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Mobile WebSiteCNC system configuration and function selection system is an important part of CNC machine tools, configuration, what kind of CNC system and choose which CNC functions are machine manufacturers and end users are concerned about the problem.
KeyWord: numerical control; position control; numerical control system;
Open-loop control system: the use of stepper motor as a driving component, there is no position and speed feedback device, so the control is simple, low price, but their load capacity is small, poor positioning control, feeding speed is low, mainly for the economy Type numerical control device;
Semi-closed-loop and closed-loop position control system: DC or AC servo motor as a driving part, you can use built-in motor pulse encoder, rotary transformer as a position / speed detection device to form a semi-closed-loop position control system can also be used directly In the table of the grating or induction synchronizer as a position detection device, to form a high-precision full closed-loop position control system.
Due to the presence of the pitch error, the amount of change in the angle of the screw rotation fed back from the semi-closed loop system position detector does not accurately reflect the linear motion position of the feed axis. However, after the NC system on the pitch error compensation, they can achieve a very high position control accuracy. Compared with the fully closed-loop system, their low price, installed in the motor internal position feedback device seal is good, work more stable and reliable, almost no maintenance, so widely used in various types of CNC machine tools.
DC servo motor control is relatively simple, the price is low, the main drawback is that the motor has a mechanical commutation device, easy to wear carbon brush, maintenance workload. Easy to run when the spark, so that the motor speed and power to improve more difficult.
AC servo motor is a brushless structure, almost no maintenance, the volume is relatively small, is conducive to speed and power improvement, has a large range of DC servo motor has been replaced.
The type of servo control unit
Separate servo control unit, which is characterized by the relative independence of the CNC system and the servo control unit, that is, they can be used with a variety of numerical control systems, NC system is given the command is related to the axis of the DC speed (such as 0 -10V), and from the machine is returned with the NC system to match the axis of the movement of the position detection signal (such as encoder - sensor synchronizer and other output signal). The setting and adjustment of the servo data are performed on the servo control unit side (with potentiometer adjustment or by digital input).
Serial data transmission type servo control unit, which is characterized by NC system and servo control unit between the data transfer is bi-directional. The command data, the servo data and the alarm signal related to the axis movement are transmitted through the corresponding clock signal line, the strobe signal number, the transmission data line, the reception data line, and the alarm signal line. From the position encoder to return to the NC device has the actual position and status of the moving axis and other information.
Network data transmission type servo control unit, which is characterized by the axis control unit installed together, by a common DC power supply unit. NC device through the FCP board network data processing module connection point SR, ST and each axis control unit (sub-station) network data processing module SR, ST points in series to form a servo control loop. The position encoder and the axis control unit of each axis are connected by two high-speed communication lines. The feedback information has the position of the motion axis and the relevant status information.
The servo parameters of the serial data transmission type and the network data transmission type servo control unit are numerically set in the NC device. When the initialization is started, the servo control unit is installed, and the modification and adjustment are very convenient.
Network data transmission type servo control unit in the corresponding control software with real-time adjustment ability, for example, in the Hi-G-type positioning acceleration and deceleration function, according to the motor speed and torque characteristics of the corresponding function, and then its The function controls the acceleration / deceleration rate at high speed positioning, thereby suppressing vibration that may be caused when high speed positioning. Increasing the positioning speed can shorten the non-cutting time and improve the processing efficiency. Also in the Hi-Cut feed rate control function, the system can automatically recognize the part number (arc, edge, etc.) required to process the NC command after reading the part processing program, and automatically adjust the machining speed so that Good, and then achieve high-speed high-precision processing.
After the emergence of all-digital AC servo system with high-speed microprocessor and dedicated digital signal processor (DSP), the hardware servo control becomes software servo control, and some advanced algorithms of modern control theory are realized, which greatly improves the servo system Control performance.
The servo control unit is a component directly associated with the machine in the CNC system. The performance of the servo control unit is very large in relation to the cutting speed and position accuracy of the machine. It also accounts for a large part of the CNC system. Relatively speaking, the servo component failure rate is also high, accounting for more than 70% of electrical failure, so the optional servo control unit is very important.
