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Electric spindle is a new technology that integrates machine tool spindle and spindle motor in the field of CNC machine tools in recent years. Together with linear motor technology and high-speed tool technology, it will push high-speed machining to a new era. The CNC machining electric spindle is a set of components, which includes the electric spindle itself and its accessories: electric spindle, high-frequency frequency conversion device, oil mist lubricator, cooling device, built-in encoder, and tool changer.

High-speed spindle is an important key technology of high-speed cutting technology, and also an important part of high-speed cutting machine tools. It requires high dynamic balance, good rigidity, high rotation accuracy, good thermal stability, sufficient torque and power transmission, high centrifugal force, accurate temperature measuring device and efficient cooling device.

High-speed cutting generally requires that the spindle speed capability is not less than 40000r/min, and the spindle power is greater than 15kW. Usually, the electric spindle component with integrated spindle motor is used to realize direct transmission without intermediate links. Most of the motors use induction integrated spindle motors. At present, hot-pressed silicon nitride (Si3N4) ceramic bearings, hydrodynamic and static pressure bearings, and air bearings are generally used. Oil-air lubrication, jet lubrication and other technologies are mostly used for lubrication. Spindle cooling generally adopts internal water cooling or air cooling of the spindle.

1. Working principle diagram of ceramic bearing high-speed spindle

The picture above shows the working principle of the ceramic bearing high-speed spindle. It adopts C or B-grade precision angular contact ball bearings. The bearing arrangement is similar to the structure of the traditional grinding machine spindle; It is integrated with the main shaft); the characteristic value of the bearing speed (=? shaft diameter (mm) x speed (r/min)) is 1.2? to 2 times higher than that of ordinary steel bearings, and can reach 0.5 to 1×106. The rotation accuracy is high, the rotation error of the hydrostatic bearing is below 0.2μm, and the rotation error of the air static pressure bearing is below 0.05μm; the power loss is small; Up to 3×106. Aerostatic bearings have a smaller load carrying capacity.

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

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

(2) The elastic modulus of ceramics is 50% higher than that of steel, which makes the bearings have higher rigidity;

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

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

2. Magnetic bearing high-speed spindle

The picture above is the working principle diagram of the high-speed magnetic bearing main shaft. The main shaft is supported by two radial and two axial magnetic bearings. The gap between the stator and the rotor of the magnetic bearing is about 0.1mm. ? High rigidity, about 10 times the rigidity of the ball bearing spindle. The characteristic value of the speed can reach 4×106. Turning accuracy main
It depends on the accuracy and sensitivity of the sensor, as well as the performance of the control circuit, and it can reach 0.2 μm at present. The mechanical structure and circuit system are relatively complex; and due to the high heat generation, the performance requirements of the cooling system are relatively high.

The above content is the structure of the motor spindle of the cnc machining center, and I hope it can be helpful to everyone. If you want to know more about the cnc machining center, please call Xiehe cnc processing factory, we will serve you wholeheartedly.