On the bistable zone of milling processes

Area of Science:

• Mechanical Engineering
• Nonlinear Dynamics
• Manufacturing Processes

Background:

• Milling processes are susceptible to chatter, a vibration phenomenon that degrades surface quality and tool life.
• Bistability in milling systems, characterized by 'unsafe zones,' can lead to unexpected transitions from stable to unstable cutting conditions.
• Understanding the complex dynamics, including unstable quasi-periodic solutions and secondary Hopf bifurcations, is crucial for predicting and preventing chatter.

Purpose of the Study:

• To develop a modal-based model for milling machine tools under time-periodic nonlinear cutting forces.
• To identify and characterize the 'unsafe zones' of bistability in milling parameters.
• To provide a method for predicting chatter occurrence even within linearly stable parameter domains.

Main Methods:

• A modal-based model was developed to represent milling tool dynamics.
• A semi-numerical method was employed to track tool edge motion and identify bistable zone boundaries.
• The method involves tracking unstable quasi-periodic solutions and their proximity to a switching surface in phase space.

Main Results:

• The model successfully describes bistability, leading to 'unsafe zones' where chatter can be induced by perturbations.
• The semi-numerical method effectively identifies the borders of these bistable zones.
• The approach allows for the estimation of parameter domains where chatter may still occur despite linear stability.

Conclusions:

• The developed model and method offer efficient support for designing milling processes with improved chatter prediction.
• This work aids engineers in avoiding undesirable chatter by identifying critical parameter domains.
• The findings contribute to enhancing the stability and reliability of milling operations.