Abstract
Background: Ultraprecise nano-level surface finish is required in those machine components, which have relative motion among them. Especially in gears that are subjected to heavy wear due to sliding motion, surface finish is one of the critical parameters, which leads to its noisefree operation, efficient power transmission, and longer service life. However, most of the gear manufacturing processes do not produce nano finished gear surface. Therefore, gears need post-processing to finish their surface.
Objective: The present study aims to improve the surface finish of helical gears of different helix angles with the help of abrasive flow finishing (AFF) by experimentally identifying the optimum range of processing parameters.
Methods: An AFF set up was used for gear finishing using a medium of styrene-butadiene rubber and silicon carbide abrasive. A special type of fixture was developed, which allows the back and forth movement of AFF medium through the annular volume between the fixture and the gear, and at the same time, firmly holds the gear.
Results: The optimum combination of the extrusion pressure and abrasive weight percentage is 38 bar and 39.6% that produces the best results with around 75 and 69% improvement in Ra for gear of helix angle 30 and 45°, respectively.
Conclusion: Among all studied processing parameters, extrusion pressure and abrasive % were found to be the most influential parameters. The inclination angle between the incoming flow stream of medium and workpiece surface strongly influences the surface finish. This is due to the change in forces acting during finishing with the inclination angle. The helical gear of a smaller helix angle of 30° shows a better surface finish of 110 nm than 124 nm in a helix angle of 45°.
Keywords: Helical gear, helix angle, surface roughness, rheology, abrasive flow finishing, silicon carbide.
Graphical Abstract
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