Here, fs2 (us ,ls ,ψ s ) = 0 is the equation of meshing for the
shaper and the generated face gear.
C. Undercutting and pointing
The tooth of face gear can be described briefly as a rack
with varied pressure angle and teeth space at different
position. From the point of view of meshing , face gear drive
could be considered as the simulation of a spur pinion and a
rack at different longitudinal section of the pinion. In order
to explain the regular of the pressure angle and teeth space