rtu paper solution branch mechanical engineering paper

Global Institute of Technology, Jaipur ITS-1, IT Park, EPIP, Sitapura Jaipur 302022 (Rajasthan)

Solution V sem University Examination 2019

Subject Code_5ME4-03 V Semester/3rd Year

RTU Paper Solution

Branch – Mechanical Engineering

Subject Name – Manufacturing Technology

Paper Code –5ME4-03

Date of Exam – 20/11/2019



Subject Code_5ME4-03 V Semester/3rd Year Part-A

1. Cutting tools can be classified in various ways; however the most common way is based on

the number of main cutting edges that participates in cutting action at a time. On this basis,

cutting tools can be classified into three groups as given below.

Single point cutting tool—Such cutters have only one main cutting edge that

participate in cutting action at a time. Examples include turning tool, boring tool, fly

cutter, slotting tool, etc.

Double point cutting tool—As the name implies, these tools contain two cutting

edges that simultaneously participate in cutting action at a pass. Example includes

drill (common metal cutting drill that has only two flutes).

Multi-point cutting tool—These tools contain more than two main cutting edges that

can simultaneously remove material in a single pass. Examples include milling cutter,

broach, gear hobbing cutter, grinding wheel, etc.

2. Systems of description of tool geometry

Tool-in-Hand System – where only the salient features of the cutting tool point are

identified or visualized. There is no quantitative information, i.e.,value of the angles.

Machine Reference System – ASA system

Tool Reference Systems

Orthogonal Rake System – ORS

Normal Rake System – NRS

Work Reference System – WRS

3. Built-up-Edge (BUE)

In machining ductile metals like steels with long chip-tool contact length, lot of stress and

temperature develops in the secondary deformation zone at the chip-tool interface. Under

such high stress and temperature in between two clean surfaces of metals, strong bonding

may locally take place due to adhesion similar to welding. Such bonding will be encouraged

and accelerated if the chip tool materials have mutual affinity or solubility. The weldment

starts forming as an embryo at the most favourable location and thus gradually grows as

schematically shown in Fig

4. Zero rake – to simplify design and manufacture of the form tools. Clearance angle is

essentially provided to avoid rubbing of the tool (flank) with the machined surface which

causes loss of energy and damages of both the tool and the job surface. Hence, clearance



Subject Code_5ME4-03 V Semester/3rd Year angle is a must and must be positive (3

о ~ 15

о depending upon tool-work materials and type

of the machining operations like turning, drilling, boring etc.)

5. Machinability index is used to compare the machinability of different materials in the

various cutting process. It is an attempt to quantify the relative machinability of different

material. The rated machinability may vary for different cutting operation such as turning,

milling, forming etc. In order to find the machinability index, factors like tool material, tool

geometry, tool life and other cutting conditions are fixed except the speed. Then find the

speed at which tool cut the material for a pre-determined tool life. Then it is compared with a

standard material. Here machinability of standard steel is arbitrarily fixed as 100%. The

slower speed indicates, low metal removal rate and hence poor machinability.

6. Factors Affecting Tool Life

The life of tool is affected by many factors such as: cutting speed, depth of cut, chip

thickness, tool geometry, material or the cutting fluid and rigidity of machine. Physical and

chemical properties of work material influence tool life by affecting form stability and rate of

wear of tools. The nose radius tends to affect tool life.

1. Cutting speed: Cutting speed has the greatest influence on tool life. As the cutting

speed increases the temperature also rises. The heat is more concentrated on the tool

than on the work and the hardness of the tool metrix changes so the relative increase

in the hardness of the work accelerates the abrasive action. The criterion of the wear is

dependent on the cutting speed because the predominant wear may be wear for flank

or crater if cutting speed is increased.

2. Feed and depth of cut: The tool life is influenced by the feed rate also. With a fine

feed the area of chip passing over the tool face is greater than that of coarse feed for a

given volume of swarf removal, but to offset this chip will be greater hence the

resultant pressure will nullify the advantage.

3. Tool Geometry: The tool life is also affected by tool geometry. A tool with large rake

angle becomes weak as a large rake reduces the tool cross-section and the amount of

metal to absorb the heat.

4. Tool material: Physical and chemical properties of work material influence tool life by

affecting form stability and rate of wear of tool.



Subject Code_5ME4-03 V Semester/3rd Year 5. Cutting fluid: It reduces the coefficient of friction at the chip tool interface and

increases tool life.

