Research status of hollow shaft forming technology

    Abstract: the comparison of the hollow shaft and solid shaft bending and torsional section coefficient, found the same outer diameter of the hollow shaft and solid shaft in the function of the composite of transmission torque, bending moment and bending and twisting when the difference is not big, but hollow shaft can greatly reduce the weight of the shaft, so the application of hollow shaft has been more and more attention, urgently needs to solve the problem of forming of hollow shaft. Summarized the methods for the forming of the hollow shaft, the brief analysis of the radial forging + machining, forging, rotary forging, extrusion or extrusion + machining, cross wedge rolling, the power spinning, spinning compression, internal high pressure forming, forging + rolling axial punch, injection and hydrostatic extrusion + internal high pressure forming principle and characteristics of the forming methods and the blank form, forming temperature, lubrication, forming time, dimensional accuracy, surface quality and forming cycle, etc. In the future, there will be more and more demand for hollow shaft, and the forming method will develop to the direction of high efficiency, precision and flexibility.

    Shaft is one of the most important parts of a machine. All kinds of rotary driving parts support driving parts, transfer motion and power through shaft. According to the different loads on the shaft, the shaft can be divided into: the mandrel which only bears bending moment and does not transmit torque, such as the wheel shaft of high-speed railway; A drive shaft that transmits only torque and does not withstand bending moments, such as a car's drive shaft; A shaft that transmits both torque and bending moment, such as the shaft of an automobile gearbox.

     With the increasingly strict national energy conservation and emission reduction policies and the requirements of sustainable economic development, the production of resource-saving and environment-friendly products is an inevitable choice for the industry. Among them, there is an increasing demand for light weight, such as material saving and consumption reduction. For example, the light weight of automobiles can reduce material consumption in the manufacturing stage, reduce energy and emissions in the application stage, and have better load and handling.

    Compared with the solid shaft, the hollow shaft has the following advantages under the condition of ensuring the use requirements :(1) reduce the material consumption and reduce the weight of the shaft; (2) for parts with high rotating speed, the inertia of hollow shaft is small; (3) reduce vibration. Hollow shafts are particularly advantageous for vehicles such as cars, high-speed trains and aircraft.

    Therefore, this paper compares the effect of hollow shaft and solid shaft in transferring bending moment and torque. It is found that hollow shaft and solid shaft with the same outer diameter have little difference in use function, but their weight can be greatly reduced, which is of great significance for lightweight. Therefore, more and more attention is paid to the forming of hollow shaft. Hollow shaft forming methods include: forging + machining, radial forging, rotary forging, extrusion + punching (drilling), cross wedge rolling, internal high pressure forming, shearing spinning, rolling extrusion, etc. More mature methods include forging + machining, radial forging, rotary forging, extrusion, etc. In the future, with the development of lightweight, there will be more and more demand for hollow shaft, and the forming method will develop towards the direction of high efficiency, precision and flexibility.