Numerical and experimental investigation on grinding-induced exit burr formation

Exit burrs are easily generated on workpiece edges. In grinding process, particularly, exit burrs could deteriorate the highly required precision and even affect the functionality of components. Therefore, to understand the burr formation mechanism and control it in grinding process is of great significance. To this end, this paper investigates the features and mechanism of exit burr formation, as well as the influence of grinding conditions including grinding speed, grinding depth, wheel granularity, and grinding pass sequences on the exit burr formation of 12CrMoV stainless steel using the Al2O3 grinding wheels. A 3D finite element (FE) model of single-grit scratching process was developed for explaining the exit burr formation procedures. The effects of different grinding conditions on the exit burr sizes were analyzed, and the characteristics of the exit burr sizes and hardness were observed via experiments. It was found that the whole procedure of exit burr formation during grinding could be divided into six stages: steady-state grinding, pre-initiation, appearance of the fourth deformation zone, formation of plastic deformation band, burr development, and finish of burr formation. The burr sizes were strongly determined by the wheel granularity and grinding depth, rather than the grinding speed. For the same required grinding depths, using whether single pass or multiple passes of the grit has a very small impact on the exit burr sizes. The hardness of the burr root part is relatively stronger than that of the burr rollover part, while the burr hardness would increase when decreasing the grinding depth.