Experimental study on the precise electrochemical machining of internal spur gears

Manufacturers are constantly facing new challenges in gear production, as conventional manufacturing processes are increasingly reaching their limits in terms of feasibility and cost-effectiveness when machining high-performance materials. In addition, thermal distortion after heat treatment requires undesirable and often time-consuming rework. An alternative manufacturing technology for the production of gear geometries is pulsed electrochemical machining (PECM). The manufacturing process, which is based on anodic metal dissolution, dissolves metallic materials regardless of their mechanical properties. As the tool is never in contact with the workpiece, the components are machined without damaging the boundary zones, without burrs and without wear to the shaping tool.
The study methodically examines the production of a internal spur gear with module 2 and 39 teeth using PECM. First, the electrochemical dissolution characteristics of a heat-treatable steel 1.8519 QT are determined using electrochemical material characterization in sodium nitrate according to DIN SPEC 91399. In the second step, the accuracy of removal is analyzed by means of experiments with an removal fixture at various process parameters. Based on the results, achievable gear qualities and production speeds are determined.
The results of the experiments show that the process accuracy is strongly affected by voltage and pulse length, but also by the material-specific ablation zones. The process accuracy was increased by selecting a removal zone with surface passivation. The requirements of the gear application were achieved without optimizing the design of the removal fixture. With the help of the used methodology, further applications of PECM technology can also be derived in order to be able to manufacture these cost-effectively and accoring to the requirements.