Roughness characterization and formation mechanism of abrasive air jet micromachining surface studied by power spectral density

Roughness of abrasive air jet micromachining surface has a significant influence on electro-osmotic flow characteristics, optical properties and adhesion properties. The characterization of surface roughness based on power spectral density approach is studied. The formation mechanisms of surface topography are analyzed. The influence of process parameters on the roughness of abrasive air jet micromachining surface is discussed. The results show that surface profiles with close values of usual roughness parameters can be distinguished by power spectral density curves. The power spectral density curves can be classified into four categories based on the marked knee points on spatial frequency of 0.01 μm−1 and 0.1 μm−1 approximately. Power spectral density curve can be divided into three regions, namely, low frequency region, intermediate frequency region and high frequency region. The roughness of low frequency region and the roughness of intermediate frequency region play dominant roles in the surface roughness, while the contribution of the roughness of high frequency region is negligible. The low frequency region is associated with the overlap of craters. The intermediate frequency region is associated with the indentation removal mechanism and edge cutting mechanism. The high frequency region is associated with micro-dents removal. The roughness of low frequency region increases with an increase in air pressure, while it decreases with an increase in standoff distance. The roughness of low frequency region decreases firstly and then it increases with an increase in nozzle traverse speed. The roughness of intermediate frequency region increases firstly and then it decreases with an increase in air pressure, standoff distance and nozzle traverse speed. The Rq increases with an increase in air pressure, while it decreases with an increase in standoff distance. The Rq decreases firstly and then it increases with an increase in nozzle traverse speed.