Features of closed-loop CNC system
It directly detects the actual position of moving parts. Theoretically, it can eliminate errors, backlash, and loss of motion in the entire drive and transmission system. It has very high position control accuracy.
Because the frictional characteristics, rigidity, and clearance of many mechanical transmission components within the position loop are nonlinear, system instability can easily occur, making the design, installation, and debugging of the closed-loop system quite difficult. This system is mainly used in high-precision boring machines, ultra-precision lathes, ultra-precision grinding machines, and larger CNC machine tools.
In fully closed-loop controlled machine tools, it is sometimes necessary to shield the linear encoder before machining to determine if there are any abnormalities in the encoder. The following parameter table can be used as a reference!
( 16i-MB system)
Sometimes, various alarms may occur due to incomplete parameter settings. Based on the setting table provided by NTC machine tools, the specific meaning and calculation method of each parameter are explained.
Features of CNC machine tool open-loop system
1. Characteristics of Open-Loop CNC Systems
Without a position measuring device, the signal flow is unidirectional (from the CNC device to the feed system), resulting in good system stability. However, without position feedback, the accuracy is relatively lower compared to a closed-loop system; its accuracy primarily depends on the performance and precision of the servo drive system and the mechanical transmission mechanism. A power stepper motor is typically used as the servo drive element.
These systems have advantages such as simple structure, stable operation, convenient debugging, simple maintenance, and low price, and are widely used in applications where high precision and speed requirements are not high and driving torque is not large. They are generally used in economical CNC machine tools.
Features of CNC machine tool semi-closed loop system
2. Characteristics of Semi-Closed-Loop CNC Systems
It draws its input from the drive unit (usually a servo motor) or lead screw, samples the rotation angle for verification, and does not directly detect the actual position of the moving parts. The semi-closed loop does not include or only includes a small number of mechanical transmission links, thus achieving stable control performance. Although its system stability is not as good as that of an open-loop system, it is better than that of a closed-loop system.
Motion errors caused by lead screw pitch error and gear backlash are difficult to eliminate. Therefore, its accuracy is worse than closed-loop but better than open-loop. However, these errors can be compensated for, thus satisfactory accuracy can still be obtained.
Semi-closed-loop systems are simple in structure, easy to test, and have high precision, and therefore have been widely used in modern CNC machine tools.
Features of CNC machine tool closed-loop system
3. Characteristics of Closed-Loop CNC Systems
It directly detects the actual position of moving parts. Theoretically, it can eliminate errors, backlash, and loss of motion in the entire drive and transmission system. It has very high position control accuracy.
Because the frictional characteristics, rigidity, and clearance of many mechanical transmission components within the position loop are nonlinear, system instability can easily occur, making the design, installation, and debugging of the closed-loop system quite difficult. This system is mainly used in high-precision boring machines, ultra-precision lathes, ultra-precision grinding machines, and larger CNC machine tools.
