Whether the production of gears or shafts is inseparable from forging and blank making, normalizing, high-precision turning, rubbing / rolling / gear shaping, gear shaving, heat treatment, grinding and meshing finishing. These processes play a key role in the production of automobile transmission.
Forging process
Forging blank is the process of obtaining part blank by forging method, in which hot die forging is the most widely used blank forging process for automotive shaft and gear parts. Previously, the most widely used forging methods were hot forging and cold extrusion to obtain blanks, but these two methods were not particularly ideal in terms of accuracy and subsequent machining allowance. 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 subsequent machining allowance, but also has significantly better production efficiency than other methods.
Normalizing process
Normalizing, also known as normalization, is the final temperature at which the workpiece is heated until all free ferrite is transformed into austenite. In order to obtain the hardness suitable for subsequent machining and prepare the structure for the final heat treatment, automobile shafts and gear parts must be normalized to effectively reduce the deformation of heat treatment. Non isothermal normalizing is greatly affected by operators, processing equipment, environment and other factors, so it is difficult to accurately control the cooling speed and uniformity of the workpiece. This causes large hardness dispersion and uneven metallographic structure of the workpiece, which directly affects machining and final heat treatment. The parts produced in this way often have large and irregular thermal deformation, the quality of parts can not meet the requirements, and the loss of tools is also great, especially in the process of rubbing teeth, which is under great stress. Therefore, it is necessary to adopt isothermal normalizing process. Practice has proved that isothermal normalizing can effectively improve the disadvantages caused by general normalizing process, make the product quality more stable and reliable, and prolong the service life of cutting tools.
Finishing process
In order to meet the positioning requirements of high-precision gear machining, the finishing machining of blanks must be completed by CNC lathes. Taking the gear as an example, the finishing machining of the inner hole and the positioning end face should be carried out first, and then the finishing machining of the other end face and the outer diameter should be completed synchronously. This not only meets the requirements of the perpendicularity between the inner hole and the positioning end face, but also reduces the size dispersion of each gear in the process of mass gear blank production, so as to improve the precision of gear blank and ensure the processing quality of subsequent gears. Another advantage of choosing CNC lathe processing is that it greatly improves the processing efficiency, reduces the number of equipment, saves processing costs, and can bring better economic benefits.
Rubbing / rolling / gear shaping
Ordinary gear hobbing machines and gear shapers are still widely used in gear processing. Although it is convenient to adjust and maintain, the production efficiency is low. If a large capacity is completed, multiple machines need to be produced at the same time. With the development of coating technology, the second coating after grinding of hobs and plungers can be carried out conveniently. The coated tool can significantly improve the durability, generally more than 90%, effectively reducing the number of tool changes and grinding time, with significant benefits.
Shaving
Radial gear shaving technology is widely used in the mass production of automotive gears because of its high efficiency and the easy realization of the modification requirements of the designed tooth shape and direction. The tooth shape and direction have a great influence on the noise of the vehicle. The transmission noise of the transmission can be reduced by modifying its shape and anti twisting. Wechat for metal processing, with good content, deserves attention.
heat treatment
Automobile gears require carburization and quenching To ensure the good mechanical performance required by its design. For products that are no longer grinded after heating, stable and reliable heat treatment equipment is indispensable.
Grinding
The essence of metal grinding is the process in which the ground metal surface of the workpiece is extruded instantaneously by countless abrasive particles, deformed under the action of friction, and then turned into abrasive debris, forming a smooth representation. It is mainly for the inner hole of the gear after heat treatment. Finish machining of the end face, the outer diameter of the shaft and other parts to improve the dimensional accuracy and form and position accuracy. Gear processing adopts pitch circle fixture for positioning and clamping, which can effectively ensure the machining accuracy of the tooth and the installation benchmark, and obtain satisfactory product quality. The grinding accuracy usually reaches the tolerance level of IT6 ~ it7, and the surface roughness can reach ra1.25 ~ 0.16um.
Butt trimming
This is to check and clean the bumps and burrs on the teeth of the transaxle gear before assembly, so as to eliminate the noise and abnormal noise caused by them after assembly. Listen to the sound through single pair engagement or observe the engagement deviation on the comprehensive tester. Automatic counter meshing instrument is often used to check burr, center distance and runout.