Finite element modeling of low speed reaming vibrations with reamer geometry modifications

Reaming is a finishing process used to remove a small amount of material from a predrilled hole. In low speed cutting processes, it is the formation of lobed or multi-cornered holes that is of concern, rather than tool chatter, which occurs at high speed near the natural frequency of the tool. Using a quasi-static model in the characteristic form for the reaming process, a finite element modeling for the low speed reaming process, based on the Euler–Bernoulli beam model, was developed. Cutting and rubbing forces were applied as concentrated and distributed forces on a variable engagement length of the reamer. The variable engagement length is considered to simulate the actual applied forces length as the reamer advances to the workpiece. The time dependant changes in the bending stiffness of the reamer were included in the governing equation of the equilibrium of the reamer, and its stability analysis was performed at different time steps. Using this model, the vibration damping effect of uneven spacing of reamer teeth was investigated. The results demonstrate that uneven spacing of reamer teeth reduces the tool vibration, and therefore leads to a more stable condition. Finally, the optimum configuration of uneven tooth pitch angles for a six-flute reamer, in order to have the highest vibration decay rate during the reaming, was presented.