Seminar On Advanced Fine Finishing Processes report Download
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 and 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.
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).
MAGNETORHEOLOGICAL FINISHING (MRF)
Precision lenses are usually made of brittle materials such as glass, and they tend to crack during machining I finishing. Even a single microscopic crack can drastically hinder a lens’s performance and make it to fail in performing its intended function. Manufacture of a lens usually involves two operations – grinding and finishing. Grinding operation makes a lens close to the desired size while finishing removes the cracks and surface imperfections either created by grinding or could not be removed during grinding. Manual grinding and polishing are non-deterministic and a high local pressure may lead to subsurface damage. To take care of these difficulties, Magnetorheological-finishing (MRF) process has been developed which is automatic in nature.
Magnetic Float Polishing (MFP)
This process was developed for gentle finishing of very hard materials like ceramics, which develop defects during grinding leading to fatigue failure. To achieve low level of controlled forces, magnetic field is used to support abrasive slurry in finishing ceramic products like ceramic balls and bearing rollers. This process is known as Magnetic Float
Polishing (MFP). The MFP technique is based on the Ferro- magnetic behaviour of a magnetic fluid that can levitate a non-magnetic fluid and abrasives suspended in it by magnetic field. The levitation force applied on the abrasives is proportional to the field gradient and is extremely small and highly controllable. It is a good method for super finishing of brittle materials with flat and spherical shapes
ION BEAM MACHINING (IBM)
Nano-technology is the target of ultraprecision machining having capabilities of producing surface finish of the order of 1nm or less which means approaching towards the ultimate surface finish. Ion beam machining is a molecular manufacturing (or atomic size stock removal) process based on the sputtering off phenomenon of work material by bombardment of energised ions of 1 to 10 keV and current density of 1 mill amphere/cm2. This process can be applied to manufacture ultra-fine precision parts of lectronic and mechanical devices. The sputtering off is basically a knocking out phenomenon of surface atoms of workpiece by the kinetic momentum transfer from incident ions to the target atoms. Removal of atoms from the work surface will occur when the actual energy transferred exceeds the usual binding energy of 5- 10 ev.
Ions of higher energy may transfer enough momentum such that more than one. atom causes a cascading effect in the layer near the surface, removing several atoms. Ions of still higher energy may get implanted deep within the material after ejecting out
several atoms or molecules. But the bombardment of so much high energy ions is not desirable to avoid any kind of damage to the workpiece surface.
ELASTIC EMISSION MACHINING
This process removes material from the workpiece surface to atomic level by mechanical methods, and gives completely mirrored, crystallographically and physically undisturbed finished surface. It can give surface of the order of atomic dimensions (~ 0.2 nm to 0.4 nm) [17-20]. Using ultrafine particles to collide with the workpiece surface, it may be possible to finish the surface by the atomic scale elastic fracture without plastic deformation [19,20], and the process is known as Elastic Emission Machining (EEM). Fig.shows working principle of EEM through the schematic diagram. The polyurethane ball used during EEM is of about 56 mm diameter. This ball is mounted on a shaft whose axis of rotation is inclined at about 45° to the vertical axis, and it is driven by a variable speed motor. The workpiece is immersed in the slurry of zrO2 or A12O3 (size 20 nm to 20 ìm) abrasives and water as carrier. The slurry is circulated in the gap by a diaphragm pump, and maintained at constant temperature with a heat exchanger. The proposed mechanism of material removal due to slurry and work interaction involves erosion of the surface atom by the bombardment of abrasive particles without the introduction of dislocation.
The importance of ultrafine finishing processes using abrasive as cutting tool, and their capabilities to achieve nanometer order surface finish is discussed. Working principle of seven such advanced finishing processes, viz. AFM, MAFM, MAP, MFP, MRAM, EEM
and IBM have been explained in brief. It has been observed that the precise control of forces on abrasive particles using non-traditional methods discussed in this paper, proved useful in performing ultra precision finishing. Fine finishing of brittle materials like ceramics, glasses, and semiconductor wafers can be easily done in nanometer range. The exact mechanics of abrasive interaction with the workpiece surface in most of these processes is still subject of in-depth research, and need involvement of multidisciplinary sciences.