Development Of Height Trace Control System In Capacitive Laser Cutting Head

In order to improve the quality and stability of laser cutting, laser focus should be maintained in appropariate position during the whole laser cutting process. Therefore, the laser cutting head need a height trace control system. This system could make adjustment to the undulating surface of the workpiece, ensure laser focus always in ideal position. So far, the laser cutting head with height trace system has been released in foreign countries. But it is very expensive. The past ten years in China,the laser cutting head height trace system has experienced a rapid development process. Many companys has launched correlation products, although they had low precision, slow response and other demerits.A method, based on capacitance displacement measuring, using PCAP01 micro capacitance measuring chip as the core of capacitance sensor, using STM32F407 microcontroller as the core of controller, using servo motor as motor execution unit, was presented in this thesis. The system divice commonly consists of four part, inductive plate at the nozzle, capacitance sensor, main controller and servo motor. Capacitance sensor continuously detect the capacitance between inductive plate and workpiece. The capacitance was transformed to distance information by main controller. According to this real-time distance, main controller addjust the servo motor to ensure the distcane between laser cutting head and workpiece has been in ideal range, which means that laser focus was always in ideal position.In height trace control system experiment, the capacitance measuring accuracy, capacitance calibration and height trace effect in real laser cutting condition were tested. The results show that the distance measuring accuracy could be 0.01 mm, when distance was less len 2.5mm. And the system was feasible, stable.