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Dept of Mechanical Engineering NRIH

Source: M VENKANNABABU, Asso.Professor & HOD 1

Department

Of

MECHANICAL AND AUTOMOBILE ENGINEERING

Lab Manual for

PRODUCTION TECHNOLOGY LAB (II-Year MECH & AME II-Sem)

Prepared by

Mr. M.VenkannaBabu M.E (CAD), (Ph.D).

Asso. Professor & HOD


2

Source: M VENKANNABABU, Asso.Professor & HOD

1. TOOLS AND MACHINES USED FOR ARC WELDING

ARC WELDING:

In welding, heat generation is by electric arc is one of the most efficient method. Arc

welding process makes use of the heat produced by the electric arc to fusion weld of metallic

pieces.

In arc welding, arc is generated between two conductors of electricity, i.e., cathode and

anode, when they are touched to establish the flow of current and then separated by a small

distance. An arc is sustained electric discharge through the ionized gas column called plasma

between two electrodes.

Fig 1.1: Arc welding set-up

1. WELDING CABLES

Two welding cables are required, one from the machine to the electrode holder and

other from machine to the ground clamp. Flexible cables are used for coiling. Cable is

specified by their current carrying capacity (Amps).

2. ELECTRODES

Filler rods used in arc welding are electrodes. These are made of metallic wires called

core wires, having approximately the same composition as a metal to be welded. These are

coated uniformly with protective coating called flux. While fluxing an electrode, about 20mm

of length is left bare at one end for holding it with the electrode holder. It helps in transmitting

full current from electrode holder to the joint end of the electrode coating. Flux acts as

insulator of electricity.


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Various constituents like titanium oxide, potassium oxide, cellulose, iron or

manganese, Ferro manganese, Ferro silicates, carbonates, gums, clays, asbestos etc. are used

as coatings on electrodes, while welding the coating or flux vaporizes and provides a gaseous

shield to prevent atmospheric attack.

The size of an electrode is measured and designated by the diameter of the core wire

in SWG and length, apart from the brand and code names, indicating the purpose for which

they are most suitable.

According to BIS, six digits with a prefix letter specify the coated electrodes. The

prefix letter refers to the method of manufacture. The first 3 digits refer to performance

characteristics. The last 3 digits refer to mechanical properties of weld metal deposits. The

suffix letter of present refers to special properties.

Use of current ranges:

Size (mm) Amperage

2.15 60-80Amps.

3.15 90-130 Amps.

4.0 130-170 Amps.

5.0 160-200 Amps.

3. ELECTRODE HOLDER

The electrode holder is connected to the end of welding cables and holds the electrode.

It should be light strong and easy to handle and should not become hot while in operation.

The jaws of the holder are insulated, offering protection from electric shock.

4. GROUND CLAMP

It is connected to the end of the ground cable and is clamped to the work or welding

table to complete the electric circuit. It should be strong and durable and give a low resistance

connection.

5. WIRE BRUSH ABD CHIPPING HAMMER

A wire brush is used for cleaning and preparing the work for welding. A chipping

hammer is used for removing slag formation on welds. One end of the head is sharpened like

a cold chisel and the other to a blunt round point. It is generally made of tool steel.

6. WORKING TABLE

It is made of steel plate and pipes. It is used for positioning the parts to be welded

properly.


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7. FACE SHIELD

It is used to protect the eyes and face from the rays of arc and from spatter of flying

particles of hot metal. It is available either in hand or helmet type. The hand type is

convenient to use wherever the work can be done with one hand.

8. UNIVERSAL TESTING MACHINE

Weld strength is determined by conducting the tensile test on UTM for each set of

pieces.

9. ROCKWELL’S HARDNESS TESTER

Rockwell’s hardness tester determines hardness of the weld joint.

10. WELDING SCREEN

When people are around where welding is done, they may be protected from the rays

of the arc by means of a protected screen. In some shops, separate welding booths are

provided for the purpose.


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11. C CLAMP

It is used to hold work against an angle plate or ‘V’ block or any other surface, when

gripping is required.

12. TRY SQUARE

It is used for checking the square ness of many types of small works, when extreme

accuracy is not required. The blade of try square is made of hardened steel and the beam of

cast iron or steel. The length of the blade specifies the size of the try square.

