7370588 Pneumatically Actuated Rubber Compression Moulding Machine

8/6/2019 7370588 Pneumatically Actuated Rubber Compression Moulding Machine

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1. INTRODUCTION

There is a difference between a product and a project. What we have tried to come

up with in this project is a concept of a product which has a true marketing potential. This

may not be the most ambitious project ever attempted in this college but it sure is one of

the most original and practical projects ever undertaken

A) DEFINING THE PROBLEM

Rubber components form an integral part of most of the things we use daily,

be it automobiles, machines, household appliances (e.g. fans, mixer grinders etc.) or show

pieces. This is because rubber has some unique properties which are not found in any other

material. Rubber components are indispensable wherever seals, washers or damping is

required. Thus thousands of different rubber components have to be manufactured.

There are many different processes for manufacturing rubber components,

but due to some unique properties of rubber which include low temperature required to

bring rubber to plastic stage and curing of rubber required to give it adequate strength have

made molding of rubber the most common type of manufacturing process.

A study of different compression moulding machines at different industries

showed that most are fully manual, flywheel operated machines with low output rates.

Most owners want to upgrade to hydraulically operated automatic machines but the cost of

these machines is prohibitive.

Our project for “Pneumatically Actuated Rubber Compression

Moulding Machine” is a project to prove the viability of pneumatic power for the

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operation of such machines. Pneumatic power is cheaper than hydraulic power because of

the following reasons :-

1. The equipment for pneumatic power is cheaper than a corresponding hydraulic

system .

2. A single air compressor can power multiple machines but hydraulic machines

require individual hydraulic power packs.

3. The expense of oil required for a hydraulic systems can be saved as air is free.

4. Many workshops, puncture repair shops etc, have air compressors, which are

usually under utilized and so would require very little investment to install such

pneumatically actuated machines.

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B) SCOPE OF THE PROJECT

Our project group visited two industries :-

1) M/s Vikamshi Fabrics Ltd., Khamgaon.

2) M/s Usha Rubber Industries, Amravati.

Both of which use rubber compression moulding machines. It was found

that these manual, flywheel operated machines require upto 3 operators. Two to operate the

flywheel & one to handle the dies.

What our project intends to achieve is to eliminate the flywheel & replace it

by a pneumatic power source to operate the pressure plate and in the process eliminating

the two workers required to operate the flywheel. Pneumatic power was chosen because :

1. The advantages of pneumatics over hydraulics power for the said purpose as stated in

the previous page.

2. Because we found that most workshops & puncture repair shops have idle air

compressors available. Thus such workshops or puncture repair shops can start a side

business requiring just a single operator to manufacture rubber components with very

little investment.

Especially we found that a puncture repair shop has both the raw material

i.e. rubber (from tyres and tubes) which are used to manufacture low cost rubber

components and vastly underutilized air compressor. They usually have a single person

manning the shop who is mostly idle. Such shops can very easily afford this type of

machine and start a side business giving high profits that too with very little investment

and also utilize their idle time.

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2. SOME ASPECTS OF RUBBER

(A) RUBBER AS A MATERIAL

Rubber belongs to the class of substances termed as polymers with high

molecular weight compounds which are predominantly organic, consisting of long chain

molecules made up of repeating units usually on a backbone of carbon atoms. These high

molecular weight polymers have a lower temperature limit to their plastic state. .

Types of Rubber :-

a) Natural Rubber b) Synthetic Rubber

a) Natural Rubber

i) Ribbed smoked sheet

ii) Pale crepe

b) Synthetic Rubber

i) Styrene Butadiene Rubber (S.B.R.)

ii) Butadiene acrylonitrile

iii) Poly chloroprene

iv) Poly isoprene

v) Poly butadiene

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Physical properties of Rubber

Max. Min.

a) Viscosity (stokes) 73 14 b) Ultimate tensile strength ( kg/cm2 ) 200 160

c) Ultimate elongation Percentage 1200 800

d) Modulus 96 25

Chemical Requirement of Rubber

Specification Percentage by weight

1) Dirt content 0.05

2) Volatile matter 1.00

3) Total ash content 0.754) Copper 8.00

5) Manganese 10.00

6) Nitrogen 0.70

(B) PROCESSING OF RUBBER

i) Rubber compounding:-

Rubber is compounded with various additives to improve properties like

mechanical, physical along with cost reduction.

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Additives used for rubber compounding

Sr.N

o.

Additives Type of material Purpose

1. Fillers Carbon black, Activated silica,

Activated magnesium carbonate,

Saw dust, calcium silicate

Provides

Reinforcements

Reduction in cost

2. Pigments Red iron oxide , Titan white, ultra

marine blue, yellow iron oxide

Coloring

3. Accelerator Mercapto benzthiazole, dibenzthiazyl

disulphide

Accelerates the vulcanization

rate

4. Activator Zinc oxide, stearic Acid Activates the accelerator

5. Antioxidant Substituted phenyl group of p-

phenylene

Provide moderate oxidant

production with min

discoloration

6. Plasticizer Dioctyl pthalate

Di-Iso octyl pthalate

Aids the processing

operation of mixing.

