# A Study on Improving the Machining Performance of Scrolls
## 6 Conclusions  
To increase machining efficiency, retain machining precision, and increase the added value from scroll manufacturing, we proposed and demonstrated adaptive milling processes. These processes included adaptive feed rate planning for rough machining processes, chatter suppression for semi-fine and fine machining processes, and optimization of milling parameters for fine machining processes. The experimental tests also demonstrated the following:  
1. The method of adaptive feed rate planning could increase the material removal rate by about 14.4% and shorten the cutting time by about 12.6% with the following major machining parameters: spindle speed of 6000 rpm, cutting area per cutter tooth of 0.5 mm\({}^{2}\), maximum feed rate limit of 1000 mm/min, and maximum bending moment of 26.62 Nm; \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Experiment Number** & \multicolumn{3}{c}{**Measured \(R_{a}\) Value (\(\mu\)m)**} & \multicolumn{3}{c}{**Mean (\(\mu\)m)**} & **S/N Ratio \(\eta\) (dB)** \\ \hline
1 & 0.14 & 0.16 & 0.18 & 0.18 & 0.12 & 0.156 & 16.04 \\
2 & 0.22 & 0.18 & 0.18 & 0.14 & 0.14 & 0.172 & 15.16 \\
3 & 0.16 & 0.2 & 0.18 & 0.16 & 0.18 & 0.176 & 15.06 \\ \hline \multicolumn{6}{c}{Average} & \multicolumn{3}{c}{0.168} & 15.42 \\ \hline \hline \end{tabular}
\end{table} 
Table 18: Mean values and S/N ratios for surface roughness from verification experiments. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Factor** & **Degree of Freedom (DF)** & **Sum of Squares (SS)** & **Mean Square (MS)** & **F-Ratio (\(F_{X}\))** & **Contribution (\(P_{X}\))** \\ \hline \(A\) (spindle speed) & 2 & 8.3888 & 4.1944 & 11.2481 & 30.8\% \\ \(B\) (feed rate) & 2 & 14.9217 & 7.4609 & 20.0078 & 57.2\% \\ \(C\) (tool path) & 2 & 0.0024 & 0.0012 & 0.0032 & – \\ \hline Error & 2 & 1.4892 & 0.7446 & & \\ Total & 8 & 24.8021 & & & \\ Pooled error & 4 & 1.4916 & 0.3729 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 17: ANOVA for surface roughness. Figure 22: Scroll workpiece after the fine machining processes. The proposed methods for chatter suppression were feasible with a transition time of 80 ms, and the transition length on the workpiece surface was about 1.05 mm;
* For profile errors, the optimum combination of milling parameters obtained with a 90% confidence level was a spindle speed of 10,000 rpm, feed rate of 500 mm/min, and B-spline tool path;
* For surface roughness, the optimum combination of milling parameters obtained with a 90% confidence level was a spindle speed of 15,000 rpm, feed rate of 500 mm/min, and B-spline tool path;
* The program developed in this study can also successfully perform with and connect to the controllers made by FANUC and DELTA. As revealed in points 3 and 4, this study demonstrated the usefulness of the Taguchi method in obtained optimum milling parameters. Although it can be observed that the resulting parameters for spindle speeds were different for different profile errors and surface roughness levels, the results of the ANOVA also showed that the spindle speed was much less significant than the other two control factors (i.e., the feed rate and tool path) for profile errors. Further research developing a series of feedforward compensation algorithms to modify tool paths before machining processes is under preparation for publication. The videos of the machining of the scroll and the measurement of its profile errors can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13010286/s1](https://www.mdpi.com/article/10.3390/app13010286/s1)]([https://www.mdpi.com/article/10.3390/app13010286/s1](https://www.mdpi.com/article/10.3390/app13010286/s1)), Video S1: Scroll machining processes; Video S2: Profile error measuring processes. Conceptualization, [PERSON]-T.L., [PERSON]-L.J. and D.-M.T. ; methodology, [PERSON]-T.L., J.-L.J., M.S., D.-M.T., G.-S.H. and B.-J.L. ; software, [PERSON]-T.L. and J.-L.J. ; validation, Y.-T.L., J.-L.J., M.S., D.-M.T., G.-S.H. and B.-J.L. ; formal analysis, [PERSON]-T.L. and J.-L.J. ; investigation, [PERSON]-T.L.