13. FILES

It is a hardened steel tool, having slant parallel rows of cutting edges or teeth on its

surfaces. One end of the file is shaped to fit into a wooden handle.

Fig : Parts of a file


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2. LAP WELD JOINT

AIM: To prepare a Lap weld joint using the given two thick flat mild steel pieces of size

75x50x2 mm using AC welding machine.

TOOLS AND EQUIPMENT USED:

Rough and smooth files, arc welding machine, Mild steel pieces of 75x50x6mm, Electrodes,

Electrode holder, Helmet with safety goggles, chipping hammer, wire brush, tong,

Transformer AC supply.

THEORY:

WELDING: Welding is a process of joining similar or dissimilar by application of heat with

or without application of pressure and addition of filler material

LAP JOINT: It is used to join two overlapping plates so that the edge of the each plate is

welded to the surface of the other. The lap joint is shown in figure below.

Depending on the application, AC or DC machines are used in arc welding, but in some cases,

either of them can be used. DC supply is usually obtained from generators driven by electric

motor or if no electricity is available as AC source transformers are used. The function of

transformer is to step down the voltage from 449 volts to normal open circuit welding voltage

300

50

5

75

Fig: Lap Weld joint


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80V to 100V. In DC welding arc producing is easy and arc is steady and smooth. In DC

welding, electrode act as one terminal and the job is the other terminal. Polarity is very

significant factor in all DC welding works. They are of two types. The electrodes for DC arc

welding are coated with sodium silicate and for AC welding with potassium silicate.

STRAIGHT POLARITY: In straight polarity, the electrode forms the negative terminal and

the work piece forms the positive terminal. It is used for producing max penetration and is

used for root passes and out of welding.

REVERSE POLARITY: In reverse polarity, the electrode forms the positive terminal and

the work piece forms the negative terminal. It is used for welding thin sheets and for plates

with wide gaps.

AC WELDING: In case of AC welding there are no polarities. So, control over the heat is

not possible and the penetration pattern is intermediate to the above two. The typical AC arc

welding equipment with transformer is shown in the fig.

PROCEDURE: 1. Mild steel pieces of 75mm length are taken and are smoothened with files and made

right angles.

2. One edge of each piece is beveled to an angle of 300

and leaving nearly 1/4th

of the flat

thickness.

3. The two pieces are positioned in such a way that it is convenient and the arc is struck

using the electrode after the work piece is fastened to the table using the ground

clamp.

4. The electrode is to be fitted in electrode holder and current is to be set.

5. Using the face shield, the arc is to be started by keeping the electrode perpendicular to

the work and touching the work piece slightly.

6. As soon as the arc is struck, the electrode is moved slowly along the joint, keeping at

an angle of 150 to 25

0 from vertical and in the direction of welding.

7. At the end of the bead formation, break the arc.

8. Slag formation on the weld is removed by using the chipper.

PRECAUTIONS:

1. Always weld in well-ventilated space.

2. Do not weld around combustible or inflammable materials.

3. Never look at the arc with naked eyes.


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4. Filing should be done carefully.

5. Always wear the safety goggles, hand gloves, and apron and leather shoes.

6. Check whether the polarities are proper or not.

CONCLUSIONS:

REVIEW QUESTIONS:

1. Define lap weld joint?

2. What is an arc?

3. What is arc blow? Which current having more arc blow and why?

4. What are the different types electrodes used in arc welding?

5. What are the functions of coatings of electrodes?


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3. BUTT WELD JOINT

AIM: To prepare a Butt weld joint using the given two thick flat mild steel pieces of size

75x50x2 mm using AC welding machine and find the hardness of weld joint by using

Rockwell hardness tester.

TOOLS AND EQUIPMENT USED: Rough and smooth files, arc welding machine, Mild

steel pieces of 75x50x5mm, Electrodes, Electrode holder, Helmet, safety goggles, chipping

hammer, Transformer AC supply.

THEORY:

WELDING: Welding is a process of joining similar or dissimilar by application of heat with

or without application of pressure and addition of filler material

BUTT JOINT: It is used to join two plates, so that the edges of the plates are in a single

plane and one edge of the plate is welded to the other edge of the other plate. The butt joint is

shown in figure below.

