Vegetable oil can be used as a base oil in minimal quantity of lubrication (MQL). This study compared the performances of MQL grinding by using castor oil, soybean oil, rapeseed oil, corn oil, sunflower oil, peanut oil, and palm oil as base oils. Results revealed that 1) castor oil-based MQL grinding yields the lowest grinding force but exhibits the highest grinding temperature and energy ratio coefficient; 2) palm oil-based MQL grinding generates the second lowest grinding force but shows the lowest grinding temperature and energy ratio coefficient; 3) viscosity significantly influences grinding force and grinding temperature to a greater extent than fatty acid varieties and contents in vegetable oils. Palm oil is the optimum base oil of MQL grinding, and this base oil yields 26.98 N tangential grinding force, 87.10 N normal grinding force, 119.6 °C grinding temperature, and 42.7% energy ratio coefficient.
Top7.1 Introduction
Grinding is one of the most basic and important techniques in the machining industry. The final precision and surface quality of most machine parts are determined by grinding technique. Grinding is currently the only machining technique applicable to most difficult-to-process materials(Jia, Li, Zhang, Zhang, & Zhang, 2014; Li & Zhao, 2003). During grinding, high energy consumption is necessary to eliminate unit material volume; thus, a high amount of heat is generated in the grinding zone. Grinding depth is also small; as a result, a larger specific grinding energy is produced by grinding than by cutting and milling(Li, Chen, & Chen, 2011). Heat disperses to cuttings, tools, and workpieces. However, only a small proportion of grinding heat is removed by abrasive dust; heat is mostly transferred to grinding wheels and workpieces(Khan & Wuyi; Lefebvre, Lipinski, Vieville, & Lescalier, 2008; Vieira, Baptista, Parente, & Jorge, 2009). Grinding heat likely affects the surface quality and usability of workpieces. In particular, an excessively high energy density of a workpiece surface burns the workpiece and deteriorates surface integrity(Belentani et al., 2014; Chen, Fu, He, Zhu, & Zhang, 2017; Ding, Xu, Chen, Su, & Fu, 2010; Malkin & Guo, 2007). During grinding, the grinding zone is often cooled and lubricated by traditional cooling via flooding and lubrication. A significant amount of grinding fluid is poured into the grinding zone(Jin & Stephenson, 2008) at usually 60 L/min per unit width of the grinding wheel.
With advances in grinding technology, cooling lubrication approaches have also been developed, improved, and optimized in terms of various aspects, such as energy conservation, emission reduction, eco-friendliness, and high efficiency(Zhang, Li, Zhang, Jia, & Zhang, 2015). However, flood grinding cannot comply with green manufacturing and sustainable development in terms of environmental protection, low carbon emission, processability, and economical efficiency. Therefore, environmentally friendly, highly efficient, and low-energy-consuming grinding fluid or new cooling lubrication techniques and equipment should be developed to achieve various technical effects of cooling lubrication, high workpiece processing quality and precision, prolonged service life of grinding wheel, and low environmental pollution caused by grinding fluid(Jia, Li, Wang, Zhang, & Hou, 2014; Zhang, Li, Jia, Zhang, & Zhang, 2015). Researchers proposed a technique. In dry grinding, grinding fluid is used, but high efficiency, high processing quality, prolonged grinding wheel service life, and a reliable grinding process can be maintained. Considering grinding wheel performance, machining tools, grinding dosage, and processing mode, we should integrate manufacturing techniques and materials science, as well as other subjects, such as information technology, electronics, and management. However, dry grinding is characterized by several disadvantages, such as high grinding force and grinding temperature; as a consequence, low processing precision, short grinding wheel service life, geometric errors in workpieces, and poor processing quality are obtained(Azarhoushang, Daneshi, & Lee, 2017; Huang, Liu, & Wu, 2016; Simoes et al., 2014).