Theoretical and experimental study on hybrid laser and shaped tube electrochemical machining (Laser-STEM) process

Laser and electrochemical machining (LECM) is extensively researched due to its high efficiency and good surface quality. Laser and shaped tube electrochemical machining (Laser-STEM) is a novel hybrid process, in which both the laser beam and electrolyte jet are guided to the machining zone through the inner hole of a specially designed tubular electrode. This process could be utilized to process small holes with a larger depth and a higher controlled precision, compared with the existing LECM processes. In Laser-STEM, the direct laser processing and the enhanced electrochemical machining (ECM) rate allow the high-efficiency material removal. ECM that is synchronously occurred in the side gap guarantees the high surface quality of the processed small holes. Through the total internal reflection of the laser beam in the inner hole of the tubular electrode, the laser energy is transmitted to the machining zone in high efficiency, and the laser energy has been confined in the inner hole exit area. Theoretical and experimental results showed that the electric current density in the machining zone for ECM could be increased by the assistance of a laser, which enhances the material removal rate of ECM. With the self-developed experimental setup, microcavities with a depth of 2 mm and small holes with a depth of 5 mm have been fabricated. A comparison of the effects of various machining parameters shows that the machining precision and material removal rate were improved by 60.7% and 122.7%, respectively. Both the machining precision and the material removal rate could be increased by using higher laser power. The mechanisms of machining precision improvement by adopting laser to STEM were explored, considering the generation of the passivating layer in the machining zone. Laser-STEM was also adopted to fabricating three-dimensional structures such as groove and channel.