Modeling and prediction of surface roughness profile in longitudinal turning

This paper presents the methodology for modeling and predicting the roughness profile shape in longitudinal turning. The research considers the roughness profile as the sum of two profiles designated as Rkinem.−geomet. and Rdistorting. The profile Rkinem.−geomet. is the theoretical profile obtained as the result of the kinematical-geometrical copying of the cutting tool onto the machined surface. The input values for the modelling Rkinem.−geomet. are the feed f, the nose radius rε and the angles λs,γo,κr. Rdistorting is the profile obtained as a result of the impact of the other cutting conditions and factors that do not participate in the formation of Rkinem.−geomet. The shape of Rdistorting directly depends on the condition of the surface roughness formation process. The Parameter of statistic equality of sampling lengths in surface roughness measurement (SE) indicates the condition of the surface roughness formation process. The proposed methodology was verified on work pieces made of 42CrMo (EN) using finishing inserts. The predicted and measured roughness profiles were compared using the following indicators: visual comparison of the roughness profiles, the Ra,Rp,Rv and Rz parameters respectively, the material ratio curves and the histograms.