7. Blowing

agent

Azo compounds foaming-N

N-Nitroso compound

Provides foam like structure

8. Stabilizer White lead Prevents degration of rubber

during processing

9. Vulcanizing Sulphur Provides cross linking

10. Dusting

agent

Zinc stearate Avoids sticking of material.

Sequence of additives used during compounding :-

Rubber + Peptizer (Renasin)

Pigment + Tackifier (Rosin)

Small chemicals :- 1) Accelerator ( Mercapto benzthiazole )

2) Activator ( Stearic Acid, Zinc oxide )

Fillers :- 1) Processing aids ( white oil )

2) Special purpose agents

3) Sulphur ( Vulcanization )

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Additives Used for General Rubber Product

Sr.No. Ingredients % in weight

1. Natural Rubber ( Basic Raw Material ) 31.72. HAF Block (filler) 20

3. SRF black (colour) 28.5

4. Paraffin wax ( lubricating agent ) 5

5. Zinc Oxide (Activator) 6

6. Stearic acid (Activator) 1.6

7. Sulphur – Vulcanizing agent 2.5

8. Mercapto Benzthiazole (MTB)

( Accelerator )

0.8

9. Mercapto di Benzthiozyl di Sulphide

( Accelerator ) (MBTS)

1.4

10. Dioctyl pthalate - ( Plasticizer ) 2.5

ii) Vulcanization :-

One of the overriding and predominant technologies in the industry,

particularly with the emphasis on higher production rates and new techniques is the control

of chemical reactions leading to cross linking & bonding to metals , fabrics and rubber

break down.

The final step in the manufacturing sequence is the vulcanization or curing

of the formed product. Basically, the process is that of applying heat at a certain

temperature for a certain time. Vulcanization is most often combined with forming.

It is the process in which rubber is transferred from plastic state to elastic

state by promoting a certain degree of cross linking between chains.

This involves heating with sulphur and developing crosslinks. The

chemical changes involved in vulcanization have been given the name “Curing”.

Vulcanization process leads to the improvement of the following characteristics :-

Property Raw Rubber Vulcanized Rubber

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1) Tensile strength (kg/cm2) 200 2000

2) Percentage elongation 1200 800

3) Water absorption capacity Good Very good

4) Tackiness More Very small5) Working temp 10 – 600C - 40 to 1000C

6) Chemical Resistance Very poor Excellent

7) Elasticity Very much lower much higher

8) Resistance to oxidation abrasion

wear and tear

Very much lower much higher

3. RUBBER MOULDING

The manufacture of moulded rubber articles from compounded rubber sheet

involves one or other of the sequence of operations shown in fig below.

Block diagram for “Sequence of operations for Rubber Moulding”

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COMPOUND SHEET

CALENDER

CUTTING

HAND BUILDING

MOULDING

TRIMMING

EXTRUDED



The project “Pneumatically operated Rubber Compression Moulding

Machine” deals with the “Moulding” aspect of the sequence & on a later stage may also

include some aspects of cutting.

A) BLANK PREPARATION

In some of the large factories & most of the smaller ones moulding blanks

were prepared in a separate section, devoted exclusively to this work. In some factories

however, blanks were cut by the press operatives.

A great variety of different cutting methods were employed ; the particular

one chosen for a given blank being determined mainly by the machines available, the no.

required and the type of blank.

Classification of the different methods used is given below:-

1. Manual : This category includes hand cutting with scissors & knives, hand punching &

manually operated guillotines.

2. Punching Presses : Range from simple hand operated presses to large power presses.

Usually cutters are held in the press & rubber sheets moved beneath it.

3. Circular Knives : These are exclusively used for cutting extrusions. The knives are

usually water cooled & larger than 1 inch dia.

4. Power Gulliotines : These are usually of three types :

a. Firstly with the gulliotines mounted at the end of belt conveyor to cut off set length.

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b. Secondly – with fixed bed machines with wide blades 2-3 feet wide.

c. Thirdly - big enough to cut normal size sheets. The positioning is usually done

manually with the help of stops.

d. Finally : There are moving bed gulliotines, again with wide set blades where rubber

can be fed automatically or manual set blades where rubber can be fed automatically

or manually by means of a feed screw.

5. Volumetric Cutter : - These are large capacity machines where hot rubber strips are

fed to the machines. Here it is cut to size, compressed to required thickness and then

cut by a punch to required shape. The blanks are then dropped into a container & the

waste strip returns to the mill.

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B) METHODS OF MOULDING

Introduction : Moulding of plastics comprises forming an article to the desired shape by

application of heat and pressure to the moulding compound in a suitable mould and

hardening the material in the mould.

