The difference between open loop, closed loop and semi-closed loop servo system in CNC machining

(1) CNC machining open loop: This type of machine tool has no feedback signal from the position sensor. After the part program is processed by the numerical control system, it outputs digital instructions to the servo system to drive the machine tool to move; its structure is simple, economical, and easy to maintain, but its speed and accuracy are low. It is suitable for small and medium-sized machine tools with low precision requirements. Numerical control transformation of old machine tools.

(2) CNC machining closed loop: this type of machine tool is equipped with a position detection device to directly measure the displacement of the workpiece; its accuracy 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) CNC machining semi-closed loop: This type of CNC machine tool uses a rotation angle measuring element installed on the feed screw or the end of the motor to measure the rotation angle of the screw to indirectly obtain position feedback information; it can obtain more satisfactory accuracy and speed. Most CNC machine tools use it, such as CNC lathes, CNC milling machines and machining centers.