eme

2ND

INTERNAL ANSWER KEY - EME

PART A

1) ANY 5 LATHE OPERATIONS

Plain Turning

It is an operation in which the workpiece is reduced to the cylindrical section of

required diameter.Operation is carried out with a single point cutting tool.

Work piece is supported between the two centers permit rotation of workpiece.

Tool is fed perpendicular to the axis of workpiece to a known depth and then moved

parallel to axis of work.

Facing

An operation performed on lathe to generate flat surface.

Direction of feed is perpendicular to the axis of the lathe.

Length of the work should not be extended more than 1.5 times the diameter of the

work piece.

Knurling

Operation performed on lathe to generate serrated surface.

Tool used is called as knurling tool.

Tool consist of one upper roller and one lower roller which contains the impression.

Tool is set in such a way that both rollers touch the work.

Low speed of about 60 to 80 rpm and feed is 0.38 to 0.78mm/revolution.

Taper Turning by Swiveling the Compound Rest

Axis of the tool is moved inclined to produce the required taper.

Compound rest which supports tool post is swiveled at required taper angle and

locked.

Suitable for workpieces which require steep taper for short length.

Thread Cutting

A thread is a helical shaped groove formed on cylindrical surface of workpiece.

Thread cutting is an operation performed on lathe to produce threads by using a tool

whose shape will be same as that of thread.

Lead screw enables the tool to move longitudinally at the appropriate linear speed.

(THEORY 5 MARKS, DAIGRAM 5 MARKS)

OR

ANY 5 MILLING PROCESSES

Plain milling

It is a process used to mill flat surfaces of workpieces in such a way that the milling

cutter axis is parallel to the surface that is being milled.

End milling

End milling is a process of milling that is used to mill slots, pockets and keyways in

such a way that the axis of the milling cutter is perpendicular to the surface of the

workpiece.

Slot millingSlot milling is the process of milling slots using a different type of cutter called

slot drill which has the capacity to cut into solid material.

Angular milling

Angular mill is the milling operation used to mill flat surfaces that are neither parallel nor

perpendicular to the milling cutter axis.

Form milling

Form milling is a milling process used to machine special forms/ contours consisting of

curves using a special form mill cutter which is shaped exactly to the contour that is to be

form milled.

(THEORY 5 MARKS, DAIGRAM 5 MARKS)

2) ANY 2 ROBOTIC CONFIGURATION

Spherical configuration/ polar configurationThis configuration consists of a sliding arm (L

joint) actuated relative to the body, that can rotate about a vertical axis (T joint) and a

horizontal axis (R joint)

Cylindrical Configuration

This robot configuration consists of a vertical column, relative to which an arm assembly is

moved up and down. The arm can be moved in and out relative to the axis of the column.

A T joint to rotate the column about its axis. An L joint is used to move the arm assembly

vertically along the column. An O joint is used to achieve radial movement of the arm.

Jointed-arm robot (articulated) Configuration

This robot manipulator has the general configuration of a human arm. The joined arm

consists of a vertical column that swivels about the base using a T joint.

At the top of the column is a shoulder joint (R joint), whose about link connects to an elbow

joint (R joint)

(THEORY 5 MARKS, DIAGRAM 5 MARKS)

OR

DIFFERENT TYPES OF AUTOMATION

Automation of production systems can be classified into three basic types:

1. Fixed automation (Hard Automation)

2. Programmable automation (Soft Automation)

3. Flexible automation.

1. Fixed automation (Hard automation): Fixed automation refers to the use of special

purpose equipment to automate a fixed sequence of processing or assembly operations. Each

of the operation in the sequence is usually simple, involving perhaps a plain linear or

rotational motion or an uncomplicated combination of two. It is relatively difficult to

accomodate changes in the product design. This is called hard automation.