7. Cast iron is commonly used for machinery housings or bases due to the stable structure of

the material. It is also known for holding its shape when it is subjected to contraction and

expansion due to temperature fluctuations. This is ideal for a lathe bed

This material offers good damping, it is easy to machine, and can be made in various sizes.

Aging of the material can take up to a year and it can be more expensive than other materials

available.

8.

9. Grinding wheel is generally made from silicon carbide or aluminium oxide. It is

generally made up of particles of hard substance called the abrasive and is embedded

in a matrix called the bond. These abrasives form the cutting points in a wheel and are

termed as grains. The abrasives are of generally two types namely natural and

artificial. Emery and corundum are two natural abrasives, while carborundum and

aloxite are artificial abrasives. The hardness or softness of the wheel is dependent on

the amount and kind of the bonding material. Generally, hard wheels of aloxite are

used for grinding soft materials and soft wheels of carborundum for grinding hard

materials using various types of grinding machines known as grinders.



Subject Code_5ME4-03 V Semester/3rd Year 10. Truing is done when a new wheel is installed and before it’s used for the first time and is

necessary for precision grinding. The purpose of truing is to bring every point of the grinding

surface concentric with the machine spindle (to establish concentricity) and to introduce a

form (shape) into a wheel. No matter how precisely manufactured, there will be a slight gap

between the wheel bore and the machine spindle. Even if the gap is one thousand of a

millimeter, problems like chatter marks will occur if the wheel is not trued to the center of the

spindle. Conventional grinding wheels can be trued easily with a diamond cutter that is

harder than the wheel, while the superabrasives cannot be cut and must be ground to size.

This is done by using a sintered diamond roller or by traversing a conventional grinding

wheel.

Dressing is the process that comes after truing (especially in the case of superabrasives) and it

represents grinding wheel sharpening by exposing abrasive grits above the bond. In other

words, removing small chips of workpiece lodged in the wheel surface or removing dull

abrasives which returns the wheel to its original dimensions and provides crystal exposure.

The wheel surface after dressing is open with grits exposed.

Part-B




1.




Merchant’s Circle Diagram with cutting forces.

The significance of the forces displayed in the Merchant’s Circle Diagram is:

PS– the shear force essentially required to produce or separate the chip from the parent body

by shear

Pn– inherently exists along with PS

F – Friction force at the chip tool interface

N – Force acting normal to the rake surface

PZ– main force or power component acting in the direction of cutting velocity

The magnitude of PS provides the yield shear strength of the work material under the cutting

condition.

The values of F and the ratio of F and N indicate interaction like friction at the chip-tool

interface. The force components PX, PY, PZ are generally obtained by direct measurement.

Again

PZ helps in determining cutting power and specific energy requirement. The force

components are also required to design the cutting tool and the machine tool.

Advantages of using Merchant Circle Diagram (MCD)

Proper use of MCD enables the followings:

• Easy, quick and reasonably accurate determination several other forces from a few known

forces involved in machining

• Friction at chip-tool interface and dynamic yield shear strength can be easily determined

• Equation relating to different forces can be easily developed

2. Mechanisms and pattern (geometry) of cutting tool wear

For the purpose of controlling tool wear one must understand the various mechanisms of

wear

that the cutting tool undergoes under different conditions. The common mechanisms of

cutting

tool wear are:

1. Mechanical wear

a. thermally insensitive type; like abrasion, chipping and de-lamination

b. Thermally sensitive type; like adhesion, fracturing, flaking etc.



Subject Code_5ME4-03 V Semester/3rd Year 2. Thermo chemical wear

a. macro-diffusion by mass dissolution

b. micro-diffusion by atomic migration

3. Chemical wear

4. Galvanic wear

In diffusion wear the material from the tool at its rubbing surfaces, particularly at the rake

surface gradually diffuses into the flowing chips either in bulk or atom by atom when the tool

material has chemical affinity or solid solubility towards the work material. The rates of such

tool wear increases with the increase in temperature at the cutting zone.

Diffusion wear becomes predominant when the cutting temperature becomes very high due to

high cutting velocity and high strength of the work material. Chemical wear, leading to

damages like grooving wear may occur if the tool material is not enough chemically stable

against the work material and/or the atmospheric gases.

