Automotive gear processing technology

Gears are the main basic transmission components in the automotive industry. Usually, there are 18 to 30 teeth in each car. The quality of the gears directly affects the noise, stability and service life of the car. Gear processing machine tool is a complex machine tool system and is the key equipment in the automobile industry. The world's automobile manufacturing powerhouses such as the United States, Germany and Japan are also gear processing machine tool manufacturing powerhouses. According to statistics, more than 80% of automobile gears in China are processed by domestic gear-making equipment. At the same time, the automobile industry consumes more than 60% of gear processing machine tools, and the automobile industry will always be the main body of machine tool consumption.
Gear processing technology
1. Forging billets
Hot die forging is still a widely used blank forging process for automotive gear parts. In recent years, cross wedge rolling technology has been widely promoted in shaft processing. This technology is especially suitable for making blanks for complex stepped shafts. It not only has high precision, small post-processing allowances, but also high production efficiency.​​
2. Normalizing
The purpose of this process is to obtain hardness suitable for subsequent gear cutting and to prepare the structure for final heat treatment, so as to effectively reduce heat treatment deformation. The material of the gear steel used is usually 20CrMnTi. The normal normalizing is greatly affected by personnel, equipment and the environment, making it difficult to control the cooling rate and uniformity of the workpiece, resulting in large dispersion of hardness and uneven metallographic structure. Affecting metal cutting and final heat treatment, the thermal deformation is large and irregular, and the quality of the parts cannot be controlled. To this end, an isothermal normalizing process is used. Practice has proved that the use of isothermal normalizing has effectively changed the drawbacks of general normalizing, and the product quality is stable and reliable.​​
3. Turning
In order to meet the positioning requirements of high-precision gear processing, CNC lathes are used for the processing of gear blanks, and mechanical clamping is used to not re-grind the turning tools. The verticality requirements of the hole and the end face also ensure that the size dispersion of the production of large-scale tooth blanks is small. Thus, the precision of the gear blank is improved, and the processing quality of the subsequent gears is ensured. In addition, the high efficiency of CNC lathe processing also greatly reduces the number of equipment and is economical.​​
4. Rolling and shaping
Ordinary gear hobbing machines and gear shaping machines are still widely used in the gear processing equipment. Although the adjustment and maintenance are convenient, the production efficiency is low. If a large production capacity is achieved, multiple machines are required to produce at the same time. With the development of coating technology, the re-coating of hob and plunger after sharpening is very convenient, and the service life of the coated tool can be significantly improved, generally by more than 90%, which effectively reduces the number of tool changes. And sharpening time, the benefit is significant.​​
5. Shaving
Radial shaving technology is widely used in the production of large-scale automobile gears due to its high efficiency, easy realization of the modification requirements of tooth shape and tooth direction, etc. Since the company purchased the special radial gear shaving machine from the Italian company after technical transformation in 1995, the technology has been maturely applied, and the processing quality is stable and reliable.​​
6. Heat treatment
Automobile gears require carburizing and quenching to ensure their good mechanical properties. Stable and reliable heat treatment equipment is essential for products that are no longer subjected to grinding after heat treatment. The company introduced the continuous carburizing and quenching production line of German company Leuy, and obtained satisfactory heat treatment effect.​​
7. Grinding
It is mainly to finish the heat-treated gear inner hole, end face, shaft outer diameter and other parts to improve dimensional accuracy and reduce shape and position tolerance. The pitch circle fixture is used for positioning and clamping of gear machining, which can effectively ensure the machining accuracy of the tooth portion and the installation reference, and obtain satisfactory product quality.​​
8. Dressing
This is to check and clean up the bumps and burrs on the teeth before the transmission and drive axle gears are assembled, so as to eliminate the abnormal noise caused by them after assembly. This is done by listening to the sound of a single pair of meshes or by observing the mesh deviation on a comprehensive checker. The housing parts in the transmission produced by the manufacturing company include clutch housing, transmission housing and differential housing. Clutch housing and transmission housing are load-bearing parts, which are generally made of die-casting aluminum alloy by die-casting with special molds. The shape is irregular and complex. Bearing hole and locating pin hole → cleaning → leak test detection.