High Efficiency ELID Grinding of Garnet Ferrite

Hard and brittle materials such as ferrite, optical glass and ceramics have been widely used in many fields because of their good characteristics and still gain more attentions. However, it is difficult to machine and get good surface quality. Some parts made of these materials have large machining allowances and need to be produced with large batch, but the machining efficiency is very low with usual grinding method. So it is of great importance to research the high efficiency grinding technology of hard and brittle materials. Electrolytic in-process dressing (ELID) grinding is a new grinding technology which has been adopted to the ultra-precision machining of hard and brittle materials. With the function of in-process dressing of metal bond diamond and CBN wheel, ELID grinding has the ability to keep the sharpness of the wheel surface and is widely used in fine abrasive grinding, but it also has the potentialities to high efficiency grinding. In this paper, the mechanism of ELID grinding and its grinding performance are analyzed, then the cast iron bond diamond wheels and ELID grinding device are used on a surface grinder to research the feasibility of ELID grinding to high efficiency grinding. To make comparison, the garnet ferrite (YAG) work piece has been machined in plunge grinding both by ELID grinding and by the resin bond diamond wheel. The grinding force and surface quality are tested and analyzed. It has been found that the grinding force of the cast iron bond diamond wheel with ELID grinding is apparently smaller than that of the resin bond diamond wheel. Under the same conditions, it is about 2/5～3/5 as the force using the resin bond diamond wheel. So with the same grinder and machining conditions, ELID grinding can machine work piece with greater depth of cut. Because of the smaller grinding force, it is also beneficial to avoid the edge collapse of the work piece and keep the integrity of the grinding surface. This experiment shows that the grinding efficiency can be highly improved and the surface quality be ensured by applying ELID grinding technology and adopting large grinding depth. The results indicate that the ELID grinding technology can be effectively used in the high efficiency machining of garnet ferrite and other hard and brittle materials.

Thermomechanical coupling effect on characteristics of oxide film during ultrasonic vibration-assisted ELID grinding ZTA ceramics

Ultrasonic vibration-assisted ELID(UVA-ELID)grinding is utilized as a novel and highly efficient processing method for hard and brittle materials such as ceramics.In this study,the UVA-ELID grinding ZTA ceramics is employed to investigate the influence of thermomechanical loading on the characteristics of oxide film.Based on the fracture mechanics of material,the model of internal stress for oxide film damage is proposed.The thermomechanical loading is composed of mechanical force and the thermal stress generating from grinding temperature.The theoretical model is established for the mechanical force,thermal stress and internal stress respectively.Then the finite element analysis method is used to simulate the theoretical model.The mechanical force and grinding temperature is measured during the actual grinding test.During the grinding process,the effect of grinding wheel speed and grinding depth on the thermomechanical force and the characteristics of oxide film is analyzed.Compared with the conventional ELID(CELID)grinding,the mechanical force decreased by 25.6%and 22.4%with the increase of grinding wheel speed and grinding depth respectively,and the grinding temperature declined by 10.7%and12.8%during the UVA-ELID grinding.The thermal stress in the latter decreased by 16.3%and20.8%respectively,and internal stress reduced by 12.3%and 15.6%.It was experimentally found that the topographies of oxide layer on the surface of the wheel and the machined surface in the latter was better than that in the former.The results indicate that the action of ultrasonic vibration establish a significant effect on the processing.Subsequently,it should be well considered for future reference when processing the ZTA ceramics.