China Education Equipment Purchasing News: CNC machine tool is an automatic machine tool equipped with a program control system, which can move the machine tool and process parts according to the programmed program. It integrates the latest technology of machinery, automation, computer, measurement, microelectronics, etc., and uses a variety of sensors. The application of various sensors on CNC machine tools will be introduced below.
Sensor Introduction
A sensor is a device or device that can sense a specified measurement and convert it into a usable output signal according to a certain rule. The input signal (measured) is often non-electricity, and the output signal is often easy-to-handle electricity, such as voltage.
There are many types of sensors, with different classification standards and different names. Common ones include resistance sensors, inductive sensors, capacitive sensors, temperature sensors, piezoelectric sensors, Hall sensors, thermocouple sensors, photoelectric sensors, and digital sensors. Position sensors, etc. 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, induction synchronizers, speed sensors, etc. Mainly used to detect position, linear displacement and angular displacement, speed, pressure, temperature, etc.
CNC machine tool requirements 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 the operating environment of the machine tool;
(4) Low cost.
Different types of CNC machine tools have different requirements for sensors. Generally speaking, large machine tools require high speed response, and medium and high precision CNC machine tools mainly require accuracy.
Displacement detection
Displacement detection sensors mainly include pulse encoders, linear gratings, resolvers, and induction synchronizers.
4.1 Application of pulse encoder
A pulse encoder is an angular displacement (rotation speed) sensor that can turn a mechanical rotation angle into an electrical pulse. Pulse encoders can be divided into three types: photoelectric, contact and electromagnetic. Among them, there are many applications of photoelectric.
4.2 Application of linear grating
Linear gratings are made using the phenomena of light transmission and reflection. They are often used in displacement measurement, with higher resolution and higher measurement accuracy than photoelectric encoders, and are suitable for dynamic measurements.
In the feed drive, the grating ruler is fixed on the bed, and the pulse signal generated by it directly reflects the actual position of the carriage. The servo system that uses grating to detect the position of the workbench is a fully closed-loop control system.
4.3 Application of resolver
The resolver is an inductive micromotor whose output voltage and angular displacement are in a continuous function. The resolver consists of a stator and a rotor. Specifically, it consists of a core, two stator windings, and two rotor windings. The primary and secondary windings are placed on the stator and rotor, respectively. The electromagnetic coupling between the primary and secondary windings The degree is related to the rotation angle of the rotor.
4.4 Application of inductive synchronizer
Inductive synchronizers are made using the principle that the mutual inductance of two planar windings varies with position. Its function is to convert the angle or linear displacement into the phase or amplitude of the induced electromotive force, which can be used to measure the linear or angular displacement. According to its structure, it can be divided into linear type and rotary type. The linear induction synchronizer is composed of fixed length and sliding scale. The fixed length is installed on the bed of the machine tool. The sliding scale is installed on the moving part and moves with the worktable; the stator of the rotary induction synchronizer is a fixed disk and rotor For spinning discs. The induction synchronizer has the advantages of high precision and resolution, strong anti-interference ability, long service life, simple maintenance, long-distance displacement measurement, good manufacturability and low cost. Linear induction synchronizers are currently widely used in large-displacement static and dynamic measurement, such as coordinate measuring machines, program-controlled CNC machine tools, high-precision heavy-duty machine tools and machining center measurement devices. Rotary induction synchronizers are widely used in turntables of machine tools and instruments and various rotary servo control systems.
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