Presented by:
Shaikh Rizwaan
Aabed Khan

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ADVANCED FINE FINISHING PROCESSES
Abstract:
The technology is really spice of life. This seminar is all about latest technology which is useful for finishing materials with very high precision. These are the latest processes are called as Advanced Fine Finishing Processes. In this seminar we are going to take a overlook on some of these processes.
With the demand of stringent technological and functional requirements of the parts from micro- to nano-meter range, evolution of ultraprecision finishing processes became obvious need of the manufacturing scientists and engineers. The traditional finishing processes of this category have various limitations, for example complex shapes, iniature sizes, and 3-D parts can not be processed & finished economically and rapidly. This led to the development of advanced finishing techniques like Abrasive Flow Machining, Magnetic Abrasive Finishing, Magnetic Float Polishing, Magneto-rheological Abrasive Finishing, and Ion Beam Machining. In all these processes except Ion Beam Machining, abrasion of the workpiece takes place in a controlled fashion such that the depth of penetration in the workpiece is a fraction of micrometer so that the final finish approaches towards the nano range.
The working principles and the applications of these processes are discussed in this paper along with some recent research going on in these areas.
I. INTRODUCTION
The developments in the material science have led to the evolution of difficult-to machine, high strength temperature resistant materials with many extraordinary qualities.
Nano- materials and smart materials are the demands of the day. To make different products in various shapes and sizes, many times, the traditional manufacturing techniques do not work. One needs to use non-traditional or advanced manufacturing techniques in general and advanced machining processes in particularly [IJ. Later includes both, bulk material removal advanced machining processes as well as advanced fine finishing processes. Further, the need for high precision in manufacturing was felt by manufacturers world over, to improve interchangeability of components, improve quality control and longer wear / fatigue life [2,3]. Achieving controlled surface finish on such components is equally important.
Traditionally, abrasives either in loose or bonded form whose geometry varies continuously in an unpredictable manner during the process are used for final finishing purposes.
Nowadays, new advances in materials syntheses have enabled production of ultra fine abrasives in the nanometer range without the need for comminution (a process by which brittle materials are reduced in size).
With such abrasives, it has become possible to achieve nanometer surface finish and dimensional tolerances. There is a process (ion beam machining), which can give ultra precision finish of the order of the size of an atom or molecule of the substance. In some cases, the surface finish obtained has been reported to be even smaller than the size of an atom. This paper deals with some of the advanced fine finishing I machining processes like Abrasive Flow Machining (AFM), Magnetic Abrasive Flow Machining (MAFM), Magnetic Abrasive Finishing (MAP), Magnetic Float polishing (MFP), Magneto Rhelogical Abrasive Finishing (MRAF), Elastic Emission Machining (EEM) and Ion Beam Machining (IBM).
2. ABRASIVE FLOW MACHINING (AFM) AND MAGNETIC ABRASIVE FLOW MACHINING (MAPM)
With today's focus on total automation in the flexible manufacturing system, the abrasive
flow machining process offers both automation and flexibility .This process was developed basically to deburr, polish and radius difficult to reach surfaces and edges by flowing abrasive laden polymer, to and fro in two vertically opposed cylinders (Fig.l). The medium (mixture of viscoelastic material and abrasive particles) enters inside the workpiece through the tooling. The abrasive particles penetrate in the workpiece surface depending upon the extent of radial force acting on the abrasive particles. Due to tangential force, the material is removed in the form of chips as shown in Fig.lb and Fig.lc.
To investigate into the mechanism of material removal during AFM, their debris were collected and examined under the scanning electron microscope. It was found (Fig.lc) that very fine chips are produced. However, under certain machining conditions the occurrence of ploughing has also been observed. In this case, one may get almost zero material removal rate, and shining polished surface as has been observed during experimentation. During the AFM process, medium cylinder, hydraulic cylinder and tooling also get abraded but comparatively first two wear much lesser than the third one due to lower pressure in the cylinders which are much larger in size. There are three major elements of the AFM system- Tooling, Machine, and Medium. AFM system- Tooling, Machine, and Medium. The tooling confines and directs the medium flow to the areas where abrasion is desired. The machine controls the process variables like extrusion pressure, medium flow volume and medium flow rate. The abrasive laden polymer is medium whose rheological properties determine the pattern and aggressiveness of the abrasive action. The rhelogical properties of the medium change during the AFM process [5]. From application point of view, it has some peculiar applications where no other traditional as well as advanced finishing process can work. For example, many small diameter holes (say, diameter = 3 mm and depth = 30 mm) can be finished at a time by controlling machining parameters. It is otherwise not possible. This process can be used to control surface finish of the cooling holes in a turbine blade or surface finish of stator and rotor blades of a turbine. Some work has been reported [4,6] regarding the modelling of AFM process. Majority of these models are based on the simplified assumptions like medium is isotropic and homogeneous, medium properties are independent of the fluid temperature, and constant with time and space. The abrasive grains are considered spherical in shape and subjected to uniform load, and all the grains are of uniform size. In real practice, it is not so. The surface irregularities on the work piece are assumed to be triangular in shape. As a result of such assumptions, the discrepancy between the experimental and analytical results is likely to occur as shown in Fig.2 to Fig.5 [4, 7].
Some efforts are being made to enhance the material removal rate (MRR) during AFM by
the application of the magnetic field while using magnetic abrasive particles {MAps) in
place of simple abrasive particles. This process is named as magnetic abrasive flow machining (MAFM) [9]. The principle of working can be seen from Fig.6 where the application of magnetic field attracts and densities the MAPs near the inner wall of the workpiece. As a result, effective abrasive concentration increases near the wall as compared to the rest of the medium. It enhances the MRR as compared to normal AFM because of the two reasons: (a) increased effective concentration of the abrasive particles near the wall of the workpiece, and (b) increased radial force acting on the abrasive particles leading to the increased depth of cut and hence increased MRR and comparatively rapid improvement in surface finish in the initial stage.