Lapping of Electrical Discharge Machining Processed Tool Steel Surface Using Elliptical Tool Motion

A prototype lapping machine, which finishes surfaces by applying elliptical motions to a lapping tool in the presence of diamond compound, is developed. This paper describes the structure of the lapping machine, the 2-dimensional tool motions measured on the machine, the behavior of the diamond compounds between the tool and lapping surfaces, and the fundamental lapping performance. The tool motions are measured using a laser Doppler vibrometer and the proportional constants that are needed to obtain an objective tool motion are determined with the regression technique. The motion behavior of the diamond abrasive grains for each tool motion is directly observed with a microscope through a glass plate. Lapping experiments are conducted under the conditions with and without the work-feed. After lapping, the workpiece surface is measured using a surface profilometer for surface roughness and profile information. As a result, a surface roughness of less than $0.1μmRa$ is achieved using a $3μm$ compound and near-circular tool motion of $12.5μm$ radius.