Prediction of thrust force of step drill in drilling composite material by Taguchi method and radial basis function network

Abstract

Among material secondary machining, drilling is the most frequently applied factor to composites needing structure joining. Drill geometry is considered the most important factor that affects drill performance. A major concern in drilling of composite materials is the delamination that occurs in the exit as well as in the entrance planes. The delamination damage caused by the tool thrust is known as one of the major concerns during the drilling process. The thrust force of step drill with drilling parameters (step angle, stage ratio, feedrate and spindle speed) in drilling carbon fiber reinforced plastics (CFRP) laminates were experimentally investigated in this study. The experimental results indicate that the step angle, stage ratio, and feedrate are the most significant factors affecting the overall performance. The optimal combinations, such as A2B2C1D3 (i.e., step angle = 100 ° stage ratio = 0.4 mm/mm, feedrate = 0.01 mm/rev and spindle speed = 1,200 rpm), were used under the adopted drilling condition. An experimental approach to the prediction of thrust force produced by step drill using linear regression analysis of experiments and radial basis function network (RBFN) were proposed in this study. In the confirmation tests, RBFN (errors within 0.3%) has been shown to be a better predictive model than multi-variable linear regression analysis (errors within 28%) for quantitative prediction of drilling-induced thrust force in drilling of composite material.