A novel flexible magnetorheological fluid polishing needle for polishing slender bend tube

Abstract

The demand for ultra-precision finishing of the inner surfaces of slender bend tubes is increasing in advanced manufacturing. However, achieving high-quality surface finishes in such confined geometries remains a significant challenge due to limited accessibility and the complexity of tube shapes. To address these limitations, this study proposed a novel flexible polishing needle based on magnetorheological fluid (MRF) technology with added dispersant. The polishing needle, composed of magnets constrained by a coil spring, was systematically optimized in terms of magnet shape and arrangement through finite element (FE) simulations and experiments. The results demonstrated that the optimized magnet configuration could significantly improve both efficiency and surface quality. Experimental polishing of both straight and bent 304 stainless steel tubes showed that the average surface roughness (Ra) was reduced from 1.24 to 2.28 μm to 0.40–0.62 μm after polishing 30 min. Furthermore, the method proved effective for tubes with bend angles ranging from 15° to 90°, significantly improving both surface quality and flow efficiency. This research provides a versatile and effective solution for the polishing of slender tubes with complex geometries, offering substantial potential for practical applications in high-end manufacturing. Graphical abstract: [Figure not available: see fulltext.]