# Magnetic Abrasive Finishing of Beta-Titanium Wire Using Multiple Transfer Movement Method
## 3 Experimental Results and Analysis
### Influence of Clearance Distance  
To determine the optimum clearance distance of the workpiece, the magnetic field distribution at the finishing zone was measured using an FEMM. In addition, the chemical composition of beta-titanium wire was analyzed by EDS and the density was verified by mapping. Before the finishing process, the clearance distances between the two magnetic poles were set to 3 and 5 mm. Figure 6 shows the result of the FEMM analysis; the results obtained at the finishing zone were 2.82347 magnetic flux density (T) for 3 mm clearance and 2.56956 T for 5 mm clearance. Figure 7 shows the relationship between magnetic flux density (T) and distance from the magnetic pole. Figure 8 shows the changes in surface roughness (Ra) and processing time for different finishing gaps. The finishing conditions were conducted under the optimal conditions (rotation: 2000 rpm; abrasive: 1 \(\upmu\)m; sharp-edged magnetic pole, total finishing time: 300 s). The results showed that surface roughness continually improved from 0 s to 300 s of finishing time. The surface roughness (Ra) improved to 0.08 \(\upmu\)m for a gap of 3 mm and 0.21 \(\upmu\)m for a gap of 5 mm. This showed that the 3 mm finishing gap was much better than a 5 mm gap. Thus, a smaller finishing gap distance can provide better surface roughness (Ra) on the beta-titanium wire workpiece. According to Figure 6, a higher magnetic flux density was obtained when using smaller finishing gaps. During the finishing process, the higher magnetic flux density generated higher magnetic force, which acted strongly on the magnetic abrasive particles, resulting in a workpiece with better surface quality.  
Figure 6: Front view of sharp-edged magnetic field analyzed by FEMM.  
Figure 7: Magnetic flux density (T) vs. distance for different finishing gaps.  
The surface conditions of beta-titanium wire before and after finishing were investigated using an optical microscope (IMS-M-345) (see Figure 9). Figure 9a shows the initial surface condition before the finishing process. As shown in Figure 9a, the multiple grooves and original scratches can be found everywhere on the initial surface and surface roughness Ra is 0.32 \(\upmu\)m. Figure 9b shows the surface condition after the finishing process. From Figure 9b, the surface condition of beta-titanium wire is smoother than the initial surface condition and the multiple grooves were mostly removed. A surface roughness (Ra) after the finishing process is 0.05 \(\upmu\)m.  
Figure 10 shows EDS chemical component analysis graphs for beta-titanium wire before and after processing. Figure 10a shows the chemical components of the material detected on the surface of the beta-titanium wire alloy workpiece prior to the finishing process: 55.34% Ti, 26.68% O, 17.85% C, and 0.12% Fe. After the finishing process, Figure 10b shows a composition of 16.40% C, 21.68% O, 61.69% Ti, and 0.23% Fe. Ti and Fe increased after processing, and O and C were lower. However, no other components were found on the surface of the workpiece after the finishing process.  
Figure 8: Surface roughness (Ra) vs. processing time for different finishing gaps (vibration: 8 Hz; abrasive: 1 \(\upmu\)m; rotation: 2000 rpm; sharp edge magnetic pole).  
Figure 9: Micro-images of surface roughness before and after finishing: (**a**) before finishing (Ra = 0.32) and (**b**) after finishing (Ra = 0.05).  
This confirmed that the component magnetic abrasive tools did not affect the surface of the workpiece after the finishing process. Figure 11 shows the EDS chemical composition maps on the surface of the workpiece before and after the finishing process with optimal conditions. Table 4 shows the chemical composition of \(\beta\)-titanium wire before and after finishing.  
Figure 10: EDS graphs of the workpiece before and after the magnetic abrasive finishing process (under optimal conditions: 1 \(\upmu\)m, 3 mm, 2000 rpm, 300 s).