Selection of moulding process is largely determined by the moulding

material selected, to provide the desired physical properties in the finished moulded pieces.

Process determination is sometimes complex because there are two types of

moulding materials in general use, i.e. thermosetting and thermoplastic.

There are four basic moulding methods :

1. Compression Moulding

2. Transfer Moulding

3. Injection Moulding

4. Extrusion Moulding

Thermosetting materials are generally processed by compression and

transfer moulding. For thermoplastic materials injection and extrusion processes are used.

1. Compression Moulding : In compression and transfer moulding monomers are partially

polymerised in a separate operation and the polymerisation reaction is completed in the

mould. The partially polymerised material is prepared as pallets. It is placed in heated

mould. After the compound is softened and becomes plastic, the upper part of the die

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moves downwards, compressing the materials to the required shape and density.

Continuous heat and pressure produces the chemical reactions. The mould remains closed

until the curing is complete.

There are four basic types of processes for compression moulding

a. Flash Type

b. Positive Type

c. Landed Positive Type

d. Semi-positive Type

(a) Flash Type : As the mould closes, the excess material escapes over the land where it

forms a very thin. The fin hardens first, preventing the escapement of the mould charge.

Flash type moulds may be loaded by volume since excess material is permitted to escape.

(b)Positive Type : The characteristics of positive type mould are deep cavity and a plunger

that compresses the compound at the bottom of the mould. As there is very little

escapement of material, it is necessary to weigh the charge accurately if the size of the part

is to be controlled.

(c) Landed Positive Type : This type of mould is similar to the positive mould except that

lands are incorporated in the design to stop the travel of the plunger at a predetermined

point. The density may vary depending upon the charge.

(d)Semi positive Type : This is combination of flash type and landed positive type mould.

In addition to the flash ridges, land is incorporated to restrict the travel of the plunger while

some of the pressure is taken up by the land.

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2. Transfer Moulding : The thermosetting moulding powder is prepared by mixing filler

with resin which is only partly condensed and make it capable of being softened on

reheating. In transfer moulding, charge of moulding powder is forced from a cylinder

through a relatively restricted opening into the main mould. Thus due to flow through

restricted passage, the moulding powder becomes heated much more rapidly and uniformly

than by conduction from the walls of mould.

3. Injection Moulding : The granular moulding material is loaded into a hopper. The

injection ram pushes the material in to the heating cylinder and in doing so pushes a small

amount of heated material out of the other end of cylinder through the nozzle and mould is

then opened and piece is ejected out.

4. Extrusion Moulding : The material in granular form is placed into a feed hopper which

feeds the cylinder of the extruding machine. The hopper portion is kept cool by circulating

water. A rotating screw is used for carrying and mixing of material through cylinder and

forcing it through a die of required shape. The extruded shape coming from the die is

carried through a cooling medium by a conveyor and when it has been cool sufficiently to

retain shape, it is cut into lengths or coils.

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C) BASIS FOR SELECTION OF FLASH TYPE COMPRESSION

MOULDING OVER OTHER METHODS

This machine is made for low cost and small production runs with

minimum investment. The following methods are rejected due to the given reasons.

1) Rubber Injection Moulding :- The equipment is very expensive & viable only for

high production runs & is also plagued by many technical problems which limits its

use in the field of rubber moulding.

2) Extrusion : It is suitable only for the manufacture of pipes, tubes & solid sections

3) Transfer Moulding :- It requires very high pressure and moulding cost is very

high.

4) Positive and Landed Positive Type :- Both these methods are suitable only for

bulky material & deep drawing parts.

“ Thus flash type compression moulding is the most suitable for small

inexpensive products with small production runs. Thus we select this process.”

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D) ADVANTAGES OF COMPRESSION MOLDING

1. Wastage of material in the form of sprue, runner, and transfer-cull loss is avoided,

and there is no problem of gate erosion.

2. Internal stress in the molded article is minimized by the shorter and

multidirectional flow of the material under pressure in the mold cavity. In the case

of high impact types with reinforcing fibers, maximum impact strength is gained.

This results because reinforcing fibers are not broken up as they are when forced

through runners and gates in transfer and injection molding, and because fibers are

more randomly positioned, as compared to the more oriented fibers resulting from

flow into transfer or injection molds.

3. A maximum number of cavities can be used in a gives mold base without regard to

demands of a sprue and runner system.

4. Compression molding is readily adaptable to automatic loading of material and

automatic removal of molded articles. Automatic molding is widely used for small

items such as wiring device parts and closures.

5. This technique is useful for thin walled parts that must not warp and must retain

dimensions.

6. For parts weighing more than 3 pounds, compression molding is recommended

because transfer or screw injection equipment would be more expensive for larger

parts.

