Comparison Between 2D And 3D Surface Roughness Parameters For EDM Surfaces
For many decades engineers and researchers have been using two-dimensional (2D) instruments to measure the roughness of a surface. Several 2D surface roughness parameters have been developed, and have emerged in different countries where researches in the area of surface metrology were carried out. The most common of these is the arithmetic mean roughness (Ra), which was previously known as centre line average (CLA). However, in reality surfaces interact in three-dimension (3D), and specifying 2D surface roughness parameters can be quite restrictive and misleading. The aim of this paper is to present some results of 2D and 3D surface measurements, and to evaluate their relative merits. As part of a research programme, extensive electro discharge machining (EDM) was done so as to generate different spark eroded surfaces. Through surface texture measurements, it has been confirmed that the use of 2D parameters alone is indeed misleading. Thus, in order to comprehensively represent the topography of a surface, a combination of 3D amplitude, spatial, and volume parameters should be used.
Keywords: Electro Discharge Machine, Surface Roughness, Surface Topography, Tribological properties.