Investigation into the effects of drilling parameters on delamination by various step-core drills

Geometry and material of drill and drilling parameters have an essential influence on induced-delamination in drilling composite materials. Owing to the chips clogged inside the core drill, three step-core drills in drilling composite materials have been investigated in this study. The Taguchi method with orthogonal array of L18 (2 × 37) was selected to realize the effects of the drilling parameters (diameter ratio, feed rate and spindle speed) on induced-delamination for various step-core drill. The experimental results indicated that the diameter ratio, feed rate and spindle speed have significant influence on delamination and the best combinations found to be A2B1C3 (diameter ratio = 0.74 mm/mm, feed rate = 8 mm/min and spindle speed = 1200 rpm) for all step-core drills within the tested range. Besides, the effect of inside drill diameter and geometry for the step-core drill must be concerned on induced-delamination while first cycle drilling of composite materials.