In the cutting process of laser cutting machine, the distance between cutting head and workpiece and the perpendicularity between nozzle and workpiece surface are two extremely important factors. It directly affects the processing quality, so in order to improve the cutting quality and reduce the production of waste products, it is necessary to install some special sensors on the cutting head to ensure that it can produce stable and consistent cutting quality and increase the process safety.
When the shape of the workpiece changes and there are uneven obstacles on the surface of the laser cutting head, the sensor automatically detects the change and automatically adjusts the height according to the change, so that it is always consistent with the distance from the workpiece surface. It can process materials faster without continuous supervision. Today, the displacement sensor used at home and abroad is basically capacitive, its structure and shape adapt to the machining head, and is equipped with a detection signal processing unit.
Displacement measurement is one of the most basic measurement work. According to whether the sensor is in contact with the measured workpiece, displacement sensors can be divided into contact and non-contact types. Compared with contact sensors, non-contact sensors have fast dynamic response speed, low hysteresis error, or even zero while ensuring high resolution.
Non contact sensor, sometimes called proximity sensor, the earliest application is proximity switch, that is, when the detected object is close to a certain distance from the sensitive probe, the switch signal is given. The current proximity sensor has been developed to not only detect the presence of objects, but also give the distance between the object and the sensitive probe, and provide information about the shape and spatial position of the workpiece.
Because it can be used to measure the displacement of moving objects, this kind of sensor is also called non-contact displacement sensor. The commonly used displacement sensors include hysteresis telescopic displacement sensor, eddy current displacement sensor, capacitive displacement sensor, inductor displacement sensor, etc.
According to the principles of various sensors, capacitive sensors have high sensitivity and the following characteristics:
1. The dynamic response is good. Because the electrostatic attraction between the plates is very small, the action energy required is very small, and the movable part can be made very small and thin, its natural frequency is very high, the dynamic response time is short, and it can work at a frequency of several megahertz, which is particularly suitable for dynamic measurement.
2. It has simple structure, strong adaptability, easy to manufacture and easy to ensure high accuracy. It can be made into a small-size sensor to realize special measurement. It can work in harsh environments such as high and low temperature, strong radiation and strong magnetic field, and can withstand high pressure, high impact, overload, etc.
3. The heating is small, and its temperature coefficient is small. Since the capacitance value of the capacitance sensor is independent of the electrode material, the material with low temperature coefficient can be selected, which can ensure good stability when the external temperature is stable. Laser cutting machine
4. The larger relative variation is only limited by the linear region, and its value can reach 100% or more, which can ensure the resolution and measurement range of the sensor.