A Dynamic Model of the Cutting Force System in the Turning Process
 
 

William Joseph Endres | UIUC | MS | 1990

ABSTRACT:

The scope of this thesis is to develop a dynamic cutting force model for the turning process and implement the model as a computer simulation. Some of the important process attributes to be considered are tool and workpiece dynamics and their affect on the cutting conditions and process geometry via displacement feedback. The tool and workpiece dynamics must be modeled in a manner fit for application as a computer process simulation while still maintaining enough complexity to accurately describe the actual process. Also, the displacement feedback must be properly applied to the process inputs with respect to coupling effects between each degree of freedom and the different process inputs.

The primary objective of the model is to predict the dynamic cutting forces and the machined workpiece surface geometry. These objectives are accomplished by implementing the dynamic model as a computer simulation. the simulation must be designed to accomodate varying input for workpiece geometry, nominal tool material and geometry, annnd nominal cutting conditions. The simulation output is to be presented in both a report of numerical results as well as a graphical format. In addition, the model is to predict the onset of chatter as a result of process instability. In other words, chatter as a result of excitation of the machine tool itself are not considered in this work.

Finally, a series of experiments are performed to calibrate the model and to verify the model predictions over a range of process inputs. In the model coditioning and verification, the primary interest is that of correct modeling of the tool and workpiece dynamics and the effects of displacement feedback. In particular, the tests are run in such a manner as to isolate tool and workpiece dynamics so the effects of each can be observed independently.

The remainder of the thesis is divided into the following chapters. Chapter 2 is a review of the literature pertaining to metal cutting process modeling and dynamics. Chapter 3 discusses the development of a dynamic model from a theoretical perspective. The development and final solutions of the equations of motion are presented with references to appendix A for rigorous solutions. In addition, process inputs and their dependence on the process displacement feedback are considered. Chapter 4 focuses on process disturbances and stability. In this chapter, disturbances are classified as internal and external and effects of each on process performance and stability are examined. Chapter 5 discusses the implemntation of the dynamic cutting force model as a computer simulation program. Specifically, chip load equations are derived and solved for all combinations of tool profile geometry with Appendix B refernced for rigorous equation derivations and solutions of the chip load integrals. In addition, verification of the model and comparisons of actual and predicted process outputs are discussed. Finally, Chapter 6 summarizes the results obtained in this research. In addition, this chapter provides recommendations for model improvements and further work in this area.

If you have any comments or suggestions please e-mail jwsuther@mtu.edu.