Ao1 mechanical term paper
Transcript of Ao1 mechanical term paper
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Term paper
EXPLAIN ABOUT THE BALANCING OF
MACHINES
NAME- GAURAVCLASS- B.Tech C.S.CROLLNO- A01REG.NO-10906315
SUBMITTED TO - Er. AmritpreetSingh
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ABSTRACTA balancing machine is a measuring tool used for
balancing rotating machine parts such as rotors forelectric motors, fans, turbines, disc brakes, disc drives,
propellers and pumps. The machine usually consists of
two rigid pedestals, with suspension and bearings on top
supporting a mounting platform. The unit under test is
bolted to the platform and is rotated either with a belt-,
air-, or end-drive. As the part is rotated, the vibration in
the suspension is detected with sensors and that
information is used to determine the amount of unbalance
in the part. Along with phase information, the machine can
determine how much and where to add weights to balance
the part.
INTRODUCTIONThere are three basic types of balancing machines: static
balancing stands, hard bearing machines, and soft bearing
machines.
Static balancing stands do not require spinning up and
can correct for static or single-plane unbalance only. They
are sensitive enough for grinding wheels. They feature low
cost and safe operation.
Hard bearing balancing machines have stiff work
supports, lower sensitivity, and more sophisticated
electronics. They require a massive, stiff foundation
where they are permanently set and calibrated in place.
Background vibration from adjacent machines or activity
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can affect balancing results. They are used mostly in
manufacturing production operations where fast cycle
time is required.
Soft bearing balancing machines have flexible work
supports, high sensitivity, and simple electronics. They
can be placed anywhere, and can be moved without
affecting calibration. Their flexible work supports provide
natural isolation so nearby shop activity can continue
while the machine still achieves fine balance levels. A
belt-driven soft bearing balancing machine can always
achieve finer balance results than a hard bearing
machine. Every repair facility should have a soft bearing
balancing machine and perhaps a static balancing stand.
Hard-bearing vs. soft-bearingThere are two main types of balancing machines, hard-
bearing and soft-bearing. The difference between them,
however, is in the suspension and not the bearings.
HARD BEARING BALANCING MACHINE
In a hard-bearing machine, balancing is done at a
frequency lower than the resonance frequency of the
suspension. In a soft-bearing machine, balancing is done
at a frequency higher than the resonance frequency of the
suspension. Both types of machines have various
advantages and disadvantages. A hard-bearing machine is
generally more versatile and can handle pieces with
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greatly varying weights, because hard-bearing machines
are measuring centrifugal forces and require only a one-
time calibration. Only five geometric dimensions need to
be fed into the measuring unit and the machine is ready
for use. Therefore, it works very well for low- and middle-
size volume production and in repair workshops.
Figure 1Hard Bearing Balancing Machine
SOFT BEARINGBALANCING MACHINE
A soft-bearing machine is not so versatile with respect to
amount of rotor weight to be balanced. The preparation of
a soft-bearing machine for individual rotor types is more
time consuming, because it needs to be calibrated for
different part types. It is very suitable for high-production
volume and high-precision balancing tasks.
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Figure 2Soft Bearing Balancing Machine
Hard- and soft-bearing machines can be automated to
remove weight automatically, such as by drilling or
milling, but hard-bearing machines are more robust and
reliable. Both machine principles can be integrated into a
production line and loaded by a robot arm or gantry,
requiring very little human control.
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How it works
With the rotating part resting on the bearings, a vibration
sensor is attached to the suspension. In most soft-bearing
machines, a velocity sensor is used. This sensor works by
moving a magnet in relation to a fixed coil that generates
voltage proportional to the velocity of the vibration.
Accelerometers, which measure acceleration of the
vibration, can also be used.
A photocell (sometimes called a phaser), proximity sensor,
or encoder is used to determine the rotational speed, as
well as the relative phase of the rotating part. This phase
information is then used to filter the vibration information
to determine the amount of movement, or force, in one
rotation of the part. Also, the time difference between the
phase and the vibration peak gives the angle at which the
unbalance exists. Amount of unbalance and angle of
unbalance give an unbalance vector.
Calibration is performed by adding a known weight at a
known angle. In a soft-bearing machine, trial weights must
be added in correction planes for each part. This is
because the location of the correction planes along the
rotational axis is unknown, and therefore it is unknown
how much a given amount of weight will affect the
balance. By using trial weights, you are adding a known
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weight at a known angle and getting the unbalance vector
caused by it. This vector is then compared to the original
unbalance vector to find the resultant vector, which gives
the weight and angles needed to bring the part into
balance. In a hard-bearing machine, the location of the
correction plane must be given in advance so that the
machine always knows how much a given amount of
weight will affect the balance.
