Research On Structure Optimization Of Superfine Crushing Device With Centrifugal Impact-Squeezing Grinding

The green density of sintered NdFeB permanent magnet is a important factor to ensure machining performance of permanent magnet.There is a direct link between green density or homogeneity and the packing density of powder.In order to ensure the density of the green reached a high level,this paper presents that the particles position of NdFeB permanent magnet powder were rearranged to decrease the voidage and to increase the packing density of powder with the method of vibration.The discrete element software EDEM was used to simulate the movement process of the particles of powder.The influence of vibration frequency,vibration time,vibration direction and amplitude on the voidage and packing density of powder was studied,and the vibration characteristic parameter were optimized to guide production and practices,the main research contents are as follows:1)Hertz-Mindlin without sliding contact model was used to simulate the vibration states of the particles of NdFeB permanent magnet powder based on EDEM software,and the cloud chart of particles position was obtained,the law that the space among particles of powder was decreased and the number of particles,which were near the vessel wall,increased was founded.The conclusion that the Apparent volume and the voidage of powder decreased,the packing desity of powder increased by vibrating was given.The theory of using the method of vibration can effectively reduce the voidage and increase the density was verified.2)The nonspherical particles were designed and test under vibration condition in this paper,the influence of different vibration characteristics on the packing density of powder was analyzed,the change rule of packing density in various frequency conditions was studied.The internal voidage of powder was measured after a certain period of vibration,and the packing density was calculated and plotted,it was founded that the packing density of powder appeared to increase first and then decreased and kept stable eventually with the increase of frequency.3)According to the change rule of packing density with vibration frequency,using the single element shift method,the tests of the influence of vibration time,vibration direction and amplitude on the packing density of powder were designed and the curves of the packing density with the vibration time,vibration direction and amplitude were plotted.It is founded that the packing density increased first and then kept stable eventually with the increase of time.,and it took a shorter time with a higher frequency.The packing density of powder reached a higher level,when the vibration direction was along Z or X axis;the packing density of powder was lower than one direction under the condition of the coupling vibration of two directions;the packing density of powder was lower than the coupling vibration of two directions under the condition of the coupling vibration of three directions.It is founded that the amplitude has little effect on the packing density,after the vibration frequency has been determined.4)In order to optimize the vibration parameters,the three factors such as the vibration frequency,the vibration time and the vibration direction were tested by orthogonal test,the range analysis and variance analysis were used to analyze the test results.It is founded that the packing density of powder will reach the highest level when the vibration frequency is set at 70 Hz,the vibration time is set at 20 s,the vibration direction is set in the direction of Z axis.