In recent years, there has been a popular hydraulic forming technology in the metal forming industry in China. Many people call it water swelling machine. Through working principle, it is also called internal high-pressure molding machine. No matter what kind of name is, this kind of molding equipment fills the metal hollow pipe with high-pressure liquid under the condition of internal high-pressure forming mold, so as to make the metal hollow tube shape the required shape at one time To realize the advantages of light weight of automobile and stronger toughness of pipe material.

Stress analysis, product design, die design and appearance structure design of internal high pressure forming technology, mainly including shell hydroforming, sheet hydroforming, which is generally pressurized at 600 ~ 800MPa; hydroforming. The following section briefly analyzes which molding equipment is used for metal shell exhaust pipe molding, and how many tonnage machines are needed for metal shell exhaust pipe molding.

At present, the internal high pressure molding machine is mainly used in the automobile industry, hardware and bathroom, military industry, hardware products, stainless steel compression tube, air conditioning, refrigeration and heating copper pipe and other hardware processing industries, and can process different materials such as stainless steel, copper, iron, aluminum, automobile steel, composite materials, magnesium Aluminum alloy materials, etc. Moreover, few manufacturers can produce 2000-5000 tons of large-scale internal high-pressure molding machine equipment. Some of them are applied in Colleges and universities and used for research and commercial purposes. Through the design structure, we classify the internal high-pressure molding machine into vertical and horizontal structures, as shown in the following figure:

In the early stage, the tube is processed by multiple processes from pipe making, pipe cutting, elbow bending to preform products. Finally, the required blank is placed in the mold of forming energy equipment. The inner high pressure forming technology of pipe parts is a kind of processing technology with metal tube as blank, liquid as pressure transmission medium and internal high pressure forming, which belongs to the category of hydraulic forming. This technology originated from the traditional hydroforming process. The special forming equipment, die and control system are the most important factors. Compared with other metal plastic processing technology, this is an advanced material processing technology which is on the rise and has a good development prospect.

At present, the main application field of hydroforming technology is automobile industry. Typical products include engine bracket, exhaust pipe, camshaft, longitudinal beam, bracket, body parts, etc. the materials used are various carbon steel, stainless steel, aluminum alloy, etc. In vehicle design, automotive companies that have adopted hydroforming pipe parts include general motors, Audi, Mercedes Benz, Volkswagen, Volvo, Daimler Chrysler, Nissan, Hyundai, etc. It has a positive impact on the process of automobile lightweight, improving the strength and stiffness of parts, improving the stability and safety of vehicle operation. It can reduce the amount of subsequent machining and assembly welding, improve the production efficiency, and improve the strength and stiffness, especially the fatigue strength. High material utilization rate, up to 90% - 95%, reduce production costs. The average cost is reduced by 15% - 20%, and the mold cost is reduced by 20% - 30%.

The principle of one-time forming of shell and exhaust pipe the complete process route of producing pipe parts by using inner high pressure forming technology is as follows: tube blank blanking pre bending machining end cleaning spraying lubricant pre forming internal high pressure forming subsequent processing (such as laser cutting, welding, heat treatment, cleaning, painting, etc.). Among them, hydroforming is the core technology. Compared with the hydroforming process, the liquid pressure of hydroforming is higher and the loading path of internal pressure is strictly controlled. Therefore, large material deformation can be obtained and complex three-dimensional shape of pipe can be processed.

Tube parts hydroforming technology has unique process characteristics, technical and economic advantages. In recent ten years, it has been rapidly promoted in the international automobile industry, which has played a good role in promoting the process of automobile lightweight, with significant economic and social benefits. In this field, China is in the initial stage. In order to meet the special needs of forming process, the internal high pressure forming equipment is specially designed and developed. Its development trend is large-scale, automatic, flexible and intelligent. The key technologies of equipment development are ultra-high pressure device and servo control system.