basics of manufacturing

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Basic of Manufacturing Industry MEEG

M.Tech in Health, Safety & Environment

Engineering

Educational Qualification Improvement

Programme

(EQUIP)

SAINT-GOBAIN

Indian School of Petroleum &

Energy

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in association with

University of Petroleum & Energy Studies

S.NO. CHAPTER NAME PAGE NO.

UNIT-I Mechanical components operations 3

UNIT-IIGlass manufacturing Industry

20

UNIT-III Paint manufacturing industry 38

UNIT-IV Automobile manufacturing industry 43

UNIT -V Metal manufacturing industry

Aluminium

Iron

Stainless steel

Copper

53

56

61

68

UNIT-VI Sugar manufacturing industry 79

UNIT-VII Beer manufacturing industry 86

UNIT-VIII Paper manufacturing industry 91

UNIT-IX Petroleum and its products manufacturing 97

UNIT-X Soap manufacturing industry 104

UNIT-XI Fertilizer manufacturing industry 109

UNIT-XII Tyre manufacturing industry 116

UNIT-XIII Phosphoric acid industry 122

UNIT-XIV Sulfuric acid industry 126

UNIT-XV Pesticides manufacturing industry 130

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Basics of manufacturing

Manufacturing is the use of machines, tools and labor to make things

for use or sale. The term may refer to a range of human activity, from

handicraft to high tech, but is most commonly applied to industrial

production, in which raw materials are transformed into finished goods on a

large scale. Such finished goods may be used for manufacturing other, more

complex products, such as aircraft, household appliances or automobiles, or

sold to wholesalers, who in turn sell them to retailers, who then sell them to

end users the "consumers".

Modern manufacturing includes all intermediate processes required for

the production and integration of a product's components. Some industries,

such as semiconductor and steel manufacturers use the term fabrication

instead.

In this subjects we are dealing with mechanical components

manufacturing, glass, Automobile, paint, metals such Al, iron and stainless

steel and copper manufacturing .

Petroleum, Petrochemical products such as fertilizers, soaps, tyre and

chemical & process industry products like sugar, pesticides, paper, acids and

beer are manufactured huge quantities in our country. This material

discusses the basics of manufacturing of these products.

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1. MECHANICAL COMPONENTS MANUFACTURING

1.1 CASTING

Cupola melting This method uses a furnace in stack form as shown

in Figure. In this method is used to produce iron plates or rods from the steel

scraps. Fuel and metal to be melted are in direct contact. The stack is lined

with refractory material and alternate layers of coke and metal are placed in

it. Some minerals, primarily limestone (CaC03), are included with the metals

to be melted. Air is blown through the stack from the bottom through

openings called tuyeres. The bottom layer of coke is ignited initially. Heat

from the burning coke melts the metal, which flows to the bottom of the

cupola from where it can be removed by opening a tap hole. Slag is also

removed from the bottom, from anexit hole just above the one used to

remove molten metal. As the coke

is consumed and the metal charge

melts, the burning gradually

proceeds upward. The upper layers

are preheated by the flow of hot

gases. Additional metal, coke, and

limestone can be added from a

charging door in the upper part of

the stack as the operation proceeds.

Metal charges may consist of steel

scrap, cast iron scrap or pig iron, or,

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more commonly, a combination of them. The molten metal absorbs carbon

from the coke, so cupola melting is generally restricted to cast, malleable,

and ductile iron. The above picture shows the cross section of cupola for

melting cast iron.

SAND CASTINGS

In sand mold casting the mold is made of packed sand. Molten metal is

poured into a cavity in the sand. When the metal cools and solidifies, it has

the shape of the cavity. The sand is removed, normally by a shaking action

that is vigorous enough to cause the mold to break apart. The casting is then

cleaned of sand; flashing and sprues are cut off and any jagged or sharp

edges are ground smooth. The sand mold includes binders to hold thepacked sand together and other additives. Bentonite clay is one of the most

common binders. Organic materials and a certain amount of water are also

used. The sand is either shoveled into the mold flask, dropped or blown from

an overhead chute, or thrown by a sand slinging machine. The sand mixture

is packed around a pattern which duplicates the shape wanted in the cast

part. Various hand and machine approaches are used to compact the sand.

Ramming, squeezing, slinging, and jolting are done before add molten metal.

After the sand has been compacted, the pattern is removed, leaving a cavity

that retains the inverse of the patterns shape. The sand is held together

strongly enough so that it withstands the pressure and any eroding effects of

the melted metal; is porous enough to allow gases to escape; yet it is weak

enough to yield to shrinkage forces when the metal solidifies, and can be

broken up and removed easily from the finished casting. The pattern can be

of almost any material. In low quantity production situations, it may be made

of wood. For repetitive manufacture, steel is more common. Plastics,

aluminum, and other materials are also used. The pattern has the same

shape as the desired cast part, but is slightly larger to provide a shrinkage

allowance for the metal as it cools.

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A typical sand mold is shown in figure and is normally made in two

halves. The pattern is correspondingly split. The top half of the mold is

called the cope; the

bottom half the drag.

Both are held in a box-like

container called flasks.

An entrance channel for

the molten metal into the

mold is provided by a

basin and sprue formed in

the cope half. Runners

and gate are normally in the drag half. If the casting has some hollow or

undercut elements, one or more additional sand pieces, called cores may

be used. If a core is used, it is inserted in the mold cavity. The cope half of

the mold is made similarly to the drag half and, after the pattern is removed,

is inverted and placed over the drag. Pins in the flask insure alignment of the

mold cavity. The two mold halves are held together with a clamp or weight.

Sand mold casting can be used to make simple and complex parts from a

wide variety of metals, though cast iron is the most common. Shapes with

undercuts, contours, re-entrant angles and other complications of shape can

be cast. Castings weighing only one ounce to those of many tons can be cast

with the process.

Typical applications of sand mold casting are: automotive engine

blocks, cylinder heads, connecting rods, crankshafts and transmission cases,

machine tool bases and other mechanical components.

METAL FORMING PROCESS

Many metal forming operations can be performed with the workpiece

metal either hot or cold. The operations performed on workpiece material

that has been heated to make it more malleable for the operation involved.

Metals that are to be hot formed are heated above their recrystallization

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temperature, one that varies with each material but is normally about 0.6

times the melting temperature on the Kelvin (absolute temperature) scale.

For example, steels require a temperature above about 980C. Warm

forming involves heating to a temperature 30 to 60 percent of the melting

point, while cold forming takes place when the metal temperature is below

30% of the melting temperature.)

1.2 HOT ROLLING

It is commonly applied to convert steel ingots to blooms, billets, or

slabs, and to make these shapes into suitable forms. In the process, heated

metal is passed between two rollers whose spacing is less than the thickness

of the metal. The rotation of the rollers moves the metal forward, squeezing

and elongating it. Figure illustrates the process. The process extends and

refines the grain structure of the rolled material. A number of passes may be

required, depending on the thickness desired and the thickness of the

entering material. Reversing rollers are often used to facilitate multiple

passes. Thin sheet or foil is best rolled with small-diameter rollers that are

backed up with larger rollers to provide the necessary rolling force.

As many as twelve rollers in a cluster may be used. Shaped rollers can

produce material with various

cross sections including those

of structural shapes or special

cross sections. Low-alloy or

plain-carbon steel is heated to

about 1200C before rolling

and after being preheated in a

soaking pit. In addition to

ferrous metals, aluminum,

copper and copper alloys,

magnesium, nickel, titanium, and zinc alloys are hot rolled.

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1.3 PRESS OPERATIONS IN INDUSTRY

Press brakes, as illustrated in Figure, are mechanical or hydraulic

presses with long, narrow, stationary beds. The bed lengths range from 2or

3 ft to 30 ft and press tonnages from 10 to several thousand. The ramstroke

is short but adjustable. Dies are long, narrow, and often simple V-dies. Both

sharp and gentle bends can be made, depending on the shape of the dies.

