# Optimization of Screen-Hole-Clearing Devices for Mechanized Residual Film-Impurity Separation
## 3 Results and Discussion
### Analysis of Model Interaction Factors  
To analyze the effect of interaction factors on the response values, response surface plots of the relationship of the ratio of impurities in the residual film and the ratio of the blockage of the screen holes with each factor were constructed using the quadratic regression model [26]. As illustrated in Figure 10a, the airflow pipes were located at zero level. When the fan wind speed was high, the effects of the distance from the nozzle to the screen surface on the ratio of impurities in the residual film were not significant. When the fan wind speed was small, the ratio of impurities in the residual film increased with the increase in the distance from the nozzle to the screen surface. When the distance from the nozzle to the screen surface was small, the effects of the fan wind speed on the ratio of impurities in the residual film were not significant. When the distance from the nozzle to the screen surface was large, the ratio of impurities in the residual film decreased with an increase in the fan wind speed. This was mainly because the device was more sensitive to a change in the nozzle-to-screen distance or fan wind speed when the fan wind speed was small or the distance from the nozzle to the screen surface was large. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Source of Variation**} & \multicolumn{3}{c}{**Impurity Rate in the Residual Film**} & \multicolumn{3}{c}{**Blockage Rate of the Screen Holes**} \\ \cline{2-7}  & **Sum of Squares** & \(F\)**-Value** & \(p\)**-Value** & **Sum of Squares** & \(F\)**-Value** & \(p\)**-Value** \\ \hline Model & 120.67 & 20.2 & 0.0003 ** & 136.77 & 14.45 & 0.001 ** \\ X\({}_{1}\) & 1.37 & 2.06 & 0.194 & 0.76 & 0.72 & 0.4227 \\ X\({}_{2}\) & 11.33 & 17.07 & 0.0044 ** & 11.93 & 11.34 & 0.012 * \\ X\({}_{3}\) & 31.56 & 47.55 & 0.0002 ** & 6.73 & 6.4 & 0.0392 * \\ X\({}_{1}\)X\({}_{2}\) & 5.81 & 8.75 & 0.0212 * & 0.56 & 0.53 & 0.4884 \\ X\({}_{1}\)X\({}_{3}\) & 16.85 & 25.39 & 0.0015 ** & 0.62 & 0.59 & 0.4691 \\ X\({}_{2}\)X\({}_{3}\) & 0.12 & 0.17 & 0.6889 & 0.99 & 0.94 & 0.3643 \\ \(X_{1}\)\({}^{2}\) & 6.90 & 10.39 & 0.0146 * & 0.23 & 0.22 & 0.6519 \\ X\({}_{2}\)\({}^{2}\) & 1.33 & 2.01 & 0.1997 & 24.24 & 23.05 & 0.002 ** \\ X\({}_{3}\)\({}^{2}\) & 42.04 & 63.33 & \textless{}0.0001 ** & 85.72 & 81.49 & \textless{}0.0001 ** \\ Residual & 4.65 & & & 7.36 & & \\ Lack of Fit & 2.68 & 1.82 & 0.2840 & 5.94 & 5.56 & 0.0655 \\ Pure Error & 1.97 & & & 1.43 & & \\ Cor Total & 125.32 & & & 144.13 & & \\ \hline \hline \end{tabular} Note: ** highly significant (\(p\leq 0.01\)); * significant (\(0.01<p\leq 0.05\)).  
\end{table} 
Table 3: Box–Behnken test protocol and results. As displayed in Figure 10b, the fan wind speed was zero. When the number of airflow pipes was small, the distance from the nozzle to the screen surface had no significant influence on the ratio of impurities in the residual film. When the number of airflow pipes was large, the ratio of impurities in the residual film increased with the increase in the distance from the nozzle to the screen surface. At the same nozzle-to-screen-surface distance, the ratio of impurities in the residual film first decreased and then increased with an increase in the number of airflow pipes. The main reason was that when the number of airflow pipes was small, the screen-hole-clearing and -plugging devices were ineffective. Simply increasing the distance from the nozzle to the screen surface did not effectively reduce the ratio of impurities in the residual film. According to the results of ANOVA, the number of airflow pipes had the greatest influence on the ratio of impurities in the residual film. Therefore, the ratio of impurities in the residual film considerably fluctuated when the number of airflow pipes changed at the same distance from the nozzle to the screen surface. Figure 10c depicted that the distance from the nozzle to the screen surface was zero.