SPUR GEAR DEVELOPMENT USING RAPID PROTOTYPING BY REVERSE ENGINEERING

ABSTRACT:

This project is about application of reverse engineering. Reverse engineering helps in obtaining

the geometry of part or product which is not available otherwise. Its application makes it possible

to reconstruct the original component with its drawing and manufacturing process. It is used in

various fields but here the main application is related to broken Gear. In this present work a

broken tooth of gear of two wheeler bike has been taken. Currently this part is not available in

the market and drawing of the component does not exist. As the part is no longer available it has

to be made in-house so it will require all activities from designing to rapid prototyping. The

procedure includes various stages which will help understand the different phases of reverse

engineering.

The process starts with understanding the reverse engineering procedure. The part

geometry is first obtained with the help of scanning technology. Then with the use of

SOLIDWORKS SCAN TO 3D option the three-dimensional model of the spur gear is obtained.

Once the CAD model is obtained, the part is analyzed using SOLID WORKS simulation tool by

applying alloy steel material and by varying face width of the Gear. The stresses induced will be

low as the face width of gear increases. After the analysis, the pattern of the part is obtained

using Rapid prototyping machine. This can be used for Machining/ casting of the original part.

INTRODUCTION TO REVERSE ENGINEERING

In today’s intensely competitive global market, product enterprises are constantly seeking

new ways to shorten lead times for new product developments that meet all customer

expectations. In general, product enterprise has invested in CAD/CAM, rapid prototyping, and a

range of new technologies that provide business benefits. Reverse engineering (RE) is now

considered one of the technologies that provide business benefits in shortening the product

development cycle. Figure 1.1 below depicts how RE allows the possibilities of closing the loop

between what is “as designed” and what is “actually manufactured”.

Figure : product development life cycle

What Is Reverse Engineering?

Engineering is the process of designing, , assembling, manufacturing and maintaining products

and systems. There are two types of engineering, forward engineering and reverse engineering.

Forward engineering is the traditional process of moving from high-level abstractions and logical

designs to the physical implementation of a system. In some situations, there may be a physical

part/ product without any technical details, such as drawings, bills-of-material, or without

engineering data. The process of duplicating an existing part, subassembly, or product, without

drawings, documentation, or a computer model is known as reverse engineering. Reverse

engineering is also defined as the process of obtaining a geometric CAD model from 3-D points

acquired by scanning/ digitizing existing parts/products.

The process of digitally capturing the physical entities of a component, referred to as

reverse engineering (RE), is often defined by researchers with respect to their specific task

(Motavalli & Shamsaasef 1996). Abella et al. (1994) described RE as, “the basic concept of

producing a part based on an original or physical model without the use of an engineering

drawing”. Yau et al.(1993) define RE, as the “process of retrieving new geometry from a

manufactured part by digitizing and modifying an existing CAD model”. Reverse engineering is

now widely used in numerous applications, such as manufacturing, industrial design, and jewelry

design and reproduction For example, when a new car is launched on the market, competing

manufacturers may buy one and disassemble it to learn how it was built and how it works. In

software engineering, good source code is often a variation of other good source code. In some

situations, such as automotive styling, designers give shape to their ideas by using clay, plaster,

wood, or foam rubber, but a CAD model is needed to manufacture the part. As products become

more organic in shape, designing in CAD becomes more challenging and there is no guarantee

that the CAD representation will replicate the sculpted model exactly.

Reverse engineering provides a solution to this problem because the physical model is the

source of information for the CAD model. This is also referred to as the physical-to-digital

process depicted in Figure 1.2. Another reason for reverse engineering is to compress product

development cycle times. In the intensely competitive global market, manufacturers are

constantly seeking new ways to shorten lead times to market a new product. Rapid product

development (RPD) refers to recently developed technologies and techniques that assist

manufacturers and designers in meeting the demands of shortened product development time.

For example, injection-molding companies need to shorten tool and die

Figure : Physical-to-digital process

development time drastically. By using reverse engineering, a three-dimensional physical

product or clay mock-up can be quickly captured in the digital form, remodeled, and exported for

rapid prototyping/tooling or rapid manufacturing using multi-axis CNC machining techniques.

USE OF REVERSE ENGINEERING:

Following are some of the reasons for using reverse engineering:

• The original manufacturer no longer exists, but a customer needs the product, e.g., aircraft

spares required typically after an aircraft has been in service for several years.

• The original manufacturer of a product no longer produces the product, e.g., the original

product has become obsolete.

• The original product design documentation has been lost or never existed.

• Creating data to refurbish or manufacture a part for which there are no CAD data, or for which

the data have become obsolete or lost.

• Inspection and/or Quality Control–Comparing a fabricated part to its CAD description or to a

standard item.

• Some bad features of a product need to be eliminated e.g., excessive wear might indicate where

a product should be improved.

• Strengthening the good features of a product based on long-term usage.

• Analyzing the good and bad features of competitors’ products.

• Exploring new avenues to improve product performance and features.

• Creating 3-D data from a model or sculpture for animation in games and movies.

• Creating 3-D data from an individual, model or sculpture to create, scale, or reproduce artwork.

• Architectural and construction documentation and measurement.

• Fitting clothing or footwear to individuals and determining the anthropometry of a population.

• Generating data to create dental or surgical prosthetics, tissue engineered body parts, or for

surgical planning.

• Documentation and reproduction of crime scenes.

The above list is not exhaustive and there are many more reasons for using reverse

engineering, than documented above.

REVERSE ENGINEERING –THE GENERIC PROCESS:

The generic process of reverse engineering is a three-phase process as depicted in Figure 1.3.

The three phases are scanning, point processing, and application specific geometric model

development. Reverse engineering strategy must consider the following:

• Reason for reverse engineering a part

• Number of parts to be scanned–single or multiple

• Part size–large or small

• Part complexity–simple or complex

• Part material–hard or soft

• Part finish–shiny or dull

• Part geometry–organic or prismatic and internal or external

• Accuracy required–linear or volumetric

Figure : Reverse engineering – the generic process

Phase 1– Scanning:

This phase is involved with the scanning strategy–selecting the correct scanning technique,

preparing the part to be scanned, and performing the actual scanning to capture information that

describes all geometric features of the part such as steps, slots, pockets, and holes. Three-

dimensional scanners are employed to scan the part geometry, producing clouds of points, which

define the surface geometry. These scanning devices are available as dedicated tools or as add-

ons to the existing computer numerically controlled (CNC) machine tools. There are two distinct

types of scanners, contact and noncontact.

a. Contact Scanners

These devices employ contact probes that automatically follow the contours of a physical surface

.In the current market place, contact probe.

Figure : Contact scanning touch probe.

scanning devices are based on CMM technologies, with a tolerance range of +0.01 to 0.02 mm.

However, depending on the size of the part scanned, contact methods can be slow because each

point is generated sequentially at the tip of the probe. Tactile device probes must deflect to

register a point; hence, a degree of contact pressure is maintained during the scanning process.

This contact pressure limits the use of contact devices because soft, tactile materials such as

rubber cannot be easily or accurately scanned.

b. Noncontact Scanners:

A variety of noncontact scanning technologies available on the market capture data with no

physical part contact. Noncontact devices use lasers, optics, and charge-coupled device (CCD)

sensors to capture point data, as shown in Figure. Although these devices capture large amounts

of data in a relatively short space of time, there are a number of issues related to this scanning

technology.

• The typical tolerance of noncontact scanning is within ±0.025 to 0.2 mm.

• Some noncontact systems have problems generating data describing surfaces, which are

parallel to the axis of the laser (Figure 1.6).

• Noncontact devices employ light within the data capture process. This creates problems when

the light impinges on shiny surfaces, and hence some surfaces must be prepared with a

temporary coating of fine powder before scanning.

Figure : Optical scanning device. Originally published in Rapid Prototyping Casebook,

McDonald, J.A.

Figure : Vertical faces–touch probe versus a laser.

These issues restrict the use of remote sensing devices to areas in engineering, where the

accuracy of the information generated is secondary to the speed of data capture. However, as

research and laser development in optical technology continue, the accuracy of the commercially

available noncontact scanning device is beginning to improve.

The output of the scanning phase is point cloud data sets in the most convenient format.

Typically, the RE software provides a variety of output formats such as raw (X, Y, Z values

separated by space or commas).

Phase 2–Point Processing:

This phase involves importing the point cloud data, reducing the noise in the data collected, and

reducing the number of points. These tasks are performed using a range of predefined filters. It is

extremely important that the users have very good understanding of the filter algorithms so that

they know which filter is the most appropriate for each task. This phase also allows us to merge

multiple scan data sets. Sometimes, it is necessary to take multiple scans of the part to ensure

that all required features have been scanned. This involves rotating the part; hence each scan

datum becomes very crucial. Multiple scan planning has direct impact on the point processing

phase. Good datum planning for multiple scanning will reduce the effort required in the point

processing phase and also avoid introduction of errors from merging multiple scan data. A wide

range of commercial software is available for point processing. The output of the point

processing phase is a clean , merged, point cloud data set in the most convenient format. This

phase also supports most of the proprietary formats mentioned above in the scanning phase.

