Drop-on-Demand Printing as Novel Method of Oil Supply in Elastohydrodynamic Lubrication

The feasibility of drop-on-demand printing as a novel method for oil supply in elastohydrodynamic lubrication was tested for a single ball-on-disk contact to allow precise lubrication control at a minimal level of lubricant. It is shown that it is feasible to jet droplets of 3.3 pL for an oil of 46 mPa s viscosity at a controlled frequency which, for the conditions considered, results in droplets on the surface with a radius significantly smaller than the Hertzian contact radius. Experimental results of the film thickness evolution over time are presented from dry contact to fully flooded contact with different supply frequencies and a total oil usage of approximately 40 nL. By means of numerical simulation, the details of droplet ingestion into the contact are illustrated. It is shown that the central film thickness over time can accurately be predicted. The theoretical and experimental results provide a very strong incentive for further investigation of drop-on-demand printing as method to achieve optimal (re)lubrication at minimum level in the realistic setting of a rolling bearing.