Advantages:

1. Low unit cost

2. Automated material handling

3. High production rate.

Disadvantages:

1. High initial Investment

2. Relatively inflexible in accommodating product changes.

2. Programmable automation: In programmable automation, the production equipment is

designed with the capability to change the sequence of operations to accomodate different

product configurations. The operation sequence is controlled by a program, which is a set of

instructions coded. So that they can be read and interpreted by the system. New programs can

be prepared and entered into the equipment to produce new products.

Advantages:

1. Flexible to deal with design variations.

2. Suitable for batch production.

Disadvantages:

1. High investment in general purpose equipment

2. Lower production rate than fixed automation.

Example: Numerical controlled machine tools, industrial robots and programmable logic

controller.

3. Flexible Automation: Flexible automation is an extension of programmable automation. A

flexible automation system is capable of producing a variety of parts with virtually no time

lost for changeovers from one part style to the next. There is no lost production time while

reprogramming the system and altering the physical set up.

Advantages:

1. Continuous production of variable mixtures of product.

2. Flexible to deal with product design variation.

Disadvantages:

1. Medium production rate

2. High investment.

3. High unit cost relative to fixed automation.

(THEORY 10 MARKS)

PART B

3) WRITE A NOTE ON ANY 2 FERROUS ALLOYS

Material Composition properties applications

Pig iron

Carbon 3.5 to 4.5 %

Silicon - 0.5 to 3%

Sulphur 0.04 to 0.2 %

Manganese 0.5 to 2.5

%

Phosphorus 0.04 to

1%

Very brittle

Used to make wrought

iron, cast iron and steel.

Cast

iron

Atleast 90 % iron

Carbon 2 to 4.5%

Silicon 1 to 3%

Small amount of

sulphur, manganese and

phosphorus

Very strong and brittle

Low melting point

Wear resistant

Admirable

machinability

Resistant to

deformation

Used to manufacture

machine frames, beds and

plates, housing, flywheels,

manhole covers,

automotive parts and

machine parts which are

not subjected to tension

and shocks.

( THEORY 10 MARKS)

OR

APPLICATION OF COMPOSITES IN AUTOMOBILES AND AIRCRAFTS.

Various composite components used in aircraft Components Made of Composite

Materials

Airbus A300B2/B4 Radome, fin leading edge and tip, fin

trailing edge panels, cabin and cargo hold

furnishings. Fairing -pylon, wing/ fuselage

rear.

Airbus A310-300 Rudder, elevator, vertical stabilizer,

spoilers, cowl (inlet & fan), thrust reverser,

main & nose landing gear door of wing

leading & trailing edge panels, nacelles.

Fairings -Ion, flap track, win fuselage.

Airbus A320/A319 & A321 Aileron, horizontal and vertical stabilizer,

elevator, rudder, spoilers, flaps, engine

cowl, radome, landing gear doors (main &

nose), floor panels, wing panels (leading &

trailing edge), other access panels,

nacelles.

Fairings -flap track, wing/fuselage

(forward & rear), and main landing gear

leg.

Airbus A330 Ailerons, rudder, flaps, spoilers, elevator,

horizontal and vertical stabilizer, wing

panels (leading & trailing edge), landing

gear doors (main & nose), nacelles.

Fairings -flap track, wing/fuselage

(forward & rear).

Airbus 340 Ailerons, rudder, flaps, spoilers, elevator,

horizontal and vertical stabilizer, wing

panels (leading & trailing edge), landing

gear doors (main & nose), nacelles.

Fairings -flap track, wing/fuselage

(forward & rear).

In commercial vehicles, appearance is also important as is the functional aspect. Studies have

shown that composite panels may be used as the complete outer skin of the body to give a

unique look.

Reinforced plastic is a boon in the sense that it uses shorter lead times and tooling cost is

considerably cheaper.

Truck bodies and trailers use assemblies and parts made from reinforced plastics to a great

extent. The use of light metals, which lends itself to simple shapes and extrudable forms, is

also found to be economical. The low heat transfer coefficient of composites enables their use

in refrigerated units. Glass reinforced polyester has all the properties that make it ideal for

this purpose and has become the standard material.

