A model for surface roughness in ultraprecision hard turning

Numerical modelling procedures to predict surface roughness in turning processes have been in use for more than forty years. However, the procedures available to date do not correlate well with hard turning. A novel numerical model is presented which incorporates process disturbances such as tool cutting edge defects and machine vibration in hard turning and thus their effect on the achievable surface roughness. It includes a material partition equation to address the behaviour of chip removal and deformations during the cutting process; it also allows additional information to be derived about the mechanism of generation involved at a given point on the surface. Experimental results show good correlation of calculated with measured roughness parameters even at low feed rates.