Influence of different cooling methods on drill temperature in drilling GFRP

Abstract

Drilling of composite materials is difficult to carry out due to their anisotropic and non-homogenous structure and the high abrasiveness of their reinforced constituent. This results in high temperature during drilling, leading to rapid wear development in the cutting tool. The present work investigates the drilling of glass fibre-reinforced polymer composites with TiN/TiAlN-coated carbide drills on a computer numerical control (CNC) lathe for different cooling conditions. The objective of this work is to study the influence of different cooling conditions on drill bit temperature and drill bit wear. The signal to noise (S/N) ratio and analysis of variance (ANOVA) were employed to analyse the effect of cooling condition on drilling parameters. A linear polynomial model was developed using multiple regression analysis between drilling parameters and cooling condition with the drill bit temperature to represent the fitness characteristics. The workpiece made of GFRP is machined, and temperature is monitored during dry drilling, internal coolant and external coolant. The temperature of drill bit was measured by PFA Teflon-coated K (Chromega-Alomega) type thermocouples. From the analysis, it is evident that a linear multiple regression models developed to relate the cutting temperature with drilling parameters are with a minimum error of ±7 %. Internal coolant method reduces the average temperature by 76 % compared with dry drilling and 66 % compared with external coolant method. The reduction in tool temperature reduces the flank wear and increases the tool life by 43.75 % compared with dry drilling and 25 % compared with external coolant method.