literature review how can is processed

8/6/2019 Literature Review How Can is Processed

1/12

1.0HOW A CAN IS PROCESSED

1.1Types of Can ProcessingThere are two types of can processing, namely two-piece can processing and three-piece can

processing. Both processes will be described here. The main difference for two-piece and three-piece

can is that in two-piece can processing, the body is formed first before printing and coating is done.

Meanwhile, in three-piece can processing, the printing and coating is done first before the body is formed.

Two-piece can processing is a modern way to process can compared to three-piece can processing [1].

TWO-PIECE CAN PROCESSING [2]

Cup Blanking and Drawing: Aluminium or steel sheet usually arrives in manufacturing plant in huge

coils. The sheet is fed continuously from an uncoiler into a cupping press which cuts out thousands of

discs per minute and forms them into shallow cups. Surplus material will be recycled.

Bodymaking and Trimming: In the bodymaker, the cup is placed in front of a moving ram which forces

it through a series of precision rings, each a little smaller than the previous one. This reduces the

thickness of the metal (wall ironing) and as a result, the can gets taller. At the end of the stroke, the base

is formed and the can is removed from the ram. The trimmer cuts off the can to the correct height. The

surplus material is then recycled.

Cleaning and Drying: Trimmed cans pass through highly efficient washer to remove lubricants used

during the previous processes and to prepare the can surface for coating and printing. Cans are then dried

in an oven.

Basecoating: Cans may be externally coated with a white or clear acrylic lacquer depends on customers

requirements. Cans are dried in a pin oven.

Printing and Varnishing: Highly sophisticated decorators are used to print colours to the can. Up to

six colours can be printed onto the can in the same operation. This depends on the customers design. A

clear over-varnish is sometimes added to protect the can and give a glossy finish. Cans are then dried in a

pin oven.

Inner Spraying: The inner side of each can is sprayed with a coating. This special layer is used to

protect the product in the can from interaction with the metal.


2/12

Necking: Cans are passed through a necker or flanger which gives then the characteristics of neck shape.

The diameter of the top of the can is reduced or necked-in. The top of the can is flanged outwards to

enable the end to be seamed on after the cans are filled.

Testing: Cans are quality tested at each stage of manufacture. At the final stage, the can is put through a

series of additional tests, including a light test and internal and external inspection cameras. Any

defective cans are automatically rejected.

Packing: The cans are packed on to pallets which are then either sent to our warehouse for storage or

transported directly to the customers for filling.

THREE-PIECE CAN PROCESSING [3]

Shearing: The large coil of metal which arrives at the manufacturing plant is cut into sheets at the rate of

approximately 160 sheets per minute. The irregular ends of the sheets are designed for the maximum

number of ends per sheet.

Inner Coating: An inner protective coating is placed on the sheets and cured.

Printing: The sheets are decorated with customers design and then an overcoat of varnish is placed on

the decorated sheet and cured.

Body Forming:Body blanks are fed into a bodymaker where they are formed into cylinders and joined attheir side seams by solder, cement or weld.

Flanging: The formed cylinders come from the bodymaker to the flanger. Here the metal on both ends is

rolled to form a flange on each end of the can. This flange will at a later time accept double seaming.

Spray Coating: A final coating is placed on the interior surface of the can. This is a specially

compounded protective coating.

Baking: The final interior coating is baked and cured through a funnel type oven where the time-

temperature cycle must be controlled carefully.

Testing: A 100 per cent quality control inspection for any micro leak is given to every can.

Packing: Cans are packed into cartons or placed on pallets for delivery to customers.


3/12

1.2Can Processing In Production LineThe processes which are used in production to produce can is more complex compared to the

description in Section 1.1. In a factory, the production line is divided into stations and different

processes are carried out in each station. Below is the detailed description for each station [4].

Station 1: Blanking and Deep Drawing

The tin plate strip is unwound, its surface coated with a thin film of

lubricant and the strip continuously conveyed to the deep-drawing

press.

At first a blank is cut out at each individual tool of the press; the

drawing ram then presses this blank through the draw ring to form a

cup. The tool is made up of 9 to 10 individual tools which are

arranged next to each other and behind each other.

Station 2: Wall Ironing and End Forming

The cup is conveyed to the wall-ironing machine from the top. The

ram first pushes it through the redraw ring to reduce its diameter to

the punch diameter whilst retaining the sheet thickness. The cup is

held by a blank holder to prevent puckers.

There is a gap between the punch and the wall-ironing rings 1 to 4

immediately after the redraw ring where the wall thickness of the can

is reduced by "ironing" the tin plate and consequently lengthening the

can.


4/12

At the end of this stroke, the punch with the can comes into contact

with the base panelling tool and the can base is formed. When the ram

is withdrawn, the can is removed from the punch by a stripper and

conveyed out of the machine via an unloader belt.

Station 3: Trimming

In the trimming machine the can is held by a vacuum plate, set in

rotation and then moved axially until it reaches the required trimming

height. Then the movable cutter unit is guided to the can.

Whilst the can rotates precisely once, the can rim between the upper

and lower cutter is cut off burr-free at the required height. The rings

cut off are removed by vacuum, pressed into bales and returned to

the tin plate production facility.

Station 4: Washing

The wall-ironing lubricant used in the can forming process is

removed prior to coating the can internally and externally. The cans

are transported to the washer on a wide belt and conveyed through

several washing chambers upside down.


5/12

In this way the outside of the can is rinsed with tap water supplied

through the jets located at the top and the inside of the can by the jets

located at the bottom. Immediately downstream of the washing unit,

the can is dried with dry air at a temperature of approx. 200 in the

drying oven.

Station 5: Outside Coating

The cans are coated on the outside as protection against corrosion

and in order to apply a decorative design. White, gold or

transparent coating as well as aluminium-coloured coating can be

used according to customer specifications. Generally the coatings

are water-based.

