To mill external circular arc segment efficiently,a special milling machine for flywheels was designed based on double-spindle double-station four-turntable,which used the longitudinal feed of sliding table and circular feed of workpiece turntable to form cutting trajectory in polar coordinates,and used the rotary motion of station turntable to constitute double stations of processing and handling，each of which could mill two workpieces at the same time.Aiming at the symmetric layout of double-spindle and vibration produced easily by double cutters,the modal and harmonic responses of the spindle system were analyzed on ANSYS in order to optimize the double-spindle structure.A new linear interpolation algorithm in polar coordinates was described,which implemented the continuous processing of external circular arc segment.Processing experiment showed that machining accuracy is 0.02 mm,surface roughness isRa0.8,machining efficiency is 300～400 /h.
