Investigation of influence factors on surface roughness of micro-scale features

Surface roughness is an important indicator of surface quality. With the miniaturization of parts, the influence of surface roughness on dimensional accuracy is increased. In this paper, factors affecting the surface roughness of micro-scale features are studied based on extrusion forming. For this purpose, the surface roughness of micro extrusion samples under different forming loads and microgroove sizes are measured using white-light interferometer. The surface roughness of micro-scale feature is increased with the decreasing forming load or microgroove size. To investigate the effects of contact surface enlargement, normal pressure and the sliding distance between the specimen and the die on the surface roughness, finite element analysis of the micro-extrusion processes is performed. Results indicate that the influence of contact surface enlargement and normal pressure are mostly visible at the initial stage of micro-extrusion. At the stable stage, the influence of these two factors on the surface roughness can be neglected. The sliding distance between the specimen and the die is the primary reason factor affecting the surface quality where the surface roughness is decreased with increasing sliding distance. In addition, there exists the size effect of surface roughness under various microgroove sizes. Smaller microgroove sizes have a greater impact on the surface roughness with the change of sliding distance. This phenomenon is mainly correlated to the contact normal pressure at the initial stage in the micro-extrusion process.