Phase 3–Application Geometric Model Development:

In the same way that developments in rapid prototyping and tooling technologies are

helping to shorten dramatically the time taken to generate physical representations from CAD

models, current RE technologies are helping to reduce the time to create electronic CAD models

from existing physical representations. The need to generate CAD information from physical

components will arise frequently throughout any product introduction process. The generation of

CAD models from point data is probably the most complex activity within RE because potent

surface fitting algorithms are required to generate surfaces that accurately represent the three-

dimensional information described within the point cloud data sets. Most CAD systems are not

designed to display and process large amounts of point data; as a result new RE modules or

discrete software packages are generally needed for point processing.

Generating surface data from point cloud data sets is still a very subjective process,

although feature-based algorithms are beginning to emerge that will enable engineers to interact

with the point cloud data to produce complete solid models for current CAD environments. The

applications of RE for generating CAD data are equally as important as the technology which

supports it. A manager’s decision to employ RE technologies should be based on specific

business needs.

This phase depends very much on the real purpose for reverse engineering. For example, if we

scanned a broken injection molding tool to produce a new tool, we would be interested in the

geometric model and also in the ISO G code data that can be used to produce a replacement tool

in the shortest possible time using a multi-axis CNC machine. One can also use reverse

engineering to analyze “as designed” to “as manufactured”. This involves importing the as

designed CAD model and superimposing the scanned point cloud data set of the manufactured

part. The RE software allows the user to compare the two data sets (as designed to as

manufactured). This process is also used for inspecting manufactured parts. Reverse engineering

can also be used to scan existing hip joints and to design new artificial hips joint around patient-

specific pelvic data. This creates the opportunity for customized artificial joints for each patient.

The output of this phase is geometric model in one of the proprietary formats such as IGES,

VDA, STL, DXF, OBJ, VRML, ISO G Code, etc.

INTRODUCTION TO POWER TRANSMISSION

Power transmission states that speed and torque conversions from rotating power source to other

device. Here in our project we design and analysis the intermediate shaft for stress and

deflection, it is necessary to know the applied forces. If the forces are transmitted through gears,

it is necessary to know the gear specifications in order to determine the forces that will be

transmitted to the shaft. But stock gears come with certain bore sizes, requiring knowledge of the

necessary shaft diameter. This project will focus on an overview of a power transmission system

design, demonstrating how to incorporate the details of each component into an overall design

process.

A typical two-stage gear reduction box is been used to understand the design process. The design

sequence is similar for variations of this particular transmission system.

Fig :compound reverted gear train.

1.2 TRANSMISSION

The term power transmission is defined as the movement of energy from a source to an output

device that performs work. In mechanical power transmissions, a device is interposed between a

source of power and a specific application for the purpose of adapting one to the other. Most

mechanical transmissions function as rotary speed changers; the ratio of the output speed to the

input speed may be constant (as in a gearbox) or variable. On variable-speed transmissions the

speeds may be variable in discrete steps or they may be continuously variable within a range.

The need for a transmission in an automobile is a consequence of the characteristics of the

internal combustion engine. Engines typically operate over a range of 600 to about

7000revolutions per minute (though this varies, and is typically less for diesel engines), while the

car's wheels rotate between 0 rpm and around 1800 rpm.

The most common use of power transmission is in motor vehicles, where the transmission adapts

the output of the internal combustion engine to the drive wheels. Such engines need to operate at

a relatively high rotational speed, which is inappropriate for starting, stopping, and slower travel.

Furthermore, the engine provides its highest torque and power outputs unevenly resulting in a

torque band and a power band. Often the greatest torque is required when the vehicle is moving

from rest or traveling slowly, while maximum power is needed at high speed. Therefore, a

system that transforms the engine's output so that it can supply high torque at low speeds, but

also operate at highway speeds with the motor still operating within its limits, is required.

Transmissions perform this transformation.

The transmission reduces the higher engine speed to the slower wheel speed, increasing torque in

the process. Transmissions are also used on pedal bicycles, fixed machines, and anywhere

rotational speed and torque must be adapted.

Many applications require the availability of multiple gear ratios. Often, this is to ease the

starting and stopping of a mechanical system, though another important need is that of

maintaining good fuel efficiency.

1.3 TYPES OF POWER TRANSMISSION SYSTEMS

Transmissions types include

Manual Transmission

Automatic Transmission

Semi-automatic transmission.

1.3.1 Manual transmission

Manual transmissions come in two basic types:

A simple but rugged sliding-mesh or unsynchronized/non-synchronous system, where straight-

cut spur gear sets spin freely, and must be synchronized by the operator matching engine revs to

road speed, to avoid noisy and damaging clashing of the gears.

The now common constant-mesh gearboxes, which can include nonsynchronized, or

synchronized/synchromesh systems, where typically diagonal cut helical (or sometimes either

straight-cut, or double-helical) gear sets are constantly "meshed" together, and a dog clutch is

used for changing gears. On synchromesh boxes, friction cones or "synchro-rings" are used in

addition to the dog clutch to closely match the rotational speeds of the two sides of the

(declutched) transmission before making a full mechanical engagement.

Manual transmissions are the most common type. They are cheaper, lighter, usually give

better performance, and fuel efficiency. It is customary for new drivers to learn, and be tested, on

a car with a manual gear change.

Some manual transmissions have an extremely low ratio for first gear, called a creeper

gear or granny gear. Such gears are usually not synchronized. This feature is common on pickup

trucks tailored to trailer-towing, farming, or construction-site work. During normal on-road use,

the truck is usually driven without using the creeper gear at all, and second gear is used from a

standing start.

1.3.2 Semi-automatic

A hybrid form of transmission where the integrated control system handles manipulation of the

clutch automatically, but the driver can still - and may be required to - take manual control of

gear selection. This is sometimes called a "clutchless manual," or "automated manual"

transmission. Many of these transmissions allow the driver to fully delegate gear shifting choice

to the control system, which then effectively acts as if it was a regular automatic transmission.

They are generally designed using manual transmission "internals", and when used in passenger

cars, have synchromesh operated helical constant mesh gear sets.

Early semi-automatic systems used a variety of mechanical and hydraulic systems - including

centrifugal clutches, torque converters, electro-mechanical (and even electrostatic) and

servo/solenoid controlled clutches - and control schemes – automatic declutching when moving

the gearstick, pre-selector controls, centrifugal clutches with drum-sequential shift requiring the

driver to lift the throttle for a successful shift, etc. -and some were little more than regular lock-

up torque converter automatics with manual gear selection.

Most modern implementations, however, are standard or slightly modified manual transmissions

(and very occasionally modified automatics—even including a few cases of CVTs with "fake"

fixed gear ratios), with servo-controlled clutching and shifting under command of the central

engine computer. These are intended as a combined replacement option both for more expensive

and less efficient "normal" automatic systems, and for drivers who prefer manual shift but are no

longer able to operate a clutch, and users are encouraged to leave the shift lever in fully

automatic "drive" most of the time, only engaging manual-sequential mode for sporty driving or

when otherwise strictly necessary.

1.3.3 Automatic

These primarily use hydraulics to select gears, depending on pressure exerted by fluid within the

transmission assembly. Rather than using a clutch to engage the transmission, a fluid flywheel,

or torque converter is placed in between the engine and transmission. It is possible for the driver

to control the number of gears in use or select reverse, though precise control of which gear is in

use may or may not be possible.

Automatic transmissions are easy to use. However, in the past, automatic transmissions of

this type have had a number of problems; they were complex and expensive, sometimes had

reliability problems (which sometimes caused more expenses in repair), have often been less

fuel-efficient than their manual counterparts (due to "slippage" in the torque converter), and their

shift time was slower than a manual making them uncompetitive for racing. With the

advancement of modern automatic transmissions this has changed.

Fig 2 : Epicyclic gear train

Attempts to improve fuel efficiency of automatic transmissions include the use of torque

converters that lock up beyond a certain speed or in higher gear ratios, eliminating power loss,

and overdrive gears that automatically actuate above certain speeds. In older transmissions, both

technologies could be intrusive, when conditions are such that they repeatedly cut in and out as

speed and such load factors as grade or wind vary slightly.Current computerized transmissions

possess complex programming that both maximizes fuel efficiency and eliminates intrusiveness.

This is due mainly to electronic rather than mechanical advances, though improvements in CVT

technology and the use of automatic clutches have also helped.