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7. For high-impact, fluffy materials, compression molding normally is recommended

because of the difficulty in feeding the molding compound from a hopper to the

press or performer.

In general, compression moulds usually are less expensive to build than

transfer or injection types.

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5. DESIGN CONSIDERATIONS FOR THE PROJECT

This project is a based on the concept of using pneumatic power for the

actuation of pressure plate of rubber moulding presses. The basic concept is to prove the

feasibility of pneumatic power for such machine.

The size of such machines is specified in two ways :-

(i) the maximum force that the pressure plate can apply on the die

(ii) the maximum size of the die which can be accommodated .

As the main aim of this project is to prove the feasibility of pneumatic

power we chose to design a small m/c using a single die. Large machines which can

accommodate multiple dies would prove to be too expensive for the purpose. The various

assumptions & design considerations for the project are as follows :-

1. The max pressure from the available air compressor was found to be 9 kg/cm2.

2. With the main criterion – cost – in mind, the size of the pneumatic cylinder was chosen

first – { but one that could apply a min force of 150 kg }. The specifications arrived at

were as follows :-

3. 50 mm dia

4. 100 mm stroke

5. double acting

6. flange mounting

7. cushion ended

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iii). Once the specifications for the pneumatic cylinder had been chosen and fixed, next the

max size of the rubber component that could be manufactured was calculated, and the size

of the die for such a mould was determined.

Based on the “ S P I Plastic Engg Hand book”, the pressure required for

moulding low pressure, thermoplastic phenolics & rubbers was found to be – 350 psi (24

kg/cm2) for mouldings upto a max depth of 1.90 cm.

iv) Once the size of the die had been determined, it was fairly simple to determine the

maximum size of the heating chamber and the distance of the supporting pillars. The size

of the heating chamber should be at least equal to the size of the die, to heat the die

uniformly and the supporting pillars should be far enough not to hamper inserting &

removal of the die.

Based on the above consideration the following was determined.

1. Max force from the pneumatic cylinder = area of piston x max pressure from

compressor = kg kg 18017694

5712

≈=××

2. The size of the die considering provision for latent heat was determined as

100mm x 100mm.

3. Size of the heating chamber was chosen as – 200 mm x 200 mm to accommodate larger

dies in future.

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4. The distance between the supporting pillars was fixed at - 350mm & 250mm

respectively for easy removal of larger dies.

5. Similarly the stroke of the pressure plate was chosen as 100 mm for easy removal

of dies from the heating chamber and to allow for parts with greater moulding

depth & thus thicker dies.

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6. DESIGN OF MACHINE

A. PROPERTIES OF MATERIAL USED FOR THE PROJECT

a) The grade of steel selected for use in the project is -

Fe 310 – general purpose engg steel.

Characteristics of Fe 310 :-

i) ultimate tensile strength - 310 N/mm2

ii) yield point stress - 180 N/mm2

iii) modulus of elasticity/young’s modulus - 2.0 to 2.2 × 10 kg /cm2

iv) shear stress - 400 kgf/cm2

v) crushing stress - 900 kgf/cm2

B. STANDARD DATA FOR THE PROJECT

a) value of ‘Factor of Safety’ –

The type of load is assumed to be shock load as it is applied suddenly at the

end of the downward stroke of the pressure plate & also suddenly removed. For shock

loads the standard value of factor of safety is (F.S.) = 12

b) design/working stress (tensile) –

Ft = yield point stress/F.S. = 15 N/mm2

c) maximum pressure that the compressor can provide = 9 kgf/cm2

d) maximum force that pneumatic cylinder can provide

(cylinder of dia 50 mm) = area of piston × max. pressure of compressor

= 180 kgf = 1764 N

The further design of the m/c is based on this data.

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C. CALCULATIONS FOR THE DIMENSIONS OF THE SUPPORT PILLARS.

a) Max shear occurs where the diameter of the pillar is minimum i.e. At the core of the

threaded part (dc).

b) For design to be safe –

working stress × area of C/S. of core × No. of pillar = max load

15 × π/4 dc2 × 4 = 1764 N

dc = 6.1 mm

Therefore – core diameter of bolt (dcb) = 6.11 mm

c) From “Design Dimensions of Screw Threads, Bolts & Nuts”,

According to “IS:4218 (part IV). 1987” :-

Taking next higher value of core diameter of nut from standard table, core diameter of bolt

(dcb) = 6.647 mm

Core dia 6.647 mm represents nut & bolt size M 8.

d) Design features of standard nuts & bolts of size M 10 (all dimensions in mm) :-

1. Pitch – 1.25

2. Major or nominal diameter, nut & bolt (d=D) – 8

3. Effective or pitch diameter, nut & bolt (dp) – 7.188

4. Minor or core diameter of bolt, (dcb) – 6.466

5. Minor or core diameter of nut (dcn) – 6.647

6. Depth of thread of bolt – 0.767

7. Shear area-58.3

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e) Calculations for bolt :-

i) initial tension while tightening bolt = Pn = 1420 d = 14200 N

ii) checking for failure in shear :-

A) design or working shear stress ( Fsd) =Ultimate shear stress / F.S.