Types of Balancing machines
Static Balancing machines
Static balancing machines differ from hard- and soft-
bearing machines in that the part is not rotated to take ameasurement. Rather than resting on its bearings, the part
rests vertically on its geometric center. Once at rest, any
movement by the part away from its geometric center is
detected by two perpendicular sensors beneath the table
and returned as unbalance. Static balancers are often
used to balance parts with a diameter much larger than
their length, such as fans. The advantages of using a
static balancer are speed and price. However a static
balancer can only correct in one plane, so its accuracy is
limited.
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Figure 3STATIC BALANCING MACHINE
Blade Balancing Machine
A blade balancing machine attempts to balance a part in
assembly, so minimal correction is required later on.
Blade balancers are used on parts such as fans,
propellers, and turbines. On a blade balancer, each blade
to be assembled is weighed and its weight entered into a
balancing software package. The software then sorts the
blades and attempts to find the blade arrangement with
the least amount of unbalance.
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Figure 4 Blade Balancing Machine
Portable Balancing Machine
Portable balancing machines are used to balance parts
that cannot be taken apart and put on a balancing
machine, usually parts that are currently in operation such
as turbines, pumps, and motors. Portable balancers come
with displacement sensors, such as accelerometers, and a
photocell, which are then mounted to the pedestals or
enclosure of the running part. Based on the vibrations
detected, they calculate the parts unbalance. Many times
these devices contain a spectrum analyzer so the part
condition can be monitored without the use of a photocelland non-rotational vibration can be analyzed.
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Figure 5 Portable Balancing Machine
Vertical Dynamic Balancing Machines
Hi-tech make Hard bearing vertical balancing machines
are the best suitable choice for Pulleys, Impellers,
Grinding wheels, Turbine discs etc. HHV series are single
plane machines and HHVT series are two plane machines.
They are permanently calibrated machines.Hard bearing vertical balancing machines are rigid and
compact, which is designed to the operator's convenience
with, built in electronic compensation. Digital panel has
digital read-out systems, which includes options to suit
the various jobs like using photo-scanning system,
indication of angle and amount and unbalance. Drilling
Attachments, Reverting, Pneumatic job clamping and
other tooling system as per requirement.
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Figure 6 Vertical Dynamic Balancing Machine
Horizontal Dynamic Balancing Machines
Hi-tech make hard bearing horizontal balancing machines
are the ideal choice for balancing of different types of
rotors like pump rotors, impellers, pulleys, grindingwheels, turbine discs etc. This model is hard bearing type
horizontal two plane dynamic balancing machines with
digital based read systems. To increase the capacity of
the machines, for extra long rotors additional bed lengths
can be provided. All pedestals are designed to take 25 %
occasional over-load. Digital panel is provided with
potentiometer feeding of dimensions like A, B, C RR and
RL Amount unbalance along with angular position is
displayed separated for both correction planes. Plane
selection switch is provided to display both the planes
simultaneously.
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Figure 7 Horizontal Vertical Machine
Belt Driven Soft / Hard Bearing - Stroboscopic
Photo scanning Dynamic Balancing Machines.
Hi-tech make belt driven machines are best suited for
small rotors, impellers, armatures, grinding spindles, small
spindles, small pulleys etc. These machines eliminate the
errors due to driving couplings, adopters and connectors.
These errors are significant in small rotors and hence the
machines are more suitable for small components. Hi-tech
soft belt bearing machines are of rigid durable
construction. This machine Model-HSS-5, is specially
designed to balance self priming motor's, impellers,Rotors andV4" submersible pump rotors
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(Max.Lengthofthejob-500mm). Belt driven Dynamic
balancing machine's electronic panel is specially
designed to measure displacement measurement
principle. The controls are designed for easy and safe
operation. Vertical and / or Horizontal drilling attachment,
Reverting, Under belt drive, Tangential belt drive and any
other tooling system as per requirement.
Refrences
www.wikipedia.com
www.2dix.com
www.mst.edu/mecmovie/index.html
R.S Khurmi
Mechanical Sciences, G. K. Lal and Vijay Gupta, Narosa
Publishing house
http://www.wikipedia.com/http://www.2dix.com/http://www.wikipedia.com/http://www.2dix.com/