On the development of a dynamic cutting force model with application to regenerative chatter in turning

• Main Author: Cardi, Adam A.
• Published: Georgia Institute of Technology 2009
• Subjects: Chatter; Turning; Cutting force model; Dynamic cutting; Machining vibrations; Turning (Lathe work); Chattering control (Control systems); Mathematical models
• Online Access: http://hdl.handle.net/1853/28152

Turning is one of the most widely used processes in machining and is characterized by a cutting tool moving along the axis of a rotating workpiece as it removes material. A detrimental phenomenon to productivity in turning operations is unstable cutting or chatter. This can reduce the life of tooling, dimensional accuracy, and the quality of a part's surface finish because of severe levels of vibration. Ideally, cutting conditions are chosen such that material removal is performed in a stable manner. However, it is sometimes unavoidable because of the geometry of the cutting tool or workpiece. This work seeks to develop a dynamic cutting force model that can be used to predict both the point of chatter instability as well as its amplitude growth over time. Previous chatter models fail to capture the physics of the process from a first-principles point of view because they are oversimplified and rely on various "cutting force coefficients" that must be tuned in order to get a desired correlation with experimental results. The proposed approach models the process in a geometrically rigorous fashion, also giving treatment to the strain, strain rate, and temperature effects encountered in machining. It derives the forces encountered during a turning operation from two sources: forces due to chip formation and forces due to plowing and flank interference. This study consists of a detailed derivation of two new cutting force models. One relies on careful approximations in order to obtain a closed-form solution; the other is more explicit and obtains a solution through numerical methods. The models are validated experimentally by comparing their prediction of the point of instability, the magnitude of vibration in the time and frequency domains, as well as the machined surface topography during chatter.