Research On Height Trace And Power Control Of Laser Cutting

The processing of laser cutting is one of the advanced manufacturing technology.It has been widely used because of the advantages of low cost and high efficiency.And now the high precision and high speed laser cutting technology has become an important development direction.The height trace control between the laser focus and the workpiece and the synchronous control between laser power and cutting speed are the two most important factors that affects the quality of laser cutting.In this dissertation,a DSP-based high trace and power control system is designed.It can keep the height of laser focus to be constant and adjust the laser power to follow the change of processing speed.This dissertation analyzes the status of the research and development trend of laser cutting.On the basis of the study of the laser cutting head.A method to measure the laser focus height by capacitive sensor is designed.The mathematical model and the equivalent circuit model of the capacitive sensor are analyzed theoretically,It is useful to design the circuit to detect the capacitive sensor.At the same time,the effects of control signal,power and cutting speed on the quality of cutting are analyzed,and propose a look-up table method to control the power under different speed.On the basis of the theoretical analysis,this dissertation designed the Clapp oscillation circuit.It can convert the small capacitance signal into sinusoidal signal.The frequency of the signal is measured by the multi-cycle synchronism measurement technology.The method of least square curve fitting is used to correct the nonlinear relation between frequency and height.Then the PID feedback control system adjust the height by servo motor.At the same time,the PWM output according to different speed is used to control laser power.The software for the parameter configuration is designed and send data to DSP board with serial communication.To verify the stability and accuracy of the capacitive sensor,this dissertation designes many experiments to get data.Under the appropriate PID parameters,the height trace control meets the requirements of high accuracy and fast response.Different power control parameters are set to process samples.The good cutting results explain that the power control is useful.It also can provide references for actual production.