Investigation of a novel manufacturing technique for two-dimensional machining of Polycrystalline Cubic Boron Nitride (PCBN) tools

The Laser/Water-Jet (LWJ) hybrid machining system, introduced and developed by the Iowa State University's Laboratory for Lasers, MEMS, and Nanotechnology, was applied to overcome the major deficiencies associated with current EDM and laser machining techniques for shaping Polycrystalline Cubic Boron Nitride (PCBN) cutting tools from the blanks. For PCBN, the purpose of water in LWJ is twofold: phase transformation and thermal shock. Previously LWJ was used to perform straight line cuts on various materials including PCBN. In this work, a further investigation of an understanding of the action of water and two-dimensional contour cutting of PCBN was carried out. The role played by water in LWJ was compared with that of other fluids (argon, nitrogen, oxygen, and air) to illustrate the effectiveness of water in the controlled fracture mechanism of PCBN. In addition, a two-dimensional contour cutting of PCBN using LWJ was investigated by changing the crack direction to 60, 108, 120, 135 degrees and following a curve with 1 mm radius in accordance with the standard PCBN tool shapes. The phase transition and the cut quality were investigated using Raman spectroscopy, Scanning Electron Microscopy (SEM), and optical profilometer. Results indicated that water is the best medium to control the phase transition and apply the controlled fracture mechanism for PCBN. Also, it was shown that successful cuts were made with obtuse angles in contrast to acute angles. A preliminary qualitative model was presented to explain the observed experimental results.