Attempt at unitary magnetorheological finishing for a pierced die cavity

A novel polishing method for a pierced die cavity, unitary magnetorheological finishing (UMRF), was proposed in this study. UMRF used a permanent magnet as the polishing tool, the shape of which was the same as that of the pierced die cavity's polished surface, and the permanent magnet's size was a little smaller than that of the pierced die cavity in order to form a certain gap between them. The magnetic polishing tool absorbed ferrite particles and abrasives, which were suspended in the magnetorheological (MR) fluid. This was done in order to polish the surface of the pierced die cavity by a high-frequency reciprocating movement occurring along the die cavity surface. Owing to its shape adaptability and high flexibility, this method accomplished a unitary polishing. The whole inner cavity surface was polished in one working cycle. The polishing technology used in this method was also studied, and the influence of the MR fluid concentration, the polishing gap, the reciprocating linear velocity, and the stroke of the polishing tool on the polishing performance was investigated. The experimental results clearly showed that UMRF was an effective polishing method that polished the whole inner cavity surface to a mirror-like finish. At present, this achieved a surface polish, Raof 42 nm.