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6.6.6.6.6. Case Study Of The Foundries In HaoraCase Study Of The Foundries In HaoraCase Study Of The Foundries In HaoraCase Study Of The Foundries In HaoraCase Study Of The Foundries In Haora

6.16.16.16.16.1 BackgroundBackgroundBackgroundBackgroundBackground

TTHE FOUNDRIES IN HAORA (a suburb of Kolkata) had been in the news

in India for the air pollution that they caused. Since the pollution from

foundries was being discussed nationally, the purpose of the study

was to see if principles of Industrial Ecology could be helpful in finding a solution

to the problem. Many scientists had worked on new technologies to minimize

pollution and many agencies, including international agencies, had funded research

projects in the region. A number of studies had also been done on increasing the

energy efficiency in the industry.

The task of carrying out an Industrial Ecology Study of the foundries was very

different from the typical regional approach such as in Tirupur. The Haora study

was restricted to one type of industry and one where the processes followed by

the different units in the industry were very similar. Hence a typical waste exchange

program was not viable. Since all the units followed very similar processes, one

option was to look for recycling possibilities within each industrial unit. The second

option was to look for sharing resources in the industry with a view to better

efficiency.

In the absence of any clear working format, it was decided to follow the method

developed for the Tirupur study, which was to prepare a detailed fact file on the

region and to understand the flow of resources within each unit and in the cluster

as a whole.

6.26.26.26.26.2 Fact File on the RegionFact File on the RegionFact File on the RegionFact File on the RegionFact File on the Region

6.2.16.2.16.2.16.2.16.2.1 The RegionThe RegionThe RegionThe RegionThe Region

Kolkata (formerly known as Calcutta), the capital of the state of West Bengal,

was once the seat of the British Empire in India. It is the major and most important


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72 CASE STUDY OF THE FOUNDRIES IN HAORA

city in the eastern region of India. Since it was an important port, it was also a

major commercial center of India. Most of the international trade of the easternregion of India passes through Kolkata. The eastern region (comprising the states

of West Bengal, Bihar, Orissa and the northeastern states) is the most mineral-rich

region of the country. Among other minerals, the region accounts for most of the

countrys production of coal, which is the second-most predominant fuel used in

India (after firewood), and iron ore. West Bengal became the site for many large

engineering industries during the British rule in India and consequently, the

engineering industry here is very well developed.

India has large reserves of coal, which is a major energy source. The quality of the coal

deposits is mostly poor and the ash content is often higher than 40%. The reserves are

mainly in the eastern state of Bihar, with some smaller deposits in neighboring Madhya

Pradesh and the southern state of Andhra Pradesh.

Haora town, on the other side of the river Hugli from the metropolitan area of

Kolkata, became a major industrial center. The engineering labor here is known

to be extremely skilled and inexpensive. However, over the last three decades,

Kolkata for various reasons has lost its predominant position as an economic center

in India. The first reason has been the very militant trade unions, who in the late

sixties and early seventies scared the industries out of West Bengal. The second

reason was the endemic power shortages that plagued the region for many years.

However, in the last few years, the labor situation and the power situation have

both improved dramatically.

Except in a few states, the power generation is far from adequate and power shortages

are common in most parts of the country. Frequent blackouts are common. Many areas

get power only a few hours in a day. Business establishments, who can afford it, have

stand-by power generation systems of their own.

The result of this economic decline in the region has been that many industries,

like the foundry industry, which supplied goods and services to the other large

industrial units, suffered.

Indias coal reserves

Power supply in India


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CASE STUDY OF THE FOUNDRIES IN HAORA 73

Haora is a very overcrowded town with narrow streets and literally thousands of

industrial units humming with activity. The air is extremely polluted with smokefrom homes, thousands of small factories and thousands of vehicles on the roads.

The foundry industry in Haora is part of this industrial activity. It may be mentioned

that all the different industry groups are interdependent. The foundries often

need the small engineering units, which help in finishing the castings produced

in the foundries.

6.2.26.2.26.2.26.2.26.2.2 The FoundriesThe FoundriesThe FoundriesThe FoundriesThe FoundriesIn its essential form, in a foundry, the metal ingots are melted and poured into

moulds to take a desired shape. Some foundries melt pig iron and scrap iron, some

others steel and steel scrap. The non-ferrous foundries melt non-ferrous metals

like copper. Haora is home to all types of foundries. There are over 200 registered

cast iron foundries, in addition to an estimated 300 unregistered ones. Together

they account for a production of nearly 600,000 tonnes of cast iron annually. In

addition, there are innumerable non-ferrous foundries, which are mostly cottagescale units. It is difficult to even attempt an estimation of the production in these

non-ferrous foundries. There are also a few steel foundries, but the units are more

organized.

