Simulation of Torsional-Axial and Lateral Vibration in Drilling, Seyyed Ghazanfar Moosavi, 2008

Abstract:

Drilling process is one of the common traditional machining operations. Due to time inefficiency of the drilling process, it is considered as a critical operation that considerably affects the time of the whole machining process. Therefore, finding optimal conditions which result in increase in material removal rate (MRR) is of great importance. In order to increase cutting velocity, width of cut and feed, drilling system should be dynamically analyzed. Stability of the operation should also be investigated in different operational conditions. One of the widely used methods for stability analysis of cutting process is time domain simulation. This method involves finding an accurate general force model in order to predict applied forces during drilling process. In this research a new force model has been proposed which are validated using experimental tests. Simulation of torsional-axial vibration is carried out using Bayly's vibration model. This model is based on the fact that when twist drills “untwist", it extend in length. In other words, both twisting and axial deflection are coupled. Boundary conditions which are considered in simulation of lateral vibration are decoupled in to two parts so that they can mimic boundary conditions of the drilling process more realistically. Boundary conditions in start of drilling operation are considered to be clamped-free. They changed to clamped-pin conditions for the rest of operation when drill is completely engaged in the hole. Applying these boundary conditions, dynamic unreformed chip thickness is also determined. Simulation of lateral vibration is carried out using the proposed force model. Simulation results are verified by experiments.

Keywords:

­Drilling Simulation, Force Prediction, Lateral Vibration, Bayly's Vibration Model