Gear processing process
One method of gear processing is the forming method, which uses a forming milling cutter that exactly matches the shape of the tooth to be cut to cut out the tooth shape, such as milling teeth; the other is the generative method, which uses tools and passive gears. The machining method of cutting out the tooth profile by meshing motion, such as gear hobbing and gear shaping. Let us take a concrete look at the gear manufacturing process.
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.
The purpose of this process is to obtain the hardness suitable for subsequent gear cutting and prepare the structure for the final heat treatment, so as to effectively reduce the heat treatment deformation. 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 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.
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 adjustment and maintenance are convenient, 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. Gear shaving 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 Shenzhen Lixin-iMachining Company purchased the special radial gear shaving machine for Italian company in technological transformation in 2013, this technology has been applied maturely and the processing quality is stable and reliable.
6. Heat treatment
Gears require carburizing quenching or soft nitriding treatment to ensure their good mechanical properties. For products that no longer undergo gear grinding after heat treatment, stable and reliable heat treatment equipment is essential.
Regarding the carburizing and quenching heat treatment: Shenzhen Lixin-iMachining Company introduced a continuous carburizing and quenching production line from Germany's Laoyi Company, and achieved satisfactory heat treatment results.
The soft nitriding treatment method includes the following steps:
A. Clean the surface of the workpiece, remove iron filings and oil stains on the surface of the workpiece, and install the furnace after cleaning;
B. After the workpiece enters the furnace, the furnace is heated, and ammonia gas is introduced at the same time as the temperature is raised. The flow rate of the ammonia gas is 200-250L/h. The temperature of the furnace rises to 650℃-700℃, and then the temperature rise is stopped; Open the screw cap to pass through, ignite and burn;
C. During the combustion process, drip ethanol with a drip rate of 30-50d/m; then increase the ammonia gas intake to 300-400L/h, and then check for leaks. If there is no leak, perform a constant temperature. Constant temperature time is 120min-180min;
D. If there is no gas leakage, reduce the ammonia gas flow rate in step C to 250-280L/h, reduce the dripping speed of ethanol to 20d/m, and the diffusion time to 20min-40min;
E. Before the furnace is released, the furnace cover is raised to ignite and burn, and the exhaust gas in the furnace is discharged through combustion, and then the furnace is uncovered and air-cooled to complete the nitrocarburizing.
Shot blasting antirust treatment method in shot blasting antirust treatment: the workpiece is subjected to grinding steel shot targeted shot blasting treatment, so that the root of the tooth is fully strengthened, and the workpiece after shot blasting is soaked in antirust water for 2-4 minutes and then taken out.
It is mainly to finish the heat-treated gear inner hole, end face, shaft outer diameter and other parts to improve the dimensional accuracy and reduce the form and position tolerance.
Shenzhen Lixin-iMachining Co., Ltd.