Development of high-speed internal finishing and cleaning of flexible capillary tubes by magnetic abrasive finishing

Tube-shaped medical components such as catheter shafts, coronary stents, and biopsy needles should be precisely designed and manufactured, since surface imperfections can cause severe---possibly lethal---implications for patients. Therefore, internal machining (surface and edge finishing) is increasingly in demand for these devices, but as the tube diameter decreases, the more difficult the internal finishing becomes.;Magnetic abrasive finishing (MAF) has been studied to accomplish the internal finishing of capillary tubes. The MAF process can produce a smoothly finished inner surface of tubes by means of relative motion between magnetic abrasive and tube inner surface. To achieve successful internal finishing of capillaries, controlling the magnetic abrasive motion and lubricant inside the tube is critical. The magnetic abrasive is suspended in magnetic field generated by the magnet located outside the tube. The magnetic field is controlled by the geometry and arrangement of the magnets as well as the geometry of pole tip attached to the magnets. In the case of flexible capillary tubes, deburring the edges of laser-machined slots and removing the re-solidified material caused by laser machining process on the inner surface are required in addition to the internal surface finishing. The burrs are obstacles to magnetic abrasive, hindering the generation of smooth relative motion against the tube inner surface. The tube also easily deforms during the finishing process due to its flexibility. These factors increase the difficulty of achieving a smooth internal finish on flexible capillary tubes.;This research develops a new finishing method featuring the use of a multiple (double) pole-tip system with a special magnetic tool. This method produces smooth inner surfaces of capillary tubes and finishes multiple areas simultaneously to improve finishing efficiency. This study explains the processing principles of newly developed finishing method and describes the surface finishing characteristics. The finishing mechanism is also thoroughly investigated and described in both straight and flexible capillary tubes.