Piercing, notching, forming, shearing, edge curling, beading,

hemming, corrugating, and tube forming can be performed with

suitable dies. In bending, sheet metal, placed between the bed and the ram

is most commonly bent once with each press stroke. The bend occurs when

a shaped punch, attached to the press brake ram, descends against the

workpiece, forcing it into a suitablyshaped die, fastened to the press brake

bed. Multiple bends are made by repositioning the workpiece sheet between

press strokes. Press brakes are used in the bending of long, narrow

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workpieces and for other workpieces made in small quantities where

standard press brake tooling can be employed.

1.4 WELDING

Welded connections and assemblies represent a very large group of

fabricated steel components. The welding process itself is complex, involving

heat and liquid-metal transfer, chemical reactions, and the gradual formation

of the welded joint through liquid-metal deposition and subsequent cooling

into the solid state, with attendant metallurgical transformations.

The material in this section will provide the student with an overview of

the most important aspects of welded design. In order that the resulting

welded fabrication be of adequate strength, stiffness, and utility, the

designer will often collaborate with engineers who are experts in the broad

area of design and fabrication of elements.

ARC WELDING

Arc welding is one of several fusion processes for joining metal. By

the generation of intense heat, the juncture of two metal pieces is melted

and mixeddirectly or, more often, with an intermediate molten filler metal.

Upon cooling and solidification, the resulting welded joint metallurgically

bonds the former separate pieces into a continuous structural assembly (a

weldment) whose strength properties are basically those of the individual

pieces before welding.

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

an electric arc. The arc forms between the workpieces and an electrode that

is either manually or mechanically moved along the joint; conversely, the

work may be moved under a stationary electrode. The electrode generally is

a specially prepared rod or wire that not only conducts electric current and

sustains the arc, but also melts and supplies filler metal to the joint; this

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constitutes a consumable electrode. Carbon or tungsten electrodes may be

used, in which case the electrode serves only to conduct electric current and

to sustain the arc

between tip and

workpiece, and it is

not consumed; with

these electrodes, any

filler metal required is

supplied by rod or

wire introduced into

the region of the arc

and melted there.

Filler metal applied

separately, rather than via a consumable electrode, does not carry electric

current. Most steel welding operations are performed with consumable

electrodes. The figure shows the typical welding arrangement.

WELDING CIRCUIT ARRANGEMENT

An ac or dc power source fitted with necessary controls is connected

by a work cable to the work piece and by a hot cable to an electrode

holder of some type, which, in turn, is electrically connected to the welding

electrode. When the circuit is energized, the flow of electric current through

the electrode heats the electrode by virtue of its electric resistance. When

the electrode tip is touched to the workpiece and then withdrawn to leave a

gap between the electrode and workpiece, the arc jumping the short gap

presents a further path of high electric resistance, resulting in the generation

of an extremely high temperature in the region of the sustained arc.

The temperature reaches about 6,500F, which is more than adequate

to melt most metals. The heat of the arc melts both base and filler metals,

the latter being supplied via a consumable electrode or separately. The

puddle of molten metal produced is called a weld pool, which solidifies as the

electrode and a rc move along the joint being welded. The resulting

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weldment is metallurgically bonded as the liquid metal cools, fuses,

solidifies, and cools. In addition to serving its main function of supplying

heat, the arc is subject to adjustment and/or control to vary the proper

transfer of molten metal to the weld pool, remove surface films in the weld

region, and foster gas-slag reactions or other beneficial metallurgical

changes Filler metal composition is generally different from that of the weld

metal, which is composed of the solidified mix of both filler and base metals.

Shielding and Fluxing High-temperature molten metal in the weld pool

will react with oxygen and nitrogen in ambient air. These gases will remain

dissolved in the liquid metal, but their solubility significantly decreases as

the metal cools and solidifies. The decreased solubility causes the gases to

come out of solution, and if they are trapped in the metal as it solidifies,

cavities, termed porosities, are left behind. This is always undesirable, but it

can be acceptable to a limited degree depending on the specification

governing the welding. Smaller amounts of these gases, particularly

nitrogen, may remain dissolved in the weld metal, resulting in drastic

reduction in the physical properties of otherwise excellent weld metal.

Notch toughness is seriously degraded by nitrogen inclusions.

Accordingly, the molten metal must be shielded from harmful atmospheric

gas contaminants. This is accomplished by gas shielding or slag shielding or

both.

Gas shielding is provided either by an external supply of gas, such as carbon

dioxide, or by gas generated when the electrode flux heats up. Slag shielding

results when the flux ingredients are melted and leave behind a slag to cover

the weld pool, to act as a barrier to contact between the weld pool and

ambient air. At times, both types of shielding are utilized.

In addition to its primary purpose to protect the molten metal, the

shielding gas will significantly affect arc behavior. The shielding gas may be

mixed with small amounts of other gases (as many as three others) to

improve arc stability, puddle (weld pool) fluidity, and other welding operating

characteristics. In the case of shielded-metal arc welding (SMAW), the

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stick electrode is covered with an extruded coating of flux. The arc heat

melts the flux and generates a gaseous shield to keep air away from the

molten metal, and at the same time the flux ingredients react with

deleterious substances, such as surface oxides on the base metal, and

chemically combine with those contaminants, creating a slag which floats to

the surface of the weld pool. That slag crusts over the newly solidified hot

metal, minimizes contact between air and hot metal while the metal cools,

and thereby inhibits the formation of surface oxides on the newly deposited

weld metal, or weld bead.

When the temperature of the weld bead decreases, the slag, which has

a glassy consistency, is chipped off to reveal the bright surface of the newly

deposited metal. Minimal surface surface oxidation will take place at lower

temperatures, inasmuch as oxidation rates are greatly diminished as

ambient conditions are approached.Fluxing action also aids in wetting the

interface between the base metal and the molten metal in the weld pool

edge, thereby enhancing uniformity and appearance of the weld bead.

1.5 GAS CUTTING

Oxyfuel Cutting (OFC) Oxyfuel cutting is used to cut steels and toprepare bevel and vee grooves. In this process, the metal is heated to its

ignition temperature, or kindling point, by a series of preheat flames. After

this temperature is attained, a high-velocity stream of pure oxygen is

introduced, which causes oxidation or burning to occur. The force of the

oxygen steam blows the oxides out of the joint, resulting in a clean cut. The

oxidation process also generates additional thermal energy, which is radially

conducted into the surrounding steel, increasing the temperature of the steel

ahead of the cut. The next portion of the steel is raised to the kindling

temperature, and the cut proceeds. Carbon and low-alloy steels are easily

cut by the oxyfuel process. Alloy steels can be cut, but with greater difficulty

than mild steel. The level of difficulty is a function of the alloy content. When

the alloy content reaches the levels found in stainless steels, oxyfuel cutting

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cannot be used unless the process is modified by injecting flux or iron-rich

powders into the oxygen stream. Aluminum cannot be cut with the oxyfuel

process. Oxyfuel cutting is commonly regarded as the most economical way

to cut steel plates greater than 1 2 in thick. A variety of fuel gases may be

used for oxyfuel cutting, with the choice largely dependent on local

economics; they include natural gas, propane, acetylene, and a variety of

proprietary gases offering unique advantages. Because of its role in the

primary cutting stream, oxygen is always used as a second gas. In addition,

some oxygen is mixed with the fuel gas in proportions designed to ensure

proper combustion.

Plasma Arc Cutting (PAC)

The plasma arc cutting process was developed initially to cut materials

that do not permit the use of the oxyfuel process: stainless steel and

aluminum. It was found, however, that plasma arc cutting offered economic

advantages when applied to thinner sections of mild steel, especially those

less than 1 in thick. Higher travel speed is possible with plasma arc cutting,

and the volume of heated base material is reduced, minimizing metallurgical

changes as well as reducing distortion.