1.4 Power Transmission Devices

Mechanical power can be transmitted across large distances in a variety of ways. Shafts transfer

motion from point to point along their axis of motion. Shafts can be connected to each other by

the following ways

Gear Drive

Chain Drive

Belt Drive

1.4.1 Gear Drive

Gear drive is a mechanism consisting of toothed wheels that engage and transmit rotary motion,

usually transforming angular velocity and torques. Gear drives are the most practical and wide

spread type of mechanical transmission. They are used to transmit power— from negligibly

small values to tens of thousands of kilowatts-and to transmit circumferential forces of fractions

of a gram to 10 meganewtons (1,000 tonsforce). The main advantages of gear drives are their

significantly smaller dimensions, high efficiency (losses in precision-made, well-lubricated

drives are 1-2 percent, and, under especially favorable conditions, 0.5 percent), longer life and

greater dependability, lack of slippage, and small shaft loads. The disadvantages of gear drives

include noisy operation and the need for precision manufacture.

Gear drives are classified according to the relationship of the axes to the drives.

Fig1.3 gear driveGear drive with spur gears: (a) straight-cut,(b) helical, (c)herring bone,

(d) bevel,(e) with spiral teeth, (f) with internal gearing.

The above figure shows the spur gearing, with parallel axes; bevel gearing, with intersecting axes

and, in rare instances, spur-bevel and flat spur gearing; and screw drives (worm gears, hypoid

gears, and screws), with overlapping axes. Rack-and-gear drive is a special type of gear drive

which transforms rotary motion into translatory motion or vice versa. Most machines and

mechanisms use external gearing—that is, gears with teeth on their outer surface. Internal

gearing, in which case one gear has teeth cut into its inner surface, is used less frequently.

1.4.2 Chain drive

Chain drive is a mechanism in which mechanical energy is transmitted over a distance by a chain

that engages sprockets. Device widely used for the transmission of power where shafts are

separated atdistances greater than that for which gears are practical. In such cases, sprockets

(wheels with teeth shaped to mesh with a chain) take the place of gears and drive one another by

means of a chain passing over the sprocket teeth. The chains used in conveyor belts are

commonly block chains, and consist of solid or laminated blocks connected by side plates

and pins. The blocks engage with teeth on sprocket wheels. Depending on the material

being moved, buckets, hooks, or other devices are connected to the blocks.

The widespread use of chain drives began with the introduction of pintle chains with bushings

and precision roller chains that permit powers up to 5,000 kilowatts to be transmitted at high

chain velocities (up to 35 m per second) and high forces (up to 70,000 kg-force, or 700

meganewtons, in chain drives having several parallel, multistrand chains), with a substantial

number of gear ratios (up to 12 for a single chain drive), and with high efficiency (up to 0.99).

Under particularly light-duty operating conditions (low velocities and light loads), open-hook

chains may be used.

Fig1.4 Chain drive

The power transmission chains are made of steel and hardened to reduce wear. These chains are

classified into three categories (a) Block chain (b) Roller chain (c) Inverted tooth chain (silent

chain) Out of these three categories roller chain shown in Figure (b) is most commonly used.

The construction of this type of chain is shown in the figure. The roller is made of steel and then

hardened to reduce the wear. A good roller chain is quiter in operation as compared to the block

chain and it has lesser wear. The block chain is shown in Figure (a). It is used for low speed

drive. The inverted tooth chain is shown in Figures (c) and (d). It is also called as silent chain

because it runs very quietly even at higher speeds.

1.4.3 Belt Drive

A mechanism that transmits rotational motion from one pulley mounted on a shaft to another by

means of a belt. The belt transmits torque from the driving pulley to the driven pulley by means

of the forces of friction that arise between the taut belt and the pulleys. The type of belt used

determines whether the mechanism is flat-belt, roundbelt, or V-belt. A belt drive with a multiple

V-belt, which has several grooves on its inner surface, is now becoming increasingly common.

Flat and round belts, as a rule, are used singly in a drive, while several V-belts (usually no more

than eight) can be used together.

Fig1.5 Belt drive

Diagram of a belt drive and cross sections of the various belts: (a) flat belt, (b) V-belt, (c) round belt,(d) multiple V-belt; (1) driving pulley, (2) belt, and (3) driven pulley

Flat-belt drives are simple and convenient. They permit the use of ordinary pulleys with smooth

surfaces, and they can be operated at speeds as high as 40–50 m/sec and more. However, they are

bulky in design and low in strength, and their tension ratio usually does not exceed 5. V-belt

drives provide improved attachment of the belt to the pulleys, permit shortening of the center

distances, and allow a decrease in the size of the drive and an increase in the tension ratio (up to

10-15). Round-belt drives are now rare and are used only in mechanisms of low power, such as

those in sewing machines.

1.5 Gear Trains :

A gear train is formed by mounting gears on a frame so that the teeth of the gearsengage. Gear

teeth are designed to ensure the pitch circles of engaging gears roll on each other without

slipping; this provides a smooth transmission of rotation from one gear to the next.

Gears trains are classified into following types

Simple gear train

Compound gear train

Reverted compound gear train

Planetary gear train

1.5.1 Simple Gear Trains

The simple gear train is used where there is a large distance to be covered between the input

shaft and the output shaft. Each gear in a simple gear train is mounted on its own shaft. A simple

gear train may include many gears. Ina simple gear train each shaft carries only one train the

expression for the simple train’s velocity ratio .

1.5.2 Compound gear trainsTo get a train ratio of greater than about 10:1 with spur, helical, or bevel gears it is necessary to

compound the train. A compound train is one in which at least one shaft carries more than one

gear. This will be a parallel or series-parallel arrangement, rather than the pure series connections

of the simple gear train. The figure shows a compound train of four gears two of which, gears 3

and 4, are fixed on the same shaft and have same angular velocity.

The train ratio now:

this can be generalized for any number of gears in the train as:

Fig1.6 Compound gear train

1.5.3 Reverted compound trains:

A reverted gear train is very similar to a compound gear train. They are both used when there is

only a small space between the input and output shafts and large changes in speed or power are

needed. There are two major differences between compound and reverted gear trains.

First, the input and output shafts of a reverted train must be on the same axis (in a straight line

with one another). Second, the distance between the centers of the two gears in each pair must be

the same. Fig shows a reverted gear train.

Fig : Reverted gear train

1.5.4 Planetary Gear Trains:

A planetary gear train is a little more complex than other types of gear trains. In a planetary train

at least one of the gears must revolve around another gear in the gear train. A planetary gear train

is very much like our own solar system, and that's how it gets its name.In the solar system the

planets revolve around the sun. Gravity holds them all together. In a planetary gear train the sun

gear is at the center. A planet gear revolves around the sun gear. The system is held together by

the planet carrier. In some planetary trains, more than one planet gear rotates around the sun

gear. The system is then held together by an arm connecting the planet gears in combination with

a ring gear.

Gears :

Gear is a part, as a disk, wheel, or section of a shaft, having cut teeth of such form, size and

spacing that they mesh with teeth in another part to transmit or receive force and motion

The gears in a transmission are analogous to the wheels in a pulley. An advantage of gears is that

the teeth of a gear prevent slipping.

Gears are the most common means used for power transmission

They can be applied between two shafts which are

Parallel Collinear

Perpendicular and intersecting

Perpendicular and nonintersecting

Inclined at any arbitrary angle

Classification of gears

Figure : classification of gears

2.1.1 Spur Gears

General: Spur 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. The basic descriptive geometry for a spur gear is

shown in the figure below.

Limitations: Spur gears generally cannot be used when a direction change between the two shafts is

required.

Advantages: Spur gears are easy to find, inexpensive, and efficient.

Fig : SPUR GEAR

2.1.2 Helical Gears

General: Helical gears are similar to the spur gear except that the teeth are at an angle to the shaft, rather than parallel to it as in a spur gear. (See the references for more specific information). The resulting teeth are longer than the teeth on a spur gear of equivalent pitch diameter. The longer teeth cause helical gears to have the following differences from spur gears of the same size:

Tooth strength is greater because the teeth are longer, Greater surface contact on the teeth allows a helical gear to carry more load than a spur

gear The longer surface of contact reduces the efficiency of a helical gear relative to a spur

gearHelical gears may be used to mesh two shafts that are not parallel, although they are still primarily use in parallel shaft applications. A special application in which helical gears are used is a crossed gear mesh, in which the two shafts are perpendicular to each other:

The basic descriptive geometry for a helical gear is essentially the same as that of the spur gear, except that the helix angle must be added as a parameter.

Limitations: Helical gears have the major disadvantage that they are expensive and much moredifficult to find . Helical gears are alsoslightly less efficient than a spur gear of the same size (see above).

Advantages: Helical gears can be used on non parallel and even perpendicular shafts, and cancarry higher loads than can spur gears.

Fig3.3 helical gears

2.1.3 Bevel Gears

General: Bevel gears are primarily used to transfer power between intersecting shafts. The teeth

of these gears are formed on a conical surface. Standard bevel gears have teeth which are cut

straight and are all parallel to the line pointing the apex of the cone on which the teeth are based.