The strength-weight ratio is higher than other materials.

(THEORY 10 MARKS)

4) EXPLAIN ELECTRIC ARC WELDING PROCESS

Arc welding is one of several fusion processes for joining metals. By applying intense

heat, metal at the joint between two parts is melted and caused to intermix - directly,

or more commonly, with an intermediate molten filler metal. Upon cooling and

solidification, a metallurgical bond is created. Since the joining is an intermixture of

metals, the final weldment potentially has the same strength properties as the metal of

the parts. This is in sharp contrast to non-fusion processes of joining (i.e. soldering,

brazing etc.) in which the mechanical and physical properties of the base materials

cannot be duplicated at the joint.

Fig. 1 The basic arc-welding circuit

In arc welding, the intense heat needed to melt metal is produced by an electric arc.

The arc is formed between the actual work and an electrode (stick or wire) that is

manually or mechanically guided along the joint. The electrode can either be a rod

with the purpose of simply carrying the current between the tip and the work. Or, it

may be a specially prepared rod or wire that not only conducts the current but also

melts and supplies filler metal to the joint. Most welding in the manufacture of steel

products uses the second type of electrode.

Basic Welding Circuit

The basic arc-welding circuit is illustrated in Fig. 1. An AC or DC power source,

fitted with whatever controls may be needed, is connected by a work cable to the

workpiece and by a "hot" cable to an electrode holder of some type, which makes an

electrical contact with the welding electrode.

An arc is created across the gap when the energized circuit and the electrode tip

touches the workpiece and is withdrawn, yet still with in close contact.

The arc produces a temperature of about 6500F at the tip. This heat melts both the

base metal and the electrode, producing a pool of molten metal sometimes called a

"crater." The crater solidifies behind the electrode as it is moved along the joint. The

result is a fusion bond.

Arc Shielding

However, joining metals requires more than moving an electrode along a joint. Metals

at high temperatures tend to react chemically with elements in the air - oxygen and

nitrogen. When metal in the molten pool comes into contact with air, oxides and

nitrides form which destroy the strength and toughness of the weld joint. Therefore,

many arc-welding processes provide some means of covering the arc and the molten

pool with a protective shield of gas, vapor, or slag. This is called arc shielding. This

shielding prevents or minimizes contact of the molten metal with air. Shielding also

may improve the weld. An example is a granular flux, which actually adds

deoxidizers to the weld.

Fig. 2 This shows how the coating on

a coated (stick) electrode provides a

gaseous shield around the arc and a

slag covering on the hot weld

deposit.

Figure 2 illustrates the shielding of the welding arc and molten pool with a Stick

electrode. The extruded covering on the filler metal rod, provides a shielding gas at

the point of contact while the slag protects the fresh weld from the air.

(THEORY 7 MARKS, DIAGRAMS 3 MARKS)

OR

COMPARISON OF WELDING SOLDERING AND BRAZING.

Welding Soldering Brazing

It is a high temperature process

where base metal are heated

above their melting

temperature.

Low temperature process. Base

metals are not melted.

Base metals are not melted,

but broadly heated to a

suitable temperature.

Filler metal used is of same

material as that of the base

metal.

Filler metal is not as the same as

that of the base metal.

Filler metal is not as the

same as that of the base

metal.

Joint are formed by the

solidification of the molten

filler metal with the molten

base metal.

Joint is formed by means of

diffusion of the filler metal into

the base metal.

Joint is formed by means of

diffusion of the filler metal

into the base metal

associated with surface

alloying.

Strength of welded joint is

much stronger than the base

metal.

Comparatively low Strength lies between

welded and soldered joints.

Welded joints requires

finishing operations.

Joint can be used without any

finishing operations.

In some cases brazed joints

require finishing operations.

Since welding takes place at

high temperatures, the metal

adjacent to the weld portion

called the heat affected zone is

affected to a large extent.

There is no heat affected zone. Heat affected zone is no too

uch compared to welding.

(THEORY 10 MARKS)