ao1 mechanical term paper

8/7/2019 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/

ao1 mechanical term paper

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