TERM PAPER Dynamic Pf Mc..Mec302

7/28/2019 TERM PAPER Dynamic Pf Mc..Mec302

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TERM PAPER

MEC-302

DYNAMICS OF MACHINE

STUDY OF GYROSCOPIC EFFECT ON MILLINGMACHINE (SPINDLE)

SUBMITTED TO: SUBMITTED BY:

Mr. MANDEEP SINGH AMARJEET SINGH

M3R30A18

11111629


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ACKNOWLEDGEMENT

First and foremost, we would like to thank to our course

teacher Mr. Mandeep Singh for the valuable guidance and

advice. He inspired us greatly to work in this Term paper. His

willingness to motivate us contributed tremendously to our

Term paper. We also would like to thank him for showing us

some examples related to the topic of our project.

Besides, we would like to thank the authority of Lovely

Professional University (LPU) for providing us with a good

environment and facilities to complete this Term paper.

Finally, an honorable mention goes to our families and friends

for their understandings and supports on us in completing this

project. Without helps of the particular that mentioned above,we would face many difficulties while doing this project.

AMARJEET SINGH


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Introduction:

Gyroscope is very useful in many applications. To choose the right rate

gyro sensor, some features, such as power consumption, weight,dimension, etc., must be taken into consideration. its play very vital role

in imparting right amount of force in right direction, so in mechanical

industry it s gain ample respect and application. Its uses approx

everywhere but some very specific fields are aerospace, automobile,

manufacturing industry and robots etc. In case of milling machine its play

role in reduce chattering sound and make it more precise.

Gyroscope history:The earliest known gyroscope instrument was made by German

Johann Bohnenberger who first wrote about it in 1817. In 1832,

American Walter R. Johnson developed a similar device that

was based on a rotating disk. The French mathematician Pierre-

Simon Laplace, recommended the machine for use as a

teaching aid, and thus it came to the attention of Leon

Foucault. In 1852, Foucault used it in an experiment involving

the rotation of the Earth. It was Foucault who gave the device

its modern name, in an experiment to see (Greek skope in, to

see) the Earth's rotation (Greek gyros, circle or rotation), which

was visible in the 8 to 10 minutes before friction slowed the

spinning rotor. In the 1860s, electric motors made the concept

feasible, leading to the first prototype gyrocompasses; the first

functional marine gyrocompass was patented in 1908 by


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German inventor Hermann Anschtz-Kaempfe. In the first

several decades of the 20th century, other inventors attempted

(unsuccessfully) to use gyroscopes as the basis for early black x

navigational systems by creating a stable platform from which

accurate acceleration measurements could be performed (in

order to bypass the need for star sightings to calculate

position). Similar principles were later employed in the

development of inertial guidance systems for ballistic missiles.

During World War Two, the gyroscope became the prime

component for aircraft and anti-aircraft gun sights.

What is Gyroscope?

A gyroscope is a device for measuring or maintaining

orientation, based on the principles of conservation of angular

momentum. A mechanical gyroscope is essentially spinning

wheel or disk whose axle is free to take any orientation. This

orientation changes much less in response to a given external

torque than it would without the large angular momentum

associated with the gyroscope's high rate of spin. Since external

torque is minimized by mounting the device in gimbals, its

orientation remains nearly fixed, regardless of any motion of

the platform on which it is mounted. Gyroscopes based on

other operating principles also exist, such as the electronic,

microchip-packaged MEMS gyroscope devices found in


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consumer electronic devices, solid state ring lasers, fiber optic

gyroscopes and the extremely sensitive quantum gyroscope.

Instead of a complete rim, four point masses, A, B, C, D,

represent the areas of the rim that are most important in

visualizing how a gyro works. The bottom axis is held stationary

but can pivot in all directions. When a tilting force is applied to

the top axis, point A is sent in an upward direction and C goes

in a downward direction. FIG 1. Since this gyro is rotating in a

clockwise direction, point A will be where point B was when the

gyro has rotated 90 degrees. The same goes for point C and D.

Point A is still traveling in the upward direction when it is at the


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90 degrees position in FIG 2, and point C will be traveling in the

downward direction. The combined motion of A and C cause

the axis to rotate in the "precession plane" to the right FIG 2.

This is called precession. A gyros axis will move at a right angle

to a rotating motion (In this case to the right). If the gyro were

rotating counterclockwise, the axis would move in the

precession plane to the left. If in the clockwise example the

tilting force was a pull instead of a push, the precession would

be to the left. When the gyro has rotated another 90 degrees

FIG 3, point C is where point A was when the tilting force was

first applied. The downward motion of point C is now

countered by the tilting force and the axis does not rotate in

the "tilting force" plane. The more the tilting force pushes the

axis, the more the rim on the other side pushes the axis back

when the rim revolves around 180 degrees. Actually, the axis

will rotate in the tilting force plane in this example. The axis will

rotate because some of the energy in the upward and

downward motion of A and C is used up in causing the axis to

rotate in the precession plane. Then when points A and C finally

make it around to the opposite sides, the tilting force (being

constant) is more than the upward and downward counter

acting forces. The property of precession of a gyroscope is used

to keep monorail trains straight up and down as it turns

corners. A hydraulic cylinder pushes or pulls, as needed, on one


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axis of a heavy gyro. Sometimes precession is unwanted so two

counter rotating gyros on the same axis are used.

