Power Density

Power density for gear applications is strongly impacted by the load-carrying capacity of the mating gears’ teeth. Isotropic superfinishing can greatly improve the power density allowable by increasing the durability of a surface and derivatively its load-carrying capacity.

In terms of gears, durability under ISO 6336 considers pitting as the failure mode. For the roughness factor, the relative mean peak-to-valley roughness (Rz) is utilized, and as the roughness decreases, the permissible contact stress increases. Isotropic superfinishing lowers the Rz of a surface to below 1 µm, which generates a much more durable surface.

How significant of an improvement can be derived? Durability in the form of pitting resistance is an area that has been extensively researched in regards to isotropic superfinishing technology. One such study by Paul Niskanen et al.[1] reviewed the impact of isotropic superfinishing on spiral bevel gears using a power circulating pitting (contact) fatigue testing rig. This study showed how isotropically superfinished gears with an Ra of 2-3 µin exceeded the baseline failure results of a precision ground gear with an Ra of 9-12 µin by roughly threefold. Similar results have been obtained across a range of formal testing procedures and scenarios encompassing differing gear designs and applications.

REM’s ISF® and Rapid ISF® Processes maintain gear flank form and significantly reduce gear flank roughness while producing an optimized surface texture. These gear quality improvements open two potential design optimization routes: to apply more load to the surface, given its greater durability, or to reduce the flank width while maintaining the same load thereby reducing system weight (note—reducing flank width/gear size assumes that bending fatigue is not a design limit). Either option increases the power density of a gear system. Alternately, the increased power density allowable/load carrying capacity can be used as an increase to the operating safety margin of the gear system. In any case, the gear system has been improved.

REM’s ISF Technologies can be applied to very wide ranges of components types, sizes, and metals. These processing technologies are available via outsourced processing at a REM facility or as technology installations at a customer site. Contact us today to learn more or to start a project.


[1] Niskanen, P. W., Manesh, A., Morgan, R., “Reducing Wear With Superfinish Technology,” AMPTIAC Quarterly, Volume 7, Number 1-2003, pp. 3-8.