Galvanic wear, based on electrochemical dissolution, seldom occurs when both the work tool

materials are electrically conductive, cutting zone temperature is high and the cutting fluid

acts as an electrolyte. The usual pattern or geometry of wear of turning and face milling

inserts are typically shown in Fig

In addition to ultimate failure of the tool, the following effects are also caused by the growing

tool-wear:

increase in cutting forces and power consumption mainly due to the principal

flank wear

increase in dimensional deviation and surface roughness mainly due to wear of the tool-

tips and auxiliary flank wear (Vs)

odd sound and vibration

worsening surface integrity



Subject Code_5ME4-03 V Semester/3rd Year Mechanically weakening of the tool tip.

3.



Subject Code_5ME4-03 V Semester/3rd Year 4.

Capston lathe

S.no Capstan Lathe Turret Lathe

1 It is a Light weight machine. It is a heavy weight machine.

2

In capstan lathe the turret

tool head is mounted over the

ram and that is mounted over

the saddle.

In turret lathe the turret tool

head is mounted over the

saddle like a single unit

3

For providing feed to the

tool, ram is moved.

For providing feed to the tool,

saddle is moved.

4

Because of no saddle

displacement, Movement of

turret tool head over the

longitudinal direction of bed

is small along with the ram.

Turret tool head move along

with the saddle over the entire

bed in the longitudinal

direction.

5

Used for shorter workpiece

because of limited ram

movement.

Used for longer workpiece

because of saddle movement

along the bed.

6

Its working operations are

fast because of lighter in

constructions.

Its working operations are

slower because of heavier in

constructions.

7

Heavy cuts on the workpiece

cannot be given because of

non-rigid construction.

Heavy cuts on the workpiece

can be given because of rigid

construction of machine.

8

For indexing turret tool head,

the hand wheel of the ram is

reversed and turret tool index

automatically.

For indexing turret tool head,

turret is rotated manually after

releasing clamping lever.

9

The turret head cannot be

moved in the lateral direction

of the bed.

The turret head can be moved

crosswise i.e. in the lateral

direction of bed in some turret

lathe.

10

In capstan lathe, Collet is

used to grip the Job.

In turret lathe, power Jaw

chuck is used to grip the Job.

11

Used for machining

workpiece up to 60 mm

diameter.

Used for machining workpiece

up to 120 mm diameter.

12

These are usually horizontal

lathes.

Turret lathes are available in

horizontal and vertical lathes.




Turret lathe

5. CUTTTING SPEED- The milling cutter is circular and a large number of cutting edges (or

teeth) are arranged along its circumference. The cutter is rotated at a speed of N r.p.m. If the

cutter diameter is D, then cutting speed at the tip of teeth can be calculated as ΠDN

metres/minute.

FEED-Feed of the work piece is measured in terms of mm/minute. Actually, the correct

measure of feed is movement of work piece per revolution of cutter per teeth. If a milling

cutter has z number of teeth and if the table feed is ‘f’ mm/minute, feed per rev per teeth will

be f/NZ mm. It should therefore be clear that metal removal rate in milling operation is much

higher than in shaping or planing operations.



Subject Code_5ME4-03 V Semester/3rd Year 6. Grinding, honing, and lapping are three finishing processes that can be used on hardened

gears. Gear grinding can be based on either of two methods. The first is form grinding, in

which the grinding wheel has the exact shape of the tooth spacing (similar to form milling),

and a grinding pass or series of passes are made to finish form each tooth in the gear. The

other method involves generating the tooth profile using a conventional straight-sided

grinding wheel. Both of these grinding methods are very time consuming and expensive.

Honing and lapping, are two finishing processes that can be adapted to gear finishing using

very fine abrasives. The tools in both processes usually possess the geometry of a gear that

meshes with the gear to be processed.Gear honing uses a tool that ismade of either plastic

impregnated with abrasives or steel coated with carbide. Gear lapping uses a cast iron tool

(other metals are sometimes substituted), and the cutting action is accomplished by the

lapping compound containing abrasives.

Honing, which is used to remove material from internal cylindrical surfaces to improve the

geometry of a part or produce a finer surface finish, is performed at a slow speed — much

slower than the cutting speeds typically used in precision grinding. The cutting action is

achieved by a rotating hone, which consists of bonded abrasive sticks or stones mounted on a

metal mandrel. The workpiece, rather than being clamped in place, is fixed to allow floating

and prevent distortion that would result in an oval rather than round hole.

The hone is rotated in a controlled path over the surface of the part. In some cases, a

machinist might move the workpiece back and forth over the rotating hone, ensuring that the

part is floating rather than being pressed against the hone, to avoid an oval hole. With a

horizontal honing machine, the workpiece may be held in a self-aligning fixture while the

machine controls the speed and length of the stroke; the hone is hydraulically or mechanically

expanded until the desired hole diameter is achieved. With honing, a cutting fluid must also



Subject Code_5ME4-03 V Semester/3rd Year be used to clean small chips from the work area, cool the workpiece and hone, and lubricate

the cutting action.

