Pulsating electrolyte flow induced by workpiece vibration to enhance shape precision and surface quality of electrochemical drilling of square-small hole

The demand for high-aspect-ratio shaped holes in aviation is advancing electrochemical drilling (ECD). However, shape precision and surface quality for shaped holes (such as square holes) remain challenging. This study investigates flow-field distribution in ECD of square-small holes, revealing that the square tube electrode's non-axisymmetric structure causes an uneven flow field and a low flow velocity zone during traditional ECD, leading to electrolytic products accumulation and reducing both shape precision and surface quality. A novel workpiece-vibrated ECD (WV-ECD) method induces an intense pulsating electrolyte flow, enhances flow-field distribution, and eliminates low flow velocity zone. A multi-physics three-dimensional model of WV-ECD is developed to clarify changes in flow-field distribution. Experimental results show that with WV, the straightness error and surface roughness Ra of square-small hole are decreased from 78 and 5.798 μm to 17 and 0.828 μm; both shape precision and surface quality are significantly improved. Additionally, due to the efficient transport in electrolytic products, the distribution of current density across workpiece approaches theoretical “M” shape, and the maximum value is higher than that in traditional ECD, resulting in the change of bottom profile and improvement of machining efficiency. Optimal parameters achieved a 1.25 mm ± 0.01 mm square-small hole width, 0.644 μm Ra, 18 μm straightness error, and a 15:1 aspect ratio.