Feed drive being composed of servo motor, ball screw and milling machine worktable, there are mechanical transmission error (such as backlash, screw pitch reducer and screw nut cumulative error) and the transmission stiffness is low, these factors will affect the accuracy of position. In addition, by the servo motor and transmission mechanism, the maximum speed and acceleration are also limited. Feeding drive using milling machine linear motor, the elimination of the motor to the workbench between all the intermediate links, reducing the mechanical transmission error, transmission stiffness and positioning accuracy, fast response. At present, the linear motor is more and more used in high-speed, high-precision CNC milling machine. The picture shows the appearance and composition of the linear motor.
Linear motors are essentially AC servo motors, consisting of primary and secondary sides. On the secondary side of the linear motor, the permanent magnet is mounted alternately on the base plate. A three-phase winding is mounted on the primary side slider, which is connected to the milling machine table. The table is supported and guided by a linear rolling guide and maintains a certain air gap between the slider and the permanent magnet.
When the primary side of the three-phase AC power, the resulting air gap magnetic field along the line, the magnetic field known as the traveling wave magnetic field. The magnetic field of the secondary side permanent magnet interacts with the traveling wave magnetic field to generate electromagnetic thrust, and the primary side slider moves linearly under the action of electromagnetic force. The linear motor can be driven by a servo motor drive. The primary and secondary sides of the linear motor can be fitted with cooling components to cool and cool the linear motor. The picture shows the application of linear motor in CNC milling machine feed.