Research on the difficulties and key technologies of Hobbing

For a long time, short life, poor reliability and heavy structure have become the three major problems restricting the development and safe use of China’s gear industry, and forming manufacturing is the main reason for the three problems. There are many factors that affect the quality of gear processing. From the perspective of technology and technology, there are mainly process design factors, mechanical processing factors such as transmission clearance, stress and thermal deformation, cutting parameter selection, measurement feedback, analysis and calculation and other control factors. In the process of gear hobbing, the gear performance and service life are often affected because the error of tooth shape and direction cannot reach the accuracy standard. Therefore, we must strengthen scientific and technological innovation, break through the core key technology from two aspects of hobbing processing technology and hobbing manufacturing equipment; and because of the limitations of structure and technology, more research is to break through from the control method.

Process improvement and error control

The accuracy of gear can be divided into motion accuracy, stability accuracy and contact accuracy. The tooth shape, tooth direction error and tooth surface defect produced in gear hobbing directly affect the three major accuracy of gear. Gear hobbing is generally regarded as the first process of shaving, and its accuracy determines the shaving accuracy and gear quality.

The accuracy and efficiency of hobbing depend on the accuracy and rigidity of hobbing machine to a great extent. At present, Y3150, Y38 and other gear hobbing machines widely used by enterprises can be improved from dynamic measurement and adjustment of transmission clearance, improvement of system rigidity (hob, gear steel, machine tool), reasonable control of hobbing amount, etc., so as to reduce mechanical error and improve machining accuracy; ys3120cnc6, ygs3608cnc6 and other CNC gear hobbing machines are equipped with CNC compensation functions of electronic gear box and mechanical clearance, It can realize the function of index and differential compensation, so as to improve the transmission accuracy.

In addition, the thermal deformation in hobbing will also affect the machining accuracy. Combined with the theoretical calculation of hobbing deformation, dynamic vibration displacement and thermal deformation, the thermal error compensation model of the variation of the spindle center distance of the gear hobbing machine is established to effectively predict and control the thermal deformation and gear machining error of the gear hobbing machine, which can improve the accuracy and efficiency of gear hobbing.

Research on key technologies and hot technologies of gear hobbing equipment manufacturing

Because the transmission chain of CNC gear hobbing machine is greatly shortened, the manufacturing error, clearance and assembly error of shaft, bearing, gear and other components are reduced, and the error compensation function is provided, which greatly improves the machining accuracy. In “made in China 2025”, CNC gear hobbing machine and basic manufacturing equipment industry are listed in one of the strategic areas of China’s manufacturing industry. CNC gear hobbing machine will become the key development of CNC machine tools in the next decade. In recent years, the research and development of high-speed and high-efficiency CNC gear hobbing machine has become the focus of gear hobbing equipment manufacturing technology.

1) Development of CNC system for gear hobbing machine. Since the reform and opening up, the domestic NC system has developed rapidly and basically occupied the low-end NC system market, but most of the middle and high-end NC systems are still occupied by foreign brands, especially the special NC system. The domestic CNC gear hobbing machine generally adopts German Siemens, Japanese FANUC, French num and other systems. Therefore, the independent research and development of CNC system of gear hobbing machine has become the key to improve the manufacturing capacity of gear hobbing equipment in China. Due to the complex structure of gear hobbing machine and the lack of special CNC system, the research on CNC system of gear hobbing machine in China mainly focuses on the open CNC system. For example, Huang Qiang and others put forward the development strategy of CNC system of open gear hobbing machine based on PC and PMAC motion control card.

2) Zero programming technology. NC gear hobbing machine is usually programmed by hand, but the process and numerical calculation are complex and easy to make mistakes. In recent years, some colleges and universities in China have continued to study the automatic programming technology of NC gear hobbing, such as the embedded zero programming technology of NC gear hobbing developed by Chongqing University and the parameterized automatic programming system of gear machining graphics developed by Lanzhou University of science and technology. NC programs can be generated automatically only by inputting gear parameters and machining parameters, It provides a theoretical basis for further research and development of zero programming method and system of gear hobbing machine based on Open CNC.

3) Thermal error real-time compensation technology. Thermal error is the machining error caused by thermal deformation of machine tool. Among the factors that affect the machining accuracy of NC gear hobbing machine, thermal error accounts for the largest proportion, accounting for 45% of the total error of NC gear hobbing machine, so reducing thermal error is the key to improve the machining accuracy of NC gear hobbing machine [11]. Shanghai Jiaotong University, Sichuan University, Chongqing University and other universities have carried out thermal error compensation Modeling Research on the basis of thermal deformation test, and put forward technical schemes such as on-line thermal error compensation and automatic thermal error compensation, which is helpful to improve the quality stability of CNC hobbing and improve the intelligent level of high-grade CNC hobbing machine in China.