Effects of magnetism on the roughness of drilled holes of a glass fiber reinforced polymer composite material

Abstract

Have superior properties of the glass fiber reinforced polymer (GFRP) composite materials, the use of it is being accelerated recently. That is why the machining of these GFRP materials is a great concern for engineers. It became relevant for the researchers to analyze and introduce to improved machining. One of the most conventional way of machining is drilling process. Drilling is the mostly used in hole creating method in conventional machining. Hole creation in these composite materials is also mostly done by the drilling process. But the laminated structure of the composite material caused several types of damages and other surface irregularities during drilling process. About 60 percent of the rejections in the assembly plant are caused by the defects in the holes. The main contributor for defects in holes in the machining of the composite materials is surface roughness. These defects would create reduction in structural stiffness, which may lead to variation of dynamic performance of the whole structure. Hence, achieving the desired hole quality is of great importance for the functional behavior of the mechanical parts. In this present work, an observation is made on the effect of the permanent magnets of different magnitudes. Experiments are performed under different magnetic drilling conditions of spindle speed, feed rate and drill diameter on CNC drilling machine using three levels of factors with three different magnets of different magnitudes. A procedure has been adopted to assess and optimize the chosen factors by the use of Box-Behnken design to analyze the effects of different parameters. From the experimental results, it has been observed that the technique used is convenient to predict the main effects and their interaction effects of different influential combinations of machining parameters on surface roughness. It has been found that effect of permanent magnets on the guiding mechanism of the drill bit which lead to get improved surface roughness with better circularity ii compared to normal drilling processes and with the increase of the magnitude of the magnets, the results became better. A mathematical model has been developed for the prediction of surface roughness using permanent magnets and normal drilling processes.