Heat generation is one of the most important problems in grinding because high temperature can limit wheel life and also induce defects such as residual stress and micro cracks in workpieces. Coolant is therefore extensively used in order to reduce the heat effect....[ Read more ]

Heat generation is one of the most important problems in grinding because high temperature can limit wheel life and also induce defects such as residual stress and micro cracks in workpieces. Coolant is therefore extensively used in order to reduce the heat effect.

In order to deal with the problems associated with the existing cooling methods, an ultrasonic coolant nozzle system was designed and examined in this project. Variable ultra high frequency vibration strength can be obtained and delivered to coolant during grinding by the proposed system. Characteristic studies were carried out to find relationships between the input and output parameters.

Via the preliminary tests, the effects of coolant flow rate on surface roughness of ground samples were investigated by using the proposed system.

Under the normal coolant temperature of 22°C and a cooled coolant temperature of 4°C, experimental results show that, without use of activation, an increase in the number of nozzle n_nzl leads to a reduction in surface roughness of ground samples up to approximately 8.5%. In addition, the effects of interaction of coolant flow rate and vibration strength on surface roughness of ground samples were examined through the tests.

Based on the experimental results, it is found that an increase in coolant amount with activation leads to a reduction in surface roughness of ground samples up to approximately 13%.

Through the factorial orthogonal test, the order of importance of four input parameters in relation to surface roughness was obtained.

Key input parameters were selected for further studies. With a fixed coolant flow rate, the effects of the parameters on loading current I, surface roughness R_a, R_q, R_z and R_t were obtained.

The results show that the proposed cooling method can effectively improve workpiece surface quality. With a reduction in coolant temperature t_c from the normal coolant temperature of 22°C to a cooled coolant temperature of 4°C, the surface roughness value was reduced by up to 22%. The grinding force was increased by approximately 21%. With an increase in activation, the surface roughness value was reduced by up to approximately 14%. The grinding force was reduced by approximately 11%.

SEM images together with the experimental results show that the best results were obtained by using the actively cooled and activated coolant under the low coolant temperature and high activation strength conditions.