Lapping is used to achieve surfaces that are very flat and smooth, as well as to finish round

work, such as precision plug gages, to very tight tolerances. The process is more gentle than

honing and removes much less surface material. Therefore, the workpiece should be as close

as possible to final size — achieved, for example, through double disk grinding — because

lapping typically removes only 0.0005” to 0.005” (0.0127 mm to 0.127 mm) of material.

Unlike honing, lapping uses fine-grained, loose abrasive particles suspended in a viscous or

liquid base rather than a bonded abrasive stick or stone. The lapping process involves passing

the workpiece between one or two large, very flat lap plates along with the abrasive

suspension. Close attention is paid to controlling every detail, including the speed of the

plate(s), the pressure on the workpiece, the size and type of abrasive used, the feeding

method, and the plate temperature.

7. High Velocity Forming

The concept of high velocity forming of metal is one of the newest technological advantages

in manufacturing. These processes have proved to be very useful in solving many fabrication

processes where conventional processes are find more difficult and more costly. Increase in

size of the work piece highly heat resistant materials, deep recessing, shallow recessing and

bulging operations are the examples which led to the development of high velocity forming

methods. A major advantage of high velocity forming is the ability to form one piece

complex part shapes in single operation, where as conventional methods require several

operations and result in a welded structure.

The variety of energy sources and techniques for applying the energy to accomplish

deformation of work piece makes the scope of high velocity forming as broad as the field of

metal working operation like draw forming, cupping, bulging, swaying, flanging joining. The

other application is die forming cutting, welding and surface hardening. The variety of

materials that have been fabricated with velocity methods includes magnesium, aluminum,

beryllium, titanium, zirconium, carbon and stainless steel, superalloy and the refractory

metals and alloys.

The process is based on the principle of deformation of metal by using very high velocities,

provided on the movements of rams and dies. Since the kinetic energy is proportional to the



Subject Code_5ME4-03 V Semester/3rd Year square of the velocity, high energy is delivered to the metal with relatively small weight (ram

or die). It reduces the cost and size of the machine. Since accelerations are high, high

velocities are obtained by using short stroked of the ram. This increases the rate of

production.

There are three main high energy rate forming processes:

1. Explosive forming,

2. Magnetic forming,

3. Electro hydraulic forming.

Explosive Forming

Explosive forming, is distinguished from conventional forming in that the punch or

diaphragm is replaced by an explosive charge. The explosives used are generally high –

explosive chemicals, gaseous mixtures, or propellants. There are two techniques of high –

explosive forming: stand – off technique and the contact technique.

Standoff Technique . The sheet metal work piece blank is clamped over a die and the

assembly is lowered into a tank filled with water. The air in the die is pumped out. The

explosive charge is placed at some predetermined distance from the work piece. On

detonation of the explosive, a pressure pulse of very high intensity is produced. A gas bubble

is also produced which expands spherically and then collapses. When the pressure pulse

impinges against the work piece, the metal is deformed into the die with as high velocity as

120 m/s.

Applications. Explosive forming is mainly used in the aerospace industries but has also found

successful applications in the production of automotive related components. The process has

the greatest potential in limited – production prototype forming and for forming large size

components for which conventional tooling costs are prohibitively high.

Electro Magnetic Forming



Subject Code_5ME4-03 V Semester/3rd Year The process is also called magnetic pulse forming and is mainly used for swaging type

operations, such as fastening fittings on the ends of tubes and crimping terminal ends of

cables. Other applications are blanking, forming, embossing, and drawing. The work coils

needed for different applications vary although the same power source may be used.

To illustrate the principle of electromagnetic forming, consider a tubular work piece. This

work piece is placed in or near a coil. A high charging voltage is supplied for a short time to a

bank of capacitors connected in parallel. (The amount of electrical energy stored in the bank

can be increased either by adding capacitors to the bank or by increasing the voltage). When

the charging is complete, which takes very little time, a high voltage switch triggers the

stored electrical energy through the coil. A high – intensity magnetic field is established

which induces eddy currents into the conductive work piece, resulting in the establishment of

another magnetic field. The forces produced by the two magnetic fields oppose each other

with the consequence that there is a repelling force between the coil and the tubular work

piece that causes permanent deformation of the work piece.

