Multiple criteria optimization of finish turning operations based on a hybrid model

In this paper a multiple criteria optimization method is used to achieve the optimum selection of cutting conditions and tool inserts for finish turning operations. The utility function which maps criterion vectors into the real line is constructed based on tool-life and material removal rate. This unified objective function serves as an arbiter balancing the values of the individual objective functions. Different formats of utility functions are developed and their physical significance is analyzed. Other major machining performance characteristics such as surface roughness, cutting force, power requirements and chip breakability are used as constraints to define acceptable limits on these criteria, along with the limits on the ranges of the process variables. A hybrid process model which uses combinations of the metal cutting theories and an expandable database of experimental results is used to describe the interrelationships between the machining performance criteria and the process variables. Nonlinear programming techniques coupled with numerical methods for data interpolation are then applied to identify optimum process conditions for a given tool insert. Furthermore, for any specified application a cutting tool can be selected through comparative analyses. A sample case for a typical tool insert was studied and the results are presented.