19-07-2012, 01:39 PM
Assembly of microsystems
[attachment=28070]
TERMS OF REFERENCE
Where natural creatures grow from a single cell, manmade
artifacts, like industrial products, are mostly
assembled from different components. Assembly is
therefore a very important process in the genesis of a
product.
There are many reasons why products may consist of
different parts. Different functions require different
materials in one and the same device. In mechanisms,
pivots require flexible materials while the links themselves
must be stiff. Electrical actuators are made of conducting
as well as isolating materials. The rotor and the stator of a
motor are different parts by their very nature. Products
may be too complex to be produced as a single part.
Some parts are wearing out and must be regularly
replaced.
MARKET PROSPECTS FOR MEMS AND MST [2]
In 1998, NEXUS (The European Network of Excellence in
Multifunctional Microsystems) established a task force
entitled ‘Market Analysis MST’ to prepare an applicationsoriented
in-depth analysis of MST markets from 1996
through the year 2002.
ASSEMBLY PROBLEMS IN THE MICROWORLD
The main difference between macro- and micro-assembly
is the required positional accuracy of automatic assembly
machines. In the macroworld, a precision of a few
hundred microns is typical for serial link robotic
manipulators with four to six axes. In the microworld,
submicron precision is often required, comparable to
wafer stepper precision. This degree of precision is
beyond the calibration range of conventional open-loop
precision assembly devices used in industry. Closed-loop
strategies are required to compensate for poor kinematic
models and thermal effects. Real-time vision feedback is
perfectly suited for this application.
Assembly by microrobots
As tolerances in micromechanics lie in the nanometre
range, assembly robots should be very precise. The
manipulation accuracy of conventional robots is
mechanically limited, since disturbing influences which
are often negligible in the macroworld, such as fabrication
defects, friction, thermal expansion or computational
errors, play an important role in the microworld.
Furthermore, these robots are subject to mechanical
wear, and must undergo regular maintenance and
calibration, which makes them expensive.
Vacuum gripper
A vacuum gripper is very simple as it consists mainly of a
thin tube or pipette connected to a vacuum pump. This
makes this kind of gripper cheap and easy to replace.
This is important as microtools are fragile and have to be
replaced frequently [23].
A particular problem when manipulating microparts is that
the tube has to be very thin and, therefore, is easily
obstructed by small particles. An interesting alternative is
to generate the vacuum in the gripper itself as presented
in [44]. The surface of the tip is covered by microholes of
10 or 15 μm diameter.
[attachment=28070]
TERMS OF REFERENCE
Where natural creatures grow from a single cell, manmade
artifacts, like industrial products, are mostly
assembled from different components. Assembly is
therefore a very important process in the genesis of a
product.
There are many reasons why products may consist of
different parts. Different functions require different
materials in one and the same device. In mechanisms,
pivots require flexible materials while the links themselves
must be stiff. Electrical actuators are made of conducting
as well as isolating materials. The rotor and the stator of a
motor are different parts by their very nature. Products
may be too complex to be produced as a single part.
Some parts are wearing out and must be regularly
replaced.
MARKET PROSPECTS FOR MEMS AND MST [2]
In 1998, NEXUS (The European Network of Excellence in
Multifunctional Microsystems) established a task force
entitled ‘Market Analysis MST’ to prepare an applicationsoriented
in-depth analysis of MST markets from 1996
through the year 2002.
ASSEMBLY PROBLEMS IN THE MICROWORLD
The main difference between macro- and micro-assembly
is the required positional accuracy of automatic assembly
machines. In the macroworld, a precision of a few
hundred microns is typical for serial link robotic
manipulators with four to six axes. In the microworld,
submicron precision is often required, comparable to
wafer stepper precision. This degree of precision is
beyond the calibration range of conventional open-loop
precision assembly devices used in industry. Closed-loop
strategies are required to compensate for poor kinematic
models and thermal effects. Real-time vision feedback is
perfectly suited for this application.
Assembly by microrobots
As tolerances in micromechanics lie in the nanometre
range, assembly robots should be very precise. The
manipulation accuracy of conventional robots is
mechanically limited, since disturbing influences which
are often negligible in the macroworld, such as fabrication
defects, friction, thermal expansion or computational
errors, play an important role in the microworld.
Furthermore, these robots are subject to mechanical
wear, and must undergo regular maintenance and
calibration, which makes them expensive.
Vacuum gripper
A vacuum gripper is very simple as it consists mainly of a
thin tube or pipette connected to a vacuum pump. This
makes this kind of gripper cheap and easy to replace.
This is important as microtools are fragile and have to be
replaced frequently [23].
A particular problem when manipulating microparts is that
the tube has to be very thin and, therefore, is easily
obstructed by small particles. An interesting alternative is
to generate the vacuum in the gripper itself as presented
in [44]. The surface of the tip is covered by microholes of
10 or 15 μm diameter.