In the machine tool feed system, the linear motor is directly driven. The biggest difference from the original rotary motor transmission mode is that the mechanical intermediate transmission link from the motor to the table (the carriage) is eliminated, that is, the length of the machine feed chain is Shortened to zero, this type of transmission is called "direct drive", also known as "zero drive." Direct drive avoids the disadvantages of backlash, inertia, friction and insufficient rigidity in the screw drive. The development and application of linear motor systems has caused a sudden change in the traditional feed mechanical structure of the machine tool industry; through advanced electrical control, not only the feed mechanism is simplified, but also the performance index of the machine tool is greatly improved, mainly in the performance Here are a few things:

(1) High speed responsiveness
          In general, mechanical transmissions are orders of magnitude larger than the dynamic response time of electrical components. Because some mechanical transmission parts such as lead screws with large response time constant are eliminated in the system, the dynamic response performance of the whole closed-loop control system is greatly improved, and the reaction is extremely sensitive and quick.
(2) High precision
        Since the mechanical transmission mechanism such as the lead screw is eliminated, the tracking error caused by the delay of the transmission system during the interpolation is reduced. Through the linear position detection feedback control, the positioning accuracy of the machine tool can be greatly improved.
(3) High transmission rigidity and stable thrust
      "Direct drive" increases its transmission stiffness. At the same time, the layout of the linear motor can be arranged according to the shape and surface structure of the machine guide rail and the force applied during the movement of the table. It is usually designed to be evenly symmetrical, making its motion thrust smooth.
(4) Fast speed, short acceleration and deceleration process
         Linear motors were first used mainly for maglev trains (up to 500km/h) and are now used in machine feed drives to meet the maximum feed rates for ultra-high-speed cutting (up to 60-100m/min or higher). It is ok. Due to the high-speed responsiveness of the “zero transmission”, the acceleration and deceleration process is greatly shortened, so that the high speed can be achieved instantaneously at the time of starting, and the instantaneous stop can be instantaneously performed at high speed. The acceleration can generally reach 2 to 10 g (g = 9.8 m / s 2).
(5) Unlimited length of stroke
          By linearly stepping the stator of the motor on the guide rail, the stroke length of the moving member can be extended indefinitely.
(6) Low noise during operation
          Since the mechanical friction of the components such as the drive screw is eliminated, the guide rail pair can adopt the rolling guide or the magnetic pad suspension guide (no mechanical contact), so that the motion noise is greatly reduced.
(7) High efficiency
          Since there is no intermediate transmission link, the energy loss during mechanical friction is eliminated.

(8) Adopt full closed loop control system

          Since the mover of the linear motor has been combined with the work table of the machine tool, unlike the ball screw feed unit, the linear motor feed unit can only use the full closed loop control system.