Gear machining process introduction

Gears are the main basic transmission components in the automotive industry. Usually there are 18-30 teeth in each car. The quality of gears directly affects the noise, stability and service life of the car. Gear processing machine tools are a complex machine tool system and a key equipment in the automotive industry. The world’s automotive manufacturing powerhouses such as the United States, Germany and Japan are also powerful manufacturers of gear processing machine tools. According to statistics, more than 80% of China’s automobile gears are processed by domestically made gears. 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 billet

Hot die forging is still a widely used rough forging process for automotive gear parts. In recent years, cross wedge rolling technology has been widely promoted in shaft machining. This technology is particularly suitable for making blanks for more complex stepped shafts. It not only has high precision, small subsequent machining allowances, but also high production efficiency.

2. Normalizing

The purpose of this process is to obtain the hardness suitable for subsequent gear cutting and prepare the organization for the final heat treatment, so as to effectively reduce the heat treatment deformation. The material of the gear steel used is usually 20CrMnTi. 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 differences in hardness and uneven metallographic structure. Affect metal cutting and final heat treatment, making thermal deformation large and irregular, and the quality of parts cannot be controlled. To this end, an isothermal normalizing process is adopted. Practice has proved that the use of isothermal normalizing has effectively changed the shortcomings of normal normalizing, and the product quality is stable and reliable.

3. Turning

In order to meet the positioning requirements of high-precision gear processing, all the gear blanks are processed by CNC lathes, and the turning tools are mechanically clamped without heavy grinding, which realizes the simultaneous completion of the hole diameter, end face and outer diameter processing under one clamping, which not only ensures the internal The perpendicularity requirements of the hole and the end face ensure the small size dispersion of the mass production of tooth blanks. Therefore, 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 the economy is good.

4. Rolling and shaping

Common gear hobbing machines and gear shaping machines are still widely used for processing gears. Although it is easy to adjust and maintain, the production efficiency is low. If a large capacity is completed, multiple machines are required to produce at the same time. With the development of coating technology, the re-coating after sharpening of hobs and inserts is very convenient. Coated tools can significantly increase the service life, generally by more than 90%, which effectively reduces the number of tool changes. And sharpening time, the benefit is significant.

5. Shaving teeth

Radial gear shaving technology is widely used in the production of high-volume automobile gears due to its high efficiency, easy realization of the modification requirements of the designed tooth profile and tooth direction. Since the company purchased the special radial gear shaving machine for Italian company in its technological transformation in 1995, this technology has been applied maturely and the processing quality is stable and reliable.

6. Heat treatment

Automobile gears require carburizing and quenching to ensure their good mechanical properties. For products that no longer need to be ground after being heated, stable and reliable heat treatment equipment is essential. The company introduced a continuous carburizing and quenching production line from Germany’s Laoyi Company, which achieved satisfactory heat treatment results.

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 form and position tolerances.

The gear processing adopts the pitch circle fixture to position and clamp, which can effectively ensure the processing accuracy of the tooth part and the installation datum, and obtain satisfactory product quality.

8. Trimming

This is the inspection and cleaning of the bumps and burrs of the gears before assembly of the transmission and drive axle gears to eliminate the abnormal noise caused by them after assembly. It is completed by listening to the sound of a single pair of meshing or observing the meshing deviation on a comprehensive inspection instrument. The housing parts of the transmission produced by the manufacturing company include a clutch housing, a transmission housing and a differential housing. The clutch housing and transmission housing are load-bearing parts, which are generally made of die-cast aluminum alloy by special die casting. The shape is irregular and complex. The general process is milling the joint surface → machining process holes and connecting holes → rough boring bearing holes → fine boring Bearing hole and locating pin hole→cleaning→leak test detection.

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