Gear is a mechanical part that relies on the meshing torque of teeth. It can change the torque and direction of machinery. But for the manufacturing process of high precision gear, especially the gear with many teeth, large diameter, long tooth surface and high precision, there are strict requirements in the hobbing process, including billet, fixture, tool, machine tool, cutting oil, etc.

I. Forging of Gear Blanks

Hot die forging is still the blank forging technology widely used in automobile gears, but cross wedge rolling technology has been widely used in shaft gears. Suitable for the complex step shaft billet, it has the characteristics of high precision, small post-sequence allowance and high efficiency.

Types of Cutting Equipment

Gear cutting machine tool is a kind of complex machine tool, which is the key equipment in automobile manufacturing industry. According to the different gear cutting technology, it can be divided into hobbing machine, gear shaper, milling machine, shaving machine, grinding machine, honing machine, extruder and so on. It is necessary to select appropriate machine tools and equipment according to the technology.

Selection of Cutting Oils

In the following processes of automobile gear manufacturing, such as blank turning, tooth profile manufacturing and grinding, the selection of gear cutting oil directly affects the efficiency and accuracy of the process. Therefore, the physical properties of automobile gear cutting oil should be selected according to the size of the workpiece, cutting quantity, cutting speed, cutting tools, and other factors such as oil viscosity and chemical properties.

IV. Matters of Cutting Blanks

Elastic deformation is easy to occur when the bigger diameter billet is clamped, and it is difficult to make up for the loss of gear meshing accuracy on the machine tool. Because the gear hole and end face are often used as the datum plane of the tooth surface, the accuracy of the gear blank mainly depends on the accuracy of the size and shape of the gear hole, and the accuracy of the hole and end face. Generally, two methods are adopted to ensure that: (1) direct clamping turning (finish turning with one installation of holes and reference end faces); and (2) axle-piercing turning (finish turning with hole as reference). No matter which method is adopted, the billet should meet the requirements and a high precision hobbing datum should be obtained.

V. Gear Cutting Technology

Datum has a direct impact on the accuracy of tooth profile, and the pinion hole, gear journal and end face are usually selected as datum. The gear teeth end cutting has chamfering, chamfering and deburring, which can remove the sharp edges of the teeth end to prevent cracking after carburizing and quenching. The base hole of gear is deformed after quenching. In order to ensure the quality of gear profile finishing, the base hole must be corrected.

6. Testing of Gear Accuracy

This is to check and clean up the burrs on the gears before assembling, so as to eliminate the noise abnormal noise caused by them after assembling. It is accomplished by listening to the sound of a single pair of engagements or observing the engagement deviation on the synthesizer. Workpieces that fail to pass the test need to be corrected by grinding process again.