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PAC is a thermal and mechanical process. To utilize PAC, the material

is heated until molten and expelled from the cut with a high-velocity stream

of compressed gas. Unlike oxyfuel cutting, the process does not rely on

oxidation. Because high amounts of energy are introduced through the arc,

PAC is capable of extremely high-speed cutting. The thermal energy

generated during the oxidation process with oxyfuel cutting is not present in

plasma; hence, for thicker sections, PAC is not economically justified. The

use of PAC to cut thick sections usually is restricted to materials that do not

oxidize readily with oxyfuel.

WELDING SAFETY

Welding is safe when sufficient measures are taken to protect the

welder from potential hazards. When these measures are overlooked or

ignored, welders can be subject to electric shock; overexposure to radiation,

fumes, and gases; and fires and explosion. Any of these can be fatal.

Everyone associated with welding operations should be aware of the

potential hazards and help ensure that safe practices are employed.

Infractions must be reported to the appropriate responsible authority.

Oxygen is incorrectly called air in some fabricating shops. Air from the

atmosphere contains only 21 percent oxygen and obviously is different from

the 100 percent pure oxygen used for cutting. The unintentional confusion of

oxygen with air has resulted in fatal accidents. When compressed oxygen is

inadvertently used to power air tools, e.g., an explosion can result. While

most people recognize that fuel gases are dangerous, the case can be made

that oxygen requires even more careful handling

1.6 LATHE AND OTHER OPERATIONS

Lathe operations

It produce, with a cutting action, surfaces of rotation (surfaces having a

round or partly-round cross section), both external and internal, in a work

piece. The work piece is rotated in a lathe, screw machine, or chucking

machine. It is held between centers or in a chuck or collet, or fastened to a

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face place. The cutting tool is fed into the work or along the work, or both, to

produce a part of the desired shape. There are several basic types of lathes

and related machines as described below and many varieties of tools that

can be fed against the workpiece. These machines are used extensively in

the production of parts that contain surfaces of rotation. The basic

operations performed on lathes are the following:

Turning - is the most prevalent lathe operation. In its most common form, a

single-point cutting tool is moved on a precise path with respect to a rotating

workpiece. When the tool moves parallel to the axis of rotation, straight

turning takes place and the surface machined is cylindrical or part of a

cylinder. When the cutting tool moves uniformly closer or farther from the

axis of rotation as it moves longitudinally, a tapered surface is generated

Grooving - The cutting tool, usually ground to the width and bottom shape

required, is fed into the work, cutting a groove of the desired dimensions.

Groves can be cut into any external or internal surface that such a cutting

tool can reach. (Internal grooves are usually called recesses.)

Knurling - is not really a machining (cutting) operation because the knurl is

formed, not cut, in the workpiece. Knurling is a common lathe or screw

machine operation. The hardened hurling tool rolls against the cylindrical

surface of the rotating workpiece with high pressure, causing the surface

material of the workpiece to flow into peaks and valleys according to the

pattern of the hurling tool.

Facing - produces flat surfaces whose plane is at right angles to the axis of

rotation of the part As the part rotates in the lathe, the cutting tool moves

radially toward the axis of rotation, removing material as it advances. It can

also move outward from the center, but the other direction is much more

common. The operation is used to produce flat surfaces on castings and

other parts that usually also require turning or some other lathe operation

Cutting off (parting) - When parts are made in lathes and screw machines

from bar stock, the final operation is to sever the part from the remaining

bar material. This is accomplished by advancing the cutoff tool, a narrow

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grooving tool, radially into the work. When the cutting edge advances to the

axis of rotation of the part, the part is severed and falls to the bed of the

machine. Some machines, which make blanks for further machining or other

operations, are designed to perform only cut off operations and other simple

ones on bar and tubular stock.

Common Lathe operations are shown in figure.

1.7 DRILLING OPERATION

Drilling - The most common tool for drilling, a twist drill, is a rod with helical

flutes and two or more cutting edges at the end. It is rotated about its axis

and fed axially into the work. As it advances, it produces or enlarges a round

hole in the workpiece. The chips are carried away from the hole by the flutesin the drill. When drilling an axial hole with a lathe, the workpiece rotates

rather than the drill.

There are other types of drills that may not have helical flutes. Others may

have only one cutting edge. The drilling process is very common and is used

with a wide variety of machines ranging from the most sophisticated

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computer controlled or multiple spindle machines to hand-held electric or

crank-driven drills.

1.8 GRINDING AND ABRASIVE MACHINING

At the point where the cutting takes place, grinding is very similar to other

machining operations, the difference being that the workpiece is cut by the

sharp edges of small pieces of abrasive material, rather than the edge of a

hardened steel or carbide cutting tool. The irregularly-shaped abrasive

particles may be bonded to a wheel or coated belt, or may be used loose.

The particles commonly consist of aluminum oxide, silicon carbide, cubic

boron nitride, diamond, or other hard materials. The individual abrasive

grains are each smaller than a conventional metalworking cutting tool, andthe grains on a typical wheel make a multitude of minute cuts (Some grains,

depending on their shape, do not cut but instead rub or slightly deform the

surface of the workpiece.) Cutting speeds are high but the depth of cut from

each grain is shallow. A water or water-oil emulsion is often sprayed on the

wheel and workpiece to control the dust that otherwise arises and to

overcome the heating effect of the operation.

Grinding wheels are often porous, especially those designed for use with

softer materials. Asthe wheel cuts, it wears, causing some abrasive particles

to become smooth but causing others to fracture, exposing new sharp

edges. New wheels, and those that have become worn, are dressed with a

diamond tool that removes some of the abrasive material and bonding

agent, exposing sharp edges of new abrasive grains and providing a

straighter, more uniform, cutting surface. Grinding is most commonly a

finish-machining operation to provide a smoother surface or greater

dimensional accuracy, particularly with hardened materials. When used as

the primary metal removal method, the term, abrasive machining is often

used.

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1.9 MILLING

Milling is a means of creating a desired surface with a rotating multi-toothed

cutter. Each tooth of the cutter removes material as the workpiece advances

against it. The axis of rotation of the cutter may be either horizontal or

vertical. The cutter can provide cutting action on its side or at its end (face),

or both. The cutter rotates rather rapidly and its position is normally

stationary; the work moves past the cutter with a suitable depth of cut at a

relatively slow feed rate. Milling is the most common machining operation for

producing flat surfaces, but slots, and contoured or stepped surfaces and

screw threads can also be produced.

The different types of millings are face milling, peripheral milling, slabmilling, form milling, gand milling, straddle milling, fly cutter milling etc.

1.10 SAWING

Sawing is the parting of material through the use of a narrow cutter, a saw,

which contains a series of cutting edges that pass against the work in a

continuous or reciprocating motion. As the cutter is advanced into the work,

material is removed by each tooth, and a slot is formed, eventually

extending through the entire thickness of the workpiece, and severing it into

two pieces.

The chip produced by each tooth is carried in the space between the teeth

until the teeth exit the workpiece. The cutter can be in disk, band, or

reciprocating blade form. Cutting teeth are typically set, i.e., offset slightly

and alternately from both sides of the saw blade to provide a slightly wider

cut (kerf) than the thickness of the blade so that there is room for its

passage. The operation is used to cut billets, extrusions, castings, forgings,

and various other shapes into blanks for further operations. Bars of various

cross sections, rods, angles, and various other structural sections are cut to

length by sawing.

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Circular sawing - uses a saw in the form of a circular disk, with cutting

teeth on the periphery. As the circular saw rotates, it is fed against the

workpiece, machining a narrow slot in the workpiece and eventually severing

it. Circular saws for metal cutting are sometimes called cold sawsbecause

they dont significantly heat the workpiece as friction saws do. They often

have inserted cutter teeth of carbide rather than teeth formed of the blade

material, or have cutter segments fastened to a center disc. Blades are

sometimes large in diameter to permit the sawing of bulky workpieces. Kerfs

are considerably wider than

those on band or hack-saws

because the circular blade must

be thick enough to provide

rigidity. Accurate and smooth

cut surfaces are feasible with

this method. The circular saw

process is used to make blanks

for subsequent operations or to

cut structural members to the

desired length. Figure illustrates

a circular cutoff saw (coldsaw).