All the steel foundries use electrical energy for melting the metal. A few cast iron

foundries, particularly the large and organized ones, use electrical energy. However,

most of the smaller cast iron foundries as well as the non-ferrous foundries use

coke for melting. The problem associated with pollution in processes usingelectrical energy is relatively very less. However, the units using coke cause

considerable air pollution. The level ofSuspended Particulate Matter (SPM) in the

air is very high as well as the emissions of other gases such as sulfur dioxide,

typical problems associated with combustion of coke.

The details of the process of producing castings are given in Annex 6.1.

6.2.36.2.36.2.36.2.36.2.3 The Pollution ProblemThe Pollution ProblemThe Pollution ProblemThe Pollution ProblemThe Pollution ProblemAlthough foundries have existed in this region for decades, the pollution problem

is believed to have come into focus due to developments in the city of Agra (about

2,000 km north-west of Kolkata), the site of the famous Taj Mahal. There has been

a great deal of concern in the last few years, about the danger posed to the


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monument, by industrial pollution. Many causes were identified for the gradual

yellowing of the white marble with which the Taj Mahal is constructed. Amongthe possible causes was the pollution caused by the numerous cast iron foundries

in the city. Public interest petitions were filed in the law courts, which started

taking serious note of the pollution problem. The Supreme Court took special

interest in these cases, which attracted the attention of the whole country. With

this, the pollution caused by the foundries came into sharp focus and the pollution

control authorities kept a close vigil on the operations of the foundries. The

authorities work hard to ensure, that the foundries stay within the specified

emission standards. This concern about the foundries is believed to have extended

to other places such as Haora.

Since Haora was such a major center of foundries, the units here were the most

affected, particularly the over 500 cast iron foundries. The authorities were reported

to be less harsh on the non-ferrous foundries as most of them are too small and

belong to the cottage sector, although these units were also major polluters. Hence,

for purposes of this case study, the discussion is restricted to the coke-based castiron foundries.

The pollution from foundries is essentially associated with the combustion of

coke. Most of the foundries have installed dry gas cleaning systems, which are

available in the country. Along with installation of gas cleaning system, some of

the foundries have changed over to divided blast systems, which have improved

the coke-metal ratio from 1:4 to 1:9. Gaseous emissions have reduced due to the

lower quantity of coke used, as well as the installation of the gas cleaning systems.

6.2.46.2.46.2.46.2.46.2.4 The Ambience in a FoundryThe Ambience in a FoundryThe Ambience in a FoundryThe Ambience in a FoundryThe Ambience in a Foundry

The level of dust in a typical foundry is extremely high. In addition to the

tropical heat in Haora, the heat from the process makes the foundry very warm.

Many of the workers wear minimum clothing,

often no footwear and do not use any safety

equipment. These workers scurry around thefoundry, manually carrying hot molten metal

in crude ladles to pour into the moulds. One

false move could maim the worker for life.

Molten metal being handled in afoundry in Haora


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6.2.56.2.56.2.56.2.56.2.5 The Business ClimateThe Business ClimateThe Business ClimateThe Business ClimateThe Business Climate

As mentioned earlier, the industry in this region has suffered from the economicdecline in the state. New foundries have been set up at many other industrial

growth centers in India, such as Jullunder in Punjab or Coimbatore in Tamil Nadu.

The engineering industries, which are the major buyers of castings, preferred to

source their castings from foundries nearby, both to save on transportation costs

as well as to have better and easier interaction with the supplier. This resulted in

lack of orders for the foundries in Haora. This also resulted in the foundries in

Haora concentrating on the manufacture of standard products like manhole coversfor the domestic and export markets. The profit margins on castings supplied to

the engineering industry are much better than those on standard products. A few

(very few) foundries in Haora, which operate with better levels of technology,

have managed to retain their clientele for high precision, high priced castings and

supply their products all over the country. The majority of the foundries, though,

fiercely compete in an extremely price sensitive market for standard products.

Hence, their operating margins are wafer-thin.

It was widely felt that the industrialized nations were now choosing to source

their general-purpose castings from developing countries, because of the higher

cost of production in the developed countries caused by adherence to their strict

emission standards. India was competing with countries like China and Taiwan in

this business.