Spiral bevel gears are also available which have teeth that form arcs. Hypocycloid bevel gears

are a special type of spiral gear that will allow non-intersecting, non-parallel shafts to mesh.

Straight tool bevel gears are generally considered the best choice for systems with speeds lower

than 1000 feet per minute: they commonly become noisy above this point. One of the most

common applications of bevel gears is the bevel gear differential.

Limitations: Limited availability. Cannot be used for parallel shafts. Can become noisy at high

speeds.

Advantages: Excellent choice for intersecting shaft systems.

Fig3.4 bevel gears

2.1.4 Worm Gears

General: Worm gears are special gears that resemble screws, and can be used to drive spur gears

or helical gears. Worm gears, like helical gears, allow two nonintersecting 'skew' shafts to mesh.

Normally, the two shafts are at right angles to each other. A worm gear is equivalent to a V-type

screw thread. Another way of looking at a worm gear is that it is a helical gear with a very high

helix angle.

Worm gears are normally used when a high gear ratio is desired, or again when the shafts are

perpendicular to each other. One very important feature of worm gear meshes that is often of use

is their irreversibility: when a worm gear is turned, the meshing spur gear will turn, but turning

the spur gear will not turn the worm gear. The resulting mesh is 'self locking', and is useful in

ratcheting mechanisms.

Limitations: Low efficiency. The worm drives the drive gear primarily with slipping motion,

thus there are high friction losses.

Advantages: Will tolerate large loads and high speed ratios. Meshes are self locking (which can

be either an advantage or a disadvantage).

Fig3.5 Worm Gears

2.1.5 Racks (straight gears)

General: Racks are straight gears that are used to convert rotational motion to translational motion by

means of a gear mesh. (They are in theory a gear with an infinite pitch diameter). In theory, the torque

and angular velocity of the pinion gear are related to the Force and the velocity of the rack by the radius

of the pinion gear, as is shown below:

Perhaps the most well-known application of a rack is the rack and pinion steering system used on

many cars in the past.

Limitations: Limited usefulness. Difficult to find.

Advantages: The only gearing component that converts rotational motion to translational motion.

Efficiently transmits power. Generally offers better precision than other conversion methods.

Fig3.6 Racks (straight gears)

2.1.6 Hypoid Gears

These are about the same as spiral bevel gears except that the pinion is not on the same plane and

the shafts would do intersect. The prime use for these gears is for machinery where surrounding

equipment would conflict with the drive shaft location. A good example is the car differential.

Fig3.7 Hypoid gear

METHODOLOGY USED FOR CASE STUDY OF GEAR

A case study of broken teeth of spur Gear is done for the purpose of obtaining point cloud data

which was exported into associate nursing .stl format of the CAD program. The best method to

approximate a 3D geometrical model is by approximating it with lots of triangular aspects.

Figure : Gear from two wheeler bike which has broken teeth

Figure : Broken teeth detailed view

A. THE TYPICAL REVERSE ENGINEERING PROCESS CAN BE

SUMMARIZED IN FOLLOWING STEPS:

1. Physical model which needs to be redesigned or to be used as the base for new product.

2. Scanning the physical model to get the point cloud. The scanning can be done using various

scanners available in the market.

3. Processing the points cloud includes merging of points cloud if the part is scanned in several

settings. The outlines and noise is eliminated. If too many points are collected then sampling of

the points should be possible.

4. To create the polygon model and prepare .stl files for rapid prototyping.

5. To prepare the surface model to be sent to CAD/CAM packages for analysis.

6. Tool path generation with CAM package for suitable CNC machine manufacturing of final

part on the CNC machine.

In this thesis we are producing the Gear C of shaft 2nd of Hero bike.The below shown figures are

the Gear C of 29 teeth.

Figure : front view of Gear which has to be produced

Figure : side view of Gear which has to be produced

Figure : Back view of Gear which has to be produced

Figure : Isometric view of Gear which has to be produced

The Gear has been scanned in a Roland Model lpx-600 laser scanner .

The Roland Model lpx-600 laser scanner is a medium sized scanner used to scan object of

maximum height of around 150 mm and diameter of 120 mm. It operates with interface of

computer with software Dr. Picza which helps in setting up the scanning parameters and also

shows the scanning process. It stores the scanned file in .stl format. The scanner is shown in fig.

Figure : Roland Model LPX-600 Laser Scanner

Once the scanned image of object is obtained using scanner it is exported into .stl format shown

in fig.. The parameter set in the above software decides the quality of scanned image. As the time

for scanning increases the quality of scanned image improves.

Figure : . Stl Image File of Scanned Component

B. OBTAINING THE SOLID GEOMETRY FROM THE POINT CLOUD DATA

The original .stl data is scattered and contains some noise around the boundary of model. The

noise creates a problem while generating a solid model so it has to be cleaned from the data.

Solid works software has Scan to 3D option which help to point out the noise from the data and

with the help of noise reduction tool the noise is reduced. Then we get a clean .stl data which can

be used for further processing.

SOLID WORKS

Solid Works is mechanical design automation software that takes advantage of the familiar

Microsoft Windows graphical user interface.

It is an easy-to-learn tool which makes it possible for mechanical designers to quickly sketch

ideas, experiment with features and dimensions, and produce models and detailed drawings.

A Solid Works model consists of parts, assemblies, and drawings.

Typically, we begin with a sketch, create a base feature, and then add more features to

the model. (One can also begin with an imported surface or solid geometry).

We are free to refine our design by adding, changing, or reordering features.

Associativity between parts, assemblies, and drawings assures that changes made to one

view are automatically made to all other views.

We can generate drawings or assemblies at any time in the design process.

The Solid Works software lets us customize functionality to suit our needs.

INTRODUCTION TO SOLID WORKS:

Solid works mechanical design automation software is a feature-based, parametric solid

modeling design tool which advantage of the easy to learn windows TM graphical user interface.

We can create fully associate 3-D solid models with or without while utilizing automatic or user

defined relations to capture design intent.

Parameters refer to constraints whose values determine the shape or geometry of the model or

assembly. Parameters can be either numeric parameters, such as line lengths or circle diameters,

or geometric parameters, such as tangent, parallel, concentric, horizontal or vertical, etc.

Numeric parameters can be associated with each other through the use of relations, which allow

them to capture design intent.

Design intent is how the creator of the part wants it to respond to changes and updates. For

example, you would want the hole at the top of a beverage can to stay at the top surface,

regardless of the height or size of the can. Solid Works allows you to specify that the hole is a

feature on the top surface, and will then honor your design intent no matter what the height you

later gave to the can.several factors contribute to how we capture design intent are Automatic

relations,Equations,added relations and dimensioning.

Features refer to the building blocks of the part. They are the shapes and operations that

construct the part. Shape-based features typically begin with a 2D or 3D sketch of shapes such as

bosses, holes, slots, etc. This shape is then extruded or cut to add or remove material from the

part. Operation-based features are not sketch-based, and include features such as fillets,

chamfers, shells, applying draft to the faces of a part, etc.

Building a model in Solid Works usually starts with a 2D sketch (although 3D sketches are

available for power users). The sketch consists of geometry such as points, lines, arcs, conics

(except the hyperbola), and splines. Dimensions are added to the sketch to define the size and

location of the geometry. Relations are used to define attributes such as tangency, parallelism,

perpendicularity, and concentricity. The parametric nature of Solid Works means that the

dimensions and relations drive the geometry, not the other way around. The dimensions in the

sketch can be controlled independently, or by relationships to other parameters inside or outside

of the sketch.

Several ways a part can be builded like

1. Layer-cake approach :

The layer-cake approach builds the part one piece at a time, adding each layer, orfeature, onto

the previous one.

2. Potter’s wheel approach :

The potter’s wheel approach builds the part as a single revolved feature.As a single sketch

representing the cross section includes all the information and dimensions necessary to make the

part as one feature.

3. Manufacturing approach :

The manufacturing approach to modeling mimics the way the part would be manufactured. For

example, if the stepped shaft was turned a lathe ,we would start with a piece of bar stock and

remove material using a series of cuts.

In an assembly, the analogue to sketch relations is mates. Just as sketch relations define

conditions such as tangency, parallelism, and concentricity with respect to sketch geometry,

assembly mates define equivalent relations with respect to the individual parts or components,

allowing the easy construction of assemblies. Solid Works also includes additional advanced

mating features such as gear and cam follower mates, which allow modelled gear assemblies to

accurately reproduce the rotational movement of an actual gear train.

Finally, drawings can be created either from parts or assemblies. Views are automatically

generated from the solid model, and notes, dimensions and tolerances can then be easily added to

the drawing as needed. The drawing module includes most paper sizes and standards.

A Solid Works model consists of parts, assemblies, and drawings.

(1) Part: Individual components are drawn in the form of part drawings.