Band sawing - is most commonly a cut-off operation. Instead of a circular

disk, the saw is an endless steel band with cutting teeth on one edge. The

blade moves as it cuts in one direction. Cutting is continuous and blade

wear is uniform over the whole length of the blade. Since the blade is

normally thin, little material is lost to chip waste and power requirements are

modest. The work piece or the blade can be fed manually or mechanically.

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2.0 GLASS MANUFACTURING

2.1 INTRODUCTION

Glassmaking involves three basic steps: batching, melting, and

forming. Batching is the preparation of a mixture of sand and stabilizing

oxides, all in fine granular form. Melting involves the heating of the mixture

to change it into a liquid and to further homogenize the various ingredients.

Forming is the creation of useful objects or products from the molten mixture

before it has completely solidified. The process can be carried out on either a

batch or continuous-flow basis, the latter being used in mass production

situations. Normally, forming operations take place immediately after thebasic glassmaking, with the molten glass being cooled to increase its

viscosity for forming.

There are many different kinds of glass. Soda lime glass is used for bottles,

window panes and drinking glasses. Lead-alkali silicate glass has lead oxide

in place of much of the calcined lime and is used for highly worked shapes

including decorative glassware (lead crystal) that is engraved. Borosilicate

glasses, which contain boric oxide, are used when chemical and temperature

change resistance is important, for example, in pharmaceutical containers,

chemical process components and lamp envelopes. Aluminosilicate glasses

are used where high temperature conditions exist. Several other mixtures

may be used when optical properties are important.

2.2 RAW MATERIALS

Silica sand (SiO2) is the most common glass ingredient and has

excellent resistance to attack, low thermal expansion, and resistance to

devitrification (crystallization which impairs the optical and mechanical

properties). However, in its unalloyed state, silica sand is difficult to process

because of its high melting temperature and high viscosity when melted.

Various other oxides are added to silica to improve its processibility and

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modify the properties of the finished glass. When soda-lime glass, the most

common variety, is made, the ingredients consist of about 73 percent sand

(SiO2), about 14 percent soda ash or sodium carbonate (Na2C02) and about

13 percent limestone (CaC03). Sodium oxide, (Na20) is an effective fluxing

agent, i.e., a means for reducing the melting temperature, but too much can

produce glass that is water soluble. Calcium oxide, calcined lime (CaO),

increases the hardness and resistance of the glass to moisture. Alumina

(A1203) improves durability and reduces thermal expansion. Potassium oxide

(K20) from potash, increases durability and helps prevent devitrification,

which has adverse effects. Other glass ingredients include borax or boric

acid for boric oxide (B203), fluorspar (CaF), litharge or lead oxide (PbO),

barium carbonate (BaC03), magnesium oxide (MgO), zinc oxide (ZnO), and

other inorganic materials, some of which are colorants. Glass cullet (factory

scrap or recycled glass), may be added to the mixture. It provides fluxing

action and reduces the energy required for melting. About 30 to 40% cullet

provides the maximum furnace efficiency. In some mixtures, cullet content

can reach 66 percent. A typical commercial mixture has from 7 to about 12

different minerals, 4 to 6 of which are major ingredients.

2.3 COLORING MATERIALS - Glass is colored by adding small quantities

(usually less than 0.5 percent) of certain metal oxides or other metallic

compounds to the glass batch. Copper produces light blue; chromium - green

and yellow; iron - bluish green or yellowish brown; cobalt - intense blue;

nickel grayish brown, yellow, green, blue or violet depending on the glass

matrix; neodymium - reddish violet; manganese - violet; vanadium - green or

brown.

2.4 BATCHING - involves weighing, milling as necessary, and mixing to

produce the glass furnace charge, a blend that can be melted to provide the

composition desired. Quality control, including chemical analyses, must

precede these steps to insure that each raw material is of the proper

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composition with impurities within limits. and of the proper grain size. Grain

or particle size is important and must be controlled so that materials do not

segregate during mixing, storage, and handling and so that they melt

properly. Overly-fine particles of some materials may retard the elimination

of gas bubbles from the melted charge. Milling and screening of raw

materials may be required for some mixtures, though the common practice

is to have suppliers of raw materials provide them with the desired grain size

and size distribution. Water may be added to the batch to the extent of 2 to

4percent to prevent segregation prior to melting. More recently, methods

have been developed to consolidate the batch material in a form that more

easily preserves the uniformity of the batch mixture, provides easier

handling, improved melting, and better uniformity of the glass mixture

during melting.

These consolidation methods usually involve the following steps:

1. reducing and controlling the grain size of the batch materials by various

milling operations and screening, mixture,

2. adding wetting and binding agents to the

3. thoroughly mixing the mixture and additives,

4. consolidation - briquetting, pelletizing or other means of holding the

mixture into a stable but easily handled form, and

5. preheating the consolidation before melting.

Alc. melting - Melting the glass materials, known as the batch, enables the

ingredients to be completely blended to produce glass of the desired

properties and puts the glass in condition for forming. Typical melting

temperatures are approximately 1450 to 1600. Heat is provided by gas, oil

or electricity. Natural gas is the major fuel; propane is used as a standby.

When quantities are small, melting is performed on a batch basis in pot

furnaces or day tanks. High production melting is done in continuous

furnaces that have output levels ranging to several hundred tons per day.

Pots are made of refractory clay and are heated in brick furnaces. Day tanks

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are larger pots for batch production and are typically run on a one-day cycle,

with melting at night and production and refilling the next day. Ten tons is a

typical daily production quantity. Pots are typically round crucibles made of

one piece of refractory material with individual capacities of one to two tons

of glass. Several pots may occupy one furnace. Day tanks are made from

refractory blocks. Continuous furnaces are used for flat glass and for mass-

produced containers and other highproduction items. They are lined with

refractory ceramics and are divided into a large melting section and a small

refining section called a forehearth. The forehearth is used to cool glass from

the melt temperature to a suitable temperature for whatever forming

operation follows. Daily production levels are on the order of 100 to 400 tons

of glass.

The glass charge is fed from one end of the melting area. Temperatures in

the melting area are as high as the glass mixture can tolerate in order to

drive off carbon dioxide, steam, trapped air, and other gases, which could

cause bubbles in the glass. Convection currents in the molten glass, which

result from natural unevenness of heating and cooling from side walls,

provide stirring that helps the glass mixture to become homogeneous. The

molten glass that passes to the refining section does so through an opening

below the surface of the melt, thus preventing any surface foam or scum

from entering the forehearth. The temperature in the forehearth is typically

cooler than that in the melting section by 100 to 200C.

Furnaces may operate continuously for approximately a year before

rebuilding is necessary. With gas and oil furnaces the glass is heated by

exhaust gases that travel above the molten glass. Air for combustion is

preheated by either a preheating chamber in the furnace or by regeneration

where the cold air and cold gas are made to flow through brickwork that

shortly before carried hot exhaust gases from the furnace. The flow is

typically reversed at half-hour intervals. Immersed electrodes are used when

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heat is provided by electrical resistance. This resistance is that of the glass

when current is passed through the molten glass from electrode to electrode.

Electric heating is sometimes used as a booster in gas- or oilfired furnaces.

Electrical heating has quality and environmental advantages and is more

common for batch production of specialty glasses, particularly those with a

volatile component. Electrical induction heating is used for small quantity

work.

2.5 PRIMARY FORMING PROCESSES

Pressing - A gob of molten glass is placed in a mold by an automatic gob-

feeding machine. A plunger descends and presses against the gob of glass

which flows upward around the plunger and outward to fill the mold cavity.

When the glass cools and solidifies, the plunger is withdrawn, the mold is

opened, if necessary (because of undercuts in the part), and the part is

removed. In some cases, excess glass may have to be trimmed from the

part. The process is illustrated by Figure. In production situations, a turntable

is used to carry the molds and may have as many as twenty. As the

turntable indexes to new positions, each mold proceeds step by step through

the full cycle of loading, pressing, cooling, trimming, and ejection or removal.

