한국정밀공학회 2013 년도 춘계학술대회논문집
1. Introduction
Recently, the utilization of electrochemical discharge machining (ECDM) has proved to be a potential technology for enhancing the machining efficiency and accuracy in micro-milling for glass. However, the surface quality and edge shape quality are the main disadvantage of this process. In this study, a hybrid machining process of ECDM and micro grinding using polycrystalline diamond (PCD) tools was researched. The machining characteristic of micro ECDM as well as micro grinding PCD were studied. Finally, various channels were fabricated with good surface quality, and sharp edge by this hybrid process in Quartz instead of Glass material.
2. ECDM process
(a) 10 µm/s (b) 20 µm/s
(c) 40 µm/s (d) 100 µm/s Fig. 1 Effect of feedrate in ECDM process
The machining voltage type has a great influence on the discharge performance of ECDM process. For
enhancing the surface quality as well as machining efficiency, the offset voltage should be used instead of DC voltage or pulse voltage. When using the high pulse voltage or offset voltage, the feedrate can be increased significantly [1]. However, the surface quality gets bad and the edge of channel also cannot be sharp because of the heat affected-zone.
Figure 1 shows the effect of machining feedrate in ECDM process. As the figures, lower feedrate will result in deeper micro-channels, but the quality of the micro-channel will be decreased. Conversely, the tool will be broken if the feedrate is too high and larger than material removal rate. By using suitable pulse voltage and offset voltage, the high temperature at the tip of the tool can transfer to the bottom of groove at a short time and soften this layer. Therefore the tool can remove soften material by squeezing process. Finally, various micro channels in Quartz can be fabricated with machining condition: Ø 350 µm tool diameter, 40 V pulse voltage, 25 V offset voltage, 0.5 ms/0.5 ms pulse on/off-time ratio, 500 rpm rotational speed, 10 µm machined layer depth, 70 µm/s feedrate, 60 µm micro groove depth.
3. Micro grinding
Micro grinding using PCD tools is a well-known process that improves machining surface in glass material with low feedrate [2]. However, the characteristic of Quartz is different. In this study, the effect of tool feedrate and rotational speed were researched using the PCD tool 300 µm in diameter
전해방전과 미세연삭을 이용한 석영의 미세 채널 가공
특성
Micro channel machining in quartz by ECDM and grinding
응웬하1, 이평안1, *#김보현1
K. H. Nguyen1, P. A. Lee1, *#B. H. Kim([email protected])1 1숭실대학교 기계공학과
Key words : ECDM, Quartz, PCD
한국정밀공학회 2013 년도 춘계학술대회논문집
with Quartz material. Fig. 2 shows the machined surfaces with different machining condition. The results showed that the surface quality is better with feedrate of 0.5 µm/s and rotational speed of 3000 rpm.
(a) 3000 rpm, 0.1 μm/s (b) 3000 rpm, 0.5 μm/s
(c) 3000 rpm, 1 μm/s (d) 4500 rpm, 0.5 μm/s Fig. 2 The groove surfaces ground by PCD tool with
different rotational speed and feedrate
(a) After ECDM (b) After grinding
(c) After ECDM (d) After grinding Fig. 3 Comparison surface quality and edge shape
quality between ECDM and hybrid machining After ECDM process, the surface quality is not good, and the edge is not sharp because of heat affected-zone in ECDM process, so it is necessary to improve the surface quality as well as make sharp edge for the channel by grinding. Figure 3 shows that the surface quality was increased significantly and
the rims and edges are sharp after grinding process. 4. Conclusion
The machining process combining ECDM and micro grinding was used to machine the micro channel in quartz. The micro channel of 390 μm in width, 60 μm in depth can be machined with good surface quality and sharp edges by hybrid machining process.
ACKNOWLEDGEMENT
"This research was supported by the MKE(The Ministry of Knowledge Economy), Korea, under the Convergence-ITRC (Convergence Information Technology Research Center) support program (NIPA-2013-H0401-13-1004) supervised by the NIPA
REFERENCES
1. Abou Ziki, J.D., T. Fatanat Didar, and R. Wüthrich., “Micro-texturing channel surfaces on glass with spark assisted chemical engraving,” International Journal of Machine Tools and Manufacture, Vol. 57, pp. 66~72, 2012.
2. Cao, X.D., Kim, B.H. and Chu, C.N., “Hybrid Micromachining of Glass Using ECDM and Micro Grinding,” International Journal of Precision Engineering and Manufacturing, Vol. 14, No. 1, pp. 5~10, 2013.