Depending on the application, AC or DC machines are used in arc welding, but in some cases,

either of them can be used. DC supply is usually obtained from generators driven by electric

motor or if no electricity is available as AC source transformers are used. The function of

transformer is to step down the voltage from 449 volts to normal open circuit welding voltage

80V to 100V. In DC welding arc producing is easy and arc is steady and smooth. In DC

welding, electrode act as one terminal and the job is the other terminal. Polarity is very

600

Fig: Butt weld joint

75

5

50


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significant factor in all DC welding works. They are of two types. The electrodes for DC arc

welding are coated with sodium silicate and for AC welding with potassium silicate.

Straight Polarity: In straight polarity, the electrode forms the negative terminal and the work

piece forms the positive terminal. It is used for producing max penetration and is used for root

passes and out of welding.

Reverse Polarity: In reverse polarity, the electrode forms the positive terminal and the work

piece forms the negative terminal. It is used for welding thin sheets and for plates with wide

gaps.

AC Welding: In case of AC welding there are no polarities. So, control over the heat is not

possible and the penetration pattern is intermediate to the above two. The typical AC arc

welding equipment with transformer is shown in the fig.

Table: Variation of Rockwell hardness number with distance from outer edge

Thickness of the plate: 5mm.

Size of the electrode (diameter + flux): 3.15mm (2.15+1.0)

Current value: 200 – 250amps.

Distance from the

weld bead

Rockwell hardness

number

PROCEDURE:

1. Mild steel pieces of 75mm length are taken and are smoothened with files and made

right angles.

2. One edge of each piece is beveled to an angle of 300

and leaving nearly 1/4th

of the flat

thickness.

3. The two pieces are positioned in such a way that it is convenient and the arc is struck

using the electrode after the work piece is fastened to the table using the ground

clamp.

4. The electrode is to be fitted in electrode holder and current is to be set.

5. Using the face shield, the arc is to be started by keeping the electrode perpendicular to

the work and touching the work piece slightly.


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6. As soon as the arc is struck, the electrode is moved slowly along the joint, keeping at

an angle of 150 to 25

0 from vertical and in the direction of welding.

7. At the end of the bead formation, break the arc.

8. Slag formation on the weld is removed by using the chipper.

9. Finally hardness of the butt weld joint was found by using Rockwell hardness tester.

PRECAUTIONS:

1. Always weld in well-ventilated space.

2. Do not weld around combustible or inflammable materials.

3. Never look at the arc with naked eyes.


5. Always wear the safety goggles, hand gloves, and apron and leather shoes.

6. Check whether the polarities are proper or not.

CONCLUSIONS:

REVIEW QUESTIONS:

1. Define butt weld joint?

2. What are the different types of weld joints?

3. What is meant by HAZ in welding? What is the variation hardness in HAZ?

4. Which is the most preferable current for arc welding and why is it so?

5. What is effect of polarities in DC current on penetration?


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4. RESISTANCE SPOT WELDING

AIM: Perform resistance spot welding operation for the given mild steel plate of thickness

3.0mm using rocker arm type resistance spot-welding machine.

TOOLS AND EQUIPMENT USED: Resistance Spot Welding Machine with Heavy-duty

transformer resistance with electromagnetic contactor, solid-state electronic timer, current

selector, Rough and smooth files, two lines of 3-415volts 25amps AC power supply.

MATERIALS USED: Two mild steel pieces of size 75*25*3 mm.

INTRODUCTION: Resistance welding process is a fusion welding process where both heat

and pressure are applied on the joint but no filler metal or flux is added. The heat necessary

for the melting of the joint is obtained by the heating effect of the electrical resistance of the

joint and hence, the name resistance welding.

PRINCIPLE: In resistance welding (RW), a low voltage (typically 1V) and very high current

(typically 15000A) is passed through the joint for a very short time (typically 0.25 sec.). This

high amperage heats the joint, due to the contact resistance at the joint and melts it. The

pressure on the joint is continuously maintained and the metal fuses together under this

pressure. The heat generated in resistance welding can be expressed as

H = k*I2

R t

Where, H= the total heat generated in the work, J

I= electric current, A

t=time for which the electric current is passing through the joint, S

R= the resistance of the joint, ohms

k = a constant to account for the heat losses from the welding joint.

