On CNC machine tools, servo control system is an indispensable part. Its task is to convert numerical control information into machine feed motion, thereby achieving precise control. Due to the high requirements of CNC machine tools for product processing, the module relay servo control system used is crucial.
The servo control system used on CNC machine tools has the main advantages of high accuracy. The accuracy of the servo system refers to the degree to which the output quantity can reproduce the accuracy of the input quantity. Including positioning accuracy and contour machining accuracy; Good stability refers to the ability of a system to reach a new or restored equilibrium state after a brief adjustment process under given input or external interference. Directly affecting the accuracy and surface roughness of CNC machining; Quick response is an important indicator of the dynamic quality of servo systems, which reflects the tracking accuracy of the system; Wide speed regulation range, with a speed regulation range of 0-30m/min; Low speed high torque, servo control of feed coordinates belongs to constant torque control, which must be maintained throughout the entire speed range. The servo control of spindle coordinates is constant torque control at low speeds, which can provide a large torque, and constant power control at high speeds, with sufficient output power.
The servo motion control adopts a bus system solution, which has strong flexibility and high cost-effectiveness. The advantages over traditional solutions are as follows：
Firstly, save wiring costs, reduce wiring time, and decrease the probability of errors. One bus communication port of PLC can connect multiple servos, and the servos can be simply plugged in with RJ45 ports to shorten the construction period.
Secondly, there is a greater amount of information: all digital information exchange allows for bidirectional transmission of many parameters, instructions, and status data; Pulse mode can only transmit position or velocity information unidirectionally and cannot obtain more status or parameters of the servo.
Thirdly, high precision, digital communication method: no signal drift problem, instruction and feedback data accuracy can reach 32-bit.
Fourthly, it has higher reliability, stronger anti-interference ability, and will not experience pulse loss. Pulse/direction control may be unreliable during high-speed pulses.
Fifth: Reduce the total system cost. When there are more than two servos, there is no need to adjust the PLC configuration. Traditional solutions require the addition of pulse or axis control modules, and when there are a large number of servos, even higher-level PLC hardware needs to be used to meet the requirements.
Sixth: Adopting a standard motion function block library to improve programming and debugging efficiency: Adopting a CAN bus system solution avoids the problems of large programming and complex debugging in traditional pulse direction control methods, improves efficiency, and saves costs and time.
Seventh: It can achieve remote control, which is very convenient and cost-effective when the production line equipment is long or there are many servos.
Eighth: Easy to expand: It is very convenient when the equipment has optional axes or may add axes in the later stage. PLC configuration does not require additional hardware, and wiring is very simple.
Ninth: More powerful software devices can be developed without the need for additional hardware or wiring: PLC can monitor servo motor faults in real time through the bus and display them on HMI. At the same time, PLC can also monitor the actual position, actual speed, and other information of servo motors, and can automatically adjust servo parameters according to needs through the program. It is possible to set servo parameters in the HMI without having to modify them on the servo panel, which is simple, intuitive, and error free.
Tenth: Stronger maintainability, with more status and diagnostic information.
