Fabrication of micro gear with intact tooth profile by micro wire electrical discharge machining

Micro wire electrical discharge machining (micro-WEDM) provides a promising alternative for micro gear machining. However, the processing defect of non-intact tooth profile often appears due to the influence of micro gear gravity, flushing force and explosive force in micro-WEDM process. This paper presents a process change of micro-WEDM to achieve the precise fabrication of micro gear with intact tooth profile, i.e. firstly reserving a sharp corner on the gear teeth where the processing defect exists and then removing it by the second processing of micro-WEDM. The locating and clamping of the micro gear with sharp corner has been achieved using a novel self-centering flexible fixture. The machining error during the second processing is analyzed, and whilst the process datum is accurately determined. Appropriate processing parameters are obtained by performing preliminary experiments on X153CrMoV12 workpiece, indicating that high open voltage and discharge capacitance cause large kerf width, moderate reference voltage and feed rate lead to narrow kerf width. The static contact between the core jig of the fixture and the micro gear with sharp corner is theoretically analyzed using ABAQUS software and experimentally proved to be in good condition. To verify the feasibility and repeatability of the proposed approach, five micro gears with 10 gear number, 0.1 mm module and 2 mm tooth width are machined using 50 μm diameter wire electrode, exhibiting excellent conformity, machining error with less than 1.5 μm and surface roughness Ra with 0.9 μm.