CUTTING EDGE PREPARATION OF MIXED CERAMIC INSERTS BY MEANS OF GRINDING AND ITS APPLICATION IN HARD TURNING

Hard turning has been increasingly applied due to its advantages in comparison to grinding process. For the machining of hardened materials, the use of mixed ceramics cutting tools has proven to be suitable due to their high wear resistance and chemical stability, as well as the lower cost when compared to CBN tools. However, due to the high brittleness of mixed ceramics, their application requires an adequate edge preparation in order to increase tool life. Compared to traditional edge preparation processes, such as abrasive blasting or brushing, grinding process has several advantages and its features will be presented in this article. Because of its kinematic limitations, however, a continuous edge rounding cannot be produced and the discretization of the rounding by several chamfers is necessary. Thereby, the performance of mixed ceramic cutting tools, prepared with discretized rounded edges, in hard turning will be investigated in this paper. In this context, not only the tool life will be analyzed, but also the workpiece surface roughness and the cutting forces. Thus, the paper has the goal to demonstrate the potential of the developed method for preparing cutting edge by grinding. Main results showed that the tool discretized by three chamfers has better performance than that with only one single chamfer (used as reference), leading to an increased tool life and lower surface roughness.