Material removal during abrasive impregnated brush deburring of micromilled grooves in NiTi foils

• Brush deburring applied to micromilled grooves in 25 µm NiTi foils.
• Material removal mechanism is by chips and breaking off of deformed material.
• Domination of initial contact forces at 7 m/s tip velocity.
• A Hertzian static indentation model is used to predict indentation rate.
• Paris equation based model is used to predict deburring brush passes.

While abrasive impregnated brushes have been used extensively for deburring of machined parts, understanding of the associated mechanics of material removal is lacking. This paper investigates the dependence of brush deburring rate, surface roughness and change in foil thickness on spindle speed and brush nominal penetration during brush deburring of 25 μm thick Nitinol (NiTi) foils. Analysis of the surface after brushing shows that both ploughing and chip formation occur in the process. It is also seen that at bristle tip velocities of about 7 m/s the penetration of abrasives into the foil is dominated by initial contact forces while at about 2 m/s it is dominated by bristle stiffness. Long, slender burrs are removed by fatigue fracture under cyclic loading of the bristles. Burr roots are removed in small chunks as cracks formed by abrasive indentation propagate under cyclic loading of the bristles. A model based on Hertzian contact mechanics is proposed to predict the rate of indentation during brushing and is validated using experiments. The surface roughness initially reduces but subsequently increases with further brushing. Change in foil thickness in all cases is ≤1 μm. A fracture mechanics model for predicting the deburring rate is also proposed and validated.