## 5 Process Parameter Optimization of Laser Control System for MCR Frequency Modulation  
### Laser Characteristics Analysis of MCR Frequency Modulation  
In the laser processing of MCR frequency modulation, the laser power, laser frequency and laser processing speed play a decisive role in frequency modulation production. Experiments with different parameters are carried out. The results of MCR electrode surface processing are observed under a microscope and the results are depicted in Figure 13. The laser power, laser frequency and laser processing speeds of group A are 5 W, 200 KHz and 800 mm/s, the parameters of group B are 8 W, 400 KHz and 400 mm/s, and the parameters of group C are 10 W, 500 KHz and 200 mm/s. When the selected laser power and frequency are too low and the laser processing speed is too fast, it is difficult to etch the silver layer of the electrode of the MCR, and the frequency modulation fails. The higher the laser power, the greater the heat flux acting on the surface of the electrode silver layer of the MCR per unit time, the more heat absorbed by the silver layer per unit area, the larger gasification and melting area of the silver layer and the greater the frequency change of the MCR. The higher the laser frequency, the more times the laser pulse acts on the silver layer per unit time and the faster gasification of the silver layer. If the processing speed is too fast, it is difficult for the electrode silver layer to absorb enough heat to gasify, and it is impossible to adjust the frequency of the MCR to the target frequency. When the selected laser power is too high, the laser frequency is too high, the laser processing speed is too slow and the etching depth and width of the electrode silver layer of the MCR will increase. However, when the processing is carried out with large laser power and laser frequency and slow laser processing speed, the melting area of the silver layer will also increase, and these areas will be oxidized and blackened after cooling, which affects the appearance of the MCR [23]. In order to ensure that the electrode silver layer of the MCR can be quickly etched without excessive black edges, according to the experimental data, it is determined that the laser power is between 6 W and 9 W, the laser frequency is between 200 KHz and 500 KHz and the laser processing speed is between 200 mm/s and 800 mm/s. Orthogonal Experiment and Result Analysis of Laser Processing Control Parameters for MCR Frequency Modulation  
Because laser power, laser frequency and laser processing speed have influence on the frequency modulation, the single-variable control method can only reflect the influence of each parameter on the results of MCR frequency modulation. In order to obtain appropriate laser processing control parameters and comprehensively consider the influence of various control parameters on frequency modulation results, orthogonal experiments are used for analysis. The three control parameters--laser power, laser frequency and laser processing speed--are selected as experimental factors, represented by A, B and C, of the orthogonal experiment. Based on the experimental results of laser control parameters, the range of laser power is from 6 W to 9 W, the range of laser frequency is from 200 KHz to 500 KHz and the range of laser processing speed is from 200 mm/s to 800 mm/s. Each factor has four levels, and the factor level table is listed in Table 7.  
According to the above analysis, the orthogonal experiment is designed as an experiment of three factors and four levels. The L\({}_{16}\)(4\({}^{5}\)) orthogonal table is selected for the orthogonal experiment, and the two extras are set as blank columns. Sixteen representative experimental combinations are selected from the experiment, and the orthogonal experiment design and experimental results are listed in Table 8.  
The range analysis method of the orthogonal experiment is used to analyze the influence degree of each laser control parameter on the evaluation index.