Fine finishing of internal surfaces using cassava starch medium

Cassava starch, a sort of cheap and easily purchased material, whose main components from nature can be recycled without causing environmental and workpiece pollution, is applied in abrasive flow machining (AFM) processing to obtain a fine finish on internal surfaces efficiently. The cassava starch medium with the concentration of cassava starch more than 37% has the characteristics of order-dependence of magnitude increase in viscosity, and its rheological properties are investigated to prepare shear thickening polishing slurry (STP-s). Subsequently, a theoretical model is developed to reveal the material removal behavior in the processing based on the theory of Archard sliding wear and fluid dynamics, and the maximum error between theoretical and experimental values is 13.1%. Processing experiments prove that using cassava starch medium can achieve low roughness (∼20 nm Ra) of the workpiece. Besides, the temperature which causes a change in the rheological curve plays a crucial role in processing efficiency. When the temperature of STP-s exceeds 50 ℃, the ability of efficient finishing is basically lost. Observation experiments show that the micro-processing mechanism of AFM processing is friction and wear by the clusters action coming from shear thickening behavior. The processing capability using the cheap cassava starch medium is, for the first time, achieved in internal surface finishing and indicates the precision processing prospect in other finishing techniques.