A nested circle-fitting method for micro-hole centering and its application in electrochemical deburring

To solve these problems (i.e. the accuracy rate and stability of the centering) of enabling secondary machining of micro-holes with a size of 0.1 to 1 mm in high-performance metal alloy parts, a non-standard nested circle-fitting least-square method, with a linear constraint passing through the center (least square method with linear constraint [LSLC]), is proposed in this article. The experimental results show that the center of the circle is fitted with a maximum deviation of ±1.5 µm and good fitting precision, compared to other existing approaches. At the same time, the accuracy rate is increased by at least 20%, delivering a result of more than 99%, so the accuracy of the fitting and the stability of the centering are significantly improved. Finally, the new method is applied in actual micro-hole electrochemical deburring study. With the overall goal of ensuring centering, a rough-and-fine deburring process has been explored. On the premise that the hole is not expanded, the burrs have been quickly and completely removed, and machined surface roughness, Ra, has also reduced from 1.2 to 0.52 µm. The experiment has provided concrete validation of the feasibility of the nested circle-fitting method we have proposed.