Presentation on Spur Gear

Fabrication Of Spur Gear

Supervised by Md.Golam Kader Professor, Md Rasedul Islam Lecturer, Department of Mechanical Engineering, KUET

Course ME 3118

Khulna University Of Engineering & TechnologyDepartment of Mechanical Engineering

Submitted By

Md Rezowan Kabir [1205016]Md Hasanuzzaman [1205017]Md Abul Kashem Hemel [1205018]Md Ashik Mahmud [1205019]Saikat Biswas [1205020]

Chapter 1

Khulna university of Engineering &Technology

Objectives

To Study about gear.To Study about the classification of gear.To Study about spur gear.Fabrication of spur gear.To Study of advantages and disadvantages of spur gear.

Khulna university of Engineering & Technology

IntroductionA gear is a rotating machine part having cut teeth, which mesh with another toothed part to transmit torque, in most cases with teeth on the one gear being of identical shape, and often also with that shape on the other gear.

Two or more gears working in a sequence are called a gear train or, in many cases, a transmission; suchGear arrangements can produce a mechanical advantage through a gear ratio and thus may be considered a simple machine.


Introduction (Continued)Gears are Used to Control Power Transmission in These Ways1. Changing the direction through which power is transmitted (i.e. parallel, right angles, rotating, linear etc.)2. Changing the amount of force or torque3. Changing RPM

When two gears mesh, and one gear is bigger than the other (even though the size of the teeth must match), a mechanical advantage is produced, with the rotational speeds and the torques of the two gears differing in an inverse relationship.


Types Of Gears According to the position of axes of the shafts.Parallel

1.Spur Gear2.Helical Gear3.Rack and Pinion

Intersecting1.Bevel Gear

Non-intersecting and Non-parallel1.worm and worm gears


Spur GearSpur gears are the most commonly used gear type. They are characterized by teeth which are perpendicular to the face of the gear. Spur gears are by far the most commonly available, and are generally the least expensive. Teeth is parallel to axis of rotation Transmit power from one shaft to another parallel shaftleast expensive


Applications of Spur GearIn mechanical systems where we’ll require simple design, more efficient power transfer, and low speed applications where noise does not matter, we should go for spur gears.Spur gears have a wide range of applications. They are used in:

Metal cutting machines Power plants Marine engines Mechanical clocks and

watches Fuel pumps Washing Machines

Gear motors and gear pumps

Rack and pinion mechanisms

Material handling equipments

Automobile gear boxes Steel mills Rolling mills


Chapter 2

CONTENTS


GEAR TERMINOLOGY

Pitch surface : The surface of the imaginary rolling cylinder (cone, etc.) that the toothed gear may be considered to replace.

Pitch circle: A right section of the pitch surface.

Root (or dedendum) circle: The circle bounding the spaces between the teeth, in a right section of the gear.Addendum: The radial distance between the pitch circle and the addendum circle.Dedendum: The radial distance between the pitch circle and the root circle.Clearance: The difference between the dedendum of one gear and the addendum of the mating gear.


GEAR TERMINOLOGY(CON’D)

Face of a tooth: That part of the tooth surface lying outside the pitch surface.

Flank of a tooth: The part of the tooth surface lying inside the pitch surface.

Circular thickness (tooth thickness) : The thickness of the tooth measured on the pitch circle. It is the length of an arc and not the length of a straight line.

Tooth space: The distance between adjacent teeth measured on the pitch circle.

Backlash: The difference between the circle thickness of one gear and the tooth space of the mating gear.



Module m: Pitch diameter divided by number of teeth. The pitch diameter is usually specified in inches or millimeters; in the former case the module is the inverse of diametral pitch.

Fillet : The small radius that connects the profile of a tooth to the root circle.

Pinion: The smaller of any pair of mating gears. The larger of the pair is called simply the gear.

Velocity ratio: The ratio of the number of revolutions of the driving (or input) gear to the number of revolutions of the driven (or output) gear, in a unit of time.



Pressure angle: Pressure angle in relation to gear teeth, also known as the angle of obliquity, is the angle between the tooth face and the gear wheel tangent. It is more precisely the angle at a pitch point between the line of pressure (which is normal to the tooth surface) and the plane tangent to the pitch surface.

Fig: Pressure angle of spur gear[1]


GEAR TERMINOLOGY

Fig2: Spur gear terminology[2] Fig3: Spur gear terminology[3]

PROBLEMIt is desired to transmit 30 hp at 1800 rpm of the pinion; intermittent service; with light shock (§13.18); preferably not less than 20, 20o -full-depth teeth on the pinion; strength reduction factor Kf = 1.25 should be conservative; mw =1.5 Decisions must be made concerning the material and quality of cutting the teeth. Since the design is for strength only, it will be convenient to express Ft , Fd , vm ,face width b in terms of pitch Pd and arrange an equation containing s and Pd convenient for iteration. Weak material results in a relatively large pinion with high peripheral speed. A very strong material may be unnecessarily expensive. On a production bases carefully cut teeth should have a reasonable cost. Specify material, accuracy of cutting, pitch, face width, and tooth numbers.


SOLUTION


SOLUTION(CON’D)


SOLUTION(CON’D)


Pd = 8b=8.5/Pd

Np= 20 , Ng Np =mw

Ng=20*1.2=24b=1.0625Np=20Ng=24So the pitch diameter of the gear Pd = 8Face width b =1.0625 inchNumber of teeth = 24

Drawing & Dimensions


Rendering Image


Chapter 3

CONTENTS


MATERIAL

1.Steel2.Cast Iron3.Stainless Steel4.Aluminum5.Bronze6.Nylon7.Non-metallic phenolic


Why we choose Cast Iron?

• High tensile strength to prevent failure against static loads.• High endurance strength to withstand dynamic loads.• Low coefficient of friction.• Good manufacturability.• Low cost.• High availability.


MANUFACTURING PROCESS OF SPUR GEAR

1.Casting2.Milling3. Broaching4. Gear hobbing5. Gear forming


Why we choose Milling Process?

1. It is Compatible with All Materials2. Flexible Use3. Short Lead Times4. Better accuracy


Milling Process

This is one of the initial and best known and metal removal process for making gears. This method requires the usage of a milling machine. It is also to be noted that this method can produce nearly all types of gears. The method involves the use of a form cutter, which is passed through the gear blank to create the tooth gap. This method is right now used only for the manufacture of gears requiring very less dimensional accuracy. To put it correctly this method is currently outdated.


Milling Process

Fig: Milling Process


Final Project


Fig: Manufactured Spur Gear

References[1] FAIRES VIRGIL MORING, “DESIGN OF MACHINE ELEMENTS”, 4th edition, The Macmillan Company, New York/Collier-Macmillan Limited, London

[2] Jain R.K., “ Production Technology”, 16th edition, 2-B, Nath Market, Nai Sarak, Delhi-110006

[3]http://www.brighthubengineering.com/manufacturing-technology/7118-gear-manufacturing-methods

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Presentation on Spur Gear

Engineering

Transcript of Presentation on Spur Gear