# Research and Progress on Truing and Sharpening Process of Diamond Abrasive Grinding Tools
## 3 Dressing Method of Diamond Abrasive Grinding Tools
### Sharpening Technology of Diamond Abrasive Grinding Tools
#### 3.2.4 Laser Sharpening Method
\begin{table}
\begin{tabular}{c c c c c} \hline
**Material** & **Name** & **Symbol** & **Unit** & **Numerical Value** \\ \hline \multirow{8}{*}{Bronze} & Atomic mass & \(m\) & kg & \(1.038\times 10^{-25}\) \\  & Density & \(\rho_{s}\) & kg\(\cdot\)m\({}^{-3}\) & 8620 \\  & Melting temperature & \(T_{m}\) & K & 1173 \\  & Gasification temperature & \(T_{l}\) & K & 2770 \\  & Thermal diffusivity & \(k\) & cm\({}^{2}\cdot\)s\({}^{-1}\) & 0.14 \\  & Thermal conductivity & \(k_{s}\) & W\(\cdot\)m\({}^{-1}\cdot\)K\({}^{-1}\) & 41.9 \\  & Specific heat capacity & \(c_{s}\) & J\(\cdot\)kg\({}^{-1}\cdot\)K\({}^{-1}\) & 352 \\  & Absorption rate & \(\beta\) & — & 0.38 \\  & Density & \(\rho_{s}\) & kg\(\cdot\)m\({}^{-3}\) & 3.52 \\  & Melting temperature & \(T_{m}\) & K & 3550 \\  & Gasification temperature & \(T_{l}\) & K & 4830 \\  & Refractive index & \(n\) & — & 2.42 \\  & Thermal diffusivity & \(k\) & cm\({}^{2}\cdot\)s\({}^{-1}\) & 3.11 \\  & Thermal conductivity & \(k_{s}\) & W\(\cdot\)m\({}^{-1}\cdot\)K\({}^{-1}\) & 2000 \\  & Specific heat capacity & \(c_{s}\) & kg\({}^{-1}\cdot\)K\({}^{-1}\) & 1827 \\  & Absorption rate & \(\beta\) & — & 0.25 \\ \hline \end{tabular}
\end{table} 
Table 1: Thermophysical parameters of the bronze and diamond. \begin{table}
\begin{tabular}{c c c c} \hline
**Name** & **Symbol** & **Unit** & **Numerical Value** \\ \hline Laser wavelength & \(\lambda\) & nm & 1064 \\ Electron mass & \(m_{e}\) & kg & \(9.1\times 10^{-31}\) \\ Average ionization energy & \(U\) & eV & 7.63 \\ \hline \end{tabular}
\end{table} 
Table 2: Calculation parameters. Figure 17 shows the experimental equipment for laser dressing the bronze-bonded diamond abrasive grinding wheels. In the experiment, the wavelength of the fiber laser was 1064 nm, the pulse frequency was 50 kHz, the pulse width was 210 ns, and three laser power densities of 1.68 \(\times\) 108 W/cm\({}^{2}\), 2.52 \(\times\) 108 W/cm\({}^{2}\), and 3.36 \(\times\) 108 W/cm\({}^{2}\) were selected for the dressing experiment. As can be seen from Figure 17, the single-mode optical fiber was focused by a lenticular lens with a focal length of 180 mm inside the pulsed laser ablation head, and then the surface on the bronze-bonded diamond abrasive grinding wheel was vertically irradiated; the defocus amount was 0. During the laser dressing process, the bronze-bonded diamond abrasive grinding wheel (model is 100D \(\times\) 10T \(\times\) 5X \(\times\) 31.75H \(\times\) 80#) was fixed on the surface grinding machine and was driven by the main shaft to rotate counterclockwise at a speed of 300 r/min. Figure 16: Temperature changes in the pulsed fiber laser dressing bronze material and diamond. (**a**) Bronze material, laser power density: 1.68 \(\times\) 108 W/cm\({}^{2}\); (**b**) Diamond, laser power density: 1.68 \(\times\) 108 W/cm\({}^{2}\); (**c**) Diamond, laser power density: 2.52 \(\times\) 108 W/cm\({}^{2}\); (**d**) Diamond, laser power density: 3.36 \(\times\) 108 W/cm\({}^{2}\). Figure 17: Laser dressing the bronze-bonded diamond abrasive grinding wheel experimental equipment. The surface topography of the bronze-bonded diamond abrasive grinding wheel ablated by pulsed fiber laser was photographed with a three-dimensional ultra-depth-of-field microscope under magnification (200 times). Through observation, it was found that the topography of the bronze-bonded diamond abrasive grinding wheel dressed by different laser power density was different. Figure 18a shows the surface topography of the bronze-bonded diamond abrasive grinding wheel when the laser power density was 1.68 \(\times\) 10\({}^{8}\) W/cm\({}^{2}\). At this time, the ablation threshold of the bronze bond material had been reached and the removal of the bronze material had been realized. There was almost no change in the diamond abrasive grains and the dressing effect was slight. Figure 18b shows the surface topography of the bronze-bonded diamond abrasive grinding wheel when the laser power density was 2.52 \(\times\) 10\({}^{8}\) W/cm\({}^{2}\).