In the last few years, in addition to problems associated with margins and markets,

the industry has had to grapple with pressure from the West Bengal PollutionControl Board. Under pressure from the Board, most of the foundries have set up

pollution control equipment, mainly to deal with particulate emissions. The

industry, according to their representative association, is holding discussions with

the state government, to consider the possibility of shifting the industry to a less

populated area about 100 kilometers away.

All the foundries in the region are members of the Indian Foundry Association,

which is the representative body of the industry. The Association also assists the

industry in the procurement of its requirements of pig iron. Most of the membership

is corporate. The Indian Foundrymens Association has as its members, individuals

who work in the industry and could include persons employed in foundries.


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6.36.36.36.36.3

Approach to the StudyApproach to the StudyApproach to the StudyApproach to the StudyApproach to the Study

A very approximate Resource Flow Analysis was attempted for the industry as a

whole, in order to assist in setting priorities.

The steps that were taken to get a quick assessment were:

Study a small number of foundries (who were willing to cooperate with the team) to

understand the typical material flows per ton of production

Gather information about the total number, types and sizes of foundries in the region,

through discussions with the Indian Foundry Association as well as with other Government

departments

Find a suitable method to extrapolate the material flow data gathered from the few

foundries over the entire industry

It was realized that the estimates that would be generated would not be veryaccurate. However, this was attempted as a first step to understanding the issues

of concern in the industry.

The data collection was quite a challenge, as is usual with the small industry in

India. In fact, even to get a comprehensive list of foundries in the region, along

with their capacities of production was extremely difficult, as many of the foundries

are not registered with any statutory authorities. However, the lists collected from

the Foundry Association as well as from a few statutory authorities were cross-checked.

With the cooperation of a sample of 8 foundries, a fact sheet about the process and

the flow of materials (per unit production) was prepared.

6.3.16.3.16.3.16.3.16.3.1 The ProcessThe ProcessThe ProcessThe ProcessThe Process

Pig iron, cast iron scrap and coke are charged from the top of a cupola, which

could be typically a cylindrical tower about 10 meters high and 1 meter in diameter.

Some limestone is also added as a flux. The coke performs the double role of a

fuel for combustion as well as a reducing agent. Molten metal is tapped out of the

bottom of the cupola, which is collected manually in ladles and poured into the


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ready moulds. Slag, which is a glass-like blackish substance, is separated and

dumped in the vicinity.

The material consumption in a typical foundry is shown in Figure 6.1. In order to

identify and set priorities, it was necessary to consider if any of these is a scarce

resource in the region.

As can be seen from this figure, the major resources flowing through a foundry

are the metal, coke, electrical energy and water. All these are abundant in the

region. Only two resources were considered worthy of serious study. One was

electrical energy, which is scarce for the country as a whole and the other was

coke, which was the cause of the pollution problem.

6.3.26.3.26.3.26.3.26.3.2 Extrapolation for the Foundry Industry in HaoraExtrapolation for the Foundry Industry in HaoraExtrapolation for the Foundry Industry in HaoraExtrapolation for the Foundry Industry in HaoraExtrapolation for the Foundry Industry in Haora

On extrapolation, the indicative consumption of materials and energy in the

industry were as under (Table 6.1) for a total annual production of 2 million tonnes

of finished castings.

Table 6.1: Material and Energy Consumption in the Foundries in HaoraTable 6.1: Material and Energy Consumption in the Foundries in Haora

Pig Iron (tonnes) 800,000

Purchased Scrap (tonnes) 1,320,000

Coke (tonnes) 320,000

Electrical Energy (kWh) 30,000,000

Limestone (tonnes) 110,000

Raw Materials + Other InputsRaw Materials + Other Inputs Industry Consumption: AnnualIndustry Consumption: Annual

6.3.36.3.36.3.36.3.36.3.3 The Importance of EnergyThe Importance of EnergyThe Importance of EnergyThe Importance of EnergyThe Importance of Energy

To understand the importance of the total energy component in the operations

of a foundry, a rough costing of the casting operations was carried out. The average

direct cost of production per tonne of finished casting was as shown in Table 6.2.


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F I G U R E 6.1

Pig Iron 400 kg

Scrap Iron 660 kg

Plant Recycles 100 kg

Coke 160 kg

Limestone 55 kg

Energy 15 kWh

Electrical

CAST IRONFOUNDRY

1 Tonne

Finished Casting

Slag 60 kg

Cyclone Dust 4 kg

Volatiles 112 kg +

Sand, Refractories, etc.

