NC Actuation System: Three
types of actuation system are commonly used in NC equipment:
i) Electromechanical
ii) Hydraulic
iii)
Pneumatic
Group of mechanical,
electrical, hydraulic or pneumatic components to control position of machine
slide is known as servo. There are two basic servo control systems.
i)
Open Loop Servo Control System
ii)
Closed Loop Servo System
Open Loop Servo System: Stepper motor is used as driving component to provide machine spindle motion. It responds in incremental steps for each impulse of 10-20 Volts of digital input signal. Its rotor moves precisely in steps. Open loop application is restricted to smaller machines because of lower output. Typical power output is 4.5 KW and torque 200NM, maximum pulse rate is 8000 pulse per second. Open loop system saves cost.
Closed
loop Servo system: It uses position transducer as feed back
device. The sensing device measures actual position of slide. The difference in
desired position and actual position is detected by comparator circuit and this
difference is used to actuate the positioning system. Resolution of such system
is up to 0.0001 mm and speed reaches to 10m/min.
