Studies on the fabrication of metallic bipolar plates—Using micro electrical discharge machining milling

Owed to the advantages of highly precise and flexible machining, micro electrical discharge machining milling (micro EDM milling) can machine higher aspect ratio micro flow channels than the micro flow channels made from etching or deposition techniques, which have aspect ratio of only 0.5–0.7.This study reports on the production of micro flow channels in metallic bipolar plates, using micro EDM milling. Through the use of micro EDM milling with tungsten carbide electrodes, this study succeed in machining channels with a depth and rib width of 500 μm, and height of 300 μm, 600 μm (aspect ratio of 0.6 and 1.2), respectively, in a reaction area 20 mm × 20 mm, on 50 mm × 50 mm × 1 mm SUS 316L stainless steel.In single cell tests, the cell performance in metallic bipolar plates with aspect ratio of 1.2 is higher than that of other tests, and this result shows that the aspect ratio can promote performance of micro fuel cells. Moreover, under the same condition regarding cell size, single cell performance in metallic bipolar plates of aspect ratio of 1.2 with micro EDM milling in this study is higher than the performance in metallic bipolar plates with electroforming or electrochemical machining techniques, and the metallic bipolar plate can promote power per unit volume.

Research highlights▶ Micro EDM milling can machine micro flow channels of high aspect ratio. ▶ This study succeed in machining channels with aspect ratio of 0.6 and 1.2. ▶ The power density of channel aspect ratio of 1.2 was higher than that of 0.6.