A Study on Forces, Tool Wear and Surface finish in Orthogonal Machining of Aluminum 6061 T6 alloy and AISI 1020 Steel with HSS and Uncoated Carbide tool inserts under different gaseous cutting environments

Abstract

The current study is a statistically designed Orthogonal tube turning experiment to evaluate different cutting environments that can be used in machining aluminum 6061 T6 alloy and AISI 1020 Steel alloy. Two different tool material types, solid uncoated carbide and High Speed Steel (HSS) inserts were used along with different levels of uncut chip thickness in a classic orthogonal tube turning experiment. Three different rake angles of 0°, 7° and 15° using customized tool holders were designed and made to hold the inserts which had identical cutting angles. The cutting fluids used in this study are Nitrogen, Liquid Nitrogen and Cold Compressed "shop" air the performance of which were compared to the results obtained from dry machining. The force data (cutting force and the thrust force) were collected using a Kistler force dynamometer and processed using LabVIEW software. The tools are subjected to 1 minute of cutting at two different feed rates of 0.002”/rev. and 0.004”/rev at a constant depth of cut of 0.125” and at a constant speed. The tool inserts after 1 minute of cutting are studied for tool wear using a Keyence 3- D microscope. The surface finish of the work piece surface (average surface roughness) after one minute of cutting is examined under a contact type profilometer. The force data was used to calculate the different cutting parameters using classic orthogonal expressions as derived by Merchant and Payton and variation trend was validated against the literature. The ratio of the force along the shear plane to the force normal to the shear plane was studied and was found to be varying only with the cutting geometry (feed in this case) while remaining statistically unaffected by, tool rake angle and environment, suggesting that it is a material constant. Payton’s corrected Merchant’s force diagram (MFD) is revisited to obtain expressions to calculate the shear stress and shear strain. The mechanisms of dislocation movement are applied on the activation plane to obtain expression for activation energy. A finite element model to simulate the cutting process was used, results of which shows that, the cutting force values and shear strain were within 10% variation from the experimental value while the thrust force predicted by the model largely varied.