(1) NC machining open-loop: this kind of machine has no feedback information from the position sensor. The CNC system processes the part program, transmits the digital instruction to the servo system, and drives the machine to move. The structure of the CNC system is simple, economical and easy to care for, but the speed and precision are low, which is suitable for the small and medium-sized machine tools with low precision requirements, and it is mostly used for the CNC transformation of the old machine tools.
(2) NC machining closed-loop: this kind of machine tool is equipped with a position detection device, which directly measures the displacement of the workpiece; its precision is high, but the system design and adjustment are troublesome, the structure is complex, and the cost is high. It is mainly used in some boring and milling machines, ultra-fine lathes, ultra-fine milling machines, machining centers, etc. with high precision requirements.
(3) NC machining semi closed loop: this kind of NC machine selects the angle measuring element installed on the feed lead screw or the end of the electric motor to measure the rotation angle of the lead screw, to obtain the position feedback information tactfully; it can obtain the more desired accuracy and speed, and numerous NC machine tools choose it, such as the numerical control lathe, NC milling machine and machining center.
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