Forced running-in lubrication is a method for smoothening tooth flank roughness on new or turned large gears during operation. It is used when running-in with stepwise load increase over a longer period is not possible.
The effect of forced running-in lubrication is based on the principle of material removal. Enough material is removed to ensure optimum long-term operation, but no more than is technically safe. For forced running-in lubrication, the same speciality lubricant (type D) as for repair lubrication is used. It removes considerably more material than B-type lubricants.
The hardened layer on the gears is hardly affected. Only a few µm to several 1/10 mm of material is removed. This method aims at reducing the remaining roughness of the newly manufactured gears as fast as possible upon commissioning in order to increase loads rapidly. It is vital to prevent the tooth flanks from being overstressed or even suffering damage such as scuffing, cold welding or initial pitting as may arise from insufficient lubricant film formation.