Region-confined electrochemical float machining with conductive compliant tool

Ultrahard materials such as silicon carbide (SiC) are increasingly used in advanced optical and semiconductor applications that require atomic and close-to-atomic scale manufacturing (ACSM). However, its high hardness and brittleness present challenges to ultra-precision surface machining. This study proposes a novel electrochemical float machining (EC-FM) method for non-contact, high-efficiency machining of SiC surfaces. A flow electrochemical model based on fluid-structure interaction was established revealing that shear stress not only governs material removal but simultaneously enhances the local mass transport of oxidation reactants and oxide layer removal, thereby enabling region confinement of oxidation reaction, and the region confinement, which is further regulated by bipolar voltage. In-situ electrochemical characterization was performed to provide the theoretical insights for optimizing process parameters. Material removal rate (MRR) of electrochemical float machining method with silica slurry was significantly improved compared to float machining with diamond slurry. A saddle-shaped freeform with a Sag value of 25 nm and a shape error below 3 nm was fabricated. Low-voltage electrochemical polishing method achieved an atomically smooth surface with a surface roughness (Sa) of 0.103 nm.