= 400/12

= 33.33 kgf/cm2

B) calculated value of shear stress across threads (bolt) :-

Fs = P / π.dcb.b.n = 1.91 N/ mm = 19.5 kgf/cm2

Where-

dcb = core diameter of bolt

b = width of thread at root = pitch

n = no. of threads engaged

Therefore Fs = 1764/4

Fs = 19.5 kgf/cm2

As the calculated value of shear stress across threads( Fs= 19.5 kgf/cm2) is

lower than the design stress (Fsd = 33.33 kgf/cm2) , the design is safe.

iii) Calculation for shear stress across threads of nut:-

Fsd = P/4.π.d.b.n. = 15.9 kgf/cm2 is less than the working shear stress Fsd = 33.33 kgf/cm2,

the design is safe.

f) For reasons of structural rigidity & to accommodate the drilling & tapping

operations the size of the support pillars is chosen as 20 mm diameter.

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D. DESIGN OF TOP PLATE

a) dimension of top plate = 400 mm × 300 mm × 8mm

b) 4 holes of diameter 8mm at 4 corners at a distance of 25mm from each edge

c) design for shear-

As the plates rest on the support pillars & are fixed to them using M8 size bolts &

washers of internal diameter 8mm & external diameter 15mm,

shear force on plate = P/ 4.π.D1.t < = design shear stress (3.266 N/mm2)

therefore t = 2.149 mm

d) design for bending :-

as the guide rods cannot be allowed to deflect or bend , therefore assuming that there is

zero deflection of guide rod.

The max deflection of plate allowable = 0.05 cm

Dimension of plates are 400 × 300 × t

Therefore, bending will occur on the largest supported span is 400mm.

As the bending load is applied by pneumatic cylinder, at the center of the plate and at the

end of forward stroke.

Therefore, bending force = 180 kgf

= 1764 N

Max deflection due to a point load at the middle of a body with both ends fixed

Therefore y = + FL3/ 193 EI

0.05 = 1/192 × 180 × 383 / 2.2 × 106 × I

I = 0.467

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As I = bt3/12 = 0.467

t = 5.8 mm

As the value is larger than the value of shear, therefore minimum acceptable

value = 5.8 mm.

We take the plate of the thickness 8mm for added safety, rigidity and higher

factor of safety.

Thus, thickness of 8mm if more than sufficient for a safe design of the top plate.

E. DESIGN OF BOTTOM PLATE

For added stability & lower centre of gravity of the machine , a heavy base

plate is used of dimensions – 400mm × 300mm × 20mm

(All other design parameters and considerations for base plate is the same as the Top

Plate.)

F. DESIGN OF HEATING CHAMBER

The heating chamber has to take the same stresses as the top plate & thus is

made from 10mm M.S. plate.

The size of the heating chamber is 300mm × 200mm with a height of 60mm

& one side open.

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7. DESIGN OF PNEUMATIC SYSTEM

a) PNEUMATIC CIRCUIT

For the actuation of the pressure plate, a simple pneumatic circuit, utilizing a single

4 way, 3 position, spring return , manually operated valve is used in conjunction with the

pneumatic cylinder.

The circuit diagram for the circuit is shown in fig –

Pneumatic

Cylinder 1 2

4/3 DCVA c B

From cylinder

FRL unit

To operate the pr plate the operator first shifts the manually operated lever of the

4/3 DCV to position A.

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By doing this air flows from the compressor, through the FRL (Filter regulator &

lubricating) unit, into port 1 of the pneumatic cylinder causing forward stroke of the

cylinder. The cylinder initially moves at a fast rate but as it is cushion ended , towards the

end it slows down & makes a soft contact with the top of the die.

When the cylinder has moved forward to the max limit ( i.e. when the two halves of

the die are closed), the operator switches the lever to position C and thus holds the pressure

on the die.

When the curing process has been completed the lever is switched to position B

causing the cylinder to retract speedily.

A 3 position value is used instead of a 2 position value so that the operator can stop

the ram at any position he wants. This is especially helpful when dies with low heights do

not require the ram to be retracted fully.

b) MOUNTING AND COUPLING OF PNEUMATIC CYLINDER :-

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The pneumatic cylinder is of flange mounting type with the flange having

dimensions 65 mm x 100 mm x 12 mm

The flange was provided with four holes at four corners having a dia of 12

mm and length wise and width wise centre distance between the holes at 90 mm and 45

mm. The shaft of the pneumatic cylinder was of 20 mm diameter with a standard thread of

designation of M 18.

