Formability improvement of hot embossing for functional micro-array structures with a novel exhaust punch

Surface microstructures can endow materials with excellent functions such as enhanced heat transfer. However, with the continuous improvement of function enhancement, it is urgent to develop the manufacturing technology of more complex multiscale functional microstructures. Herein, an exhaust hot embossing based on a novel multi-block assem-bled punch is developed to fabricate micro-array structures, and the microformability of conventional process and exhaust process is compared. The combined processing tech-nology of slow-feeding wire cut electrical discharge machining and micro electrical discharge machining is adopted to manufacturing the assembled exhaust punch with numerous micro-holes and complex multiscale features. The processing quality of the assembled punch is better than the integrated punch, and the surface roughness of each position of the assembled punch is Ra < 0.2 mm. During hot embossing experiments, it is found that the exhaust process could significantly improve the filling performance. At 300 degrees C, the exhaust process realizes complete filling of the microstructures under the maximum load of 25 kN, whereas the conventional process requires 50 kN. Meanwhile, it is also found that the exhaust process can significantly improve warping and surface coarsening defects compared to the conventional process. The pool boiling test was carried out on the fabricated micro-array structures, and it was found that its heat transfer per-formance is significantly enhanced compared with other tested surfaces, which will be applied in enhanced heat transfer.(c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).