| How is corrugated made?
1/ From paper to corrugated board
the papers used in the production of corrugated
are specific grades called «Linerboard» and
the adhesive which is applied to the tips of
the flutes is starch usually originating from
products of natural origin the most common being
The corrugator machine
A corrugator is a set of machines in line,
designed to bring together three, five or seven
sheets of paper to form single, double or triple
wall board. This operation is achieved in a
The reels of paper are fed into the corrugator,
the paper is conditioned with heat and steam
and fed between large corrugating rolls which
give the paper its fluted shape in the Single
Facer. Starch is applied to the tips of the
flutes on one side and the inner liner is glued
to the fluting. The corrugated fluting medium
with one liner attached to it is called single
face web and travels along the machine towards
Double Backer where the single face web meets
the outer liner and forms corrugated board.
The corrugated board is then cut and stacked.
The main parts of a corrugator are the splicer and
These are the machines which feed the paper rolls into
the corrugator and enable rolls to be changed without
interrupting the production of corrugated board.
The single facer:
This machine transforms the paper into a series of
connected arches called « flutes » thanks to the corrugating
rolls that are large cylinders with a corrugated profile.
If the flute profile has to be changed, then the corrugating
rolls need to be changed.
The double backer:
It glues the outer liner to the fluting to obtain
single, double or triple wallboard. The single face
web is pre heated, starch is applied to the tips of
the flutes. The outer liner is then bonded to the
single face web to form corrugated board. It is a
complex operation that requires great expertise in
the pre-heating, moisture control and gluing processes.
This enables the Double Backer to run at different
speeds from the Single Facer especially when reel
or order changes take place. This is achieved by the
single face web forming festoons that are controlled
at the Single Facer station.
The glue unit and double backer:
Here, the single face web is prepared for glueing
to the outer liner.
It is roughly the same process as the single facer
unit with some variations of the pre-heating and gluing
The hot plate section:
It is at this stage that the single face web is combined
with the outer liner. The heating section ensures
that the bond is strong by gelling the glue and removing
The rotary shear:
After the board emerges from the Double Backer it
passes under a rotary shear that cuts across the whole
width of the web. This is used to chop out damaged
lengths of board or to effect a change over from one
grade of board to another.
The slitter / scorer:
This operation slits and scores the board in the
machine direction, with the scoring which determines
the style of the finished box.
The cut-off knives:
These cut the board to the exact required lengths
to obtain the corrugated sheet used in the making
of corrugated packaging.
Finally, corrugated sheets are automatically stacked.
Then they are moved directly to the conversion machine
or sent to a converting plant.
2/ The Conversion process: the
This is the final stage of the process that consists
in printing and then slotting, folding and gluing the
corrugated board to manufacture a corrugated container.
Different operations are carried out according to the
customer’s specification and according to the type of
The three main categories are the "regular slotted
case", the flat bed "die-cut" container and the rotary
"die-cut" container. Die-cutting concerns packaging
which requires very precise cutting and which can have
a complex design.
The converting process varies according to the type
Whatever the type of packaging, printing on corrugated
sheets is always possible.
The flexographic print process is commonly used for
printing on corrugated.
This process uses the relief printing technique and
is characterised by:
and an excellent quality/price ratio
Printing can be done « in-line » or « off-line ».
The regular slotted cases (RSC):
Most of them are produced with an in-line flexographic
Printer/ Slotter Folder Gluer which, in one operation,
prints, cuts, folds and glues the blank into its final
The packaging is then palletised and ready to be shipped
flat to the customer.
The die-cut packaging:
The die-cut containers are manufactured on a die-cutter
that cuts and creases the board. It is usually reserved
for a more sophisticated pack style.
This process requires a « form » that can be mounted
around a cylinder, in which case the machine is called
a rotary die-cutter, the other variant is called a flatbed
die-cutter. As indicated by its name its form is flat.
Once the converting process is over, the corrugated
packaging is put on a pallet and can be delivered to