1) Mounting the cylinder

To mount the cylinder four holes were drilled in the top plate with centre

distances of 45 mm (width wise) and 90 mm lengthwise and with a dia of 12 mm. The

pneumatic cylinder was then mounted on the top plate with the help of four nuts and bolts

of designation M 10 ( Major/nominal dia of 10 mm )

2) Coupling of Pneumatic Cylinder shaft to Pressure Plate :-

As M.S. bar of 30 mm diameter and 20 mm length was welded on to the

pressure plate. A hole of 17 mm diameter was drilled and then a hand tapping tool for

internal threads of designation M 18 ( major dia 18 mm) was used to tap the hole.

The shaft of the pneumatic cylinder was then attached to the pressure plate

using the above mentioned threaded fastening and a corresponding locking nut.

8. DESIGN OF ELECTRICAL CIRCUIT

The curing of rubber requires both heat and pressure

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The provision for heating is provided by means of a heating coil fitted in an

insulated fixture and placed under the heating chamber

For proper curing of rubber, a temperature between 140 0 C and 1600 is

usually required to control the temp within this range a thermostat is connected in series

with the coil and directly mounted on the side of the heating chamber.

It is properly calibrated using a thermometer of break the circuit when the

temp reaches a given specified point between 1400 C and 1600 C under steady state

operating condition.

When the top plate of the heating chamber reaches the specified

temperature the bimetallic strip in the thermostat bends, causing the circuit to break.

9. ASPECTS OF DIE DESIGN.

a) Die design theory :-

29

Heating Coil + Frame

for 1500 watt.

Thermostat

230 V a.c. supply



Moulds are made of a variety of materials depending on the use and

conditions of moulding. Cast iron and steel are very common materials. In the moulding

process, it must be remembered that shaping and curing are being done at the same time. It

is essential that the rubber must flow and take shape of the mould before actual

vulcanization starts. This is extremely important in precision moulding, since any structure

developed before moulding pressure is applied will cause a variation in shrinkage after the

product is removed from the mould.

There must be sufficient stock in the mould to fill it, otherwise the cured

article will be light in the corners, i.e. corners will be round, when they should be sharp

and rubber product may show porosity both externally and internally.

Some moulds are provided with sprue rings to take small amount of

overflow, to accommodate the amount of rubber that must overflow. Even then if

excessive rubber is put in mould, the two halves will not close properly.

In intricate mould designs, such as treads of pneumatic tyres, it is necessary

to cut little holes or “vents” right through the mould to get rid of trapped air.

Unless very precise products are required, it is not necessary to consider

tolerances for expansion and ejection.

b) Design of Die :-

1. Maximum force available from the pneumatic cylinder = 180 kgf .

2. Based on data from “ S P I Plastic Engg Hand Book”, the pressure required for

moulding low pressure phenolics and rubber = 350 psi = 24 kg/cm2

upto depth of 1.9 cm

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3. The maximum size of rubber component that can be moulded = 180/24 = 7.5 cm2

i.e. with surface area upto 7.5 cm2 and depth or thickness upto 1.9 cm.

4. It was decided to make a mould for the manufacture of rubber washers because the

design of the mould is simple.

5. Size of the rubber washer planned for manufacture has dimensions of

15 mm internal dia

30 mm external dia and thickness of 4 mm

6. The surface area of the mould is = 222 cm3.5)dD(4

=−π

and is therefore acceptable.

7. The size of the die was chosen as 100 mm x 100 mm to be able to store sufficient

latent heat and also, if needed, to be converted into a multiple die in future.

8. Two handles were welded to the bottom half of the die for easy removal of die from

inside machine.

CHART NO : 01

Name of the Part : Top Plate

Raw Material – M.S. Plate. 1 No.

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M.S.Plate Size: 400 x 300 x 8 mm

S

r.No

.

Operation Standard

machine

Used

Description of

operation

Tool used Gauge use Operation

Time

1. Filing - Edge

preparation &

surface finish

for the plate

Rough &

Smooth

File

Tri-square 30 min.

2. Drilling Drilling m/c Drilling of 4

holes at corner,

as per

specification

10mm

drill

- 20 min.

3. Drilling Drilling m/c Drilling of

centre hole of φ

40mm in plate

40mm

drill tool.

- 10 min.

4. Drilling Drilling m/c Drilling of φ 12

mm holes

(4nos.) for

mounting of

pneumatic

cylinder

12 mm

drill

- 15 min.

CHART NO : 02

Name of the Part : Basic Plate

Raw Material – M.S. Plate. 1 No.

M.S.Plate Size: 400 x 300 x 15 mm

32



S

r.No

.

Operation Standard

machine

Used

Description of

operation


Time

1. Filling - To obtain better

surface finish

Rough &

Smooth

file

Tri-Square 30 min.

2. Drilling Drilling m/c Drilling of 4

holes at corners

as per

specification

8 mm

Drill

- 20 min.

