In order to reduce the surface roughness of the inner rotor of cycloidal pump, a polishing method was proposed to realize a uniform surface polishing by using abrasive flow machining(AFM)on the surface of inner rotor. A mold core was made and installed outside the inner rotor in such a way that the gap between the core and the rotor keeps being constant to establish a uniform flow field around the rotor and allow the rotor surface experiences nearly the same wall shear stress. A power law model was established to represent the rheological property of the abrasive and water mixture and used to analyze the distribution of shear rate and shear stress in AFM process; further the distributions of velocity, shear rate and shear stress of the abrasive media over the processed surface were simulated by means of COMSOL Multiphysics CFD module. The results showed that if there was no mold core installed the non-uniform shear stress leaded to uneven roughness over the processed rotor surface; however, after the mold core was available, the rotor surface experienced uniform shear stress. In this case, the maximum difference in surface roughness Ra was reduced to 0.277 μm from 0.847 μm after 20 processing cycles. The processing efficiency and surface finish quality have been improved substantially.
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