Pressing is used to make drinking glasses and other household glassware,

lenses, lamp globes, and TV tube parts.

Blowing - is similar to blow molding of plastics. As in blow molding of

plastics, there are two operations, one to make the parison and the other to

make the hollow glass object from the parison. The operation can be manual,

with or without a mold to control the shape of the finished part, or automatic

with a number of process variations.

Hand blowing into the open air, without a mold, but with shaping of the

bubble with the aid of hand tools, has been practiced for centuries. The basic

process with molds is illustrated in Figure. Blowing is used extensively in the

production of glass bottles, containers, and vases and jars.

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Electrically heated

Typical glass pot furnace for melting glass.

Manual blowing - The skilled artisan uses a glassworkers blowpipe

consisting of a metal tube with a wooden handle and mouthpiece at one end

and a nose or gathering head at the other end. Making a container, vase,

drinking glass, etc. with purely manual methods, involves the following

steps:

1. Gathering - The nose end of the blowpipe is immersed in melted glass and

is rotated slowly. The viscous glass sticks to the end of the blowpipe. For

large objects, several repeats of gathering may be required.

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2. The blowpipe is continually rotated to keep the gob of glass centered and

the artisan blows a small amount of air from the mouth through the pipe,

making a bubble in the center of the glass gob and thereby creating a

parison.

3. Marvering - The parison (hollow gob) is rolled against a surface of metal or

stone or wet wood, cooling the surface and imparting a straight or curved

side to the object.

4.The parison is enlarged by further blowing. Further contact of the parison

with the work surface and with hand-held shaping tools in a series of steps,

gradually produces the desired shape.

Some reheating may be required and continual rotation of the blowpipe is

carried out to keep the workpiece circular and centered. Selective cooling or

heating, cutting with shears, and attachment of glass handles or other

elements may be carried out before the object is completed. Figure

illustrates a typical sequence in making a glass pitcher. Figure shows a

collection of glassblowers hand tools. For repetitive blowing of some

particular object, the glassworker may blow the parison into a mold made

from water-soaked wood (beechwood has been traditionally used), graphite,

or cast iron. This reduces or eliminates much of the tool and workpiece

manipulation required, speeds the operation, and reduces the skill required

by the glassworker. Because of the high level of skill required, the use of

manual methods of blowing has declined in favor of machine blowing except

for artistic work. The method is still used for art work, prototypes, and mall

quantity production of bottles, containers, laboratory vessels, and other

specialty glassware.

Lampworking (lamp blowing, and scientific glass blowing) - is the

forming of glass articles from tubing and rods by heating in a gas flame

(lamp). The operation i s essentially manual, but differs from the manual

glass blowing described above in that it starts with a tube or rod rather than

a gob of molten glass. Its primary application is the fabrication of laboratory

apparatus and instruments. Medical, veterinary, food processing, and

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chemical industries require apparatus that use glassware made with this

approach. The tubing or rod is heated by a gas flame and then formed by

any of a variety of manual operations including blowing, bending, flaring,

cutting, sealing, joining, and working with a large number of hand tools. In

higher production situations, the end of a glass rod is heated and placed in a

die that presses the softened material into a small part and severs it from

the rod. Tubing can be similarly heated at the end, which can then be formed

by blowing in a suitable mold. Scientific glass blowing has broadened in

recent years to include working with flat and powdered glass as well as

tubing and rods, and working with a variety of glass types and surface

treatments.

Machine blowing Automatic machine blowing is used in the production of

glass bottles, jars, drinking glasses, and other glass containers that are

manufactured in mass-production quantities. Machine blowing methods have

the following elements:

1. equipment for feeding a gob of melted glass to the machine,

2.a means for converting the gob into a parison, i.e., introducing a hollow in

the gob for later blowing,

3. inflation of the hollow gob (parison) against the inner surfaces of a mold,

4.a means for forming the elements at the open end of the object molded,

5. a means for trimming any excess material from the finished object, and,

6. annealing the finished product.

Material in process may be reheated during the operation sequence. Notable

machine methods are the press-blow, blow-blow, suck-blow and

rotary-mold (paste mold) processes.

SUCKFLOW PROCESS

The original machine developed by M. J. Owens was put into production

around 1904 but has been much further developed since then. The glass is

brought into the parison mold by suction, hence the name, suck-blow

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process. The work is performed on a large rotary table. Motion of molds and

other elements is controlled by cams.

The operating sequence is as follows: The parison mold, with an open

bottom, is lowered into the surface of molten glass. Suction applied to the

top of the mold draws glass into the mold cavity. A pin with a rounded end

puts The neck portion of the bottle is also formed in this mold.

The parison mold is lifted and a knife passes across the bottom of the mold,

severing any excess glass from the parison. At the same time, the rounded

pin at the top is withdrawn, and air pressure in the resulting opening

enlarges the

top of the parison, forming a bubble. The mold opens, freeing the parison

which is held by neck rings at its upper end. The parison is out in the open as

the machine table rotates. The parison elongates from the effects of gravity

and from several puffs of air into the bubble.

The parison enters the blow mold, which closes around it. Air is blown into

the bubble, expanding the parison against the mold walls The neck rings

open and the mold with the bottle inside drops below the pot as the table

continues to rotate. The mold and bottle cool. mold opens and the bottle is

discharged. Figure illustrates the molding action schematically. The machine

is used for largescale production. With smaller bottles, double and triple

molds are used so that each cycle of the machine produces two or three

bottles.

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Suck flow

process

FLAT CLASS PROCESS:

Drawing sheet glass (the

Fourcault process) - The

Fourcault process was the first

successful mechanized production

method for drawing sheet glass

directly from a tank. It was first

carried out on a production basis in

1914. Prior to that, the production

of flat glass was at least partly a

manual operation. The method is

keyed to the debiteuse, a long

clay block with a lengthwise slot.

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The block floats on the molten glass but, when it is pressed slightly down,

into the molten glass, some glass rises out of the slot. This glass is grasped

by an iron bait and is pulled upward past a cooling station and into an

annealing tower. The tower contains rollers that draw the glass upward and

the operation is thereafter continuous. The rate of drawing, among other

factors, determines the thickness of the glass. (Slower drawing yields greater

thickness.) The length of the slot in the debiteuse determines the width of

the ribbon. Width is maintained by pairs of knurled rollers at the edges that

maintain a constant side pull on the ribbon. The drawback of the process is a

tendency toward a small amount of waviness in the sheet, which cannot be

avoided. There may also be fine marks on the glass surface left by the rollers

and some tendency to devitrification caused by the refractory material from

which the debiteuse is made. Figure illustrates the process

Drawing sheet glass (the Colburn or Libby-Owens process) - This

process, seen in Figure, is similar to the Fourcault process but does not use

the debiteuse. Instead, the initial ribbon of glass is picked up from the tank

with a metal bait and immediately controlled by chilled rollers at the

edges. It also is

diverted into a

horizontal

direction by a

polished roller

after traveling

upward only

about 27 in (70

cm). It is

stretched,

flattened, and

supported by

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transporting rollers as it moves into a 200 ft (60 m) annealing l hr. The

drawing speed with the Colburn process is twice that used with Fourcault.

