In-process tool life evaluation by cutting force ratio analysis

Abstract

Optimization and control of automated manufacturing processes have been rendered difficult due to the probabilistic nature of tool life. Several adaptive control systems, developed to monitor machining operations, have been relatively unsuccessful due to the nonavailability of a performance index for the process evaluation. The ratio of the tangential component of cutting force to the feed force in turning processes is used as an index for the measurement of in-process tool wear. The relationship between the cutting force ratio, tool wear and cutting conditions is investigated. The statistical design of the experiment used in this research is a central composite design consisting of a 2('4) factorial experiment. General linear models and stepwise regression methods are used to develop the postulated first and second order models for the cutting force ratio. Analysis of the experimental results indicates that the force ratio is a function of the cutting tool flank wear. The force ratio, in most of the cases, decreases with the increase of flank wear. The relationship can be represented, with acceptable accuracy, either by first or second order equations. During machining of steel, the Hafnium Nitride coated tools have negligible crater wear as compared to the uncoated tools. The type of tool significantly affects the force ratio. Hence, the force ratio models have been developed separately for coated and uncoated tools. ...