(2) Assembly: The individual parts are assembled in this region.

(3) Drawings: This contains detailed information of the assembly.

SOLID WORKS SCAN TO 3D:

Using the Solid Works software’s ScanTo3D functionality, you can open scan data from any scanner (mesh or point cloud files) or curve data from mathematics software, prepare the data, then convert it into a surface or solid model.

ScanTo3D significantly reduces the time required to build complex 3D models from non-digital data. Designers can use ScanTo3D for various purposes:

Medical designers - Create anatomical objects for reference.

Figure : Example of a solid created from scanned data of a hand, using the Surface Wizard's Automatic creation.

Consumer product designers - Create quick representations of physical components made

from clay, foam, etc.

Machine designers - Create quick references to OEM parts.

Figure: Scan to 3D overview

Two Methods for Converting Scan Data to a Solid Model.

Semi-manual Creation: Direct Mesh Referencing

Direct mesh referencing is useful for very complex surfaces, such as consumer products.

Semi-automated Creation Using Wizards

The Mesh Prep and Surface Wizards guide you through the ScanTo3D process

MESH PREPARATION WIZARD:

Mesh Prep Wizard - Welcome Property Manager

The Mesh Prep Wizard prepares and cleans up mesh or point cloud files. The wizard produces a mesh feature from which you can create surfaces and a solid model using direct mesh referencing or the Surface Wizard.

Orientation Property Manager

Align the mesh or point cloud feature to the global origin and planes, which is important for accurate downstream manipulation of the model.

Noise Removal Property Manager

For point cloud data, this tool divides the cloud into partitions and removes points that are outside the average distribution, resulting in the removal of noise points.

Removing Noise From Point Clouds or Meshes

You can remove noise using the Noise Removal Property Manager. Noise is defined as either points that are outside the average distribution, or separate mesh patches that are small in area.

Extraneous Data Removal Property Manager

Extraneous data typically exists in point cloud data and comes from the fixture used to hold the part in place while you scan it. Choose a tool to select extraneous data, then click Delete to remove the data.

Mesh Boundaries

Mesh boundaries form along boundary edges. ScanTo3D can create boundary curves only along boundary edges. Boundary edges are commonly found on meshes that represent surfaces or have large holes in them.

SURFACE WIZARD CREATION MANAGER :

Surface Wizard - Welcome Property Manager

The Surface Wizard converts a mesh feature into surfaces and a solid model.

Solid/Surface Creation Property Manager

The Surface Wizard can automatically create surfaces or guide you to create surfaces.

Automatic Creation

Automatically create solids based on the desired amount of detail.

SURFACE EXTRACTION PROPERTY MANAGER :

Use this Property Manager to extract sub-meshes from the model as surfaces. You later can

convert the surfaces into solids using the Solid works surface tools such as Trim, Knit,

and Thicken. To manually extract surfaces, select a sub-mesh, then select a surface type

under Face Settings.

Figure : Model before surface extractionModel after extracting two cylindrical and two b-spline surfaces

When you extract surfaces, you might see salient sub-meshes (arrows), which are transitions

between primary mesh regions. Transition regions usually show a large variation in geometry,

such as curvature. You usually do not convert salient sub-meshes as surfaces during guided

surface creation, but instead you create these surfaces later in Solid works.

Surface creation is complete. To recreate the surfaces with more control, click   to return to

the Solid/Surface Creation Property Manager and select Guided creation.

We use the Solid Works application surfacing tools, such as Trim, Knit, and Thicken to turn the

extracted surfaces into a solid model. Apply fillets as necessary using the original mesh for

reference.

Figure : Extracted surfaces using ScanTo3D

Figure : Solid model created from the extracted surfaces using Untrim, Trim, Extend,Knit,

and Thicken tools.

Exporting files :

After you import a mesh or cloud point file into a Solid works document using ScanTo3D, We

export the document as another file type that contains the mesh or cloud point data.

1. Click File > Save As.

2. Select a file format in Save as type:

ScanTo3D (*.xyz)

ScanTo3D (*.wrl).

ScanTo3D (*.stl).

ScanTo3D (*.3ds)

ScanTo3D (*.iges)

The scanned file is imported in solid works software which helps to extract geometry from

the .stl file or point cloud data shown in figure below to Solid geometry.

Figure : .Stl file imported to solid works Scan to 3D

By using Mesh preparation wizard meshing of the .Stl file is done.

Increasing the global smoothness then entering into surface wizard manager for adjusting surface

resolution.

Figure : surface failure areas

Figure : individual sub meshes are identified

Now all the surface are extracted as shown below

Figure : surfaces extraction

Figure : model is completed with extra surfaces

Finally the base model is complete by using Trim,knit ,fillets and chamfer options for generating

solid model.The file is saved in .STL format.

Figure : Final model after trimming the surfaces

Figure : Four views of the Gear

The drawings are generated for the Gear model and the following dimensions are obtained.

Figure : Isometric view of the Gear model

Figure : Three views of the gear

Figure : Back view of the gear

symbol parameter Gear

m Module 1.79 ˷ 2mm

b Face width 8.5mm

T No. of teeth 29

D Pitch circle diameter 52mm

Profile 20 degree full depth

involute

Table: Dimensions obtained for Gear

INTRODUCTION TO SOLID WORKS SIMULATION :

Solid Works® Simulation is a design analysis system fully integrated with Solid works. Solid

Works Simulation provides simulation solutions for linear and nonlinear static, frequency,

buckling, thermal, fatigue, pressure vessel, drop test, linear and nonlinear dynamic, and

optimization analyses.

Powered by fast and accurate solvers, Solid works Simulation enables you to solve large

problems intuitively while you design. Solid works Simulation comes in two bundles: Solid

works Simulation Professional and Solid works Simulation Premium to satisfy your analysis

needs. Solid works Simulation shortens time to market by saving time and effort in searching for

the optimum design.

Figure: simulation example

Benefits of Simulation:

After building your model, you need to make sure that it performs efficiently in the field. In the

absence of analysis tools, this task can only be answered by performing expensive and time-

consuming product development cycles. A product development cycle typically includes the

following steps:

1. Building your model.

2. Building a prototype of the design.

3. Testing the prototype in the field.

4. Evaluating the results of the field tests.

5. Modifying the design based on the field test results.

This process continues until a satisfactory solution is reached. Analysis can help you accomplish

the following tasks:

Reduce cost by simulating the testing of your model on the computer instead of

expensive field tests.

Reduce time to market by reducing the number of product development cycles.

Improve products by quickly testing many concepts and scenarios before making a final

decision, giving you more time to think of new designs.

Basic Concepts of Analysis :

The software uses the Finite Element Method (FEM). FEM is a numerical technique for analyzing

engineering designs. FEM is accepted as the standard analysis method due to its generality and

suitability for computer implementation. FEM divides the model into many small pieces of simple shapes

called elements effectively replacing a complex problem by many simple problems that need to be

solved simultaneously.

CAD model of a part Model subdivided into small pieces (elements)

Elements share common points called nodes. The process of dividing the model into small pieces

is called meshing.

The behavior of each element is well-known under all possible support and load scenarios. The

finite element method uses elements with different shapes.

The response at any point in an element is interpolated from the response at the element nodes.

Each node is fully described by a number of parameters depending on the analysis type and the

element used. For example, the temperature of a node fully describes its response in thermal

analysis. For structural analyses, the response of a node is described, in general, by three

translations and three rotations. These are called degrees of freedom (DOFs). Analysis using

FEM is called Finite Element Analysis (FEA).

A tetrahedral element. Red dots represent nodes. Edges of an element can be curved or straight.

The software formulates the equations governing the behavior of each element taking into

consideration its connectivity to other elements. These equations relate the response to known

material properties, restraints, and loads.

Next, the program organizes the equations into a large set of simultaneous algebraic equations

and solves for the unknowns.

In stress analysis, for example, the solver finds the displacements at each node and then the

program calculates strains and finally stresses.

The software offers the following types of studies:

Study type Study icon    

Static Modal Time History

Frequency Harmonic

Buckling Random Vibration

Thermal Response Spectrum

Design Study Drop Test

Nonlinear Static Fatigue

Nonlinear Dynamic Pressure Vessel Design

Analysis Steps :

The steps needed to perform an analysis depend on the study type. You complete a study by

performing the following steps:

Create a study defining its analysis type and options.

If needed, define parameters of your study. A parameter can be a model dimension,

material property, force value, or any other input.

Define material properties.

Specify restraints and loads.

The program automatically creates a mixed mesh when different geometries (solid, shell,

structural members etc.) exist in the model.

Define component contact and contact sets.

Mesh the model to divide the model into many small pieces called elements. Fatigue and

optimization studies use the meshes in referenced studies.

Run the study.

View results.