Manufacturing Sequence for Plate glass

1) Raw materials are received and stored2) Materials are weighed and mixed

3) Batch is fed to furnace and melted

4) Molten glass flows from the furnace through forming rolls to form a rough,

continuous ribbon

5) Ribbon is stretched slightly to improve flatness

6) Ribbon travels through annealing l hr

7) Both top and bottom surfaces are ground flat by a series of vertical

spindle, large-disc grinding machines as the ribbon travels past them

8) Both surfaces are polished with similar machines using finer abrasive

9) An acid wash removes grinding residue

10) Sheets are cut from the ribbon

11) Sheets are inspected and sent to storage for later final cutting and

shipment

STEAM BLOWING

Steam blowing - Streams of molten glass flowing from a melting tank

through sievelike platinum bushings are impinged upon by jets of steam. The

jets approach the glass streams at a small included angle, and push them at

a faster rate, causing them to draw into finer fibers. If the steam jets are

strong enough, the fibers will break into shorter lengths. The strength of the

steam jets determines how discontinuous and fine the final fibers will be. The

fibers can be processed in several ways. When used to make thick pads or

wool, they are sprayed with a binder and fall on to a conveyor where they

pile up into wool. The binder is dried and the wool is cut into discrete batts of

fibrous glass. Figure illustrates this process. When made into glass mat, the

fibers are allowed to fall into a thin, web-like mat that is then immersed into

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a bath of binder and then passed through a drying oven. A major use for

such mat is the reinforcement of fiber glass-reinforced plastic products.

PORCELAN

The term porcelain refers to a wide range of ceramic products that

have been baked at high temperatures to achieve vitreous, or glassy,

qualities such as translucence and low porosity. Among the most familiar

porcelain goods are table and decorative china, chemical ware, dental

crowns, and electrical insulators. Usually white or off-white, porcelain comes

in both glazed and unglazed varieties, with bisque, fired at a high

temperature, representing the most popular unglazed variety.

Raw Materials

The primary components of porcelain are clays, feldspar or flint, and

silica, all characterized by small particle size. To create different types of

porcelain, craftspeople combine these raw materials in varying proportions

until they obtain the desired green (unfired) and fired properties. Although

the composition of clay varies depending upon where it is extracted and how

it

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To make porcelain, the raw materials such as clay, felspar, and silica are first

crushed using jaw crushers, hammer mills, and ball mills. After cleaning to

remove improperly sized materials, the mixture is subjected to one of four

forming processes soft plastic forming, stiff plastic forming, pressing, or

casting depending on the type of ware being produced. The ware then

undergoes a preliminary firing step, bisque-firing.It is treated, all clays vitrify (develop glassy qualities), only at extremely high

temperatures unless they are mixed with materials whose vitrification

threshold is lower. Unlike glass, however, clay is refractory, meaning that it

holds its shape when it is heated. In effect, porcelain combines glass's low

porosity with clay's ability to retain its shape when heated, making it both

easy to form and ideal for domestic use. The principal clays used to make

porcelain are china clay and ball clay, which consist mostly of kaolinate, a

hydrous aluminum silicate.

Feldspar, a mineral comprising mostly aluminum silicate, and flint, a type of

hard quartz, function as fluxes in the porcelain body or mixture. Fluxes

reduce the temperature at which liquid glass forms during firing to between

1,000 and 1,300 degrees Celsius. This liquid phase binds the grains of the

body together.

Silica is a compound of oxygen and silicon, the two most abundant elements

in the earth's crust. Its resemblance to glass is visible in quartz (its

crystalline form), opal (its amorphous form), and sand (its impure form).

Silica is the most common filler used to facilitate forming and firing of the

body, as well as to improve the properties of the finished product. Porcelain

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may also contain alumina, a compound of aluminum and oxygen, or low-

alkali containing bodies, such as steatite, better known as soapstone.

The Manufacturing Process

After the raw materials are selected and the desired amounts weighed, they

go through a series of preparation steps. First, they are crushed and purified.

Next, they are mixed together before being subjected to one of four forming

processessoft plastic forming, stiff plastic forming, pressing, or casting; the

choice depends upon the type of ware being produced. After the porcelain

has been formed, it is subjected to a final purification process, bisque-firing,

before being glazed. Glaze is a layer of decorative glass applied to and fired

onto a ceramic body. The final manufacturing phase is firing, a heating step

that takes place in a type of oven called a kiln.

Crushing the raw materials

First, the raw material particles are reduced to the desired size, which

involves using a variety of equipment during several crushing and grinding

steps. Primary crushing is done in jaw crushers which use swinging metal

jaws. Secondary crushing reduces particles to 0.1 inch (.25 centimeter) or

less in diameter by using mullers (steel-tired wheels) or hammer mills,

rapidly moving steel hammers. For fine grinding, craftspeople use ball mills

that consist of large rotating cylinders partially filled with steel or ceramic

grinding media of spherical shape.

Cleaning and mixing

The ingredients are passed through a series of screens to remove any under-

or over-sized materials. Screens, usually operated in a sloped position, are

vibrated mechanically or electromechanically to improve flow. If the body is

to be formed wet, the ingredients are then combined with water to produce

the desired consistency. Magnetic filtration is then used to remove iron from

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the slurries, as these watery mixtures of insoluble material are called.

Because iron occurs so pervasively in most clays and will impart

After bisque firing, the porcelain wares are put through a glazing operation,

which applies the proper coating. The glaze can be applied by painting,

dipping, pouring, or spraying. Finally, the ware undergoes a firing step in an

oven or kiln. After cooling, the porcelain ware is complete.

Forming the body

Next, the body of the porcelain is formed. This can be done using one of four

methods, depending on the type of ware being produced:

Soft plastic forming, where the clay is shaped by manual molding, wheel

throwing, jiggering, or ram pressing. In wheel throwing, a potter places the

desired amount of body on a wheel and shapes it while the wheel turns. In

jiggering, the clay is put on a horizontal plaster mold of the desired shape;

that mold shapes one side of the clay, while a heated die is brought down

from above to shape the other side. In ram pressing, the clay is put between

two plaster molds, which shape it while forcing the water out. The mold is

then separated by applying vacuum to the upper half of the mold and

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pressure to the lower half of the mold. Pressure is then applied to the upper

half to free the formed body.

Stiff plastic forming, which is used to shape less plastic bodies. The body

is forced through a steel die to produce a column of uniform girth. This is

either cut into the desired length or used as a blank for other forming

operations.

Pressing, which is used to compact and shape dry bodies in a rigid die or

flexible mold. There are several types of pressing, based on the direction of

pressure. Uniaxial pressing describes the process of applying pressure from

only one direction, whereas isostatic pressing entails applying pressure

equally from all sides.

slip casting, in which a slurry is poured into a porous mold. The liquid is

filtered out through the mold, leaving a layer of solid porcelain body. Water

continues to drain out of the cast layer, until the layer becomes rigid and can

be removed from the mold. If the excess fluid is not drained from the mold

and the entire material is allowed to solidify, the process is known as solid

casting.

Bisque-firing

After being formed, the porcelain parts are generally bisque-fired, which

entails heating them at a relatively low temperature to vaporize volatile

contaminants and minimize shrinkage during firing.

Glazing

After the raw materials for the glaze have been ground they are mixed with

water. Like the body slurry, the glaze slurry is screened and passed through

magnetic filters to remove contaminants. It is then applied to the ware by

means of painting, pouring, dipping, or spraying. Different types of glazes

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can be produced by varying the proportions of the constituent ingredients,

such as alumina, silica, and calcia. For example, increasing the alumina and

decreasing the silica produces a matte glaze.

Firing

Firing is a further heating step that can be done in one of two types of oven,

or kiln. A periodic kiln consists of a single, refractory-lined, sealed chamber

with burner ports and flues (or electric heating elements). It can fire only one

batch of ware at a time, but it is more flexible since the firing cycle can be

adjusted for each product. A tunnel kiln is a refractory chamber several

hundred feet or more in length. It maintains certain temperature zones

continuously, with the ware being pushed from one zone to another.

Typically, the ware will enter a preheating zone and move through a central

firing zone before leaving the kiln via a cooling zone. This type of kiln is

usually more economical and energy efficient than a periodic kiln.

During the firing process, a variety of reactions take place. First, carbon-

based impurities burn out, chemical water evolves 100 to 200 degrees

Celsius, and carbonates and sulfates begin to decompose 400 to 700

degrees Celsius. Gases are produced that must escape from the ware. On

further heating, some of the minerals break down into other phases, and the

fluxes present (feldspar and flint) react with the decomposing minerals to

form liquid glasses 700 to 1,100 degrees Celsius. These glass phases are

necessary for shrinking and bonding the grains. After the desired density is

achieved 1,200 degrees Celsius, the ware is cooled, which causes the liquid

glass to solidify, thereby forming a strong bond between the remaining

crystalline grains. After cooling, the porcelain is complete.

