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Shell hydroforming involves using a closed polyhedral shell of a specific shape as a preform. After the closed polyhedral shell is filled with liquid, pressure is applied within it through the liquid medium; under this internal pressure, the shell undergoes plastic deformation and gradually takes on its final shape. The final shell shape can be spherical, elliptical, toroidal, or other shapes. Main advantages of shell hydroforming: ① No molds or presses are required. From a mechanical perspective, the principle of this technology lies in utilizing the self-balancing force system generated by the internal pressure within the fully enclosed shell; in other words, the shell itself serves both as a deformable body and as a medium for achieving force balance, thereby enabling the formation of large-scale shells without the need for presses or molds. ②It is easy to change the wall thickness and diameter of the housing. Since no molds or presses are required, for shells of the desired diameter and thickness, a properly designed preform can be used to form the closed polyhedral shell by direct pressure application. With traditional molding techniques, one set of molds is required for a spherical shell of a certain diameter, and several sets of molds are needed for an ellipsoidal shell of the same specification. ③The product has high precision. By changing the shell manufacturing process from the traditional \"form first then weld\" approach to \"weld first then form\", the forming step serves to correct the welding-induced deformation, resulting in high dimensional accuracy of the final product. ④Reduce costs and shorten the manufacturing cycle. Since no molds or presses are used, the profiling time and mold costs are saved. The main disadvantages of hydroforming for housings are as follows: ① Since this technique involves \"welding first and then forming,\" the welds of multi-faced closed housings undergo certain plastic deformation during the forming process. If there are issues with the quality of these welds, cracking can occur, resulting in the entire housing becoming unusable. For thick plates and low-alloy steels, this problem is more severe. Therefore, controlling welding quality is crucial. ②For large shells, providing support during the forming process is difficult and costly. For example, a spherical shell with a diameter of 12.3 m and a volume of 1000 m3 requires a foundation capable of supporting 1000 tons of water as well as the weight of the shell itself.