Gears are mechanical parts that rely on the meshing torque of teeth to change the torque, direction, etc. of the machine. However, for high-precision gear manufacturing processes, especially gears with a large number of teeth, large diameters, long tooth surfaces, and high precision requirements, strict processes are required during the hobbing process, including tooth blanks, fixtures, cutters, machine tools, cutting oil, etc. .
1. Forging of gear blanks
Hot die forging is still a widely used blank forging process for automobile gears, but the cross-wedge rolling process has been widely used in shaft gears. It is suitable for making blanks for relatively complex stepped shafts. It has the characteristics of high precision, small post-order margin, and high efficiency.
2. Types of cutting equipment
The gear cutting machine tool is a complex machine tool and a key equipment in the automobile manufacturing industry. According to the different gear cutting processes, it can be divided into: gear hobbing machine, gear shaping machine, gear milling machine, gear shaving machine, gear grinding machine, gear honing machine, gear extrusion machine, etc. It is necessary to select the appropriate machine tool equipment according to the process.
3. Selection of cutting oil
In the subsequent blank turning, tooth profile manufacturing, grinding and other processes of automotive gear manufacturing, the selection of gear cutting oil directly affects the efficiency and efficiency of the process. Accuracy. Therefore, the physical properties of automotive gear cutting oil should be selected based on the size of the workpiece, cutting amount, cutting speed, tool, etc. In addition, factors such as the viscosity and chemical properties of the oil should also be considered.
IV. Matters concerning cutting gear blanks
Tooth blanks with larger diameters are prone to elastic deformation when clamped, and it is difficult to compensate for the loss of gear meshing accuracy on machine tools. Since the tooth surface is often based on the gear hole and end face, the accuracy of the gear blank mainly has higher requirements on the dimensional accuracy and shape accuracy of the gear hole, and the accuracy of the hole and end face. Generally, two methods are used to ensure this: ① direct clamping turning (finishing the hole and reference end face in one installation): ② through-axis turning (taking the hole as the reference to complete the turning of the end face and outer circle). No matter which method is used, the gear blank should meet the requirements and have a high-precision hobbing reference surface.
5. Gear cutting process
The datum has a direct impact on the tooth profile accuracy. The center hole, gear journal and one end face are usually selected as the datum. The gear tooth end cutting includes rounding, chamfering, chamfering and deburring, etc., which can remove the sharp edges of the tooth end to prevent cracking after carburizing and quenching. After the gear is quenched, the reference hole will be deformed, and the reference hole must be corrected to ensure the quality of the tooth shape.
6. Inspection of gear accuracy
This is to check and clean the burrs on the teeth before assembly of the transmission gear to eliminate the noise and abnormal noise caused by them after assembly. This is accomplished by listening to the sound of a single pair of meshing or observing the meshing deviation on a comprehensive instrument. Workpieces that fail the inspection need to be re-corrected in the grinding process.