Investigation of dimensional accuracy in forming of metallic bipolar plates with serpentine flow field

In this study, the dimensional accuracy of metallic bipolar plates with stainless steel 316 was investigated in diagonal, longitudinal, and transverse direction (directional dimensional accuracy). The results showed that directional dimensional accuracy (uniformity of channel depth) would increase by raising the applied force. In addition, increasing the rubber hardness and rubber thickness leads to higher directional dimensional accuracy. After that, the dimensional accuracy in constant direction (total dimensional accuracy) was investigated. According to the result, central channels have lower channel's depth than lateral channels. Difference between central and lateral channel's depth was decreased when the applied force was increased. Also, total dimensional accuracy increased by increasing hardness and thickness of rubber. Most accurate bipolar plate is fabricated by 450 kN applied force and rubbers with hardness of Shore A 90 and 30 mm thickness. However, dimensional accuracy in conventional rubber forming process was not satisfying. Thus, a new method was used in order to improve the dimensional accuracy of fabricated bipolar plates named semi-stamp rubber forming. The results indicated that using semi-stamp rubber forming instead of conventional rubber forming would lead to 8.35, 3.72, and 3.3% improvement in directional dimensional accuracy and also 1.075% improvement in total dimensional accuracy.