There are four main shape parameters of spur gears: cumulative pitch error, tooth thickness error, tooth direction error and tooth shape error.
1) Cumulative pitch error: the distance from one side of a spur gear tooth to the same side of the next tooth. Compared with the standard condition, the difference accumulated successively. It is distributed in steps and measured by full teeth.
2) Spur gear tooth thickness error: the difference curve between the actual tooth thickness and the standard tooth is a straight line in theory.
3) Spur gear tooth profile error: the distribution curve of the distance from the actual tooth root to the tooth top is a straight line in theory.
4) Spur gear tooth direction error: also known as radial error, the micro error value of surface morphology in the width direction of spur gear is also linear in theory.
Because the tooth profile error and tooth direction error of spur gear can best reflect the change of gear wear before and after the test, the parameter test and comparative analysis of spur gear profile error and tooth direction error are mainly carried out.