# A Novel Optimization Design Method of Form Ginding Wheel for Screw Rotor
## 3 Installation Parameter Optimization Design Method
### Profile Analysis of Form Wheel Grinding  
In order to obtain the best installation parameters within the range of requirements, the characteristics of the contact line and the profile features of wheel grinding under different installation parameters need to be investigated. The lengths of the contact line under different installation parameters are shown in Table 2.  
Table 2 shows the length values of the contact lines under different installation parameters. When the installation angle remains unchanged, the length of the contact line increases with the increased center distance, and vice versa. In contrast, the length of the contact line decreases as the installation angle increases under the condition in which the center distance stays constant, and vice versa. According to the grinding mechanism, it is well known that the longer the contact line, the better the heat dissipation during the grinding process. Thus, long contact lines are conducive to improving the grinding quality of the screw rotor.  
In order to evaluate the profile features of wheel grinding under different installation parameters, the slope and curvature of the cross-section profile of the grinding wheel were determined, as shown in Figure 9. When the center distance remains unchanged, the slope and curvature of the shaft section profile of the grinding wheel both increase with the increase in the installation angle, and vice versa. In contrast, the slope and curvature of the shaft section profile of the grinding wheel decrease as the center distance increases in the condition in which the installation angle stays constant, and vice versa. The smaller the slope and curvature, the smoother the shaft section profile of the grinding wheel and the easier it is to dress the grinding wheel. In addition, the smoother the profile, the better the wear resistance of the grinding wheel. During the actual grinding process, the radius of the grinding wheel is usually reduced from large to small, and the center distance becomes increasingly smaller. Therefore, the installation angle must be controlled as a priority.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Installation Angle (\({}^{\circ}\))** & **Center Distance (mm)** & **Length of Contact (mm)** \\ \hline
44.09 & 129.45 & 119.2523 \\
44.09 & 149.46 & 125.8969 \\
44.09 & 169.45 & 131.4853 \\
44.09 & 189.45 & 136.2507 \\
44.09 & 209.45 & 140.3629 \\
45.09 & 129.45 & 113.7053 \\
45.09 & 149.46 & 119.7477 \\
45.09 & 1 Figure 9: _Cont._  
In summary, through the above profile analysis of wheel grinding, some conclusions can be drawn as follows. Different installation parameters correspond to different contact line lengths; the slope and curvature of the shaft section profile of the grinding wheel also vary with the installation parameters. The installation angle should be properly selected to ensure the good dressing and grinding performance of the form grinding wheel. When these situations are considered holistically, a small installation angle should be selected under the condition where the meshing relationship between the screw rotor and the form grinding wheel is satisfied.