There are many problems in the deviation of gear and rack, which can be found from the parts of rack mechanical equipment and processing environment.

1. Tooth profile error of gear hobbing machine

The first kind of machine tool is a gear processing machine tool which combines the generating motion mechanism and the gear dividing motion mechanism, such as gear hobbing machine, gear shaping machine, etc. For this kind of machine tools, the main factors that affect the gear profile error are the manufacturing edge grinding, installation error of the cutting tool and the higher harmonic component in the transmission error of the gear dividing transmission chain, such as the periodic error of the dividing worm and the pitch error of the gear driving the cutting tool

2. Base section deviation

Base pitch deviation refers to the difference between the actual base pitch and the nominal base pitch of the gear. As we know, one of the conditions for the angular engagement of involute gears is that the base joints of two gears are equal. If there is a base pitch deviation in a pair of meshing gears, their gear teeth will produce instantaneous transmission ratio change when entering or exiting the meshing, causing impact and vibration. In Figure 5, it is standard to set the base section of driven gear. When the base section of driving gear is larger than the base section of driven gear, the first pair of teeth AA and the second pair of teeth BB have not entered into the engagement when the engagement is finished, then the top part of tooth a and the root part of tooth a continue

3. Pitch deviation

Pitch deviation refers to the difference between the actual pitch and the nominal pitch on the indexing circle. It differs from the base pitch in that the base pitch is measured along the direction of the engagement line, while the pitch is measured on the indexing circle pitch. The pressure angle error is reflected in the tooth profile error. Therefore, from the point of view of evaluating the stability of gear transmission, the pitch deviation can sometimes be used to replace the base pitch deviation, which is mainly caused by the short period error of the indexing mechanism of the machine tool.