Many machine tool designs nowadays mostly have a gravity axis, such as the X axis of the inclined bed of the horizontal CNC lathe and the Z axis of the vertical CNC lathe, the Z axis of the CNC milling machine and the vertical machining center, etc. These axial motors are affected by The influence of gravity can cause axial fall. We hope that the servo motor will stop and lock when the power is off. After the machine is powered on and the servo is ready, the lock will be cancelled. This article teaches two types of servos for the machine tool. Motor braking method!
1. Servo motor electromagnetic brake:
Generally, the servo motors of CNC machine tools use electromagnetic brakes, which are composed of two parts: a brake electromagnet and a brake shoe; the coil of the electromagnetic brake is connected in parallel with the motor, and the electric steam is connected to the power supply. At the same time, the electromagnetic brake coil is also When the armature is energized, the armature pulls in, the tension of the customer service spring separates the brake shoe from the brake wheel, and the motor runs normally; disconnect the switch or contactor, the motor loses power, and the solenoid brake coil loses power at the same time, the armature acts on the spring tension The lower part is separated from the iron core, and the brake shoe of the brake tightly embraces the brake wheel, and the motor is braked and stops rotating;
When the servo feed motor is powered off, because the motor brake (motor brake) will lock the motor rotor, the motor will not slide due to the influence of gravity, but we don’t want it after the machine is powered on Locking, because the feed will move at any time, this requires the motor brake to stop working, and the motor provides its own force to offset the influence of gravity; but this method will cause the motor and the screw to heat up, affect the life of the motor and the screw, and more The important thing is to affect the machining accuracy.
2. Counterweight brake
Counterweight braking can be divided into mechanical counterweight, pneumatic counterweight, etc. according to the counterweight method. The counterweight is designed to allow its gravity axis to achieve gravity balance with the counterweight. The mechanical counterweight is widely used because of its simple structure and low failure rate. The disadvantage is that when the speed and acceleration increase, part of the weight loses weight, resulting in accuracy deviation, which is not suitable for high-speed cutting.
3. Whether it is electromagnetic braking or counterweight braking, there will be a few micrometers of decline when the emergency stop, servo ready signal is disconnected, and the machine tool is powered off. This kind of decline is undesirable.
