“Detailed Explanation of the Composition and Requirements of Servo System for Machining Centers”
I. Composition of servo system for machining centers
In modern machining centers, the servo system plays a crucial role. It is composed of servo circuits, servo drive devices, mechanical transmission mechanisms, and actuating components.
The main function of the servo system is to receive the feed speed and displacement command signals issued by the numerical control system. First, the servo drive circuit will perform certain conversion and power amplification on these command signals. Then, through servo drive devices such as stepper motors, DC servo motors, AC servo motors, etc., and mechanical transmission mechanisms, the actuating components such as the machine tool’s worktable and spindle headstock are driven to achieve work feed and rapid movement. It can be said that in numerical control machines, the CNC device is like the “brain” that issues commands, while the servo system is the executive mechanism, like the “limbs” of the numerical control machine, and can accurately execute the motion commands from the CNC device.
Compared with the drive systems of general machine tools, the servo system of machining centers has essential differences. It can accurately control the movement speed and position of actuating components according to command signals, and can realize the movement trajectory synthesized by several actuating components moving according to certain rules. This requires the servo system to have a high degree of accuracy, stability, and fast response ability.
In modern machining centers, the servo system plays a crucial role. It is composed of servo circuits, servo drive devices, mechanical transmission mechanisms, and actuating components.
The main function of the servo system is to receive the feed speed and displacement command signals issued by the numerical control system. First, the servo drive circuit will perform certain conversion and power amplification on these command signals. Then, through servo drive devices such as stepper motors, DC servo motors, AC servo motors, etc., and mechanical transmission mechanisms, the actuating components such as the machine tool’s worktable and spindle headstock are driven to achieve work feed and rapid movement. It can be said that in numerical control machines, the CNC device is like the “brain” that issues commands, while the servo system is the executive mechanism, like the “limbs” of the numerical control machine, and can accurately execute the motion commands from the CNC device.
Compared with the drive systems of general machine tools, the servo system of machining centers has essential differences. It can accurately control the movement speed and position of actuating components according to command signals, and can realize the movement trajectory synthesized by several actuating components moving according to certain rules. This requires the servo system to have a high degree of accuracy, stability, and fast response ability.
II. Requirements for servo systems
- High precision
Numerical control machines process automatically according to a predetermined program. Therefore, to process high-precision and high-quality workpieces, the servo system itself must have high precision. Generally speaking, the precision should reach the micron level. This is because in modern manufacturing, the precision requirements for workpieces are getting higher and higher. Especially in fields such as aerospace, automobile manufacturing, and electronic equipment, even a small error may lead to serious consequences.
To achieve high-precision control, the servo system needs to adopt advanced sensor technologies such as encoders and grating rulers to monitor the position and speed of actuating components in real time. At the same time, the servo drive device also needs to have a high-precision control algorithm to accurately control the speed and torque of the motor. In addition, the precision of the mechanical transmission mechanism also has an important impact on the precision of the servo system. Therefore, when designing and manufacturing machining centers, it is necessary to select high-precision transmission components such as ball screws and linear guides to ensure the precision requirements of the servo system. - Fast speed response
Fast response is one of the important signs of the dynamic quality of the servo system. It requires that the servo system has a small following error following the command signal, and has fast response and good stability. Specifically, it is required that after a given input, the system can reach or restore the original stable state in a short time, generally within 200ms or even dozens of milliseconds.
The fast response ability has an important impact on the processing efficiency and processing quality of machining centers. In high-speed machining, the contact time between the tool and the workpiece is very short. The servo system needs to be able to respond to the command signal quickly and adjust the position and speed of the tool to ensure the processing precision and surface quality. At the same time, when processing workpieces with complex shapes, the servo system needs to be able to respond quickly to the changes of command signals and realize multi-axis linkage control to ensure the processing accuracy and efficiency.
To improve the fast response ability of the servo system, high-performance servo drive devices and control algorithms need to be adopted. For example, using AC servo motors, which have fast response speed, large torque, and wide speed regulation range, can meet the high-speed machining requirements of machining centers. At the same time, adopting advanced control algorithms such as PID control, fuzzy control, and neural network control can improve the response speed and stability of the servo system. - Large speed regulation range
Due to different cutting tools, workpiece materials, and processing requirements, to ensure that numerical control machines can obtain the best cutting conditions under any circumstances, the servo system must have a sufficient speed regulation range. It can meet both high-speed machining requirements and low-speed feed requirements.
In high-speed machining, the servo system needs to be able to provide high speed and acceleration to improve processing efficiency. While in low-speed feeding, the servo system needs to be able to provide stable low-speed torque to ensure the processing precision and surface quality. Therefore, the speed regulation range of the servo system generally needs to reach several thousand or even tens of thousands of revolutions per minute.
To achieve a large speed regulation range, high-performance servo drive devices and speed regulation methods need to be adopted. For example, using AC variable frequency speed regulation technology can realize stepless speed regulation of the motor, with wide speed regulation range, high efficiency, and good reliability. At the same time, adopting advanced control algorithms such as vector control and direct torque control can improve the speed regulation performance and efficiency of the motor. - High reliability
The operation rate of numerical control machines is very high, and they often work continuously for 24 hours. Therefore, they are required to work reliably. The reliability of the system is often based on the average value of the length of time intervals between failures, that is, the average time without failure. The longer this time is, the better.
To improve the reliability of the servo system, high-quality components and advanced manufacturing processes need to be adopted. At the same time, strict testing and quality control of the servo system are needed to ensure its stable and reliable performance. In addition, redundant design and fault diagnosis technologies need to be adopted to improve the fault tolerance and fault diagnosis capabilities of the system so that it can be repaired in time when a fault occurs and ensure the normal operation of the machining center. - Large torque at low speed
Numerical control machines often perform heavy cutting at low speeds. Therefore, the feed servo system is required to have a large torque output at low speeds to meet the requirements of cutting processing.
During heavy cutting, the cutting force between the tool and the workpiece is very large. The servo system needs to be able to provide sufficient torque to overcome the cutting force and ensure the smooth progress of processing. To achieve low-speed high-torque output, high-performance servo drive devices and motors need to be adopted. For example, using permanent magnet synchronous motors, which have high torque density, high efficiency, and good reliability, can meet the low-speed high-torque requirements of machining centers. At the same time, adopting advanced control algorithms such as direct torque control can improve the torque output ability and efficiency of the motor.
In conclusion, the servo system of machining centers is an important part of numerical control machines. Its performance directly affects the processing precision, efficiency, and reliability of machining centers. Therefore, when designing and manufacturing machining centers, the composition and requirements of the servo system need to be fully considered, and advanced technologies and equipment need to be selected to improve the performance and quality of the servo system and meet the development needs of modern manufacturing.