Evaluation of Surface Profile Parameters of a Machined Surface Using Confocal Displacement Sensor

Abstract

This paper describes the use of non-contact type chromatic confocal displacement sensor for estimation of surface profile parameters such as Ra, Rq and Rt of different machined surfaces. The confocal displacement sensor can measure surface roughness of the order of 5nm on conducting and non-conducting material. The surface irregularities of the profile measured over the evaluation length is related to the response of chromatic confocal displacement data. Confocal sensor response is analyzed to determine the displacement variations from the profile data points of the surface. Based on the confocal chromatic image principle, a new technique is used to measure the micro level surface finish. The new method is validated by measuring surface roughness of kwon specimen in the range of 1.6 - 3.2μm using an experimental setup developed and by stylus method. The estimated profile parameter values are in good agreement with the values obtained by stylus method and hence the confocal displacement based method can be implemented to measure surface roughness parameters.