Resource Flows in Cast Iron Foundry

As is evident from the cost of production, energy by itself is not an importantelement of cost in a cast iron foundry and accounts for just about 0.5% of the total

direct cost of production as against 6.5% for labor and over 80% for raw material.

Thus, just the concept of reducing the energy cost in the operations is not likely to

have great appeal to the foundry managers.


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Hence, the issue of coke became the center of attention, only because it was the

root cause of the pollution problem.

72.00 (3600)

85.80 (4290)

9.60 (480)

1.20 (60)

12.50 (625)

181.98 (9099)

0.88 (44)

Cost per tonne US$ (Ind. Rs)Cost per tonne US$ (Ind. Rs)Raw Materials + Other InputsRaw Materials + Other Inputs

Pig Iron

Purchased Scrap

Coke

Electrical Energy

Labor

Total Production Cost

Limestone

Table 6.2: Average Direct Cost of Production in a Foundry in HaoraTable 6.2: Average Direct Cost of Production in a Foundry in Haora

6.3.46.3.46.3.46.3.46.3.4 Technology Developments and its ImpactTechnology Developments and its ImpactTechnology Developments and its ImpactTechnology Developments and its ImpactTechnology Developments and its Impact

In addition to setting up traditional effluent treatment systems, as has been

explained earlier, one of the options being explored by many interest groups was

the possibility of replacing the use of coke with natural gas. The National

Metallurgical Laboratory, a premier research institution in Kolkata, has developed

technology for converting the traditional foundries to use natural gas. It is expected

that this technology will be commercially marketable very shortly. This would

completely eliminate the problem of high particulate matter in the effluent and

would also probably ease the housekeeping in the foundries, as the level of dust

would reduce.

This development could create unexpected difficulties for the Haora foundries.

Once this new technology was available, the pollution control authorities would

insist that the foundries switch over to it. However, natural gas is not easily available

locally and transporting gas from other regions could render the process

uneconomical. In regions like the west of India, where natural gas is freely available,

this technology could be extremely attractive.


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If the use of coke is to be eliminated from the foundries in Haora, it may be

necessary to consider options other than natural gas. Ideally, the replacementmaterial should be available in plentiful supply in the region.

6.3.56.3.56.3.56.3.56.3.5 Looking for a CauseLooking for a CauseLooking for a CauseLooking for a CauseLooking for a Cause

From the initial study it appeared that applying any concepts of Industrial

Ecology would not be really relevant in the region. Energy saving systems, which

many researchers were already working on, did not seem of paramount importance,

as the energy cost as a portion of the total cost of production was very small.Saving water was not an issue as it is not scarce in the region and also the quantity

used by the industry is not significant.

6.46.46.46.46.4 An Approach to a SolutionAn Approach to a SolutionAn Approach to a SolutionAn Approach to a SolutionAn Approach to a Solution

As a next step, it was decided to scan the major resource flows in the region,

although time did not permit the team to make accurate assessments of suchflows.

The area borders on the coal and steel belt of India. The neighboring region is

home to some of the largest coal and steel producing units and other related

industries.

A study of the major industries in the region revealed the existence of many

independent coke ovens. In this process, coal is combusted under controlled

conditions so that the resultant coal (called coking coal) is devoid of many volatile

substances. This is done to make it more suitable for use in metallurgical processes.

This process yields coke oven gas as a by-product. This gas is often wasted when

there is no user process in the vicinity. Where such coke ovens are associated

with steel plants, the coke oven gases are used in the process of steel making.

The study team felt that if natural gas can be used in the process, then it should be

possible to use the coke oven gases.

Composition of Coke Oven Gas

Raw coke oven gas coming from the coke oven battery has the following typical

composition (Table 6.3).


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47%

55%

25%

10%

6%

3%

2%

29%

13%

3%

2%

1%

5%

Actual Composition(water saturated at 176F)

Actual Composition(water saturated at 176F)Dry Basis

Dry BasisConstituentConstituent

Water Vapor

Hydrogen

Methane

Carbon Monoxide

Carbon Dioxide

Hydrocarbons(ethane, propane, etc.)

Nitrogen

Table 6.3: Composition of Coke Oven GasTable 6.3: Composition of Coke Oven Gas

Source: Mick Platts, Thysenkrupp Encoke, USA, American Iron and Steel Institute.

The calorific values of different fuels are given in Table 6.4, which shows thatcoke oven gas with its good calorific value can be a substitute for coal or natural

gas.

