A new internal surface polishing method for sub-millimeter slender tube with varying diameters

A new abrasive flow polishing method with a ferromagnetic blockage placed inside tube was proposed for finishing internal surface of slender tubes with varying diameters. A mathematic model was established to calculate the blockage's profile. Results indicate that the special designed ferromagnetic blockage provides an effective tool to adjust the flow velocity and pressure, and thus controlling local material removal. Axial tool marks were removed by rotating the workpiece during polishing. A uniform internal surface (Sa < 40 nm) was achieved when finishing a puncture needle with diameters ranging from 0.3 to 0.7 mm (initial Sa 600 - 1200 nm).