Comprehensive Analysis of Spin Forming Technology: Classification, Characteristics and Future Prospects

　　Technical Principle
　　Spin forming is a process that uses tools such as rollers to apply pressure to a rotating metal blank (metal sheet or tube) on a lathe, causing continuous localized plastic deformation. This process ultimately forms the required hollow rotating part, and is a low/no-cutting machining process. This technology not only has low forming force and simple tools, but also small dimensional tolerances, high material utilization rate, and low cost, while the product performance is also quite excellent. This has led to the widespread application of spin forming technology in various manufacturing fields such as aerospace, military equipment, vehicles, and household appliances.
　　Classification
　　Traditional spin forming technology classification is mainly based on the deformation characteristics of the metal material, the relative position of the roller and the blank, and whether heating is required. Specifically, it can be divided into two categories: ordinary spin forming and high-energy-rate forming.
　　In the ordinary spin forming process, the metal blank mainly produces contraction or expansion in diameter, while the wall thickness remains basically unchanged or only slightly changes. This process is particularly suitable for processing cylindrical parts, hemispheres and other simple-shaped products, so it has been widely used in civilian fields such as utensils, tableware and some parts manufacturing with low precision requirements.
　　In contrast, in the high-energy-rate forming process, the metal blank not only changes significantly in shape, but also the wall thickness is greatly reduced or thickened. This process is more suitable for processing various complex-shaped products, such as cylindrical, conical, and irregularly shaped shells, mainly to meet the manufacturing needs of large-scale precision thin-walled rotating parts in the aerospace, shipbuilding, nuclear industry, and chemical industries.
　　(2) The relative position of the roller and the blank determines the type of spin forming. According to this classification standard, spin forming can be divided into internal spin forming and external spin forming. In traditional spin forming methods, the mandrel is usually placed inside the workpiece, while the roller is used to spin form from the outside of the workpiece, causing it to deform. This is the so-called external spin forming method. However, in some specific situations, we need to change the positions of the mandrel and the roller, thus forming the internal spin forming method. This internal spin forming method is widely used in expanding spin forming, bulging spin forming, and rib spin forming processes.
　　(3) According to whether heating is used in the spin forming process, spin forming can be divided into cold spin forming (room temperature spin forming) and hot spin forming. At room temperature, most metal materials can be spin formed, and the mechanical properties of the formed workpieces will be significantly improved, especially the fracture strength, fatigue strength, yield strength, and hardness, but the plasticity will be reduced. Hot spin forming is mainly used for refractory metals with poor plasticity at normal temperature, such as titanium, tungsten, molybdenum and their alloys. In addition, some special spin forming processes, such as the closing and bottoming of gas cylinders, must be carried out under heating conditions.
　　(4) Looking to the future, the continuous progress of spin forming technology has significantly improved the manufacturing capabilities and process level of complex thin-walled shells. In order to meet the urgent needs of high-end fields such as aerospace, national defense and military industry, and nuclear industry for high-performance components, spin forming technology and equipment are constantly developing towards lightweight, high-performance, and high-reliability directions. In the next few years, the research on multi-process parameter collaborative technology will become an important topic, which will involve multiple factors such as roller motion trajectory, spin forming speed, and temperature control, in order to optimize the forming size and performance of spin formed parts. At the same time, a deeper understanding of the forming mechanism of spin formed parts will also provide strong support for technological progress.
　　(2) In-depth exploration of cross-scale material flow under multi-energy field coupling. Currently, the plastic deformation theory of spin forming is mainly limited to two-dimensional plane theoretical components, which is difficult to cope with the increasingly complex spin forming challenges. In fact, the spin forming process is subject to the coupling effect of multiple energy fields such as heat and force, and the material flow mechanism is extremely complex. At the same time, the dynamic evolution of the internal microstructure of the spin formed part has a profound impact on the final product shape and performance. Therefore, it is particularly important to construct a macro-meso-micro-nano cross-scale, multi-energy field coupled spin forming model to reveal the forming and forming mechanism in the spin forming process. This will not only help improve the spin forming manufacturing process level, but also provide theoretical support for the research and development of high-performance spin formed components.
　　(3) Promoting the research and development of large-size, high-precision, and digital spin forming equipment. With the urgent need for large-size, high-precision, and high-performance spin formed components in the aerospace field, future spin forming equipment will develop towards large-size, high-precision, and digital directions. Advanced equipment will be equipped with key digital devices such as a size online monitoring system based on machine vision, a high-efficiency component heating and temperature control system, and a spin forming numerical simulation and process decision-making system. By continuously improving the motion accuracy and execution stability of various mechanisms of the equipment, the manufacturing performance of spin forming equipment will be effectively improved to meet the application needs of high-end fields.