 1980:

In 1986, the Canadian Standard Tube (now brazed unit) in Woodstock, Canada, a company producing pipes and tubes, received the first patent in North America to apply hydroforming technology to large frame components (Cudini 1986), standard The tube is called a process change tube, and the company's department is now known as a hydroforming company, and the variant standard tube develops these technologies as their work on the pipe. Typically, assemblies made using tubes of conventional bending and/or mold forming operations have higher springback and lower surface size control. The use of fluid pressure within the tube pushes the metal onto the walls of the mold cavity to make it more uniform and achieve a larger surface size. control. The standard tube patent limits the length of the section of the "expansion" line to 5% or less. Further improvements to patents 4744237 (Cudini 1988) and 4281803 (Cudini 1989) emphasize the benefits of pressurizing the blank during the mold closing phase of the forming cycle. The flow of fluid as a mandrel reduces the material from excessive wrinkling during the mold closing phase. This process is called pressure sequential hydroforming (PSH). Sanshui Power Technology's patents -5,353,618; 5,481,892; and 5,890,387 (Roper and Webb 1994, 1996, 1999) emphasize the axial end feed, the hydraulic stratification of the holes, the partial cam forming and the large automotive frame parts. Two-way bending achieves the importance of higher expansion. In-plane bending can be produced in the hydroforming mold to eliminate the CNC bending operation. To date, axial feed of materials has only been applied to small parts, and axial feeds have been used in large frames. A very efficient structure can be obtained by expanding the structure without being significantly thinned. This patent also describes the use of local cams in tools. Otherwise, the part features that result in a clamping condition can be formed using a cam driven by a hydraulic cylinder.