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Abstract
Minimum quantity lubrication is a technique to have the advantages that cutting fluids bring yet keeping their use at minimum. For the cutting fluids, inedible vegetable oils are potential for minimum quantity lubrication machining. Castor oil was selected in this study as the cutting fluid for turning of hardened stainless steel (hardness of 47-48HRC). The hard turning was with minimum quantity lubrication (50 mL/h flow rate and 5 bar air pressure) at various cutting speeds (100, 135, and 170 m/min) and feeds (0.16, 0.20, and 0.24 mm/rev). The machining responses were tool life, surface roughness, and cutting forces. Design of experiments was applied to quantify the effects of cutting parameters to the machining responses. Empirical models for tool life, surface roughness, and cutting forces were developed within the range of cutting parameters selected. All machining responses are significantly influenced by the cutting speed and feed. Tool life is inversely proportional to cutting speed and feed. Surface roughness is inversely proportional to cutting speed yet is proportional to feed. Cutting forces are more influenced by feed than by cutting speed. A combination of low cutting speed and feed was the optimum cutting parameters to achieve long tool life, low surface roughness, and low cutting forces.
Keywords
Machining, minimum quantity lubrication, hard turning, tool wear, surface roughness, cutting forces, design of experiments
Date received: 17 March 2015; accepted: 29 June 2015
Academic Editor: Pedro AR Rosa
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Introduction
Machining involves cutting action in separating the chip from the bulk (machined workpiece) as well as friction in contact regions between cutting tool and chip and between cutting tool and workpiece. This nature induces high temperature in cutting region as well as high cutting forces, particularly in high production machining. These might lead to rapid wear of cutting tool, dimensional deviation of the machined parts, and damaged surface integrity.1 To tame the negative effects of high cutting temperature and forces, cutting fluids are commonly used. Cutting fluids work well to some extent. However, in high production machining, cutting fluids are at times not effective to strip the heat generation out of the cutting zone. Another concern is that the cost for use and handling (including disposal) of cutting fluids is high, can be...