Applications

Electromagnetic forming process is capable of a wide variety of forming and assembly

operations. It has found extensive applications in the fabrication of hollow, non – circular, or

asymmetrical shapes from tubular stock. The compression applications involve swaging to

produce compression, tensile, and torque joints or sealed pressure joints, and swaging to

apply compression bands or shrink rings for fastening components together. Flat coils have

been used on flat sheets to produce stretch (internal) and shrink (external) flanges on ring and

disc – shaped work pieces.

Electromagnetic forming has also been used to perform shearing, piercing, and rivettting.

Electro Hydraulic Forming

Electro hydraulic forming (EHF), also known as electro spark forming, is a process in which

electrical energy is converted into mechanical energy for the forming of metallic parts. A

bank of capacitors is first charged to a high voltage and then discharged across a gap between

two electrodes, causing explosions inside the hollow work piece, which is filled with some

suitable medium, generally water. These explosions produce shock waves that travel radially

in all directions at high velocity until they meet some obstruction. If the discharge energy is

sufficiently high, the hollow work piece is deformed. The deformation can be controlled by

applying external restraints in the form of die or by varying the amount of energy released.




Advantages

1. EHF can form hollow shapes with much ease and at less cost compared to other forming

techniques.

2. EHF is more adaptable to automatic production compared to other high energy rate forming

techniques.

3. EHF can produce small – to intermediate sized parts that don't have excessive energy

requirements.

Accuracy of parts produced Accuracy of electro hydraulically formed parts depends on the control of both the magnitude

and location of energy discharges and on the dimensional accuracy of the dies used. With the

modern equipment, it is now possible to precisely control the energy within specified limits,

therefore the primary factor is the dimensional accuracy of the die. External dimensions on

tubular parts are possible to achieve within ± 0.05 mm with the current state of technology.

Part-C



Subject Code_5ME4-03 V Semester/3rd Year 3. Selection of Cutting Fluid

The benefit of application of cutting fluid largely depends upon proper selection of the type

of the cutting fluid depending upon the work material, tool material and the machining

condition. As for example, for high speed machining of not-difficult-to-machine materials

greater cooling

type fluids are preferred and for low speed machining of both conventional and difficult-to

machine materials greater lubricating type fluid is preferred. Selection of cutting fluids for

machining some common engineering materials and operations are presented as follows :

• Grey cast iron: Generally dry for its self lubricating propertyAir blast for cooling and

flushing

chips.Soluble oil for cooling and flushing chips in high speed machining and grinding

• Steels : if machined by HSS tools, sol. Oil (1: 20 ~30) for low carbon and alloy steels and

neat oil with EPA for heavy cuts .If machined by carbide tools thinner sol. Oil for low

strength

steel, thicker sol.Oil ( 1:10 ~ 20) for stronger steels and staright sulphurised oil for heavy and

low speed cuts and EP cutting oil for high alloy steel. Often steels are machined dry by

carbide tools for preventing thermal shocks.

•Aluminium and its alloys: Preferably machined dry Light but oily soluble oil Straight neat

oil

or kerosene oil for stringent cuts.

• Copper and its alloys: Water based fluids are generally used Oil with or without inactive

EPA for tougher grades of Cu-alloy.

• Stainless steels and Heat resistant alloys: High performance soluble oil or neat oil with

high concentration with chlorinated EP additive.

The brittle ceramics and cermets should be used either under dry condition or light neat oil in

case of fine finishing.

Grinding at high speed needs cooling ( 1:50 ~ 100) soluble oil. For finish grinding of metals

and

alloys low viscosity neat oil is also used.

4. Marking system for conventional grinding wheel:

The standard marking system for conventional abrasive wheel can be as follows:

51 A 60 K 5 V 05, where

The number ‘51’ is manufacturer’s identification number indicating exact kind of

abrasive used.

The letter ‘A’ denotes that the type of abrasive is aluminium oxide. In case of silicon

carbide the letter ‘C’ is used.

The number ‘60’ specifies the average grit size in inch mesh. For a very large size grit

this number may be as small as 6 where as for a very fine grit the designated number may

be as high as 600.



Subject Code_5ME4-03 V Semester/3rd Year The letter ‘K’ denotes the hardness of the wheel, which means the amount of force

required to pull out a single bonded abrasive grit by bond fracture. The letter symbol can

range between ‘A’ and ‘Z’, ‘A’ denoting the softest grade and ‘Z’ denoting the hardest

one.

