Investigation on three-stage stamping of micro-channels with titanium ultra-thin sheet used for PEM fuel cell bipolar plates

To reduce the weight and volume, and extend the life of the proton-exchange membrane fuel cell (PEMFC) which is considered as a kind of near zero emission green energy, titanium ultra-thin sheet is selected to fabricate the core components — bipolar plates for its smaller density and high corrosion resistance. In order to break through the bottlenecks in the manufacture of micro-channels with big ratio of depth and width, a kind of three-stage stamping was investigated for its characters such as high productivity and low cost. Finite element (FE) simulation and optimization of three-stage stamping was carried out considering the reduction of thickness by analyzing the effect of the radius of punch and female die corner, punch displacement, and ratio of rib and channel width, etc. Then, the mold was designed, and experiments were performed using a servo drive machine. The arc design of punch end in the first stage can decrease the reduction of thickness from 47 to 22%. The best ratio between rib and channel width is 0.4–0.6, and radius of final channel corner is 0.15 mm. Experimental results of three-stage stamping show that the max reduction of thickness is about 24%, which is similar with that obtained from FE simulation. Microstructure with uniform small grain size and high surface quality are both helpful for improving the properties of bipolar plates required by PEMFC. This means that the developed three-stage stamping process is very suitable for massive manufacturing the bipolar plates with titanium ultra-thin sheet.