Milling process:Milling is the process of machining flat, curved, or irregular

surfaces by feeding the work piece against a rotating cutter

containing a number of cutting edges. Milling is a process

where material is removed by a spinning tool, which has several

cutting teeth. The main difference between modeling the

milling and the turning process is that the chip thickness in

milling is not constant, but periodic. Some process parameters

are shown:

1. Feed per tooth f,.

2. Axial depth-of-cut up

3. Spindle speed w


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Several types of milling exist:

Up milling, where the entry angle is zero and the exit angle is

non-zero,

Down-milling, where the entry angle is nonzero and the exit

angle is zero,

Face milling, where the entry angle PHI and exit angle PHI of

the milling cutter relative to the work piece are nonzero,

Slotting, where the entry angle is zero and the exit angle is180.

GYROSCOPIC EFFECT ON MILLING MACHINE:

The process of milling is used widely in many sectors of

industry. The milling of large structures is done in e.g. the

airplane building industry, where large amounts of material areremoved. To make the process the most efficient, the speed of

the process should be as high as possible while maintaining a

high quality level. During the milling process chatter can arise at

certain combinations of spindle speed and depth-of-cut. This

behavior is usually undesired, because in such a case a non-

smooth surface of the work piece is caused by heavy vibrationsof the cutter. In addition the machine and cutting tool wear out

rapidly. Several studies have been done to understand and

model the phenomenon chatter. Both linear and nonlinear


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models have been developed, where nonlinearities are

modeled in several different ways. Early studies have shown

that the border between stable and unstable cuts in terms of

the depth-of-cut can be visualized as a function of spindle

speed. This results in a Stability Lobe Diagram (SLD). With the

help of these diagrams it is possible to find the point with a

combination of spindle speed and depth-of-cut which has the

largest metal removal rate while avoiding chatter.


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GYROSCOPIC EFFECT AS A FUNCTION OF SPINDLE

SPEED:

For low spindle speeds (100-400 rpm) a stability analysis is

applied, where the mean chip thickness is measured. The

model is validated by experiments. Experiments and

simulations done are down milling of 30' helix angle end mill set

at an radial depth-of-cut of 1.5 mm and an axial depth of cut of

6,4 mm. In the experiments, three parameters are varied at a

spindle speed of 135 rpm:

Radial depth of cut Number of flutes. The federate per minute is held

constant, so the feed per tooth f, increases if the number

of flutes decreases

Federate per minuteNote that on the vertical axis, the average chip thickness is

shown. Chip thicknesses above the line result in an unstable

cut, whereas chip thicknesses below the line result in a chatter-

free cut.


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Figure shows the limit of stability decreases with an increasing

feed. If the federate is 70mm/min, the chip thickness is above

the stability border. If the federate decreases then chip


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thickness also decreases, this increases the stability of milling

machine spindle.

Gyroscopic couple in case of milling machinespindle:

A new dynamic milling model of a rotating spindle is developed

and the gyroscopic effect of the spindle on the stability

characteristics of the milling system is investigated for the first

time. The results show that although the gyroscopic effect of

the rotating spindle does not change the instability regions in

milling, it increases the real parts of the Eigen values of thesystem or reduces the critical axial depth of cut. In other words,

it makes the stability prediction less conservative. Its pure

application of gyroscopic effect, because when the cutting done


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with help of tool, there are certain force which directly work on

spindle, which bound it to some short of motion, so for

avoiding that, and avoiding such important disturbance which

enhance productivity gyroscopic effect is very important.

For the milling process aided by AMB, shown in Fig. 6, the

cutting force, Fc, is mainly determined by the axial cut depth, a,

feed rate, f, and spindle speed, . However, at normal

operation mode, the spindle speed and feed rate are generally

retained constants. Therefore, the axial cut depth, a, is, in fact,the key factor to determine the pattern of cutting dynamics. In

order to counterbalance the cutting force and regulate the

spindle position deviation, d, the models of the subsystems,


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shown in Fig. 6, are to be constructed by experiments at first. In

Fig. 6a, the lateral force to the spindle, Fm, represents the

magnetic force exerting on the spindle by the AMB while the

cutting process is not engaged at all. The spindle model at idle

operation mode, shown in Fig.6a, is constructed in order to

explore the link of the shaft position deviation, d, against the

corresponding exerted force, i.e., the magnetic force, Fm.

Similarly, the dynamic model shown in Fig. 6b represents the

spindle position deviation, d, against the axial cut depth, a. By

comparison of the two dynamic models in Fig. 6, the resulted

cutting force, due to milling process, can be estimated for a

given axial cut depth and the available measurement of spindle

position.

Conclusion:

Several researchers have studied and modeled the

phenomenon chatter. Chatter is the result of several causes.

Primary chatter is the consequence of friction effects between

the tool and the chip, mode coupling or thermodynamics of the

cutting process. Secondary chatter is caused by regeneration of

waviness of the surface of the work piece. Both linear and

nonlinear models have been developed in different ways. The

friction force can be modeled as a nonlinear function of the

cutting parameters. Partial tool jump-out can be modeled. Also

the gyroscopic effect of the spindle speed has been modeled.


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Experiments are performed to study chatter and to validate the

models. Several researchers conclude that nonlinearities should

be modeled for a more accurate prediction of chatter. They

show that the milling process contains phenomena which

cannot be modeled using linear models. Gyroscope is very

important and powerful arrangement for removing direction a

alignment and for maintain balancing, its device which used in

balance the specimen like milling machine spindle and lots

more.

References:

www.Google.com www.Wikipedia.org Theory of machine by R.S khurmi www.gyroscope.com/Gyroscopes/


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