Cutting fluids are mainly used for cooling, lubricating, and chip removing. The use of minimum/minimal quantity lubrication (MQL) in machining processes not only reduces the cost of cutting fluids but also has the potential to alleviate the environmental impact. In addition, the MQL technique could be a viable choice to decrease the damage to the miniature machines due to the near-dry lubrication. Therefore, the objective of this study is aimed at the mechanical performance of MQL for micro-grinding of SK3 steels based on surface finish and tool life. In this study, it is observed that tool breaks in dry grinding or air blow grinding, and it is also found that workpiece surface is burned in dry grinding. However, these phenomena are not observed in MQL grinding. The reason is that the use of MQL reduces the friction between the tool and workpiece and improves the chip removal in micro-grinding. The use of MQL in micro-grinding also leads to better surface roughness and the tool life is more than seven times compared to dry grinding. Experimental results show that the best surface finish is achieved in MQL grinding when the use of cutting fluids is 1.88 ml/hr with the air flow rate of 30 l/min among the lubrication conditions in this study.

Cutting fluids have some drawbacks, like health hazards, extra manufacturing cost and environmental contamination. To decrease the disadvantages of using cutting fluids, conventional cutting is a better choice. However, conventional cutting has no advantages of using cutting fluids, such as lubrication. Therefore, vibration assisted cutting (VAC) is a new technology to achieve both purposes of the above machining techniques. Hence, the goal of this study focuses on the mechanical performance of vibration assisted grinding (VAG) for micro grinding of SKD61 steel based on tool life and surface finish. In this study, it is observed that chatter happens under VAG in the condition of feed 5.76 £gm/rev. Surface roughness (Ra) for the condition of feed 1.92 £gm/rev is better than that of 5.76 £gm/rev. The best surface finish is 0.05 £gm in this study when the feed is 1.92 £gm/rev. Spindle speed does not have significant effect on surface roughness in this study. However, the tool life is short under high spindle speed (35000rpm). Experimental results show that tool life will be prolonged two-thirds for VAG combined with MQL. As changing the amplitude of vibration (for a fixed frequency of 9 kHz) , the larger the amplitude, the better the surface roughness.

In this study, the new predictive model for the micro-grinding process was developed by consolidating mechanical and thermal effects within the single grit interaction model at microscale material removal. The size effect of micro-machining was also included in the proposed model. In order to assess thermal effects, the heat partition ratio was experimentally calibrated and compared with the prediction of the Hahn model. Then, on the basis of this predictive model, a comparison between experimental data and analytical predictions was conducted in view of the overall micro-grinding forces in the x and y directions. Although there are deviations in the predicted micro-grinding forces at low depths of cut, these differences are reduced as the depth of cut increases. On the other hand, the optimization of micro machine tools was performed on the basis of the proposed design strategy. Individual mathematical modeling of key parameters such as volumetric error, machine working space, and static, thermal, and dynamic stiffness were conducted and supplemented with experimental analysis using a hammer impact test. These computations yield the optimal size of miniaturized machine tools with the technical information of other parameters.