Research On The 3kW RF Slab CO₂ Laser Control System Based On MC68376

The diffusion cooling RF slab CO2 laser of 2kW-4kW with beam quality nearly k=0.95 is one of the most widely accepted light source for the applications of laser cutting and welding. As being applied to 3kW RF slab CO2 laser, the implementation method has been studied in this thesis for laser control system, real-time signal acquisition and laser state-detection using MC68376 microcontroller. The main contents are classified as follows.(1) The operating mechanism and key technologies has been analyzed for the 3kW RF- slab CO2 laser. This laser was mainly composed by the vacuum box, water cooling system, RF power supply, matching network, flat electrode, hybrid waveguide unstable resonator and beam shaping system. Resonator with hybrid waveguide structure could make efficient use of the gain region and obtain significant beam propagation ratio. After proper beam shaping system, nearly circular quasi- Gaussian beam can be obtained.(2) The controlling signal and technology of the 3kW RF slab CO2 laser discharge at the frequency of 81.36 MHz have been studied. Pulse Width Modulation(PWM) was used to control laser output mode. The control system had the following features: high voltage detection, current detection, alarm signal output. The main functions of the controlling system included time sequence of laser on and laser off, parameters detection and controlling, making sure the duty cycle of the PWM wave between 5% to 95% and steady power output of the laser.(3) The Freescale MC68376 hardware circuit has been designed, including the main control chip, peripheral circuit, extension storage, communication circuit and anti-interference measures. TLP181 optical coupling isolation was used in the digital signal input and output. INA117 high common-mode voltage differential amplifier was applied to the analog signal input. MAX526 digital-to-analog converter and AD7856 analog-to-digital converter have been applied in this hardware circuit. The control system has good stability and anti-interference ability.(4) It has been established for the start-testing procedures, high voltage start, data reading and transmission module flowchart based on CodeWarrior software development platform, to achieve the detection of boot, cooling water, the shutter, open filament signal and so on. Through calling the function setcheck() start checking, after the checking filament turned on,the high-voltage start up with another 30 s delay.(5) According to the test of slab CO2 laser RF analog signal, the relationships between test values(y) and input analog(x) value about Current, voltage, gas pressure and vacuum degree are linear?The relationship between analogs and display values of microcomputer and the relationship between preset parameters are similar. Tailored blanks welding experiments have been performed to test the performance of the 3kW RF slab CO2 laser. Taking 3mm thickness clod steel as sample, the weld velocity was 1.8 m/min. the seam quality could be estimated by cupping test.