Fabrication of deep micro holes by laser and electrochemical machining based on laser transmission utilizing optical fiber: A theoretical and experimental study

Hybrid laser and electrochemical machining (LECM) enables high-efficiency and high-surface integrity machining of difficult-to-machine materials. However, the performance of LECM was affected by laser coupling accuracy and stability, and the flexibility of the hybrid machining head was limited. This paper proposed LECM based on laser transmission utilizing optical fiber (LECM-OF), which achieves the integration of optical fiber and hybrid machining head using an optical base. The hybrid machining head could move in all directions without affecting the laser coupling by virtue of the high flexibility of the optical fiber. The effects of laser power, inner diameter of hybrid tubular electrode, electrolyte concentration, and pressure on laser coupling efficiency were explored. The distribution of the laser power intensity could be regulated by controlling the inner diameter. A higher laser coupling efficiency could be obtained with the lower electrolyte pressure and concentration, and the smaller inner diameter. A laser coupling efficiency of 67% was achieved with the optimal parameters. Moreover, simulation of LECM-OF was conducted to investigate the profile evolution of the micro holes and the effects of the laser on the distribution of temperature and current density. Experiments were carried out to verify the simulation results. The maximum feeding rate of the hybrid tubular electrode was increased by 133.3% during LECM-OF with a coupling power of 10 W compared with that without a laser. Finally, deep micro holes with a diameter of 0.8 mm and a depth of 10 mm were processed by using LECM-OF, free of recast layer and microcracks.