The cans are spaced by an intake wheel and drawn on to the coating

mandrel of the mandrel wheel by means of a vacuum. They are then

set in rotation around their own axis by the rotation belt. The

coating film on the coater cylinder is then transferred to the cans

positioned on the rotating coating mandrels. The coated cans are

then blown off the coating mandrels and transported to the drying

oven on a magnetic conveyor belt. The coating is pumped from a

coating container to the engraved cylinder which transfers the

appropriate quantity to the rubber-coated coating cylinder from

where it is transferred to the cans.

Station 6: Printing

The externally coated cans are spaced by the intake wheel, as in the

coating machine, and drawn on to the mandrel wheel mandrels by

means of a vacuum. The mandrels are set in rotation around their

own axis by a rotation belt.


6/12

The can positioned on the mandrel rolls synchronously over the

blanket and absorbs the complete decorative design with all the ink

colours from it. The individual colours are transferred by the inking

units to the blankets via ink boxes, various rollers and the clich

cylinder with mounted printing plate. The high pressure printing

clichs only absorb ink in the parts in which they are raised.

Therefore each inking unit presses one colour ink onto the rubber

blanket. Prior to the can coming into contact with the blanket, all the

ink colours are on the rubber blanket entering the inking section;

here the printed image is mirror-inverted. The inks are transferred to

the can by rolling the can over the rubber blanket and the printed

image becomes positive. The printed cans are then blown off the

mandrels and conveyed to the drying oven by a magnetic conveyor

belt.

Station 7: Drying

The drying oven is basically divided into 3 zones (2 heating zones

and 1 cooling zone). The heating zones serve to heat the cans and to

evaporate the fluid constituents as well as to cross link the coating

and the printing ink. The air in the heating zones is recirculated to

reduce the amount of fresh air which has to be heated.

The exhaust air is supplied to the thermal incineration unit where the

exhaust gases from the oven are incinerated to carbon dioxide and

water without any residue. After leaving the heating zone, the cans

are conveyed to the cooling zone and are adapted to the ambienttemperature.


7/12

Station 8: Initial Internal Coating

Inside the internal coating machine, the can is conveyed to a coating

turret and positioned on a vacuum plate. It is set into rotation and

passes two spray guns, the first one which coats the lower section of

the body and the second the body and the base.

When the spray guns have applied the required amount of coating,

the can is conveyed via a discharge belt to a collective conveyer andto the internal coating drying oven connected downstream.

Station 9: Necking In

The diameter of the can which is still cylindrical needs to be reduced

in the upper section to accommodate the smaller end. During thenecking in process the can is loaded on to a lifter and the axial

movement of the lifter presses the open edge into the outer tool.

There the upper rim of the can is bent inwards and the diameter

cylindrically reduced by approx. 1 mm. The lifter is then withdrawn,

the can is pushed out of the tool using compressed air and conveyed

to the next station. There the diameter is reduced further following

the same procedure. A total of 15 stations are required in order to

obtain the required final diameter.


8/12

Station 10: Flanging

The flange is required in order to seal the filled can securely to the

end. The flange is produced in the 16th station of the necking in and

flanging unit.

The can is again loaded on to a lifter and pressed axially on to a

flanging head.

The open end of the can is bent outwards by the rotation of the

three rollers of the flanging head spaced around the circumference

and the flange is formed according to the geometry of the neck

roller.

Station 11: End Coating

The metallic bright can end is coated from the outside in the end

coating machine. The cans are conveyed via the intake turret to the

working turret. Each of the 6 magnetic chucks picks up one can at

the flange and sets it in rotation around its own axis.


9/12

Six spray guns rotate synchronously with the working turret and

spray-coat the base of the respective allocated cans.

Station 12: Second Internal Coating

Depending on the application for which the can is intended, it is then

given a second internal coating. The procedure for the second internal

coating is identical to the first.

Station 13: Testing For Holes and Internal Cracks

We test all the cans produced for holes and flange cracks. These

two types of defect can occur due to the great degree to which the

tin plate is formed. Each can is picked up by a support spindle and

immediately moved in an axial direction until the open side has

reached the flange seal.

It is then conveyed passed a series of lights by the turret wheel.

That means that light is shed on to the body of the can. If a hole or a

flange crack allows light into the inside of the can, then the sensor

on the open side of the can reacts in such a manner that this

defective can is ejected whilst the machine is operating at full

speed.

Station 14: Testing For Internal Defects


10/12

This test is a continuous 100% test of the inside of the can. It

is performed by a CCD line scan camera system comprising

five cameras.Camera no. 5 monitors the end and the lower

section of the can. Cameras nos. 1, 2, 3 and 4 concentrate on

the respective internal section of the can allocated to them.

The images from the five cameras are compared with a specified

image in the computer system connected downstream. As soon as

one of the five camera images does not correspond to the specified

data in the computer system, then the can is removed from the can

flow via a blow-off station.

Station 15: Palleting

The palleting unit assembles the cans in up to 23 layers to a

package unit almost 3 m high. The palleting process starts

by picking up an empty pallet. Layers of cans and interim

layers are pushed on to the pallet until the required number

of layers has been reached.

A cover frame made of steel forms the top layer. Plastic

strips are wrapped around the package criss-crossing twice in

order to make it stable for transport.


11/12

REFERENCES:

[1] http://www.cannedfood.co.uk/microsite/teachers/lesson_zone/making_cans/intro.html

[2] http://www.rexam.com/sectors/index.asp?pageid=74

[3] http://www.cancentral.com/howMade.cfm

[4] http://www.ball-europe.com/382_717_ENG_PHP.html?parentid=791


12/12

literature review how can is processed

Documents