MAGNETIC ABRASIVE FINISHING

MAGNETIC ABRASIVE FINISHING

1. Magnetic Abrasive Finishing Process Hiran Gabriel D J

2. History of Magnetic Abrasive Finishing Magnetic abrasive finishing has origins dating back to the 1930s , during which it was used by manufacturing companies in the United States. The first patent for magnetic abrasive finishing was filed with the United States Postal and Trademark Office (USPTO) . By the 1980s , magnetic abrasive finishing was a well-known and frequently used finishing process in the manufacturing industry.

3. Magnetic Abrasive Finishing (MAF) Process Also known as magnetic field-assisted finishing , magnetic abrasive finishing is a finishing process that involves the use of a magnetic field to apply or remove particulate matter onto the surface of a workpiece or object. The magnetic field is used to force abrasive particles against the target surface The purpose of magnetic abrasive finishing is to remove or coat materials in order to provide superior finish. The magnetic field forcefully pushes the particular matter of the powder onto the workpiece or object thus able to provide a superfinished surface.

4. Working of MAF Magnetic Assisted Finishing or "MAF" is essentially the manipulation of a homogeneous mixture of magnetic particles and abrasive particles with a magnetic field to impart a machining force on a workpiece. Relative motion between the particle mixture and the workpiece surface result in material removal. Since MAF does not require direct contact with the tool, the particles can be introduced into areas which are hard to reach by conventional techniques. Careful selection of magnetic particles and abrasive particles give rise to surface texture and roughness control that was previously impossible especially for hard to access areas

5. Sources of magnetic field The magnetic field source in MAF is typically an electromagnet or a rare earth permanent magnet . A permanent magnet offers high energy density, lack of overheating resulting in a constant flux density, low cost, ease of integration into existing CNC equipment, and simplicity. Some applications require adjustment of the flux density during finishing, or require a switching magnetic field, which is only attainable with an electromagnet since the magnetic field in a permanent magnet cannot simply be switched off.

6. Working of MAF Relative motion between the magnetic/abrasive particle mixture and the workpiece is essential for material removal. There are several options for achieving the necessary motion. A common setup is the rotation of the magnetic pole tip. This is done by either rotating the entire permanent magnet setup or by rotating only the steel pole. Another method which is commonly utilized in internal finishing is the rotation of the workpiece, this is unfortunately limited to axial symmetric workpieces. In addition to rotational motion there is oscillatory and vibrational configurations that are applicable.

7. Equipment for MAF Fig 1: Equipment for MAF (a) Side view (b) Top view

8. Equipment for MAF Fig 2: Equipment for MAF (a) Polishing (b) Burnishing

9. Common magnetic and abrasive materials White Alumina + Iron Diamond + Iron Tungsten Carbide + cobalt Iron and its oxides Cobalt Nickel Steel and Stainless steel Synthetic diamond Cubic boron nitride CBN Aluminum oxide Silicon carbide Magnetic materials Abrasive materials Commonly used mixture

10. Applications of MAF Prosthetics Cutting Tools Turbine Blades Airfoils Optics Sanitary Pipes Food Industry Capillary Tubes in Medical Field Stents, Catheter shafts, Needles, Biopsy Needles, etc Curved Pipes