Regulating electric field with electrode rotation to enhance surface quality in sinking electrochemical milling of groove

Abstract

This research introduces a method of regulating electric field with electrode rotation to enhance surface quality in sinking electrochemical milling of groove. A tube electrode with partial insulation on sidewall is employed, when the exposed part of tube electrode’s sidewall faces the machining area, the power supply is activated for material dissolution and then switched off if the exposed part rotates to already machined area, reducing stray corrosion. Based on the correlation between electrode rotation angle and power supply state within one full rotation, four regulation modes were developed. In mode 1, power supply keeps switch-on during a full rotation of electrode, and the on-time ratio is 100 % (360°/360°). The ratio is 50 % (180°/360°) in mode 2, as the power supply is switched on in half of rotation. It’s 40 % (144°/360°) in mode 3, and 30 % (108°/360°) in mode 4. Simulations revealed that the already machined area suffered from pulse current density with peak gradually decreased in mode 1, exposing it to low current density. This issue was effectively eliminated in other modes. Experiments showed a significant reduction of corrosion pits on already machined surface from mode 1 to mode 4, with surface roughness decreased from 2.78 μm to 1 μm. Oxygen content in the already machined area also decreased. Further analysis indicated that uneven breakdown of oxide films at low current density led to poor surface quality of already machined area, and mode 4 effectively prevented this, enhancing surface quality. This research advances sinking electrochemical milling for high-quality manufacturing.