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3. PAINT MANUFACTURING

Paint is a term used to describe a number of substances that consist of

a pigment suspended in a liquid or paste vehicle such as oil or water. With a

brush, a roller, or a spray gun, paint is applied in a thin coat to various

surfaces such as wood, metal, or stone. Although its primary purpose is toprotect the surface to which it is applied, paint also provides decoration.

Perhaps the greatest paint-related advancement has been its proliferation.

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The first step in making paint involves mixing the pigment with resin,

solvents, and additives to form a paste. If the paint is to be for industrial use,

it usually is then routed into a sand mill, a large cylinder that agitates tiny

particles of sand or silica to grind the pigment particles, making them

smaller and dispersing them throughout the mixture. In contrast, most

commercial-use point is processed in a high-speed dispersion tank, in which

a circular, toothed blade attached to a rotating shaft agitates the mixture

and blends the pigment into the solvent. Today, paints are used for interior

and exterior housepainting, boats, automobiles, planes, appliances,

furniture, and many other places where protection and appeal are desired.

Raw Materials

A paint is composed of pigments, solvents, resins, and various additives. The

pigments give the paint color; solvents make it easier to apply; resins help it

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dry; and additives serve as everything from fillers to anti fungicidal agents.

Hundreds of different pigments, both natural and synthetic, exist. The basic

white pigment is titanium dioxide, selected for its excellent concealing

properties, and black pigment is commonly made from carbon black. Other

pigments used to make paint include iron oxide and cadmium sulfide for

reds, metallic salts for yellows and oranges, and iron blue and chrome

yellows for blues and greens.

Solvents are various low viscosity, volatile liquids. They include petroleum

mineral spirits and aromatic

solvents such as benzol, alcohols,

esters, ketones, and acetone. Thenatural resins most commonly

used are lin-seed, coconut, and

soybean oil, while alkyds, acrylics,

epoxies, and polyurethanes

number among the most popular

synthetic resins. Additives serve

many purposes. Some, like calcium

carbonate and aluminum silicate,

are simply fillers that give the

paint body and substance without

changing its properties. Other additives produce certain desired

characteristics.

Paint canning is a completely automated process. For the standard 8 pint

paint can available to consumers, empty cans are first rolled horizontally

onto labels, then set upright so that the point can be pumped into them. One

machine places lids onto the filled cans while a second machine presses on

the lids to seal the cons. From wire that is fed into it from coils, a bailometer

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cuts and shapes the handles before hooking them into holes precut in the

cans. In paint, such as the thixotropic agents that give paint its smooth

texture, driers, anti-settling agents, anti-skinning agents, defoamers, and a

host of others that enable paint to cover well and last long.

Design

Paint is generally custom-made to fit the needs of industrial customers. For

example, one might be especially interested in a fast-drying paint, while

another might desire a paint that supplies good coverage over a long

lifetime. Paint intended for the consumer can also be custom-made. Paint

manufacturers provide such a wide range of colors that it is impossible tokeep large quantities of each on hand. To meet a request for "aquamarine,"

"canary yellow," or "maroon," the manufacturer will select a base that is

appropriate for the deepness of color required. (Pastel paint bases will have

high amounts of titanium dioxide, the white pigment, while darker tones will

have less.) Then, according to a predetermined formula, the manufacturer

can introduce various pigments from calibrated cylinders to obtain the

proper color.


Making the paste

Pigment manufacturers send bags of fine grain pigments to paint plants.

There, the pigment is premixed with resin (a wetting agent that assists in

moistening the pigment), one or more solvents, and additives to form a

paste.

Dispersing the pigment

The paste mixture for most industrial and some consumer paints is now

routed into a sand mill, a large cylinder that agitates tiny particles of sand or

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silica to grind the pigment particles, making them smaller and dispersing

them throughout the mixture. The mixture is then filtered to remove the

sand particles.

Instead of being processed in sand mills, up to 90 percent of the water-based

latex paints designed for use by individual homeowners are instead

processed in a high-speed dispersion tank. There, the premixed paste is

subjected to high-speed agitation by a circular, toothed blade attached to a

rotating shaft. This process blends the pigment into the solvent.

Thinning the paste

Whether created by a sand mill or a dispersion tank, the paste must now be

thinned to produce the final product. Transferred to large kettles, it is

agitated with the proper amount of solvent for the type of paint desired.

Canning the paint

The finished paint product is then pumped into the canning room. For the

standard 8 pint (3.78 liter) paint can available to consumers, empty cans are

first rolled horizontally onto labels, then set upright so that the paint can be

pumped into them. A machine places lids onto the filled cans, and a second

machine presses on the lids to seal them. From wire that is fed into it from

coils, a bailometer cuts and shapes the handles before hooking them into

holes precut in the cans. A certain number of cans (usually four) are then

boxed and stacked before being sent to the warehouse.

Byproducts/Waste

A recent regulation concerning the emission of volatile organic compounds

(VOCs) affects the paint industry, especially manufacturers of industrial oil-

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based paints. It is estimated that all coatings, including stains and varnishes,

are responsible for 1.8 percent of the 2.3 million metric tons of VOCs

released per year. The new regulation permits each liter of paint to contain

no more than 250 grams of solvent. Paint manufacturers can replace the

solvents with pigment, fillers, or other solids inherent to the basic paint

formula. This method produces thicker paints that are harder to apply, and it

is not yet known if such paints are long lasting. Other solutions include using

paint powder coatings that use no solvents, applying paint in closed systems

from which VOCs can be retrieved, using water as a solvent, or using acrylics

that dry under ultraviolet light or heat.

A large paint manufacturer will have an in-house wastewater treatmentfacility that treats all liquids generated on-site, even storm water run-off. The

facility is monitored 24 hours a day, and the Environmental Protection

Agency (EPA) does periodic records and systems check of all paint

facilities. The liquid portion of the waste is treated on-site to the standards of

the local publicly owned wastewater treatment facility; it can be used to

make low-quality paint. Latex sludge can be retrieved and used as fillers in

other industrial products. Waste solvents can be recovered and used as fuels

for other industries. A clean paint container can be reused or sent to the

local landfill.

4.0 AUTOMOBILE INDUSTRY

Raw Materials

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Although the bulk of an automobile is virgin steel, petroleum-based products

(plastics and vinyls) have come to represent an increasingly large

percentage of automotive components. The light-weight materials derived

from petroleum have helped to lighten some models by as much as thirty

percent. As the price of fossil fuels continues to rise, the preference for

lighter, more fuel efficient vehicles will become more pronounced.

Design

With the help of computer-aided design equipment, designers develop basic

concept drawings that help them visualize the proposed vehicle's

appearance. Based on this simulation, they then construct clay models that

can be studied by styling experts familiar with what the public is likely to

accept. Aerodynamic engineers also review the models, studying air-flow

parameters and doing feasibility studies on crash tests. Only after all models

have been reviewed and accepted are tool designers permitted to begin

building the tools that will manufacture the component parts of the new

model.

Automobiles:

The production process for automobiles consists of the manufacture of all the

individual parts, including their finishing with heat treatments, plating and

painting, if used, their assembly into various mechanical subassemblies,

followed by the combination of all these subassemblies and parts into a

finished vehicle. Automatic and robotic equipment is interspersed with

human assemblers.

Many of the components assembled on the line are subassemblies that

were, themselves, manually assembled on lines with some interspersed

robotic and automatic assembly stations. Examples of these subassemblies

are the chassis, body, bumpers, fuel pumps, piping and tank, radiator,

suspension system, seats, engine, transmission, drive shaft, rear axle, wheel

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assemblies, instruments and instrument panel assembly, steering system,

brake system assemblies, electrical wiring, battery, generator or alternator,

starter, headlights and interior lighting system, as well as auxiliary

equipments such as air conditioning, radio, stereo, and cruise control.