PROCEDURE:

1. After connecting the machines, switch on the main supply.

2. Put the left timer switch to on position, right side switch to cycle side.

3. Start the water circulation pump or tap water as the case may be.

4. Now the two pieces to be welded are held between the electrode tips and the foot

pedal is pressured for welding after processing current and timing as per the thickness

of the job.

5. After the weld is completed the current cut-off takes place automatically.

6. Now the foot can be removed from the pedal for releasing the job.

PRECAUTIONS:

1. See that the joints to be extremely clean.

2. Use tongs rather than asbestos or leather gloves to handle hot metal.



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5. SOLID PATTERN (MODEL 1)

AIM: To make the wooden pattern of the given drawing giving shrinkage allowance, draft

allowance and machining allowances.

TOOLS AND EQUIPMENT USED: Wood turning Lathe, inside& outside calipers, Tennon

saw, Marking gauge, Jack plane, Bench vice, Flat ruler, Hack saw, Wood turning chisels etc.

DIMENSIONS OF THE WORK PIECE: 50X50X150mm (Teak wood)

COMPONENT DRAWING:

ALLOWANCES TABLE:

S. NO Dimension Shrinkage

allowance

Machining

Allowance

Draft

allowance

Final

Dimension

Remarks

Shrinkage Allowance: 21mm/m,

Machining allowance: 1.5mm per side

Draft Allowance: To be provided where ever necessary (10

for external dimensions)

Φ40

Φ20

Φ30

Φ30 Φ50 Φ40

Pattern Without Allowances


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PATTERN DRAWING CONSIDERING ALLOWANCES:

INSPECTION REPORT:

S.No. Actual Dimension Observed Dimension

PROCEDURE:

1. A solid wooden piece is taken and is planed using jackplane. It is checked for 90

0

with the help of try square.

2. The centers are located of each plane of the stock by using brace with counter sunk

for headstock and tailstock.

3. Maximum distance from either end of the stock is measured and made an

indentation.

4. The entire length of the stock is turned by using gauges by giving number of

feeding until a larger diameter is obtained than the diameter of the required work

piece.

Fig: Pattern with allowances


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5. Then turn the flat chisel for finishing with small feed. Dimensions are measured

with caliper. So, we will get entire length of the uniform cross section.

6. Dimensions on the work piece are to be marked.

7. Then diameter is reduced till we get required diameter by using gauges. Then steel

flat chisel is used for finishing.

8. Face both the ends of the work piece.

9. Emery papers are used for final finish of pattern.

10. Then cut the end pieces, which are fixed on either end with the help of hack saw.

11. Finally, required piece of pattern is obtained.

PRECAUTIONS:

1. The scrapping tools are kept sharp to cut with out burrs and also with out mere

pressure for chipping.

2. Maintain proper turning with gauges.

3. Handle tools properly to avoid in accuracy.

CONCLUSIONS:


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6. SOLID PATTERN (MODEL 2)

AIM: To make the wooden pattern of the given drawing giving shrinkage allowance, draft

allowance and machining allowance.

TOOLS AND EQUIPMENT USED: Wood turning Lathe, turning gauges, outside &inside

calipers, Tennon saw, Brace with counter sunk, Marking gauge, Jack plane, Bench vice, Steel

rule, Hack saw.

DIMENSIONS OF THE WORK PIECE: 50X50X150mm (Teak Wood)

COMPONENT DRAWING:

ALLOWANCES TABLE:

S. NO Dimension Shrinkage

allowance

Machining

Allowance

Draft

allowance

Final

Dimension

Remarks

Shrinkage Allowance: 21mm/ m

Machining allowance: 1.0mm per side

Draft Allowance: To be provided 10 wherever necessary

All dimensions are in mm

Φ25 Φ25 60

0 60

0 60

0

Fig: Pattern without allowances

25 25 25 25 25

Φ40


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PATTERN DRAWING CONSIDERING ALLOWANCES:

INSPECTION REPORT:

S. No Actual Dimension Observed Dimension

PROCEDURE:

1. A solid wooden piece is taken and is planed using jackplane. It is checked for 900

with the help of try square.

2. The centers are located of each plane of the stock by using brace with counter sunk

for headstock and tailstock.

3. Maximum distance from either end of the stock is measured and made an

indentation.