6.4.16.4.16.4.16.4.16.4.1 Further ActionFurther ActionFurther ActionFurther ActionFurther Action

Although this is a possible strategy option for the industry, the matter requires

further consideration. Development work needs to be initiated to find ways of

economically using this gas in the existing cupolas, so that the conversion cost tothe industry is the minimum. Additional research also has to be undertaken to

evaluate any other possible health risks possibly posed by process emissions arising

from the use of coke oven gas.

If a process is developed by which the coke oven gas can be used in the foundries,

the industry could have a steady supply of cheap raw material, which is a waste

product from another processan ideal application of Industrial Ecology principles.

If coke oven gas can be used economically in the foundries, then another question

needs to be addressed. That is, is it cheaper and more practical to shift the foundries

to the source of the coke oven gas or is it better to transport the coke oven gases to

the foundries (either through pipelines or through tankers)?


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Table 6.4: Estimated Average Gross Calorific Values of FuelsTable 6.4: Estimated Average Gross Calorific Values of Fuels

(1) Applicable to UK consumption - based on calorific value

for home produced coal plus imports and, for All consumers

net of exports.

(2) Based on a 50 per cent moisture content.

(3) Average figure covering a range of possible feedstock.

(4) Average figure based on survey returns.

(5) On an as received basis. On a dry basis 18.6 GJ per

tonne.

(6) The gross calorific value of natural gas can also be

expressed as 10.936 kWh per cubic meter. This value

represents the average calorific value seen for gas when

extracted. At this point it contains not just methane, but also

some other hydrocarbon gases (ethane, butane, propane).These gases are removed before the gas enters the National

Transmission System for sale to final consumers. As such, this

calorific value will differ from that readers will see quoted on

their gas bills.

Note: The above estimated average gross calorific values apply

only to the year 2001.The calorific values for coal other than

imported coal are based on estimates provided by the main

coal producers. The calorific values for petroleum products

have been calculated using the method described in Digest of

UK Energy Statistics, Chapter 1, paragraph 1.27. The calorific

values for coke oven gas and blast furnace gas are provided by

the Iron and Steel Statistics Bureau (ISSB).

Data reported as 'thousand tonnes of oil equivalent' have been

prepared on the basis of 1 tonne of oil equivalent having an

energy content of 41.868 gigajoules (GJ), (1 GJ = 9.478

therms) - see notes in Digest of UK Energy Statistics, Chapter1, paragraphs 1.24 to 1.26.

GJ per tonne

All consumers (weighted average) (1) 27.0 Domestic wood (2) 10.0

Power stations (1) 25.9 Industrial wood (3) 11.9

Coke ovens (1) 30.5 Straw 15.0

Low temperature carbonization plants Poultry litter 8.8

and manufactured fuel plants 30.3 Meat and bone 18.6

Collieries 29.8 General industrial waste 16.0

Agriculture 29.0 Hospital waste 14.0

Iron and steel 29.4 Municipal solid waste (4) 9.5

Other industries (weighted average) 26.7 Refuse derived waste (4) 18.5

Non-ferrous metals 24.9 Short rotation coppice (5) 10.6

Food, beverages and tobacco 9.3 Tires 32.0

Chemicals 27.1

Textiles, clothing, leather etc. 30.0

Paper, printing etc. 28.8 Crude oil (weighted average) 45.7

Mineral products 28.5 Petroleum products (weighted average) 45.8

Engineering (mechanical and Ethane 50.7

electrical engineering and

vehicles) 29.3 Butane and propane (LPG) 49.4

Other industries 30.5 Light distillate feedstock for gasworks 47.6

Aviation spirit and wide cut gasoline 47.3

Aviation turbine fuel 46.2

Domestic Motor spirit 47.1House coal 30.9 Burning oil 46.2

Anthracite and dry steam coal 33.9 Gas/diesel oil (DERV) 45.6

Other consumers 9.2 Fuel oil 43.5

Imported coal (weighted average) 28.0 Power station oil 43.5

Exports (weighted average) 32.1 Non-fuel products (notional value) 42.8

MJ per cubic meter

Coke (including low temperature 29.8 Natural gas (6) 39.8

carbonisation cokes) Coke oven gas 18.0

Blast furnace gas 3.0

GJ per tonne

Landfill gas 38.6

Sewage gas 38.6

COAL RENEWABLE RESOURCES

PETROLEUM

Coke breeze 24.8

Other manufactured solid fuel 30.6

Source: www.dti.gov.uk/energy/inform/calvalues.pdf


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6.4.26.4.26.4.26.4.26.4.2 The Conceptual PerspectiveThe Conceptual PerspectiveThe Conceptual PerspectiveThe Conceptual PerspectiveThe Conceptual Perspective

In the perspective of Industrial Ecology, the other industries in the area couldbe viewed as potential sources of raw materials. Instead of considering only the

primary natural resources, the aim would be to understand the flows of resources

and look at the wastes generated in the region as a potential source of raw materials.