Some subassemblies are put together completely with dedicated

(special purpose), high production equipment, others with a combination of

robotic and dedicated equipment, with or without manual assembly of some

components.

Robotic operation is common for such operations as welding, painting,

windshield assembly, and placement of heavy components like the engine,

transmission and body assembly. Fully automatic assembly with dedicated

equipment is most common with components such as spark plugs, hydraulic

brake cylinders, shock absorbers and other subassemblies that are used in

multiples in the car.


Automobile engines - are assemblies of many precision cast,

stamped, forged, and machined parts, some of which are electroplated or

painted. Except for specialty situations where only a very limited number of

a particular engine is built, assembly takes place on an assembly line. Some

portions of the assembly operation may be robotic or mechanized with

special equipment.

The basic engine block is normally an iron casting made in sand molds.

It is then machined extensively by milling, drilling, boring, reaming, grinding,

and honing.The crankshaft is either forged or cast , and is turned and

ground. Connecting rods are usually forged, bored and honed. Pistons are

sand cast or permanent mold cast of aluminum and turned on special

machines. Valves are forged, turned, and ground. Camshafts are forged or

cast, and turned and ground on special machines. Manifolds are cast and

machined by milling and other operations.

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Machine screws to fasten parts together are usually cold headed with

rolled threads. the engine factory or purchased, are included in the

assembly. These include parts that may be stamped from sheet metal, die

cast, or molded from plastics. They also include spark plugs, electrical wiring,

oil and air filters. bearings, seals, insulators, electronic ignition and fuel

metering parts, carburetors, fuel injection parts, coils, drive belts, and

pulleys. After assembly,

the engine is tested for correct operation and power at a test stand. If

satisfactory, it is moved to the final assembly line for installation in an

automobile. Due to the high production volumes that typically accompany

automotive production, many of the parts making operations are highly

automatic and engineered specifically for the component in question. Special

machines and transfer lines are often part of the parts-making operations.

Automobile bodies - Auto body parts are made from sheet steel

although, increasingly, fiberglass reinforced polyester plastic and formed

thermoplastic sheet parts are finding their way into current designs. With the

sheet steel parts, blanking, forming, and deep drawing operations are

performed. These operations are performed on high-production equipment

with compound dies and progressive dies, where applicable, with robotic

unloading of the stamped parts. Body parts are fastened together by

resistance welding and some arc welding, most of it robotic. Weld joints are

made smooth by application of high-lead body solder, sanded smooth. The

welded body assembly is dipped in a cleaning bath and then given a zinc

phosphate treatment to aid in corrosion resistance. Plastic sealers are

applied in locations where moisture can be trapped. The complete metal

body assembly is then painted. The first coat is often applied with the

electrophoretic method, dipping the body into a vat of water based paint.

The selected color is often applied with robotically-manipulated, electrostatic

paint guns, with some manual spray application to selected or difficult-to-

cover areas. A final clear coating is applied similarly, and is buffed and

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polished after it dries. Sound deadening materials are applied in some areas

with rubber-based adhesives.

A polyurethane coating is applied to the bottom surfaces to provide

protection against flying stones gravel and other debris. After painting,

doors, deck lids, hood, trim, windows, doors, bumpers, interior panels, the

dashboard with instruments, seats, lights, radios, speakers, carpeting, and

various hardware items are assembled to the body as part of the final auto

assembly operation. The body is then conveyed to the main assembly line

where it is assembled to the other components that make up the car.

Automobile chassis - the steel frame that supports the car, is used in

many automobiles. However, the more common auto designs now

incorporate a unitized body. With the unitized design, extra members are

added to the body to enable it to support the weight of the vehicle and to

withstand road shocks.

The supporting members then, are in the body assembly rather than part of

a separate chassis. Where a separate chassis is used, it is made from heavy

gauge sheet steel that is blanked, formed, and hole-punched. It is assembled

and arc welded with other similarly-made chassis components into a strong

and rigid assembly. Even with a unitized body, however, there normally is a

sub frame, similar to the earlier chassis but only in the front of the vehicle, to

support the engine, transmission, and front suspension. In many designs

there also is a small rear frame to support the rear axle, differential, and

suspension. These frames are also made of heavy gage steel stampings,

welded together. The net effect of the unitized body construction is a

reduction in vehicle weight.

Automobile windshields - consist of curved pieces of safety glass.

The glass is made with raw materials including potassium, magnesium, and

aluminum oxides, in addition to the more common materials, to provide

hardness and other properties. The molten glass is fed to float glass

equipment to produce a large, flat glass sheet. Each sheet is cut into smaller,

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windshield-size sheets. These are then bent to the desired curvature by

heating them and draping them over. a form of refractory material. Gravity,

and the softness of the heated sheets, causes them to take the shape of the

form. The bent sheet is tempered cleaned and assembled with an internal

layer of plastic and a second layer of glass. These three assembled pieces

are placed in an autoclave, which provides pressure to force the three layers

together and heat to bond the plastic to the glass surfaces. The finished

windshield then undergoes a plastic injection molding operation where it

becomes an insert in an injection mold and a plastic frame is molded around

it. The windshield is then ready for shipment to the automobile assembly

factory.

Components

The automobile assembly plant represents only the final phase in the

process of manufacturing an automobile, for it is here that the components

supplied by more than 4,000 outside suppliers, including company-owned

parts suppliers, are brought together for assembly, usually by truck or

railroad. Those parts that will be used in the chassis are delivered to one

area, while those that will comprise the body are unloaded at another.

Chassis

The typical car or truck is constructed from the ground up (and out). The

frame forms the base on which the body rests and from which all subsequent

assembly components follow. The frame is placed on the assembly line and

clamped to the conveyer to prevent shifting as it moves down the line. From

here the automobile frame moves to component assembly areas where

complete front and rear suspensions, gas tanks, rear axles and drive shafts,

gear boxes, steering box components, wheel drums, and braking systems

are sequentially installed.

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An off-line operation at this stage of production mates the vehicle's engine

with its transmission. Workers

use robotic arms to install

these heavy components

inside the engine

compartment of the frame.

After the engine and

transmission are installed, a

On automobile assembly lines,

much of the work is now done

by robots rather than humans.In the first stages of automobile manufacture, robots weld the floor pan

pieces together and assist workers in placing components such as the

suspension onto the chassis. The worker attaches the radiator, and another

bolts it into place. Because of the nature of these heavy component parts,

articulating robots perform all of the lift and carry operations while

assemblers using pneumatic wrenches bolt component pieces in place.

Careful ergonomic studies of every assembly task have provided assembly

workers with the safest and most efficient tools available.

Body

Generally, the floor pan is the largest body component to which a

multitude of panels and braces will subsequently be either welded or bolted.

As it moves down the assembly line, held in place by clamping fixtures, the

shell of the vehicle is built. First, the left and right quarter panels are

robotically disengaged from pre-staged shipping containers and placed onto

the floor pan, where they are stabilized with positioning fixtures and welded.

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The front and rear door pillars, roof, and body side panels are

assembled in the same fashion. The shell of the automobile assembled in

this section of the process lends itself to the use of robots because

articulating arms can easily introduce various component braces and panels

to the floor pan and perform a high number of weld operations in a time

frame and with a degree of accuracy no human workers could ever

approach. Robots can pick and load 200-pound (90.8 kilograms) roof panels

and place them precisely in the proper weld position with tolerance

variations held to within .001 of an inch. Moreover, robots can also tolerate

the

The bodyis built up on a

separate

assembly line

from the

chassis. Robots

once again

perform most

of the welding

on the various panels, but human workers are necessary to bolt the parts

together. During welding, component pieces are held securely in a jig while

welding operations are performed. Once the body shell is complete, it is

attached to an overhead conveyor for the painting process. The multi-step

painting process entails inspection, cleaning, undercoat (electrostatically

applied) dipping, drying, topcoat spraying, and baking.

As t

basics of manufacturing

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