In grinding the use of coolants is inevitable to achieve high precision surface properties under the need of high process performance and under reasonable material removal rates. In conventional grinding typically a significant share of the total production energy refers to the delivery and conditioning of the coolants due to the use of flood cooling, which contributes a significant portion to the production costs. However despite trends of minimal quantity lubrication and even dry grinding, the demand of metal working fluids is increasing worldwide. In order to reduce and optimize the use of coolants, profound knowledge about the fluid delivery into the grinding gap is important. Usually studies show the effect of coolants on the grinding process by the effect on the workpiece. They allow general conclusions about the share and distribution of the useful coolant flow, which is considered as the coolant flow into the grinding gap. On the other hand in-process methods can be used to assess the coolant flow. In a newly proposed experimental set-up the distribution by different nozzle designs and volume flows, respectively flow speeds, are studied for a cylindrical grinding process and can directly be visualized. Effects of the grinding wheel induced air-flow are fully considered. The main evaluation is done along the workpiece axis. It is shown that the distribution of the coolant flow inside the grinding gap is typically not entirely uniformly, also when nozzles with a consistent coolant supply are employed. Coolant distribution depends on the nozzle outlet cross-section, while different nozzle design can lead to even grinding results. It is shown, that the amount of cooling flow is not the main parameter. The influence region of single jet nozzles is typically much wider that their cross-section, which allows to use them in grinding. The results combined with a heuristic approach allow the optimization of coolant jet nozzles for grinding processes.
Science Journal 