Nowadays one of the new industrial requirements is high quality surfaces. The high quality surface is one that not only is without surface defects such as micro crack, but has high precision dimension and also low surface roughness. These mirror like surfaces are used in different industries such as semi conductive production, optic, military and aviation. Depending on the type of surface, there are a lot of various ways to create mirror like surface. One of the newer methods to create this kind of surface is magnetic abrasive finishing (MAF). Magnetic abrasive finishing (MAF) is one of the advanced finishing processes, which produces a high level of surface quality and is primarily controlled by a magnetic field. In MAF, the workpiece is kept between the two poles of a magnet. The working gap between the workpiece and the magnet is filled with magnetic abrasive particles. A magnetic abrasive flexible brush (MAFB) is formed, acting as a multipoint cutting tool, due to the effect of the magnetic field in the working gap. In the recent years, plenty of studies around the world are about MAF. In this method, finishing is done by using magnetic force on abrasive tool which is a kind of abrasive powder, and squeezing it on work piece surface and also making a relative motion between tool and work piece. This method is a kind of grinding, however because abrasive particles are flexible and removal rate is not so high, it is categorized as super finishing or polishing process. The process principle and the finishing characteristics of bonded and unbounded magnetic abrasive within cylindrical inner surface and free-form contour are described in this study. The unbounded magnetic abrasive is a mechanical mixture of abrasive and ferromagnetic particles with a kind of lubricant. The loosely bounded powder is prepared for experimentation by homogeneous mixing of magnetic powder (Fe powder of 100 mesh size), abrasive powder (SiC of 100 mesh size), and lubricant called silicon oil. To investigate the effects of time, rotation direction, working gap and spindle speed on material removal, change in surface finish and percent improvement in surface finish, a series of experiments have been conducted using several setups. The surface roughness is measured by Mahr roughness measurer and also atomic force microscope (AFM). In this study aluminum cylindrical parts are used for internal surface finishing at first and the results studied. The results shows 0.6?m (?Ra=1.3) surface roughness occurs in 15 min. following this experiment, a study on free form surface, as the main purpose of this project, is started. Due to the low efficiency of this step, using of combinative methods and optimizing magnetic abrasive powder combination is required. Through this research, effect of ultrasonic vibration assisted magnetic abrasive finishing is studied and also a new method for magnetic abrasive powder making is presented. Finally, because of industry's wide demand for this process, housing of vankel engine is polished using this method, successfully. The results demonstrated that surface roughness of this part with 60HRC hardness was reduced to 0.39mmRa from an initial value of 1.22mmRa within 60 min with high repeatability. Key words: Magnetic abrasive finishing, Surface roughness, Free form contour, Permanent magnet, Magnetic field.
