Study of the jet-flow rate of cooling in machining .1. Theoretical analysis

Coolants are used in most machining processes in industry to prevent cutting tools from overheating. In order to achieve the best results of cooling, general guidelines on the method of applying coolants are needed. One of the issues is how to select the jet-flow rate of cooling to cope with the progress of automation in machining manufacturing, in which high-speed machining is is often performed, and on the other hand how to satisfy environmental concerns which require minimization of using coolant. To answer this question a detailed understanding of the effect of the jet-flow rate of cooling on the cooling action in machining is needed. In this study, the effect of the jet-flow rate of cooling in machining on the cooling heat-transfer coefficient is analysed theoretically, and the effect of the jet-flow rate of cooling on the temperature distribution in the cutting region is examined through numerical simulation of machining with cooling at different how rates. In Part 1, mathematical models are developed for the heat-transfer coefficients of cooling applied in machining with a water coolant in the commonly-used cooling method: overhead-jet cooling and flank-jet cooling. The relationships between the heat-transfer coefficient and the jet-flow rate in the cooling processes are analysed using these models. The results indicate that the cooling heat-transfer coefficient increases with increasing the jet-flow rate. However, a small percentage increase in the heat-transfer coefficient requires a large percentage increase in the flow rate. In overhead-jet cooling, to increase the heat-transfer coefficient by n times, the flow rate has to be increased by about n(1/0.7) times, whilst in flank-jet cooling to increase the heat-transfer coefficient by n times, the flow rate has to be increased by about n(2) times.