18-08-2012, 12:44 PM
Magnetic field assisted abrasive based micro-/nano-finishing
Magnetic field assisted abrasive based micro-nano finishing.pdf (Size: 3.83 MB / Downloads: 149)
Introduction
Fabrication of products deals with the building of machines,
structures or process equipment by cutting, shaping, welding
and assembling of components made of the same or different
materials. Fabrication can be classified into two main categories:
macro-fabrication and micro-fabrication. The first one considers
the process of fabrication of structures/parts/products/features
that are measurable and observable by naked eye (≥1mm in
size) while the second category deals/considers the miniature
structures/parts/products/features which are not easily visible
with naked eye, and have dimensions smaller than 1mm
(1m≤dimension≤999m). There are various methods/ways by
which micro-fabrication of products can be achieved (Fig. 1). However,
deposition, and (2) material removal. This article deals with the
material removal processes only. Some of the traditional material
removal processes can be used for micro-fabrication. However,
they have some constraints hence advanced material removal processes
are more commonly used for this purpose. Fig. 2(a) shows
a classification of advanced micro-/nano-machining (MNM) and
micro-/nano-finishing (MNF) processes.
Abrasive based advanced micro-/nano-finishing processes
In today’s advanced engineering industries, the designers’
requirements on the components are stringent, for example,
extraordinary properties of materials, complex shaped 3D components
(Fig. 3(a, i–iv)), miniature features, nano-level surface
finish on complex geometries which are not feasible to achieve
by any traditional methods (say, thousands of turbulated cooling
holes in a turbine blade, Fig. 3(a, iv), making and finishing of
micro-fluidic channels in the electrically non-conducting materials
(say, glass), etc. Such objectives can be achieved only through
the advanced manufacturing processes in general and advanced
machining processes in particular. In this section, the working principles
of abrasive based advanced micro-/nano-finishing processes
(Fig. 4) are discussed.
Magnetorheological Finishing. The high precision lenses are
usually made of brittle material such as glass, which tends to crack
during machining/finishing. To overcome the difficulties being
faced in finishing the lenses, a technology has been developed to
automate the lens finishing process known as Magnetorheological
Finishing (MRF) (Fig. 4(e)) (Kordonski, 1996). This process relies on
a unique “smart fluid”, known as Magnetorheological (MR) fluid
which is a suspension of micron sized magnetizable particles such
as carbonyl iron particles (CIPs), dispersed in a non-magnetic carrier
medium like silicone oil, mineral oil, or water. In the absence
of magnetic field, an ideal MR-fluid exhibits Newtonian behavior.
Magnetorheological effect is observed on the application of
external magnetic field to the MR-fluid. In the presence of external
magnetic field it behaves as non-Newtonian fluid.