CHART NO : 03

Name of the Part : Heating Chamber

Raw Material – M.S. Plate and angle

M.S.Plate Size: 200 x 200 x 6 mm – 1 No.

Angle Size : 200 x 45 x 45 – 2 Nos.

150 x 45 x 45 – 1 Nos.

33



S

r.No

.

Operation Standard

machine

Used

Description of

operation


Time

1. Filling - To obtain better

surface finish

File Tri-square 20 min.

2. Welding Welding

m/c

First weld the 3

angles to plate

& then this

welded part is

welded to base

plate

30 min.

CHART NO : 04

Name of the Part : Pillar

Raw Material – M.S. Bar 4 Nos.

M.S.Bar Size: 25 mm x 230 mm

S

r.No

.

Operation Standard

machine

Used

Description of

operation


Time

34





Turning M.S. bar &

Facing &

Turning of M.S. plate on

both side

point

cutting

tool

Calliper

3. Drilling Drilling m/c Drilling up to

& 5 mm depth

(1 hole)

Drill Vernier

Calliper

15 mm

4. Drilling Drilling m/c Drilling up to

10 mm depth

(3 holes) oncircular

M.S.Plate

Drill - 30 mm

CHART NO : 06

Name of the Part : Die

Raw Material – M.S. Plate.

M.S.Plate Size: Two pan

S

r.No

.

Operation Standard

machine

used

Description of

operation


Time

1. facing lathe four

jaw

Facing on both

top & bottom

halves of die.

Single

point

cutting

tool

Vernier 45 min.

36



2 Grooving Lathe four

jaw

Grooving on

the face of the

die

Form tool Vernier,

Height

gauge

40 min

11. BILL OF MATERIALS

Sr. No. Particulars Quantity Specification Length

1 Base plate 1 400 x 300 x15 _

2 Support Pillars 4 φ 20 225

3 Angles 3 45 x 45 x 5 200

4 Top plate of heating

chamber

1 200 x 200 x 8 _

5 Pressure plate ( flange ) 1 φ 90 mm 10mm (thickness)

6 M.S. Bar 1 φ 30 mm 20 mm

7 Top plate 1 400x300x8 -

8 Die (top half) 1 100x100x10 -

9 Die (bottom half) 1 100 x100x15 -

10 Pneumatic cylinder 1 φ50(piston size) 100

(length of stroke)

11 Flange 1 110x65x12 -

12 Nuts & bolts 8 M-8 2513 Heating coil 1 1000W -

14 Coil frame 1 - -

15 Thermostat 1 - -

16 Wires - - 6000

17 Plug 1 - -

18 Connector 1 - -

19 Asbestos sheets 2 200x200 -

37



20 Thermostat cover 1 1 -

21 Insulating sleeves - - 500

22 Nuts & bolts 4 M12 30

12. ESTIMATION FOR THE PROJECT

Sr.No. Particulars Amount ( Rs.)

1 Estimates for procurement of raw material :

i. Base plate : { Dim-400x300x15} @ 25/kg

ii. Upper plate :{ Dim-400x300x8) @ 25/kg

iii. Supports :{Dim-φ20x225}

iv. Heating chamber (4 Nos)-

a) Top plate { Dim-20x200x8}

b) Angles { Dim-45x45x5}{Length 200}

390

193

212

83

68

2 Estimate for die 375

3 Estimate for machining charges

i) Top plate

ii) Base plate

iii) Guides

iv) Heating chamber

v) Pressure plate (Flange)

180

125

480

235

115

4 Estimates for pneumatic system

i) Pneumatic cylinder

ii) 4/3 Direction control valve

iii) Pneumatic plumbing & connectors

1785

820

110

5 Estimate for heating system

i) Heating coil + holder

ii) Thermostat +control +casing

iii) Electrical accessories ( Wires, connector, asbestos

176

365

117

38



sheet, sleeves , etc.)

6 Painting 163

7 Misc. expenses 223

Final total estimate 6215

13. ESTIMATION FOR RUNNING COST OF MACHINE

The running cost of the machine is made up of two components

a) Cost of electricity to run the heating system :-

The heating coil is of 1500 watts. As during a steady state operation the

heating system is in use for approximately 75 % of the time. Therefore cost of electricity

per operation ( assuming a average 20 operations per hour and rate of electricity Rs. 5 per

unit). = { 0.7 x (1500/1000) x 5 }

20

= Rs. 0.26 = 26 paisa.

b) Cost of operating pneumatic cylinder :-

The pneumatic cylinder can give satisfactory service bet 5 and 7 kg / cm 2

pressure.

Time taken to raise compressor pressure from 5 to 7 kg/cm2 = 10

No. of operations possible between this pressure range = 20

Therefore cost of operation of pneumatic cylinder per stroke (0.75 Hp motor)

= 0.75 x 0.746x 5 x 10

20 x 60

= Rs 0.02 = 2 paisa.

