Design of a novel linear reciprocating magnetorheological finishing device for improving surface integrity

Ti-6Al-4V alloy is widely employed in aerospace and biomedical applications due to its high specific strength, excellent corrosion resistance, and favorable biocompatibility. However, its high chemical reactivity, low thermal conductivity, and high ductility lead to poor surface consistency, thermal damage, and microcrack formation. Although magnetorheological finishing (MRF) offers flexible and low-damage machining, conventional MRF is limited by centrifugal effects and uneven abrasive distribution. To overcome these limitations, this paper proposes a novel linear reciprocating magnetorheological finishing (LR-MRF) method driven by a crank-slider mechanism to improve surface integrity, which optimizes flow field distribution and removal uniformity in the finishing zone. Firstly, kinematic analysis is performed to verify that stroke, velocity, and acceleration parameters fully meet process requirements. Secondly, a finite element method (FEM) model of single diamond abrasive scratching is established to systematically reveal the stress evolution and material removal mechanism. Then, LR-MRF experiments are conducted to evaluate the machining performance on Ti-6Al-4V alloy. The results show that the process efficiently removes inherent surface defects. The surface roughness Sa decreases to 0.044 μm with a reduction rate of 90%, and surface homogeneity is significantly improved. Rough finishing induces a grain refinement layer of approximately 2.1 μm in thickness, while fine finishing introduces negligible subsurface damage, achieving low-damage ultra-precision finishing. This study provides a new approach for ultra-precision finishing of difficult-to-machine materials.