The difference between open-loop, closed-loop and semi-closed-loop servo systems for CNC machining

- Feb 15, 2019-

(1) NC machining open loop: This type of machine has no feedback signal from the position sensor. After the CNC system processes the part program, it outputs the digital command to the servo system to drive the machine tool movement; its structure is simple, economical and convenient to maintain, but the speed and precision are low, suitable for small and medium-sized machine tools with low precision requirements, mostly used for The numerical control transformation of the old machine tool.


(2) CNC machining closed-loop: This type of machine tool is equipped with position detecting device to directly measure the displacement of the workpiece; its precision is high, but the system design and adjustment are difficult, the structure is complex, and the cost is high. It is mainly used for some high precision requirements. Boring and milling machines, ultra-precision lathes, ultra-precision milling machines, machining centers, etc.


(3) Semi-closed loop of CNC machining: This kind of CNC machine tool uses the angle measuring component mounted on the feed screw or the end of the motor to measure the rotation angle of the lead screw to obtain the position feedback information indirectly; satisfactory precision and speed can be obtained. Most CNC machines use it, such as CNC lathes, CNC milling machines and machining centers.


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