The schematic diagram of tool forefoot error is shown in the figure. When the cutter is grinding, there is an error in the rake angle of the cutter, which will affect the tooth profile of the gear and cause the tooth profile error.
In the figure, the included angle between s-plane and s-plane is the tooth surface error ∆ a, and the included angle between the tool side and the helix is A1. According to the spatial geometric relationship of the model, we can get:
Then the tooth profile error is:
Where: an is the normal pressure angle of hob; β Is the tool helix angle.