On the basis of the developed system "CNC gear-hobbling system" that covers with CNC machining of non-circular vertical gear
the meshing theory of helical gears and tool rack-skew methods
the simultaneouscontrol strategy of hobbling three order ellipse helical gear is proposed
and the graph of CNC simultaneouscontrol model is designed.Hobbling experiment that three-order ellipse helical gear can be gained proves it.When two gears engaged
they can turn flexibly and the backlash is well distributed.