Specific capabilities of Solid works Simulation :

1. Static Analysis:When loads are applied to a body, the body deforms and the effect of loads is

transmitted throughout the body. The external loads induce internal forces and reactions

to render the body into a state of equilibrium. Linear Static analysis calculates

displacements, strains, stresses, and reaction forces under the effect of applied loads.

2. Thermal Stress Analysis:

Changes in temperature can induce substantial deformations, strains, and stresses.

Thermal stress analysis refers to static analysis that includes the effect of temperature.

Perform thermal stress analysis using one of the following options:

Using a uniform rise or drop in temperature for the whole model.

Using a temperature profile resulting from a steady state or transient thermal

analysis.

Using a temperature profile from Flow Simulation.

3. Frequency analysis :

If the design is subjected to dynamic environments, static studies cannot be used to

evaluate the response. Frequency studies can help you avoid resonance and design

vibration isolation systems. They also form the basis for evaluating the response of linear

dynamic systems where the response of a system to a dynamic environment is assumed to

be equal to the summation of the contributions of the modes considered in the analysis.

4. Dynamic analysis :

Dynamic analysis includes:

Design structural and mechanical systems to perform without failure in dynamic

environments.

Modify system's characteristics (i.e., geometry, damping mechanisms, material

properties, etc.) to reduce vibration effects.

5. Buckling analysis :

Used to calculate the buckling loads and determine the buckling mode shape. Both linear

(Eigen value) buckling and nonlinear buckling analyses are possible.

6. Non-linear static analysis :

All real structures behave nonlinearly in one way or another at some level of loading. In

some cases, linear analysis may be adequate. In many other cases, the linear solution can

produce erroneous results because the assumptions upon which it is based are violated.

Nonlinearity can be caused by the material behavior, large displacements, and contact

conditions. We can use a nonlinear study to solve a linear problem. The results can be

slightly different due to different procedures.In the nonlinear static analysis, dynamic

effects like inertial and damping forces are not considered.

7. Drop test studies :

Drop test studies evaluate the effect of the impact of a part or an assembly with a rigid or

flexible planar surface. Dropping an object on the floor is a typical application and hence

the name. The program calculates impact and gravity loads automatically. No other loads

or restraints are allowed.

8. Fatigue Analysis :

Fatigue is the prime cause of the failure of many objects, especially those made of metals.

Examples of failure due to fatigue include, rotating machinery, bolts, airplane wings,

consumer products, offshore platforms, ships, vehicle axles, bridges, and bones.

Linear and nonlinear structural studies do not predict failure due to fatigue.

9. Pressure vessel Design study :

In a Pressure Vessel Design study, you combine the results of static studies with the

desired factors. Each static study has a different set of loads that produce corresponding

results. These loads can be dead loads, live loads (approximated by static loads), thermal

loads, seismic loads, and so on. The Pressure Vessel Design study combines the results of

the static studies algebraically using a linear combination or the square root of the sum of

the squares (SRSS).

STRUCTURAL ANALYSIS OF GEAR

Gear analysis can be performed using analytical methods which required a number of

assumption and simplifications which aim at getting the maximum stress values only but

gear analyses are multidisciplinary including calculations related to the tooth stresses .In this

work, an attempt will been made to analyze bending stress to resist bending of helical gears, as

both affect transmission error. Due to the progress of computer technology many researchers

tended to use numerical Methods to develop theoretical models to calculate the effect of

whatever is studied. numerical methods are capable of providing more truthful solution since

they require very lessrestrictive assumptions. However, the developed model and its solution

method must e selected attentively to ensure that the results are more acceptable and its

computational time is reasonable. The dimension of the model have been arrived at by

theoretical methods. The stress generated of the tooth have been analyzed for materials. Finally

the results obtained by theoretical analysis, AGMA calculations and finite element analysis are

compared to check the correctness.

This procedure is based on the principle of differential geometry that pertains to envelopes of

curves and surfaces.

The above equation is lewis bending equation to calculate bending stresses developed in gears.

Where

Cv =

Where v = = 4.396m/sec, D= 56mm

D= diameter of gear

N=speed .rpm =1500 rpm

Cv = = 0.577

Taking tangential load =500N and y = 0.32

RESULTS OF MAXIMUM BENDING STRESS FROM LEWIS EQUATION FOR

GEAR1 :

Face width

(mm)

Bending stress(σb)

(Mpa)

8.5 50.7

10.5 41.04

12.5 34.4

14.5 29.7

STRUCTURAL ANALYSIS OF GEAR USING SOLID WORKS SIMULATION TOOL

Sstructural analysis procedure:- The Structural analysis involves the following

procedure:

_ Pre-Processing: It include the description of the geometry or model, the physical

characteristics of the model.

Definition of type of analysis, material properties, Loads and boundary conditions

_ Solution: it involves the application of the finite element analysis

_ Run analysis to obtain solution (stresses).

_ Post-Processing: It includes the visualization and interpretation of the results of the solution.

PERFORMING STATIC ANALYSIS ON GEAR

The structural stress analysis of the gear tooth model is carry out using the FEA in

Solid works simulation .The load applied at the tooth of the gear by applying the analysis over

the tooth which is facing the load we get the stress distribution in the numeric as well as in the

form of the color scheme.

STUDY PROPERTIES :

Study name Static 1

Analysis type Static

Mesh type Solid Mesh

Thermal Effect: On

Thermal option Include temperature loads

Zero strain temperature 298 Kelvin

Include fluid pressure effects from Solid works Flow Simulation

Off

Solver type FFEPlus

Inplane Effect: Off

Soft Spring: Off

Inertial Relief: Off

Incompatible bonding options Automatic

Large displacement Off

Compute free body forces On

Friction Off

Use Adaptive Method: Off

Result folder Solid works document (C:\Users\srinivas\Desktop)

Units :

Unit system: SI (MKS)

Length/Displacement mm

Temperature Kelvin

Angular velocity Rad/sec

Pressure/Stress N/m^2

Material Properties :

Model Reference Properties Components

Name: Alloy Steel

Model type: Linear Elastic Isotropic

Default failure criterion:

Max von Mises Stress

Yield strength: 6.20422e+008 N/m^2

Tensile strength: 7.23826e+008 N/m^2

Elastic modulus: 2.1e+011 N/m^2

Poisson's ratio: 0.28

Mass density: 7700 kg/m^3

Shear modulus: 7.9e+010 N/m^2

Thermal expansion coefficient:

1.3e-005 /Kelvin

SolidBody 1(Fillet8)(srinivas gear)

Loads and Fixtures:

Fixture name Fixture Image Fixture Details

Fixed-1

Entities: 6 face(s)

Type: Fixed Geometry

Resultant Forces

Components X Y Z Resultant

Reaction force(N) 443.107 -197.792 -0.00437104 485.248

Reaction Moment(N.m) 0 0 0 0

Load name Load Image Load Details

Force-1

Entities: 1 face(s)

Type: Apply normal force

Value: 500 N

Phase Angle: 0

Units: deg

Mesh Information :

Mesh type Solid Mesh

Mesher Used: Standard mesh

Automatic Transition: Off

Include Mesh Auto Loops: Off

Jacobian points 4 Points

Element Size 2.7397 mm

Tolerance 0.136985 mm

Mesh Quality High

Mesh Information - Details

Total Nodes 27167

Total Elements 16148

Maximum Aspect Ratio 15.563

% of elements with Aspect Ratio < 3 83.9

% of elements with Aspect Ratio > 10 0.142

% of distorted elements(Jacobian) 0

Time to complete mesh(hh;mm;ss): 00:00:12

Computer name: Srinivas-PC

Study Results for face width 8.5 mm :

Name Type Min Max

Stress1 VON: von Mises Stress 30.9186 N/m^2

Node: 10906

4.7972e+007 N/m^2

Node: 1280

Name Type Min Max

Name Type Min Max

Displacement1 URES: Resultant Displacement

0 mm

Node: 698

0.00307442 mm

Node: 15382

Name Type Min Max

Name Type Min Max

Strain1 ESTRN: Equivalent Strain 8.80717e-011

Element: 5061

0.000172154

Element: 5473

Name Type Min Max

Factor of Safety1 Automatic 12.933

Node: 1280

2.00663e+007

Node: 10906

A factor of safety less than 1 at a location indicates that the material at that location has failed.A

factor of safety of 1 at a location indicates that the material at that location has just started to fail.

A factor of safety greater than 1 at a location indicates that the material at that location is safe.

So our design is safe for given loading condition.

