Flow field and cooling capacity in workpiece-tool contact zone during ultra-high speed grinding

Ultra-high speed grinding (UHSG) is a promising machining technology because it can reduce grinding force and greatly increase machining efficiency. However, a mass heat produced in the workpiece-tool contact (WTC) zone risks burning the machined surface during UHSG. Therefore, it is important to ensure timely cooling. The paper studies the flow field of the coolant and cooling capacity of WTC zone under different grinding speeds and coolant velocities by both three-dimensional (3D) finite element (FE) simulation and experiments. Results show that coolant velocity rapidly decreases after a slight initial increase with increasing the distance from the nozzle and little coolant could enter the WTC zone to cool down, which is responsible for the temperature rise in the WTC zone in UHSG. As grinding speed increases, a higher coolant velocity is needed for breaking the barrier of airflow layer to cooling. The critical coolant velocity to break the barrier and enter the WTC zone is obtained by theoretical calculation and experiment. The critical coolant velocity increases with the grinding speed, the coolant velocity needed is 19.2 m/s at the grinding speed of 120 m/s, and it rises to 30 m/s at the grinding speed of 160 m/s. This study could provide a guide to improve the cooling performance in UHSG, which is of great significance to a high-quality surface finish by UHSG.