There are many problems with the deviation of gears and racks, which can be found from the parts and processing environment of mechanical equipment for gears and racks.

1. Tooth profile error of gear hobbing machine

The first type of machine tool is a gear machining machine tool that combines a generating motion mechanism and a gear dividing motion mechanism, such as a hobbing machine, a gear shaping machine, etc. For this type of machine tool, the main factors affecting gear tooth profile error are the manufacturing and grinding of the cutting tools, installation errors, and high-order harmonic components in the transmission error of the dividing gear transmission chain, such as the periodic error of the dividing worm and the tooth pitch error of the tool transmission gear

2. Base section deviation

Base pitch deviation refers to the difference between the actual base pitch of a gear and the nominal base pitch. We know that one of the conditions for angular meshing of involute gears is that the base pitch of two gears is equal. If one of the gears in a pair of meshing gears has a base pitch deviation, their teeth will experience an instantaneous change in transmission ratio when entering or exiting meshing, causing impact and vibration. In Figure 5, assuming that the base pitch of the driven gear is standard, when the base pitch of the driving gear is greater than the base pitch of the driven gear, the first pair of teeth AA, and at the end of meshing, the second pair of teeth BB have not yet entered meshing, resulting in the occurrence of A tooth top part and A, and the tooth root part continuing

3. Tooth pitch deviation

Tooth pitch deviation refers to the difference between the actual tooth pitch on the indexing circle and the nominal tooth pitch. It differs from the base pitch deviation in that the base pitch is measured along the direction of the meshing line, while the tooth pitch is measured on the circumferential pitch of the indexing circle. The pressure angle error is reflected in the tooth profile error. Therefore, from the perspective of evaluating the smoothness of gear transmission, sometimes the tooth pitch deviation can be used instead of the base pitch deviation. The tooth pitch deviation is mainly caused by the short cycle error of the indexing motion mechanism of the machine tool.