Ultraprecision micromachining of brittle materials by applying ultrasonic elliptical vibration cutting

Ultraprecision micromachining of brittle materials with a single point diamond tool, which is extremely difficult due to brittle fracture and rapid tool wear, is realized by applying ´Elliptical Vibration Cutting´ technology, which has been developed by the authors. Ultraprecision micro grooving experiments for brittle materials such as sintered tungsten carbide, zirconia ceramics, calcium fluoride and glass, which have different material properties, are carried out to clarify the basic effects of the elliptical vibration on ductile micromachining process. As a result of the micro grooving experiments for the sintered tungsten carbide, it is confirmed that the ductile micro grooving without brittle fractures can be realized by applying the elliptical vibration cutting at a depth of cut of 1.9 μm. The surface quality is improved as the vertical amplitude of the elliptical vibration becomes small as compared with the size of sintered grains. The micro fractures of the zirconia ceramics appear relatively similar to those of the sintered tungsten carbide, since they are both sintered materials and have similar material properties. Critical depth of cut for ductile micro machining of the calcium fluoride is increased significantly by applying the elliptical vibration cutting. Values of the critical depth and the types of fractures depend on the crystal orientations, as it is a single crystal material. The critical depth is also increased significantly for an amorphous material, glass, by applying the elliptical vibration cutting. It is considered that the improvements of critical depth and surface quality by the elliptical vibration cutting are caused by significant reduction in the thickness of workpiece material cut in each cycle of the elliptical vibration.