Abstract
As a successful solution applied to hard machining, the minimum quantity lubricant (MQL) has already been established as an alternative to flood coolant processing. The optimization of MQL parameters and cutting parameters under MQL condition are essential and pressing. The study was divided into two parts. In the first part of this study, the Taguchi method was applied to find the optimal values of MQL condition in the hard milling of AISI H13 with consideration of reduced surface roughness. The L9 orthogonal array, the signal-to-noise (S/N) ratio and analysis of variance (ANOVA) were employed to analyze the effect of the performance characteristics of MQL parameters (i.e., cutting fluid type, pressure, and fluid flow) on good surface finish. In the results section, lubricant and pressure of MQL condition are determined to be the most influential factors which give a statistically significant effect on machined surfaces. A verifiable experiment was conducted to demonstrate the reliability of the results. In the second section, the optimized MQL parameters were applied in a series of experiments to find out cutting parameters of hard milling. The Taguchi method was also used to optimize the cutting parameters in order to obtain the best surface roughness. The design of the experiment (DOE) was implemented by using the L27 orthogonal array. Based on an analysis of the signal-to-noise response and ANOVA, the optimal values of cutting parameters (i.e., cutting speed, feed rate, depth-of-cut and hardness of workpiece) were introduced. The results of the present work indicate feed rate is the factor having the most effect on surface roughness.
Highlights
Hard machining has been widely applied in mechanical processing due to the many advantages included
The results indicated that the cutting parameters, which cause lower residual stress and contribute to better surface roughness
The purpose of this study is to optimize the parameters of the minimum quantity lubricant (MQL) condition to get the better surface roughness available
Summary
Hard machining has been widely applied in mechanical processing due to the many advantages included. The advantages of hard machining were indicated to be geometric accuracy, improved quality of the finished surface, the reduction of the labor expenditures [1] and a reduction in burr formation, better chip disposal, higher stability, simplified tooling [2] and flexible process design [3,4]. As a successful solution applied to hard machining, MQL is an effective, environmentally-friendly solution and has been widely used in the machining processes (i.e., turning, drilling and milling). According to Phafat et al [5], machining with MQL is a process in which a small amount lubricant utilized at a flow rate less than 250 mL/h is mixed with compressed air and sprayed onto the cutting zone.
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