4. The entire length of the stock is turned by using gauges by giving number of

feeding until a larger diameter is obtained than the diameter of the required work

piece.

600

600

600

Fig: Pattern with allowances


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5. Then turn the flat chisel for finishing with small feed. Dimensions are measured

with caliper. So, we will get entire length of the uniform cross section.

6. Dimensions on the work piece are to be marked.

7. Then diameter is reduced till we get required diameter by using gauges. Then steel

flat chisel is used for finishing.

8. Face both the ends of the work piece.

9. Emery papers are used for final finish of pattern.

10. Then cut the end pieces, which are fixed on either end with the help of hack saw.

11. Finally, required piece of pattern is obtained.

PRECAUTIONS:

1. The scrapping tools are kept sharp to cut with out burrs and also with out mere

pressure for chipping.

2. Maintain proper turning with gauges.

3. Handle tools properly to avoid in accuracy.

CONCLUSIONS:


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7. TOOLS AND EQUIPMENT USED IN SAND MOULDING

The molding operation is the heart of any sand casting process. Properly molded sand ensures

that the eventual cast is defect free. The fallowing is an account of the major tools and devices

used for sand molding in a casting schedule.

1. MOLDING BOARD

Molding board a wooden board with smooth surface on which the drag is placed. It

supports the devices while molding.

2. DRAG

It is the lower part of the mould flask assembly. It holds one half of the pattern in most

of the split piece pattern molding processes.

3. COPE

It is the upper part of the mould flask assembly. During molding operation the top

part of then Pattern, Sprue and Riser pins are placed while molding.

4. RAMMER

The device is used to give the sand proper packing in the flask. Improper ramming

makes the sand very loose and reduced strength and excessive permeability. Too tight packing

may cause low permeability and thereby blow holes in the casting. Also removal of pattern

after ramming is very difficult.

5. SHOVELS

They are used to transfer sand from the floor to the flasks. Depending on the amount

of of sand to be transferred, different types of shoves may be used.


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6. SPRUE AND RISER PINS

These are wooden/cast iron rods to provide clearance to form sprue and riser in the

mould. They are placed in the cope and after molding is completed, they are withdrawn to

form riser and sprue.

7. GATE CUTTER

This is a stain less steel plate used to cut gating system in the mould after the mould is

prepared.

8. VENT ROD

This is used to provide vent holes to the mould. These vent holes are useful for the

mould gases to escape.

9. STRIKE OFF BAR

This is made up of wood/cast-iron in the shape of rectangular in cross section. After

the ramming is over, the excess sand in the flask is completely scraped using a flat bar called

strike off bar to the level of the flask edges.

10 SLICK

Slick is used to repair the edges of sand around the pattern.

11 BELLOWS

Bellows are used to blow off the loose sand on the cope and drag interface.


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13. DRAW SPIKE

Draw spike is used to with drawn the cope and drag pattern halves and rapping the

pattern all around to slightly enlarge the mould cavity so that the mold walls are not spoiled

by the withdrawal of pattern.


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8. SAND MOULDING

AIM: To prepare a sand mould, for the given pattern of split piece type.

MATERIALS AND EQUIPMENT REQUIRED: Molding sand, facing sand, Split piece

pattern, parting sand, cope box, drag box and bottom board.

TOOLS: Sprue and Riser pins, Gate cutter, trowel, vent rod, sleek, bellow and Shovel.

PROCEDURE:

1. First a bottom board is placed either on the molding platform or on the floor, making the

surface even.

2. The drag-molding flask is kept upside down on the bottom board along with the drag part

of the pattern at the center of the flask on the board.

3. Dry facing sand is sprinkled over the board and pattern to provide a non-sticky layer.

4. Freshly prepared molding sand of requisite quality is now poured into the drag and on ht

pattern to a thickness of 30-50mm. rest of the drag flask is completely filled with the

backup sand and uniformly rammed to compact the sand.

5. After the ramming is over, the excess sand in the flask is completely scraped using a flat

bar called strike off bar to the level of the flask edges.

6. Now with a vent wire vent holes are made in the drag to the full depth of the flask as well

as to the pattern to facilitate to removal of gases during casting solidification. This

completes the preparation of the drag.

