Nowadays, the majority of spindle motors for CNC precision machining use cage-type AC three-phase asynchronous motors. It does not have the carbon brush commutation problem of the DC motor, and the vector frequency conversion technology also makes the performance of the cage asynchronous motor completely reach the level of the DC motor, and it has strong overload capacity, small size, and fully enclosed maintenance-free.
The characteristic curve of the CNC precision machining motor is divided into two parts, the cross torque at low speed and the constant power at high speed. There is a node at the intersection of these two curves, and this node is called basic speed. According to this basic speed, the mechanical parts machining factory usually designs the gearbox into two gears, which makes it easy for the controller to control. Because of the two different situations, the adjustment is fundamentally different.
1. Transverse torque at low speed, speed adjustment by way of adjusting armature voltage.
2. Constant power at high speed, speed regulation by way of adjusting the excitation current.
The spindle speed of CNC precision machining, no matter which adjustment method is used, is done through the inverter. If a permanent magnet synchronous AC service motor is used, it cannot work well in a weak magnetic state by itself, and then there is a set of auxiliary systems to complete the action of the spindle. For such a set of auxiliary systems, the structure design will be set into a separate block for control, which is the reason why some large precision mechanical parts machining machine tools use three blocks.
At present, the CNC precision machining spindle drives a constant torque speed range ratio of up to 1:100, constant power speed range ratio of up to 1:30, constant torque and constant power speed range ratio to 1:2, overload 1.5 times still can continue to work 30min. for example, the spindle rated speed 1500/min, then the gear should be separated at 500r/min position, low gear Minimum 5 / min, mechanical parts processing plant good some gear vice, able to speed down to 0.5min.
