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3. Servo system and measurement feedback system
Servo system is an important part of CNC machine tools and is used to realize feed servo control and spindle servo control of CNC machine tools. The function of the servo system is to convert the command information received from the numerical control device into the linear displacement or angular displacement of the machine tool execution part after power amplification and shaping. Since the servo system is the last link of the CNC machine tool, its performance will directly affect the technical indicators such as the precision and speed of the CNC machine tool. Therefore, the servo drive device of the CNC machine tool is required to have good rapid response performance and accurately and sensitively track the CNC device. The digital command signal sent out, and can faithfully execute the command from the numerical control device, improve the system's dynamic following characteristics and static tracking accuracy.
The servo system includes two parts: the drive device and the actuator. The drive device consists of a spindle drive unit, a feed drive unit, a spindle servo motor and a feed servo motor. Stepper motors, DC servo motors and AC servo motors are commonly used drives.
The measuring element detects the actual displacement value of each coordinate axis of the CNC machine tool and inputs it into the CNC device of the machine tool through the feedback system. The CNC device compares the actual displacement value fed back with the command value, and outputs the set value to the servo system. The required displacement command.
4. The main body of the machine tool
The machine tool host is the main body of the CNC machine tool. It includes machine parts such as bed, base, column, beam, sliding seat, worktable, spindle box, feeding mechanism, tool rest and automatic tool changer. It is a mechanical part that automatically completes various cutting processes on CNC machine tools. Compared with traditional machine tools, the main body of CNC machine tools has the following structural characteristics:
1) Adopt a new machine tool structure with high rigidity, high shock resistance and less thermal deformation. Usually, methods such as improving the static stiffness of the structural system, increasing the damping, and adjusting the quality and natural frequency of the structural parts are used to improve the stiffness and shock resistance of the machine tool host, so that the machine tool body can adapt to the needs of CNC machine tools for continuous and automatic cutting. Taking measures such as improving the structure and layout of the machine tool, reducing heat generation, controlling temperature rise, and adopting thermal displacement compensation can reduce the impact of thermal deformation on the machine tool host.
2) The high-performance spindle servo drive and feed servo drive device are widely used, which shortens the transmission chain of the CNC machine tool and simplifies the structure of the mechanical transmission system of the machine tool.
3) Adopt high transmission efficiency, high precision, no clearance transmission device and moving parts, such as ball screw nut pair, plastic sliding guide, linear rolling guide, static pressure guide, etc.
5. Auxiliary devices of CNC machine tools
Auxiliary devices are necessary supporting devices to ensure the full use of CNC machine tools. Common auxiliary devices include: pneumatic, hydraulic devices, chip removal devices, cooling and lubricating devices, rotary tables and CNC indexing heads, protection, lighting, etc. assisting equipments.
CNC machine tool is an automatic machine tool equipped with a program control system, which can make the machine tool move and process parts according to the programmed program. It integrates the latest technologies such as machinery, automation, computer, measurement, microelectronics, etc., and uses a variety of sensors. The sensors used in CNC machine tools mainly include photoelectric encoders, linear gratings, proximity switches, temperature sensors, Hall sensors, current Sensors, voltage sensors, pressure sensors, liquid level sensors, resolvers, inductive synchronizers, speed sensors, etc., are mainly used to detect position, linear displacement and angular displacement, speed, pressure, temperature, etc.
1. The requirements of CNC machine tools for sensors
1) High reliability and strong anti-interference;
2) Meet the requirements of accuracy and speed;
3) Easy to use and maintain, suitable for machine tool operating environment;
4) Low cost.
Different types of CNC machine tools have different requirements for sensors. Generally speaking, large-scale machine tools require high speed response, and medium-sized and high-precision CNC machine tools mainly require accuracy.
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