The number ‘5’ denotes the structure or porosity of the wheel. This number can assume

any value between 1 to 20, ‘1’ indicating high porosity and ‘20’ indicating low porosity.

The letter code ‘V’ means that the bond material used is vitrified. The codes for other

bond materials used in conventional abrasive wheels are B (resinoid), BF (resinoid

reinforced), E(shellac), O(oxychloride), R(rubber), RF (rubber reinforced), S(silicate)

The number ‘05’ is a wheel manufacturer’s identifier.

Marking system for superabrasive grinding wheel:

Marking system for superabrasive grinding wheel is somewhat different as illustrated

below

R D 120 N 100 M 4, where

The letter ‘R’ is manufacture’s code indicating the exact type of superabrasive used.

The letter ‘D’ denotes that the type of abrasive is diamond. In case of cBN the letter ‘B’ is

used.

The number ‘120’ specifies the average grain size in inch mesh. However, a two number

designation (e.g. 120/140) is utilized for controlling the size of superabrasive grit.

Like conventional abrasive wheel, the letter ‘N’ denotes the hardness of the wheel.

However, resin and metal bonded wheels are produced with almost no porosity and

effective grade of the wheel is obtained by modifying the bond formulation.

The number ‘100’ is known as concentration number indicating the amount of abrasive

contained in the wheel. The number ‘100’ corresponds to an abrasive content of 4.4

carats/cm3

. For diamond grit, ‘100’ concentration is 25% by volume. For cBN the

corresponding volumetric concentration is 24%.

The letter ‘M’ denotes that the type of bond is metallic. The other types of bonds used in

superabrasive wheels are resin, vitrified or metal bond, which make a composite structure

with the grit material. However, another type of superabrasive wheel with both diamond

and cBN is also manufactured where a single layer of superabrasive grits are bonded on a

metal perform by a galvanic metal layer or a brazed metal layer.

5. Hobbing machines provide gear manufacturers a fast and accurate method for cutting

parts. This is because of the generating nature of this particular cutting process. Gear

hobbing is not a form cutting process, such as gashing or milling where the cutter is a

conjugate form of the gear tooth. The hob generates a gear tooth profile by cutting several

facets of each gear tooth profile through a synchronized rotation and feed of the work piece

and cutter.



Subject Code_5ME4-03 V Semester/3rd Year Figure 1

As the hob feeds across the face of the work piece at a fixed depth, gear teeth will gradually

be generated by a series of cutting edges, each at a slightly different position. The number of

cuts made to generate the gear tooth profile will correspond to the number of gashes of the

hob. Simply put, more gashes produce a more accurate profile of the gear tooth.

The hobs several cutting edges will be working simultaneously, which provide significant

potential for fast cutting speeds and/or short cycle times. With this realization, one can see

the hobbing process’s advantage over other cutting processes.

All gear hobbing machines, whether mechanical or CNC, consist of five common elements,

which are listed below and shown in Figure 2.

1. A work spindle to rotate the work piece (shown in blue)

2. A cutter spindle to rotate the cutting tool, the hob (shown in yellow)

3. A means to rotate the work spindle and cutter spindle with an exact ratio, depending on

the number of teeth of the gear and the number of threads of the hob (shown in red)

4. A means to traverse the hob across the face of the work piece (shown in green)

5. A means to adjust the center distance between the hob and work piece for different size

work pieces and hobs

figure 2

http://www.gearhobbingsolutions.com/wp-content/uploads/2016/01/hob-cutter-machine.jpg

http://www.gearhobbingsolutions.com/wp-content/uploads/2016/01/hob-cutter-machine.jpg




While the hob and work piece are rotating, the hob normally feeds axially across the

gear face at the gear’s tooth depth to cut and produce the gear. In conventional

hobbing, the direction of feed matches the direction of the cutting motion.

Alternatively, in climb feeding, the feed is opposite to the direction of the cutting

motion. Generally, conventional hobbing produces a better finish, whereas climb

hobbing yields better tool life. For either method, the cutting forces of the hob should

be directed towards the work spindle and not the tailstock.

Figure 3

To cut a helical gear, a standard hob cutter can be used. Mechanical hobbing

machines provide a differential motion through a series of change gears to generate a

gear tooth helix. Today, CNC hobbing machines electronically provide this

necessary differential to produce helical gears.

http://www.gearhobbingsolutions.com/wp-content/uploads/2016/01/cnc-gear-hobbing-machines.jpg

http://www.gearhobbingsolutions.com/wp-content/uploads/2016/01/Types-of-Gear-cutting-Machine.jpg







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