The three-dimensional modeling of involute helical gear is carried out by UG software. Due to the structural characteristics of helical gear, in order to improve the modeling efficiency, the parametric modeling method is used to establish the three-dimensional geometric model of helical gear. Parametric modeling is based on the actual needs of helical gear. As long as the corresponding parameters are changed, a new helical gear model can be established quickly and automatically, so as to improve the work efficiency.

The tooth profile of helical gear has an important influence on the generation of contact stress of helical gear. Therefore, in order to analyze the contact stress more accurately, it is necessary to establish an accurate tooth profile model first. Firstly, the parametric modeling of involute helical gear is realized by UG software, and its modeling process is introduced in detail. It mainly includes the generation of involute, helix and single tooth profile, as well as the scanning of helical gear profile to generate three-dimensional solid model of gear. This chapter establishes a pair of accurate parametric helical gear models, which can change the size and shape according to changing some key parameters. Using this parametric helical gear model for finite element analysis can avoid the repetitive work of pre-processing modeling, so it can greatly improve the analysis efficiency and reduce the cost. In contact analysis, in order to save simulation cost and improve analysis efficiency, the errors between different local tooth models and full tooth models in dynamic and static contact analysis are studied, and finally different simplified models for dynamic and static contact analysis are determined.