Dry grinding with CBN wheels, the effect of structuring

Although some of the machining processes with defined cutting edges like milling and turning could be recently applied without coolant, the realization of the processes with undefined cutting edges like grinding is still a challenge for researches and a very interesting target for industry. Grinding involves high specific energy compared to other machining processes due to the stochastic nature of the grain distribution and negative rake angle of grains. A major part of this energy is converted to friction, generated high heat, which can have harmful effects on workpiece surface quality, and it also increases tool wear. Due to this high heat generation, the coolant is a necessary part of the process to eliminate the thermal damages. In spite of many advantages of the use of coolant to prevent such adverse effects, ecological as well as economical problems are some disadvantages which have oriented the research works in the last decades to minimize the using of coolant or even to eliminate it. However, due to the complicated nature of grinding process, this goal has not been fully achieved yet. Structuring is presented in this work as a main concept of dry grinding. The concept of structuring is based on optimization of the chip formation which causes a considerable reduction of friction and rubbing in the process. Reduction of the dynamic cutting edges using structuring causes an increase of the chip thickness as well as micro-cutting and decreases the micro-ploughing and micro-rubbing processes during the grinding. Structuring of the grinding wheels can be done using different methods and geometry. The defined structured grinding wheels are achieved by the three main methods of dressing, laser conditioning and special electroplating. The structured wheels are compared with the conventional wheels by a series of systematic tests. The quality and integrity of ground surface as well as grinding forces, specific energy, temperature and tool wear are investigated. Physical models are developed for chip thickness, grinding forces, specific energy and workpiece temperature. A neural network model is also presented to estimate the workopiece roughness and burn. The test result shows that a higher material removal rate without thermal damages and more efficient process can be achieved by proper structuring. The developed models can also be used to design the structured tools as well as optimizing the process parameters