Therefore, total running cost of machine per operation = 0.02 + 0.26 = Rs. 0.28 = 28 p.

39



14. ADVANTAGES OF THE MACHINE

a) This machine is much cheaper than any other hydraulically operated automatic m/c.

b) The no. of operator required is one and thus it eliminates one to two workers as

compared to manual machines.

c) Operator fatigue is much lower than manual machine .

d) The pressure applied is much more consistent leading to better quality products.

e) Productivity is increases greatly.

f) Its operating costs are at par with or lower than other machines. ( Both manual and

automatic).

g) Due to only single moving part maintenance costs are very low.

40



Source : “SPI Plastic Engineering Handbook”.

MOULDING DEPTH & PRESSURES FOR LOW PRESSURE, THERMOPLASTIC

PHENOLICS.

Sr. No. Mould Depth (inches) Pressure (psi)1 ¾ inch 350

2 1 inch 450

3 1 ¼ inch 550

4 1 ½ inch 650

5 1 ¾ inch 750

6 2 inch 850

7 2 ¼ inch 950

8 2 ½ inch 1050

9 2 ¾ inch 1150

10 3 inch 1250

∗Add 100 psi for every ¼ inch increase in moulding depth.

Design Dimensions of screw threads, bolts and nuts according to IS : 4218 (Part IV)1978.

41



Designation Pitch

mmMajor or nominal

diameter

Nut and

Bolt (d-D) mm

Effective or pitch

diameter Nut

and Bolt (d p)

mm

Minor or CoreDiameter (de)

mm

Bolt Nut

Depthof

thread

(bolt)

mm

Stressarea

mm2

(1) (2) (3) (4) (5) (6) (7) (8)Coarse series

M 0-4 0.1 0.400 0.335 0.277 0.202 0.061 0.074

M 0-6 0.15 0.600 0.503 0.416 0.438 0.092 0.166

M 0-8 0.2 0.800 0.670 0.555 0.584 0.123 0.295

M 1 0.25 1.000 0.838 0.693 0.729 0.153 0.460

M 1-2 0.25 1.200 1.038 0.893 0.929 0.158 0.732

M 1-4 0.3 1.400 1.205 1.032 1.075 0.184 0.983

M 1-6 0.35 1.600 1.373 1.171 1.221 0.215 1.27

M 1-8 0.35 1.800 1.573 1.371 1.421 0.215 1.70M 2 0.4 2.000 1.740 1.509 1.567 0.245 2.07

M 2.2 0.45 2.200 1.908 1.648 1.713 0.276 2.48

M 2.6 0.45 2.500 2.208 1.948 2.013 0.276 3.30

M 3 0.5 3.000 2.675 2.387 2.459 0.307 5.03

M 3.5 0.6 3.500 3.110 2.764 2.850 0.368 6.78

M 4 0.7 4.000 3.545 3.141 3.242 0.429 8.78

M 4.5 0.75 4.500 4.013 3.580 3.688 0.460 11.3

M 5 0.8 5.000 4.480 4.019 4.134 0.491 14.2

M 6 1 6.000 5.350 4.773 4.918 0.613 20.1

M 7 1 7.000 6.350 5.773 5.918 0.613 28.9

M 8 1.25 8.000 7.188 6.466 6.647 0.767 36.6

M 10 1.5 10.000 9.026 8.160 8.876 0.920 58.3M 12 1.75 12.000 10.863 9.858 10.106 1.074 84.0

M 14 2 14.000 12.701 11.546 11.835 1.227 115

M 16 2 16.000 14.701 13.546 13.835 1.227 157

M 18 2.5 18.000 16.376 14.933 15.294 1.534 192

M 20 2.5 20.000 18.376 16.933 17.294 1.534 245

M 22 2.5 22.000 20.376 18.933 19.294 1.534 303

M 24 3 24.000 22.051 20.320 20.752 1.840 353

M 27 3 27.000 25.051 23.320 23.752 1.840 459

M 30 3.5 30.000 27.727 25.706 26.211 2.147 561

42



15. CONCLUSION

The concept of this project was truly original and the advantages of this

machine over other comparable machines is not an exaggeration. This machine has a true

market potential if marketed properly.

With indispensable help from our professors and workshop staff and sincere

effort on the part of both our guide Prof. C.V. Deshmukh and the member of this team we

have been able to convert a concept into a reality.

Now it remains to be seen if someone has the initiative to market this

product properly.

Thank You.

43



BIBLIOGRAPHY

1. Machine Design

By : R.S. Khurmi

2. Production Technology

By : R.K. Jain

3. S.P.I. Plastic Engg. Hand book

4. Rubber technology

By : C.M. Blow

5. Rubber Chem Review ( Feb. 2001 issue )

Documents

7370588 Pneumatically Actuated Rubber Compression Moulding Machine