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Internal high-pressure forming (tube hydroforming, or shape forming) is a popular and advanced hydroforming technique used for manufacturing lightweight and thin-walled components. Tubular components with custom cross-sections are used for this purpose; such components have been developed since the 1990s and are widely used in the automotive industry around the world. This article introduces Xingdiyuan Machinery’s research areas, applicable industries, and advantages of the internal high-pressure forming technology. I. Research areas of internal high-pressure forming technology: Principles of internal high-pressure forming. Internal high-pressure forming (hydraulic forming of tubes, or similar components) is a popular advanced hydraulic forming technique used for manufacturing lightweight, thin-walled components. Tubular components with custom cross-sections are used for this purpose; such components have been developed since the 1990s and are widely used in the automotive industry around the world. The application areas of hydraulic forming for pipe fittings are based on three types of component structures, including reducers, bent shaft components, and tees. The basic principles and key technologies are presented, along with the hydraulic forming process parameters, defect analysis, equipment selection, die structure, and the forming of typical parts. The main research areas include tube hydroforming, sheet hydroforming, and thermoforming. The fundamentals, internal high-pressure forming processes, and equipment were studied theoretically and experimentally. Internal high-pressure forming technology is an advanced manufacturing technique for hollow, variable-section lightweight components characterized by light weight and integration, and it is attracting increasing attention. The internal high-pressure forming process of pipes is influenced by many factors, among which the matching relationship between the internal pressure applied to the pipe and the axial force is particularly important. How to determine the influence patterns of the two on forming properties and reasonably optimize their matching relationship is an important issue to be addressed in internal high-pressure forming. Simulations and analyses were conducted primarily on factors such as the load matching relationship between internal pressure and axial force that affect high-pressure forming of parts, the friction coefficient between the tube blank and the die, as well as the properties of the tube blank material. Important results were obtained regarding the forming state of the workpiece, the characteristics of material flow, stress and strain, and wall thickness distribution under different process conditions; moreover, the impact of various process parameters on the manufacturing process was analyzed. Lightweighting of vehicles is the current trend in vehicle design and manufacturing. An important aspect of achieving vehicle lightweighting is improving the body structure, by using lightweight designs to reduce the vehicle’s weight. An effective approach is to use hollow structures for components that meet mechanical requirements, which not only reduces weight and saves materials but also makes full use of the strength and stiffness of the materials. In fields such as the aerospace and automotive industries, reducing structural mass to save energy during operation has long been a goal pursued by people, and it is also one of the trends in the development of advanced manufacturing technologies. Entering the 1990s, due to the costs of fuel and raw materials as well as strict environmental regulations on exhaust emissions, lightweighting of vehicle structures became increasingly important. Lightweighting of structures is one of the main methods for vehicles such as cars and airplanes to save fuel and reduce exhaust emissions. For structures primarily subjected to bending and torsional loads, the use of hollow variable-section members allows for reducing mass while making full use of the material strength. Internal high-pressure forming is an advanced manufacturing technology in which a tube, used as a blank, is formed into the desired shape under the combined action of internal pressure and axial feeding. II. Industries suitable for internal high-pressure forming technology and its advantages: As environmental awareness grows, residential drinking water pipelines are undergoing an environmental transformation, with them being replaced by healthy, environmentally friendly, and durable metal pipes. The fittings used in these pipes are special-shaped components; previously, lead extrusion and adhesive expansion were used for their production, but neither of these methods is ideal. Xingdiyuan’s water expansion technology can overcome the shortcomings of these methods, while also helping to reduce costs and improve production efficiency. Therefore, it is inevitable that this production method will replace the existing ones. 1) Process concept: Utilizing Xingdiyuan Machinery’s internal high-pressure forming equipment, a liquid is injected into the hollow interior of metal materials (such as iron, aluminum, copper, titanium, stainless steel, and metal composite materials), which is then sealed. High or ultra-high pressure is applied to the inside of the metal, thereby forming the product as per the customer’s requirements. 2) Applicable industries: 1. Aerospace industry: such as bellows and oil hoses for aero engines, etc ； 2. Marine equipment industry: such as cylinders for offshore drilling platforms, high-pressure pipelines for ships, etc ； 3. Automotive industry: such as automotive chassis fittings, car mufflers, fuel tanks, bumpers, bellows, etc ； 4. Civil light industry: such as various types of tees and elbows made of stainless steel, faucet fittings, various cups, kettles, and lids, as well as stainless steel kitchen utensils ； 5. The home appliance industry, such as TV backplanes, washing machine drums, rice cooker pots, refrigerator backplanes, etc. Xingdiyuan Machinery has established an Engineering Technology Research and Development Center for Hydrodynamic Internal High-Pressure Forming Machinery. It also engages in long-term cooperation with institutions such as the Institute of Metal Research of the Chinese Academy of Sciences and Nanjing University of Aeronautics and Astronautics on the development of scientific research projects. After more