Basic Manufacturing Process

8/14/2019 Basic Manufacturing Process

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Basic Ceramic Tile Production Processes

Traditional manufacturing processes can be

described as follows:

Preparation of raw materials. Pressing and drying of the green

body.

Firing process with or without glaze. Additional refinements. Packaging process.

The Nature and desired appearance of the

final product will determine the method used

to form and fire the tile body. The process

followed to produce extruded rustic tiles aredifferent to those employed to manufacture

polished porcelain.

Whichever type of product is required the

first stage will involve selection and

preparation of raw materials. The basic raw

materials used to form the body of any tile

are appropriate clays, carbonates, feldspars,

kaolins and sands.

Most of these materials are used in their raw

state, as mined. These materials are

generally homogenised to ensure consistency

in composition. Following raw material

preparation the following processes will be

conducted dependant of the nature of the

product.

Once the raw materials required to form the

tile body have been mixed they are dry

milled (for extruded tiles) or wet milled and

spray dried. This later system is most widely

employed in producing ceramic wall and floortiles and porcelain.

Dry milling involves crushing raw materials in

a hammer or pendulum mill. The wet milling

process involves mixing the selected clays

and minerals with water and pumping the

mix into a large rotating cylindrical mills (ball

mills) where the selected clays and minerals

are ground into a huge volume of liquid that

is usually known as slip or body.

Excess moisture is removed by spray

drying. The general process is:

Pumping and spraying the slip. Hot gas generation and feed. Drying using a gas fired spray

dryer burner.

Producing a dry clay powderfeaturing uniform size grains.

The powder is generally stored in dry

vats ready for use. Spray drying

provides a number of advantages,

including provision of high uniform, more

or less spherical hallow granules that can

be easily transferred to the press dies

which makes the process of filling the

large dies used to press big format tiles a

lot simpler.

Dry Pressing and Extrusion.

Eventually the dry powder ismechanically placed into moulds of the

required size and the body of the tile is

pressed to that size in a hydraulic press.

The tile body is formed by application of

high compaction force. The pressed clay

usually has a moisture content of

approximately 6%. The pressure applied

ranges from 3,500 to 7,200 tons.

The extrusion process involves driving

the plastic body through a die of therequired tile shape. The tile is cut to

length by an automated cutter.

Drying.

The moisture content in the body is

reduced to the required levels by placing

the tiles in dryers, where heat is applied

by convection from hot gases applied to

the surface of the tiles.


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Glazing.

Unglazed, extruded tiles are fired after

the drying stage. Regular ceramic tiles

have a single or multiple coats of glaze

applied to provide the required aesthetic

in terms of appearance and to produce a

hard wearing, easy to clean and maintain

surface finish.

The glaze also adds texture and

enhances chemical resistance. Silica is

the prime component of glaze. Other

materials like alkalis and zinc act as

fluxes or opacifiers. A wide variety of

glazes can be obtained. Regular glassyglazes feature gloss materials like frits,

which are vitreous compounds which are

insoluble in water. Many glaze

compositions feature frits of some kind.

Porcelain glazes feature materials like

crystalline and a variety of natural and

synthetic raw materials.

The raw materials of the glaze are

ground in a ball mill, before aqueos

suspension is created which permits

constant and even application of the

glaze. Screen printing is one of the most

common method of applying glaze.

Firing.

This is the most important part of the

process because it will determine

mechanical strength, dimensional

stability, chemical resistance, ease of

maintenance and fire resistance. Thethermal cycle and kiln atmosphere are

critical.

Unglazed tiles are fired once, glazed tiles

are fired once (monocottura) after glaze

is applied to the raw tile body.

Alternatively the body can be fired and a

second firing (bicottura) can be applied

following application of glaze.

Subsequent firing can take place to add

more colour. Most floor tiles are fast fired

single glaze products fired at

temperatures of around 1220 Celsius in amere 40 minute process.

Decoration and porcelain.

Porcelain is fired around 1240 degrees

Celsius. Many factories around the world

produce between 6000 and 11000 square

meters per day. Some factories simply

produce tile bodies (bisques) which they

sell to other companies that add their

own glaze and decoration.

Many of the most important advances

have occurred in the field of decoration,

particularly in relation to porcelain tile.

Machinery manufacturers continue to

promote advances in technology which

allow tile manufacturers to create special

decorative effects and surface finishes.

Its important to recognize that until

recently decoration of porcelain was

principally made by adding colourings to

the feldspar, clay, quartz and kaolin atthe dry pressing stage. While this process

is still applied the technology is now

available to add any decoration or design

to be applied to polished porcelain,

including motifs, texture and reliefs.

These decorations are pre-designed and

added to the surface of the pressed tile

before application of a final coat of

colour, firing and final polishing.

New processes emerge annually at

Cersaie making it a herculean task for

manufactures to keep their clients up to

date with regard to the latest innovations.

One of the latest innovations comes from

an Italian company called Imola

Ceramica which has produced ceramic

products since 1874.

COLOUR DEFINITION SYSTEM


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Colour Definition System

is an innovative system that makes the

creative space of decoration of floors and

cladding potentially infinite. A very large

number of different tiles that interpret the

new concept of image and matter dynamism

in a brand new way, thanks to the

simultaneous use of different graphic

solutions. Colour Definition System is a world

of endless aesthetic solutions, as well as a

world of high graphic definition, chromaticclarity and technological quality. No limit to

the perfection of decoration (over 4,000

nozzles and 200x924 dpi resolution) and

absolutely superior aesthetic impact for

products that have a more natural and real

look, thanks to the extraordinary definition of

colours, ranges and decorations. Colour

Definition System is the greatest expression

of style and design.
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Basic Manufacturing Process