Electric spindleIt is a new technology that has emerged in the field of CNC machining machines in recent years, which integrates machine tool spindles and spindle motors.
The CNC machining electric spindle is a set of components, which includes the electric spindle itself and its accessories: electric spindle, high-frequency frequency converter, oil mist lubricator, cooling device, built-in encoder, and tool changer.

High speed spindle is an important key technology in high-speed cutting technology and a crucial component of high-speed cutting machine tools. High dynamic balance, good rigidity, high rotational accuracy, good thermal stability, sufficient torque and power transmission, high centrifugal force tolerance, accurate temperature measurement device and efficient cooling device are required. High speed cutting generally requires a spindle speed capability of not less than 40000 r/min and a spindle power greater than 15 kW. Typically, an electric spindle component that integrates the spindle motor is used to achieve direct transmission without intermediate links, and the motor is mostly an induction type integrated spindle motor. Currently, hot pressed silicon nitride (Si3N4) ceramic bearings, liquid dynamic and static pressure bearings, and air bearings are commonly used. Lubrication often uses techniques such as oil air lubrication and jet lubrication. The spindle cooling is generally achieved through internal water cooling or air cooling of the spindle.

1. Working principle of ceramic bearing high-speed spindle

The working principle of ceramic bearing high-speed spindle adopts C or B grade precision angular contact ball bearings, and the bearing arrangement is similar to the traditional grinder spindle structure; Adopting a "small bead dense ball" structure, the ball material is Si3N4; Adopting electric spindle (motor and spindle integrated); The characteristic value of bearing speed (shaft diameter (mm) × speed (r/min)) is 1.2-2 times higher than that of ordinary steel bearings, reaching 0.5-1 × 106. High rotational accuracy, with a rotational error of less than 0.2 μ m for liquid hydrostatic bearings and less than 0.05 μ m for air hydrostatic bearings; Low power loss; The characteristic speed of liquid hydrostatic bearings can reach 1 × 106, and the characteristic speed of air hydrostatic bearings can reach 3 × 106. The load-bearing capacity of air static pressure bearings is relatively small.

Compared with steel balls, the advantages of ceramic bearings are:

(1) The density of ceramic balls is reduced by 60%, which can greatly reduce centrifugal force;

(2) The elastic modulus of ceramics is 50% higher than that of steel, which gives bearings higher stiffness;

(3) Ceramic has a low coefficient of friction, which can reduce bearing heating, wear, and power loss;

(4) Ceramics have good wear resistance and long bearing life.

2. Maglev bearing high-speed spindle

The working principle of high-speed spindle with magnetic levitation bearings is that the spindle is supported by two radial and two axial magnetic levitation bearings, and the gap between the stator and rotor of the magnetic levitation bearings is about 0.1mm. The stiffness is high, about 10 times that of the main spindle with ball bearings. The characteristic value of rotational speed can reach 4 × 106.
The rotation accuracy mainly depends on the accuracy and sensitivity of the sensor, as well as the performance of the control circuit, which can currently reach 0.2 μ m. The mechanical structure and circuit system are both relatively complex; Due to the high heat generation, there is a high demand for the performance of the cooling system.