EFFECTIVENESS OF MINIMUM QUANTITY LUBRICATION WHEN POCKET MILLING ALUMINUM ALLOY 7075-T6 WITH CARBIDE TOOLS UNDER HIGH-SPEED MACHINING

Abstract

Abstract of thesis presented to the Senate of Universiti Kuala Lumpur Malaysia in fulfillment of the requirements for the Degree of Master in Engineering Technology (Manufacturing) EFFECTIVENESS OF MINIMUM QUANTITY LUBRICATION WHEN POCKET MILLING ALUMINUM ALLOY 7075-T6 WITH CARBIDE TOOL UNDER HIGH-SPEED MACHINING By KHAIRUL AZREEN BIN MOHD ZAINOL AMIR December, 2019 This study outlines the effectiveness of minimum quantity lubrication (MQL) in the pocket milling of aluminum alloy 7075-T6 under high-speed machining (HSM) on tool wear, tool life, surface roughness, and chip morphology. MQL is an environmentally friendly approach where a small amount of cutting fluid was sprayed with air aid to the cutting zone in the mist form. Previous studies have found that tool wear is a major challenge to achieve excellent surface quality, tool performance, and favorable chip formation. The experimental work was performed on the computer numerical control (CNC) five axes milling machine with uncoated carbide tools. The machining parameters with three controlled factors and two levels were designed utilizing full factorial xx design and analysis of variance (ANOVA) was then applied to determine the level of significant machining parameters. Different values of machining parameters involved were 500 and 600 m/min, 0.12 and 0.15 mm/tooth, and 1.40 and 1.70 mm, representing cutting speed, feed rate, and axial depth of cut, respectively. The radial depth of cut of 7 mm was kept constant throughout the experiment. The MQL flow rate was set at 100 mL/h. Dry cutting was done to compare the outcome result with MQL 100 mL/h. After each experiment, the tool flank wear and surface roughness were observed and measured by using an optical microscope and the surface roughness tester, respectively. The tool life criterion was determined when the tool wear failure reached 0.30 mm. The chips collected from all these machining parameters were taken to be examined using an optical microscope. The empirical model of tool life and surface roughness for the MQL and dry cutting was developed with adequate accuracy within the experimental ranges. From the result obtained, MQL 100 mL/h at cutting speed of 500 m/min, feed rate of 0.12 mm/tooth, and axial depth of cut of 1.40 mm stimulated the tool lifespan up to 20.21 minutes. The tool flank wear was observed at all the cutting conditions as a result of adhesion wear mechanism. Uncoated carbide tools with a combination of high cutting speed of 600 m/min and low feed rate of 0.12 mm/tooth produce good surface roughness. At 600 m/min and 0.12 mm/tooth under MQL 100 mL/h, the favorable chip formation was obtained, thus improve surface roughness and diminish severe localization of heat. It is recommended that the flow rate of MQL 100 mL/h should be used for high-speed machining of aluminum alloy 7075-T6 with appropriate machining parameters may potentially lead to economic benefits in terms of fluid cost saving and the better machinability.