Grinding forces in micro slot-grinding (MSG) of single crystal sapphire

Micro-slot grinding (MSG) is an important processing method for the micro-machining of hard brittle crystalline materials. Modelling the MSG of crystal material is necessary to understand its precision micro-machining aspects. In this paper, a predictive model is developed for the grinding force in MSG in three different orientations of single crystal sapphire: the C-orientation {0001}, A-orientation {112¯0} and R-orientation {11¯02} are established. The crystalline effects of the density of Al+, −Al+ and DAl+; the density of O− hollows DO−; the number of crystal layers ζ; and the weak shape of different orientations are incorporated. Three group experiments (144 paths) are performed, and the differences in the grinding forces from three orientations, {0001}, {112¯0} and {11¯02}, are discussed. The grinding forces of the A-orientation {112¯0} are higher than of the other two orientations {0001} and {1102¯}, and the number of crystal layers ζ is shown to play a vital role in determining the grinding force required for MSG of sapphire. The force ratio rF (Fx/Fy) is between 0.6 to 0.8, and the rF of {1102¯} is more stable than for the {112¯0} and {0001} orientations. A comparison with existing models and experimental data shows that the model used in this study fits the experimental data better, especially at lower feeding rates.