Effects of Cooling Conditions and Machining Parameters on Thrust Force, Surface Roughness, and Hole Quality in Machining of Fiber Metal Laminates

Abstract

The machining of Fiber Metal Laminates (FMLs), such as glass laminate aluminum reinforced epoxy (GLARE), presents significant challenges due to the varying mechanical and thermal properties of its constituent materials. This study investigates the effects of cooling conditions and machining parameters on thrust force, surface roughness, and hole quality in FMLs. A comparative analysis of two hole-making techniques—twist drilling and helical milling—is performed on two thicknesses of GLARE, under both Minimum Quantity Lubrication (MQL) and dry conditions. The experimental work utilized the Response Surface Methodology (RSM) to assess the impact of spindle speed, feed rate, and cooling conditions on thrust force, torque, surface roughness, and hole quality. Results show that helical milling significantly reduces thrust force by 66% to 81% compared to twist drilling, although it requires a 300% increase in machining time. MQL was effective in decreasing thrust force and surface roughness in both methods. The thicker GLARE samples experienced a 17% to 32% increase in thrust force, leading to higher surface roughness. Spindle speed influenced thrust force by up to 60.68% in twist drilling, whereas feed rate showed the most significant effect (64.19%) in helical milling. This study highlights the advantages of helical milling in reducing machining forces and improving surface quality, despite its longer process time. The results provide useful information for machine configuration optimization, particularly for aerospace applications that frequently use FMLs like GLARE.