| dc.description.abstract | Electrochemical machining (ECM), which is one of the non-traditional manufacturing processes, shapes workpieces by electrolysis. The advantages of ECM include not being affected by the hardness and strength of the material, no surface residual stress, fast processing speed, and no consumption of the tool. It is considered the enormous potentialities and highly added values.
The purpose of this study is to use a PCB board, combined with a tool and a mask, to process through-mask double-side electrochemical machining. Stainless steel 304 plate (0.5mm) is used as the workpiece. Grey relational analysis(GRA) is used to investigate the effect of experimental parameters, such as electrolyte concentration, applied voltage, diameter of the mask hole, and electrolyte flow rate, on the machining quality, and estimate the best combination of parameters. Compared with Taguchi method, GRA could have multi-objective optimization, while Taguchi has only single-objective optimization. Furtherance analysis of the distribution of taper angle and overcut on 6×6 array holes is also performed.
Through the experimental results, it can be found that the most important factors for the characteristics of finished product are electrolyte flow rate and electrolyte concentration. The best parameter combination is A_1 B_3 C_2 D_3 (electrolyte concentration 10wt%, applied voltage 22V, diameter of the mask hole 0.6mm, and electrolyte flow rate 3.74m/s.) The processing results were as follows: the average overcut was 0.263 mm, the average roundness error was 0.03mm and the average taper angle was 37.85 º. Compared with the original working condition(A_1 B_1 C_1 D_1 ), the GRA is increased from 0.6 to 0.79. In the distribution of the holes, the taper angle distribution in the horizontal arrangement shows that the taper angle is smaller near the electrode rod. In the overcut distribution, the overcut is larger near the electrode end. I will know the machining rate is faster than the part of middle. A wavy distribution on the overcut and taper angle are formed. Because the heat is from both ends of the electrode rods and the boundary layer effect, it cause the electrolyte temperature at both ends to be higher, the conductivity to rise, and the machining rate to increase. When the taper distribution and the overcut distribution are vertical arrangement, the downstream has a large overcut and a small taper. I determine that the downstream machining rate is faster than the upstream. Because the Joule heat accumulate on the downstream by the electrolyte flow from upstream. And the flow rate on the downstream is slower than the upstream. It cause the electrolyte temperature and the conductivity to rise. The machining rate increases.
| en_US |