Study Results for face width 10.5 mm :

Name Type Min Max

Stress1 VON: von Mises Stress 3.92889 N/m^2

Node: 11761

4.02837e+007 N/m^2

Node: 19002

Name Type Min Max

Displacement1 URES: Resultant Displacement 0 mm

Node: 674

0.00248392 mm

Node: 1646

Name Type Min Max

Name Type Min Max

Strain1 ESTRN: Equivalent Strain 5.21391e-011

Element: 5529

0.000142769

Element: 5826

Name Type Min Max

Factor of Safety1 Automatic 15.4013

Node: 19002

1.57913e+008

Node: 11761

STUDY RESULTS FOR FACE WIDTH 12.5MM :

Name Type Min Max

Stress1 VON: von Mises Stress 15.9894 N/m^2

Node: 23297

2.92143e+007 N/m^2

Node: 1113

Name Type Min Max

Displacement1 URES: Resultant Displacement 0 mm

Node: 617

0.00171887 mm

Node: 1464

Name Type Min Max

Name Type Min Max

Strain1 ESTRN: Equivalent Strain 5.93542e-011

Element: 5036

7.72139e-005

Element: 13711

Name Type Min Max

Factor of Safety1 Automatic 21.237

Node: 1113

3.88021e+007

Node: 23297

Name Type Min Max

STUDY RESULTS FOR FACE WIDTH 14.5mm :

Name Type Min Max

Stress1 VON: von Mises Stress 14.9038 N/m^2

Node: 24243

2.57757e+007 N/m^2

Node: 14953

Name Type Min Max

Displacement1 URES: Resultant Displacement 0 mm

Node: 643

0.00206972 mm

Node: 1548

Name Type Min Max

Strain1 ESTRN: Equivalent Strain 3.18208e-011

Element: 5186

9.05585e-005

Element: 12900

Name Type Min Max

Factor of Safety1 Automatic 24.07 4.16285e+007

Name Type Min Max

Node: 14953 Node: 24243

RESULTS AND DISCUSSIONS

The structural stress analysis of the gear tooth model is carry out using the FEA in Solid works

simulation. The load applied at the tooth of the gear .by applying the analysis over the tooth

which is facing the load we get the stress distribution in the numeric as well as in the form of the

color scheme. By varying the face width and keeping the other parameters constant various

models of the gear are created. For determining at any stage during the design of the gear face

width is an important parameter. The results of the variation in face width from (8.5 mm to

14.5mm) there is continuous decrement in the value of the stress of the tooth of the gear stress.

Results of theoretical and static analysis are closer, therefore the design are accepted. As it is

seen clearly from all tables and graphs the maximum bending stress values are increases with the

decrease of face width. In this work we got on two results as follow

_ Theoretical results (from Lewis equation directly)

_ static analysis results

And all results are closer as shown in graphs.

Effect of face width :

The effect face width on maximum bending stress is study by varying the face width for five

Values which are (b=8.5mm, 10.5mm, 12.5mm, 14.5mm) the magnitude of the stresses

obtained for those face widths are displayed .

COMPARISION OF THEORETICAL STRESS VALUES AND SOLID WORKS

VALUES

Face width

(mm)

Bending

stresses Mpa

(lewis equation)

Bending

stresses Mpa

(static analysis)

8.5 50.7 47.2

10.5 41.04 40.2

12.5 34.4 29.2

14.5 29.7 25.2

Table : comparison of bending stresses (theoretical and

software )

INTRODUCTION TO RAPID PROTOTYPING:

Rapid Prototyping (RP) can be defined as a group of techniques used to quickly fabricate

a scale model of a part or assembly using three-dimensional computer aided design (CAD) data.

What is commonly considered to be the first RP technique, Stereo-lithography, was developed by

3D Systems of Valencia, CA, USA. The company was founded in 1986, and since then, a number

of different RP techniques have become available.

Rapid Prototyping has also been referred to as solid free-form manufacturing; computer

automated manufacturing, and layered manufacturing. RP has obvious use as a vehicle for

visualization. In addition, RP models can be used for testing, such as when an airfoil shape is put

into a wind tunnel. RP models can be used to create male models for tooling, such as silicone

rubber molds and investment casts. In some cases, the RP part can be the final part, but typically

the RP material is not strong or accurate enough. When the RP material is suitable, highly

convoluted shapes (including parts nested within parts) can be produced because of the nature of

RP.

There is a multitude of experimental RP methodologies either in development or used by

small groups of individuals. This section will focus on RP techniques that are currently

commercially available, including Stereo-lithography (SLA), Selective Laser Sintering (SLS®),

Laminated Object Manufacturing (LOM™), Fused Deposition Modeling (FDM), 3D printing,

and Ink Jet printing techniques

Why Rapid Prototyping ?

The reasons of Rapid Prototyping are

• To increase effective communication.

• To decrease development time.

• To decrease costly mistakes.

• To minimize sustaining engineering changes

• To extend product lifetime by adding necessary features and eliminating redundant

features early in the design.

Rapid Prototyping decreases development time by allowing corrections to a product to be made

early in the process. By giving engineering, manufacturing, marketing, and purchasing a look at

the product early in the design process, mistakes can be corrected and changes can be made

while they are still inexpensive. The trends in manufacturing industries continue to emphasize

the following:

• Increasing number of variants of products.

• Increasing product complexity.

• Decreasing product lifetime before obsolescence.

• Decreasing delivery time.

4.2 Methodology of Rapid Prototyping

The basic methodology for all current rapid prototyping techniques can be summarized as

follows:

1. A CAD model is constructed, and then converted to STL format. The resolution can be

set to minimize stair stepping.

2. The RP machine processes the .STL file by creating sliced layers of the model.

3. The first layer of the physical model is created. The model is then lowered by the

thickness of the next layer, and the process is repeated until completion of the model.

4. The model and any supports are removed. The surface of the model is then finished and

cleaned

STEREO-LITHOGRAPHY

The implementation shown is used by 3D Systems and some foreign manufacturers. A moveable

table, or elevator (A), initially is placed at a position just below the surface of a vat (B) filled

with liquid photopolymer resin (C). This material has the property that when light of the correct

color strikes it, it turns from a liquid to a solid. The most common photopolymer materials used

require an ultraviolet light, but resins that work with visible light are also utilized. The system is

sealed to prevent the escape of fumes from the resin.

Fig: 4.2.1 STEREO-LITHOGRAPHY

After the layer is completely traced and for the most part hardened by the beam, the table is

lowered into the vat a distance equal to the thickness of a layer. The resin is generally quite

viscous, however. To speed this process of recoating, early stereolithography systems drew a

knife edge (E) over the surface to smooth it. More recently pump-driven recoating systems have

been utilized. The tracing and recoating steps are repeated until the object is completely

fabricated and sits on the table within the vat.

LAMINATED OBJECT MANUFACTURING

Profiles of object cross sections are cut from paper using a CO2 laser as shown in Fig. 2. The

paper is unwound from a feed roll (A) onto the stack and bonded to the previous layer using a

heated roller (B). The roller melts a plastic coating on the bottom side of the paper to create the

bond. The profiles are traced by an optics system that is mounted to an X-Y stage (C). The

process generates considerable smoke. Either a chimney or a charcoal filtration system is

required (E) and the build chamber must be sealed.

After cutting the geometric features of a layer is completed, the excess paper is cut away to

separate the layer from the web. The extra paper of the web is wound on a take-up roll (D). The

method is self-supporting for overhangs and undercuts. Areas of cross sections which are to be

removed in the final object are heavily cross-hatched with the laser to facilitate removal.

Fig: 4.2.2 Laminated Object Manufacturing

FUSED DEPOSITION MODELING

FDM is the second most widely used rapid prototyping technology, after stereo-

lithography. A plastic filament, approximately 1/16 inch in diameter, is unwound from a coil (A)

and supplies material to an extrusion nozzle (B). Some configurations of the machinery have

used plastic pellets fed from a hopper rather than a filament. The nozzle is heated to melt the

plastic and has a mechanism which allows the flow of the melted plastic to be controlled. The

nozzle is mounted to a mechanical stage (C) which can be moved in horizontal and vertical

directions

As the nozzle is moved over the table (D) in the required geometry, it deposits a thin bead of

extruded plastic to form each layer. The plastic hardens immediately after being squirted from

the nozzle and bonds to the layer below. The entire system is contained within an oven chamber

which is held at a temperature just below the melting point of the plastic. Thus, only a small

amount of additional thermal energy needs to be supplied by the extrusion nozzle to cause the

plastic to melt. This provides much better control of the process.

Fig: 4.2.3 Fused Deposition Modeling

THREE DIMENSIONAL PRINTING

The system was developed at MIT and is shown schematically in Fig. 6. The method is

very reminiscent of selective laser sintering, except that the laser is replaced by an inkjet head.

The multi-channel jetting head (A) deposits a liquid adhesive compound onto the top layer of a

bed of powder object material (B). The particles of the powder become bonded in the areas

where the adhesive is deposited.

Once a layer is completed the piston (C) moves down by the thickness of a layer. As in selective

laser sintering, the powder supply system (E) is similar in function to the build cylinder In this

case the piston moves upward incrementally to supply powder for the process and the roller (D)

spreads and compresses the powder on the top of the build cylinder. The process is repeated until

the entire object is completed within the powder bed.