Hence, when a very specific sub-system (like the foundries in this case) is chosen

for a study, a necessary first step is to scan the other industrial sub-systems of the

region and not restrict ones vision to the chosen sub-system (see Figure 6.2).

Interrelationships between different industrial processes can have far reaching

implications for the development of strategy options.

Once they have been identified, such interrelationships may appear obvious in

retrospect. In practice, however, systematic detection of possible cross-sectoral

linkages between sectors which usually ignore each other can hardly be achieved,

unless a regional resource flow analysis is done. But it is certainly worth the

effort since, in addition to saving resources and decreasing pollution, new business

and employment opportunities can result from mutual profitable exchanges of

wastes, by-products and other resources.


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F I G U R E 6.2

Subsystem1

Subsystem

2

Subsystem3

Subsystem

x

SUBSYSTEMUNDER STUDY

Interrelationship Between DifferentIndustrial Processes in a Region


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Annex 6.1Annex 6.1Annex 6.1Annex 6.1Annex 6.1

The Production of CastingsThe Production of CastingsThe Production of CastingsThe Production of CastingsThe Production of Castings

Design

The first production step for all castings takes place in the design office where ideas are converted

into manufacturing drawings which guide the production team to creating the solid metal end

products.

The designer needs to know the specified shape and size of the final product but with metal

casting, he also must know what stresses and conditions the products will have to withstand sothat the correct metal can be chosen. He will need to know how many castings are needed, too.

All these factors dictate which moulding techniques are chosen.

Pattern Making

Once the customer and the rest of the production team have approved the design, a pattern or

model is made. This can be produced in wood, metal or plastic or from a combination of all

three.

In one production technique, wax is used to form the pattern. Patterns must be precise in theirshape and finish, for any mistakes are reproduced in the moulds which are made from them

and from which the final castings are formed.

They must be made to allow for the shrinkage of the metal when it cools and they can include

channels to allow metal to flow into the casting shape.

From the initial pattern a prototype or production sample is usually made with which the

customer can experiment to ensure that the final casting will be exactly as required.

Mould-making

The next manufacturing step is moulding in which the pattern is packed in a moulding material,

usually some type of sand, and then removed to leave the right shape for the casting. Moulds

can be made by hand, or machine. In one casting process the mould is made from a heat-

resistant metal .

Moulds are usually made in at least two parts and for very large castings they may even start

out as large holes dug into the sand floor of the foundry.

Different types of sand are used for moulding with additives like water and clay and variouschemicals, depending on the size of the mould and the types of metal that are being cast.

One important feature of the mould is the running system which is a network of small channels

that leads the molten metal down into the casting shape. The shapes and sizes of these channels


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have to be carefully calculated to ensure that the molten metal does not solidify before it gets to

the casting shape and to make sure that it does not flow too fast when it could wear away the

mould.

Many castings are designed to have cavities in themengine blocks, for example. These voids,

which have to be as accurate as the outer moulds, are made by forming their shape in moulding

material. The shapes, or cores as they are known, are placed in the mould and after the molten

metal has solidified, the core material is removed leaving a precisely shaped cavity behind.

Casting

When the mould is fully assembled, molten metal, at the right temperature, is carefully pouredinto it. The metal will be of the prescribed grade with the correct mechanical and chemical

properties when it has solidified.

When the casting has solidified and cooled, it is knocked out of the mould. Superfluous metal

such as that which has solidified in the flow channels is removedthis clean up operation is

known as fettling. Grinding and often shot blasting is then used to produce a clean finish.

Some castings may also go through a series of tests, such as x-raying or pressure testing to

ensure that they do not contain any unwanted cracks or flaws. The metal may also be tested to

check, amongst other things, its strength, its resistance to sudden knocks, chemicals or high

temperatures. This is really the last step in the casting process, but many castings require some

further shaping or finishing before becoming the final engineering component. This can involve

any or all of the engineering machining processes including drilling, and turning to produce

the exact dimensions and features required. The casting can then be assembled with other

components, often other castings, and this becomes another engineering product.

Source:www.foundryonline.com

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