7. Now finished drag flask is rolled over to the bottom board exposing the pattern.

8. Using a slick the edges of sand around the pattern is repaired and cope half of the pattern

is placed over the drag pattern. Aligning it with the help of dowel pins.

9. The cope flask on top of the drag is located aligning again with the help of the pins of the

drag box.

10. Dry parting sand is sprinkled all over the drag surface and on the pattern.


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11. Sprue of the gating system for making the sprue passage is located at a small distance of

about 50mm from the pattern.

12. Then molding sand is poured in the cope box. The sand adequately rammed similar to the

drag box. The excess sand is removed by using strike off bar and vent holes are made all

over in the cope as in the drag.

13. The sprue and risers are carefully with drawn from the flask. Later the pouring basin is

cut near the top of the sprue.

14. The cope separated from the drag and any loose sand on the cope and drag interface is

blown off with the help of bellows.

15. Now the cope and drag pattern halves are with drawn by using the draw spike and rapping

the pattern all around to slightly enlarge the mould cavity so that the mold walls are not

spoiled by the with drawing pattern.

16. The sprue and riser pins are to be removed carefully without spoiling the mold cavity.

17. Now by using gate cutter make the runner passage and in-gates to the mould cavity.

18. Now the cope is placed back on the drag taking care of the alignment of the two by means

of clamping pin. Now the mold is ready for pouring molten metal.

PRECAUTIONS:

1. Sand should be rammed properly neither too hard nor too soft.

2. The pattern split pieces should be aligned properly while preparing the cope.

3. While removing the pattern care should be taken not to deform the mould.

CONCLUSIONS:

REVIEW QUESTIONS:

1. What are the different ingredients of moulding sand used for green send moulds?

2. What is the effect of moisture on permeability and strength?

3. What are gating elements, and their functions?

4. What are the properties of moulding sand and their importance?

5. What is importance of sand testing?

6. What is meant by directional solidification?


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9. INJECTION MOULDING

AIM: To Prepare a plastic cap of specified dimensions by injection Moulding.

APPARATUS: Injection Moulding machine, Die made of stainless steel, Granules.

DESCRIPTION: The injection Moulding equipment consists of the following apparatus.

1) Ram 2) Hopper to hold granular moldable

material 3) 3) Heating element to heat the moldable plastic 4) Nozzle to aid proper injection

into die

5) Hydraulic machinery to operate plunger or ram 6) Hydraulic tubing to operate plunger or

ram

7) Sump to hold hydraulic fluid 8) Pump to drive fluid through tubing

9) Heat controls to monitor temperature 10) Pressure control to set the injection

pressure 11) Die of required product to be made.

THEORY: Injection Moulding is based on the principle “Thermoplastic materials soften on

heating”. The granular thermoplastic material fed into the hopper is heated to a pre-

determined temperature. The higher the temperature, lower is the viscosity, easier is the

injection. Once the temperature is attained, plastic is forced into a die and then cooled. Since

no chemical change is induced, soften and hardening. The heating and cooling can be done

any number of times, without changing significantly, the properties of the material.


25


Fig: Injection moulding set up.

PROCEDURE:

1. The plastic is fed into the hopper in required quantity.

2. The heating coil is excited by power supply and the temperature controls are set to

required Moulding temperature.

3. A gap of time is allowed between feeding and before the product is extracted.

4. Some time elapses before raw material attains sufficient fluidity to be injected into the

die.

5. Once the plastic reaches Moulding temperature, the motor is switched on and plunger

lever operated, to move the ram downwards, onto the plastic in molten state.

6. As the plastic begins to flow out of the injection nozzle, the die is placed below the

nozzle and centered properly. It is locked properly to prevent plastic to squeeze out.

7. The ram is allowed to exert pressure (150MPa to 200Mpa) for about 5 seconds, during

which, material flows and occupies the shape of the die.

8. A few seconds are allowed for the plastic to solidify in the die. Then the die is opened

and required job is removed.

9. The job obtained is checked for the dimensions and the values are recorded.

PRECAUTIONS:

1. The die has to be properly centered under the nozzle of injector.

2. The plastic should not be over heated, to prevent uneven surface or incomplete filling

of die cavity.

3. The pressure setting should be in concurrence with the capacity of machine to prevent

the damage.

CONCLUSIONS:

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