1、 Working principle:

Linear motor is a kind of transmission device which can directly convert electric energy into linear motion mechanical energy by expanding closed magnetic field into open magnetic field without any intermediate conversion mechanism

2、 Structure:

The structure of linear motor can be seen as a rotating motor along the radial section, and the motor circumference is expanded into a straight line. The stator is equivalent to the primary of the linear motor, and the rotor is equivalent to the secondary of the linear motor. When the primary current is applied, the traveling wave magnetic field is generated in the air gap between the primary stages, and the driving force is generated under the action of the traveling wave magnetic field and the secondary permanent magnet, so as to realize the linear motion of the moving parts. In recent years, some developed countries in the world began to apply the linear motor technology to the linear motion drive system of CNC machine tools, replacing the traditional servo motor + ball screw drive system, and achieved great success.

Comparison between linear motor and traditional rotary motor + ball screw motion system

In the feed system of machine tool, the difference between the linear motor direct drive and the original rotary motor drive is that the mechanical drive link from the motor to the worktable (carriage) is cancelled, and the length of the feed drive chain of machine tool is shortened to zero, so this drive mode is also called "Zero drive". It is precisely because of this "Zero drive" mode that the original rotating motor drive mode can not achieve the performance index and advantages.

1. High speed response because some mechanical transmission parts (such as lead screw) with large response time constant are directly eliminated in the system, the dynamic response performance of the whole closed-loop control system is greatly improved, and the response is extremely sensitive and fast.

2. The precision linear drive system eliminates the transmission gap and error caused by the mechanical mechanism such as the lead screw, and reduces the tracking error caused by the lag of the transmission system during the interpolation movement. Through the feedback control of linear position detection, the positioning accuracy of the machine tool can be greatly improved.

3. High dynamic stiffness. Due to the "direct drive", it avoids the motion lag phenomenon caused by the elastic deformation, friction and wear of the intermediate transmission link and the reverse clearance when starting, changing speed and reversing, and also improves the transmission stiffness.

4. High speed, short acceleration and deceleration process. Since linear motor has been mainly used in maglev train for a long time (the speed can reach 500km / h), it is no problem to meet the ultra-high cutting speed (the requirement is 60-100m / min or higher) in the machine tool feed drive. Because of the high speed response of the "Zero drive", the acceleration and deceleration process is greatly shortened. In order to achieve instant high speed when starting and instant quasi stop when running at high speed. High acceleration can be obtained, generally up to 2-10g (g =), while the acceleration of ball screw drive is only ～.

5. The stroke length is not limited. The stroke length can be extended infinitely by connecting the linear motor in series on the guide rail.

6. The movement is quiet and the noise is low. Because the mechanical friction of the drive screw and other parts is eliminated, and the guide rail can use rolling guide rail or magnetic pad suspension guide rail (no mechanical contact), the noise during the movement will be greatly reduced.

7. High efficiency. Because there is no intermediate transmission link, the energy loss caused by mechanical friction is eliminated, and the transmission efficiency is greatly improved.