Servo systems for CNC machine tools can be classified in various ways, with different types suited to specific machining requirements:
Classification by Control Feedback Method
Open-loop Servo System
Characteristics: Lacks position detection feedback; commands are transmitted unidirectionally; features a simple structure and low cost.
Applications: Economical CNC machine tools with low precision requirements, engraving machines, and CNC retrofitting of older machine tools.
Semi-closed-loop Servo System
Characteristics: An encoder is mounted on the motor shaft to detect the motor's rotation angle rather than directly measuring the machine table's displacement; balances precision and stability.
Applications: The vast majority of standard machining centers; the most widely used type in the industry.
Fully Closed-loop Servo System
Characteristics: A linear scale is installed on the machine table to monitor the actual position in real-time, allowing errors to be controlled at the micron level.
Applications: High-end CNC machine tools requiring extreme precision, such as ultra-precision lathes and precision mold machining equipment.
Classification by Drive Motor Type
Stepper Servo System
Characteristics: Converts electrical pulses into angular displacement; simple structure and low cost, but offers poor high-speed performance and limited precision.
Applications: Simple CNC equipment with low speed and precision requirements.
DC Servo System
Characteristics:Fast response and high precision; however, the presence of brushes and commutators necessitates regular maintenance, and motor capacity is limited.
Applications: Early low-to-mid-range CNC machine tools; currently being gradually replaced by AC servo systems.
AC Servo System
Characteristics: Available in asynchronous and synchronous types; AC synchronous servos offer high precision, fast response, and smooth operation with minimal maintenance.
Applications: The mainstream configuration for current mid-to-high-end CNC machine tools.
Linear Servo System
Characteristics: Directly converts electrical energy into linear mechanical motion, eliminating intermediate transmission components like lead screws; offers extremely fast response speeds.
Applications: High-speed, high-precision machining equipment; significantly enhances machining efficiency and accuracy.
