World Journal of Engineering Research and Technology

Charles O. Eze*, Swift N. Onyegirim, Kennedy C. Owuama and Obiora C. Okafor

ABSTRACT

The negative impacts of conventional cutting fluids on the manufacturing cost, human health and environment have necessitated its replacement with vegetable oil coolants. This study was centered on determining the optimal vegetable oil cutting fluid from among the considered oils: Castor oil, Neem oil and Gmelina oil that would produce the best surface finish or low surface roughness value for mild steel material. The three oils were extracted from their various seeds using pressing and solvent extraction methods. A minimum quantity lubrication (MQL) system was set-up and was used to regulate the flow of the cutting fluid on the tool-workpiece interface. A vertical drilling machine with a 20mm drill bit attached to it, was used to drill a through hole on the mild steel material with the MQL system being used to supply cutting fluids to the drilling interface of tool-workpiece. The experimental design that was done with Minitab software 21.0 using spindle speed and feed rate as independent variables and surface roughness as response variable was meticulously adhered to while performing the experiment. The values of the response variable at each design point were measured with a surface roughness testing device and noted. Statistical analysis was done in order to determine the individual and interactive effects of the independent factors on the response variable. Mathematical models were also developed for each of the cutting fluids being studied. The response was optimized using response surface methodology (RSM) tool in quest of getting an optimal coolant. From the results obtained, it was deduced that at high spindle speeds and low feed rates, small values of surface roughness will be obtained. Also, each of the independent factors all had an individual and interactive significant effects on the response variable. The type of vegetable oil applied to the drilling zone had the highest significant effect, followed by a two-factor interactive effect of feed rate-oil type and then spindle speed-oil type. The mathematical models that were developed, had a good coefficient of correlation (Castor oil, R= 0.986; Neem oil, R= 0.994; and Gmelina oil, R=1.0), therefore the models are suitable for response prediction at any considered factor levels. In addition, from the optimization outcome, Gmelina oil had the highest composite desirability value of 1.0 and a predicted surface roughness value of 1.3 at a factor combination of: spindle speed- 290 rpm and feed rate- 0.08967mm/rev. Hence, Gmelina oil should be employed to the drilling zone of mild steel material if good surface integrity is desired.

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