than a decade of production and continuous innovation and research, Xingdiyuan Machinery has obtained over 20 invention patents and utility model patents; this number continues to grow at a rate of 2 to 4 new patents per year. 3) Features of Xingdiyuan’s high-pressure water swelling forming equipment: 1. This machine is equipped with an independent rapid low-pressure water injection system that quickly expels the air from the mold cavity during the descent of the main cylinder, filling it with the swelling liquid. Once the molds are closed, a low-pressure liquid chamber free of air is created, allowing the booster to inject high-pressure liquid rapidly and thus reducing the forming time ； 2. The main motor utilizes a Siemens energy-saving motor, which offers numerous advantages such as high starting torque, a wide operating range, low noise, long service life, and low energy consumption ； 3. The equipment features a vertical structure, which effectively increases the opening height of the device; this height can reach 1500 mm, and the height of the formed parts can reach 600 mm. Rapid water swelling equipment with an even larger opening height can be customized to meet specific customer requirements ； 4. Liquid is injected into the mold cavity through the filling hole on the workbench to serve as back pressure; based on the bulging effect caused by this back pressure, defects such as cracking and wrinkling are effectively reduced, thereby increasing the drawing ratio. Xingdiyuan’s rapid hydroexpansion forming hydraulic equipment is mainly suitable for the hydroexpansion forming process of tubular components. The water swelling process for vacuum flasks, thermoses, kettles, as well as other tableware, utensils, stair handrails, and decorative fittings made of materials such as stainless steel, copper, aluminum, iron, etc. Replacing traditional processes such as rubber bulging, it enables the manufacturing of parts with complex surface shapes, offering numerous advantages including high production efficiency, low space requirement, excellent performance, precise and sensitive control, as well as safety and reliability. 4) Applications of internal high-pressure forming technology in the automotive industry: The use of internal high-pressure forming technology for automotive tubular subframes, as well as specialized hydraulic presses for the internal high-pressure forming of automotive chassis components; this technology enables one-time forming of large automotive chassis parts, mufflers, and complex bent tubes. For many years, internal high-pressure forming has been widely used in the manufacturing of exhaust components, most of which involve extremely complex shapes. After undergoing hydroexpansion and internal high-pressure forming, automotive fittings have a longer service life, are lighter in weight, offer better cost-efficiency in terms of materials used, as well as a shorter development time. In today’s society, efficiency is of primary importance. In the field of automobile frame manufacturing, the demand for materials has been reduced, thereby lowering the purchasing and production costs for customers; previously, frames were made by welding several components together. Now the precision is higher. From processes such as bending, flanging, and bulging. The internal high-pressure forming method is primarily used in the manufacturing of frames and tracks. Products manufactured by this method have become a standard in the field of automotive engine components, combining lightweight structural elements with complex, high-stress functional parts. Xingdiyuan’s products are widely used in the field of vehicle lightweighting, and it serves as an important equipment supplier to numerous reputable parts manufacturers in China. The end customers of these services include SAIC Group, BAIC Group, Dongfeng Motor, Geely Automobile, Brilliance China, Brilliance BMW, Beijing Mercedes-Benz, BYD, Chery Automobile, Hongqi Automobile, Changan Automobile, FAW Group, Great Wall Motor, Brilliance Auto, Haima Automobile, and others. Internal high-pressure forming makes it possible to produce parts with complex shapes entirely, without any welds. It is currently expanding within the industry, with a focus on reducing weight, saving energy, and achieving integrated products. Improve accuracy. Reducing the processing steps lowers costs: the vehicle’s weight is reduced by 10%, fuel consumption is decreased by 6%–8%, and exhaust emissions are reduced by 5%–6%. Today, foreign passenger cars weigh 8% to 9% less per decade, while commercial vehicles see a weight reduction of 10% to 15%; in the next decade, passenger cars will lose another 20% in weight. 5) Comparative advantages of internal high-pressure forming technology over traditional manufacturing: Traditional manufacturing methods mostly involve stamping using presses and then welding the parts together in a half-by-half manner; therefore, internal high-pressure forming has advantages over these approaches. Feeding and material replenishment in different directions can be carried out using the hydraulic press molding die to form hollow components with varying cross-sections along the component’s axis. Its advantage lies in reducing the overall weight of the product and saving raw materials; internal high-pressure formed parts are 20%-40% lighter than stamped parts, while hollow stepped shafts can be 40%-50% lighter. It enables the production of one part per mold, thereby reducing the costs associated with stamping molds. For example, the manufacturing process for auto parts involves up to 6 steps; when using hydroforming molds, the forming process is fast and precise, and welding is not required. Taking the heater bracket as an example, the heat dissipation area increases by 43%, the number of solder joints decreases from 174 to 20, the number of processing steps drops from 13 to 6, and productivity improves by 70% ； Automotive parts manufactured by internal high-pressure forming mainly include: chassis components made from materials such as carbon steel, stainless steel, aluminum alloy, copper alloy, and nickel alloy – including subframes, rear axles, longitudinal beams, and bumpers; seat frames, upper beams, and roof beams; as well as manifold and exhaust components. Body components include radiator brackets, cam shafts, dashboard support beams, and drive shafts. The steering and suspension systems involve control arms and steering rods.