Fig: 4.2.4 Three Dimensional Printing

After completion the object is elevated and the extra powder brushed away leaving a "green"

object. Parts must usually be infiltrated with a hardener before they can be handled without much

risk of damage.

SELECTIVE LASER SINTERING

The process is somewhat similar to stereo-lithography in principle as can be seen from

Figure. In this case, however, a laser beam is traced over the surface of a tightly compacted

powder made of thermoplastic material (A). The powder is spread by a roller (B) over the

surface of a build cylinder (C). A piston (D) moves down one object layer thickness to

accommodate the layer of powder

The power supply system (E) is similar in function to the build cylinder. It also comprises a

cylinder and piston. The piston moves upward incrementally to supply powder for the process.

Heat from the laser melts the powder where it strikes under guidance of the scanner system (F).

The CO2 laser used provides a concentrated infrared heating beam. The entire fabrication

chamber is sealed and maintained at a temperature just below the melting point of the plastic

powder. Thus, heat from the laser need only elevate the temperature slightly to cause sintering,

greatly speeding the process. A nitrogen atmosphere is also maintained in the fabrication

chamber which prevents the possibility of explosion in the handling of large quantities of powder

After the object is fully formed, the piston is raised to elevate the object. Excess powder is

simply brushed away and final manual finishing may be carried out. It may take a considerable

time before the part cools down enough to be removed from the machine. Large parts with thin

sections may require as much as two days of cooling time

Fig: 4.2.5 Selective Laser Sintering

No supports are required with this method since overhangs and undercuts are supported by the

solid powder bed. This saves some finishing time compared to stereo-lithography. However,

surface finishes are not as good and this may increase the time. No final curing is required as in

stereo-lithography, but since the objects are sintered they are porous. Depending on the

application, it may be necessary to infiltrate the object with another material to improve

mechanical characteristics. Much progress has been made over the years in improving surface

finish and porosity. The method has also been extended to provide direct fabrication of metal and

ceramic objects and tools.

Fig: Selective Laser Sintering Machine (RPT Systems).

PROTOTYPING OF THE GEAR USING SELECTIVE LASER SINTERING –

RAPIDPROTOYPING SYSTEM:

FORMIGA P 100 - small, fast, efficient, e-Manufacturing in the Compact Class Plastic

laser-sintering system for the direct manufacture of series, spare parts and functional prototypes.

Fig: 4.4.3 RP Systems

The FORMIGA P 100 represents laser-sintering in the compact class. With a build envelope of

200 mm x 250 mm x 330 mm, the FORMIGA P 100 produces plastic products from polyamide

or polystyrene within a few hours and directly from CAD data. The machine is ideally suited for

the economic production of small series and individualized products with complex geometry –

requirements which apply among others to the medical device industry as well as for high-value

consumer goods. At the same time, it provides capacity for the quick and flexible production of

fully functional prototypes and patterns for plaster, investment and vacuum casting. With

turnover times of less than 24 hours the FORMIGA P 100 integrates itself perfectly in a

production environment that requires the highest level of flexibility. The system distinguishes

itself also by comparatively low investment costs.

Technical Specifications :

Technical Data :

TABLE NO – 1 :

Effective building volume 200 mm x 250 mm x 330 mm (7.9 x 9.8 x 13 in)

Building speed (material-dependent) up to 24 mm height/h (0.94 in/h)

Layer thickness (material-dependent) typically 0.1 mm (0.004 in)

Support structure not necessary

Laser type CO2, 30W

Precision optics F-theta lens

Scan speed during build process up to 5 m/s (16.4 ft/sec)

Power supply 16 A

Power consumption (nominal) 2 Kw

Nitrogen generator integrated (optional)

Compressed air supply minimum 6,000 hPa; 10 m3/h (87 psi; 13.08 yd3/h)

Dimensions :

TABLE NO – 2 :

Machine with powder

containers and touch screen

1,320 mm x 1,067 mm x 2,204 mm

(51.97 x 42.01 x 86.77 in)

Recommended installation

space3.2 m x 3.5 m x 3 m (126 x 137.8 x 118.1 in)

Weight Ca. 600 kg (1,323 lb)

Powder mixing station 700 mm x 500 mm x 1,000 mm (27.56 x 19.69 x 39.37 in)

Unpacking and sieving station 1,200 mm x 700 mm x 1,500 mm (47.24 x 27.56 x 59.06

in)

Data preparation :

TABLE NO – 3 :

PC current Windows operating system

Software EOS RP Tools; Magics RP (Materialise)

CAD interface STL. Optional: converter to all common formats

Network Ethernet

Certification CE

RAPID PROTOTYPING OF GEAR:

After the .STL file of gear is imported into the fused deposited machine. The 3D printing has

been done for 3hrs.The following prototype has been obtained .The material used is ABS

material.

Figure :Front view of the Gear [RPT file]

Figure :Side view of Gear [RPT]

Figure : Back view of Gear[RPT]

Figure: RPT gear and normal gear front views

Figure: Back view of RPT gear

Figure: isometric view of Gear [RPT] and Normal gear

CONCLUSIONS

Reverse engineering helps in obtaining the geometry of part or product which is not available

otherwise. Its application makes it possible to reconstruct the original component with its

drawing and manufacturing process. It is used in various fields but here the main application is

related to broken Gear.

The process starts with understanding the reverse engineering procedure. The part

geometry is first obtained with the help of scanning technology. Then with the use of

SOLIDWORKS SCAN TO 3D option the three-dimensional model of the spur gear is

obtained.

In theory of Gear, we are considering that the load is acting at one point and the stress is

calculated. The calculation of maximum stresses in a gear at tooth root is three

dimensional problems. The accurate evaluation of stress state is complex task. The

contribution of this thesis work can be summarized as follows:

The strength of gear tooth is a crucial parameter to prevent failure. In this work, it is

shown that the effective method to estimate the root bending stress using three

dimensional model of a gear and to verify the accuracy of this method the results with

different face width of teeth are compared with theoretical values.

The face width is an important geometrical parameter in design of gear as it is expected

in this work the maximum bending stress decreases with increasing face width.

After the analysis, the pattern of the part is obtained using Rapid prototyping machine

{Fused depositing machine}.

REFERENCES

[1]. Cheng, Y., and Tasy C.B., Stress Analysis Of Helical Gear Set With Localized Bearing

Contact, Finite Element In Analysis And Design, 38,Pp. 707-723, 2002

[2]. Vijayarangan, s., and Ganesan, n., a static analysis of composite helical gears using three

dimensional finite element method, computers & structures, 49,pp.253-268,1993.

[3]. Huston, R.L., Mavriplis, D., Oswald, B.F., and Liu Y.S., A Basis for Solid Modeling of Gear

Teeth with Application In Design And Manufacturing, NASA Technical Memorandum

105392, 1992.

[4]. Zhang, J.J., East, I.I., Shi, And Y.H., Load Analysis with Varying Mesh Stiffness, Computer

And Structures, 70, pp.273-280, 1999

[5]. Zhang, Y., And Fang. Z, Analysis Of Teeth Contact and Load Distribution of Helical Gears

With Crossed Axes, Mechanism And Machine Theory, 34,Pp.41-57, 1999.

[6]. Litvin, L.F., Fuentes, A., Perez, I.G., and Sep, T.M., New Version Of Nivikon-Wildhaber

Helical Gears: "Computerized Design, Simulation of Meshing and Stress Analysis",

Computational Methods In Applied Mechanics And Engineering, 191, Pp.5707-5740, 2002.

[7]. Hedlund, J., And Lethovaara, A., Modeling Of Helical Gear Contact With Tooth

Defection,Tampere University Of Technology, Machine Design, P.O. Box 589,33101 Tampere,

Finland.

[8]. Vera, N.S., And Ivan, C., The Analysis Of Contact Stress on Meshed Teeth_S Flanks Along

The Path Of Contact For A Tooth Pair, Mechanics Automatic Control and Robotics, 3,

Pp, 1055-1066, 2003.

[9]. Pushpendra Kumar Mishra, Dr. M. S. Murthy", Comparison of Bending Stresses for

Different Face Width of Helical Gear Obtained pp45-51, 2013.

[10]. Ajeet Kumar Rai and Mustafa S Mahdi, “A Practical Approach to Design and Optimization

of Single Phase Liquid to Liquid Shell and Tube Heat Exchanger”, International Journal of

Mechanical Engineering & Technology (IJMET), Volume 3, Issue 3, 2012, pp. 378 - 386, ISSN

Print: 0976 – 6340, ISSN Online: 0976 – 6359.

[11]. Ajeet Kumar Rai and Ashish Kumar, “A Review on Phase Change Materials & Their

Applications”, International Journal of Advanced Research in Engineering & Technology

(IJARET), Volume 3, Issue 2, 2012, pp. 214 - 225, ISSN Print: 0976-6480, ISSN Online: 0976-

6499.