MAGNETIC ABRASIVE
FINISHING PROCESS
Finishing processes may be employed to: improve appearance, adhesion or wettability, solderability, corrosion resistance, tarnish resistance, chemical resistance, wear
resistance, hardness, modify electrical conductivity, remove burrs and other surface flaws, and control the
surface friction. In
limited cases some of these techniques can be used to restore original
dimensions to salvage or repair an item. An unfinished surface is often called mill
finish.
Abrasive machining is a machining process where material
is removed from a work piece using a multitude of small abrasive particles.
Common examples include grinding, honing, and polishing. Abrasive processes are
usually expensive, but capable of tighter tolerances and better surface finish
than other machining processes. Abrasive machining processes can be
divided into two categories based on how the grains are applied to the work
piece, in bonded abrasive processes, the particles are held together within a
matrix, and their combined shape determines the geometry of the finished work
piece. For example, in grinding the particles are bonded together in a wheel.
As the grinding wheel is fed into the part, its shape is transferred onto the work
piece. In loose abrasive processes, there is no structure connecting the
grains. They may be applied without lubrication as dry powder, or they may be
mixed with a lubricant to form a slurry. Since the grains can move
independently, they must be forced into the work piece with another object like
a polishing cloth or a lapping plate.
Traditionally
finishing processes are crucial, expensive uncontrolled and a labour intensive
phase in the overall production. It also includes total production cost and
time. The ever increasing demand from the industry for better quality &
cost competitive product with complex design material need to good surface
finishing. In case of some application like internal finishing of capillary
tube, machining of titanium alloy, aircraft application, medical application where
high surface finish parts are required. Magnetic abrasive finishing (MAF) is
the process which capable of precision finishing of such work pieces. Since MAF
does not require direct contact with the tool, the particles can be introduced
into area which are hard to reach by conventional techniques.
MAF Process can be
classified based on the type of magnetic field used and type of work piece
BASED ON TYPE OF MAGNETIC
FIELD
1. Magnetic Abrasive Finishing with
Permanent Magnet
2. Magnetic Abrasive Finishing with
Direct Current
3. Magnetic Abrasive
Finishing with Alternating Current
BASED ON
1. Lathe based MAF
2. Milling based MAF
MAF is process in which mixture of non-ferromagnetic abrasive and
ferromagnetic iron particle is taken and magnetically energized using a
magnetic field. The work piece is kept between the two poles (N&S POLE) of
a magnet. The working gap between the work piece and a magnet is filled with
magnetic abrasive particle (MAPs). MAPs can be used as bonded or unbounded. The
magnetic abrasive particles join each other along lines of magnetic force and
form a flexible magnetic abrasive brush (FMAB). This brush behaves like a multi point cutting tool for the finishing operation.
The main advantages of
Magnetic abrasive finishing process are
1. The
setup is independent of work piece material; it can efficiently
finish ceramics, stainless steel, brass,
coated carbide and silicon.
2. This
method can have used to finish ferromagnetic materials but as well
as no ferromagnetic materials.
3. Self-adaptability
and controlability.
4. Due to the flexible magnetic abrasive
brush, it can finish any
Symmetric work piece shape, if electromagnet designed accordingly.
5.
The finishing tool requires neither compensation nor dressing
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