Corrugated Packaging BASICS

Corrugated Board Structure

Corrugated board is a made up of layers of paper including one or more middle layers where the paper is “corrugated” into a ridges pattern (the “fluting”) sandwiched between flat paper layers (“liners”) glued to either side of the corrugated fluting.

This physical structure with corrugations makes the resulting board thicker and stronger than the sheet paper would otherwise be. In particular the corrugations effectively become “columns” running in one direction which make the board resistant to bending or crush deformation along the direction of those “flutes” – which is why most boxes are designed so the corrugations in the board run from top to bottom of the box (rather than from side to side).

The profile of the “fluting” (ie the height and frequency of the corrugations) is categorised by letters: eg. A, B, C and E flute and the board is also so specified according to the weight and type pf paper used both for the corrugated fluting but more particualrly for the liner paper top and bottom.


Board may also have double or triple layers of fluting (“Double Wall” & “Triple Wall”). The most common is “BC flute” indicating that the board consists of both a layer of B flute and a layer of C flute. Each flute layer is separated by a flat liner paper and, of course, a top and bottom liner paper will also be present.

The centre fluting is made from a recycled waste based paper. The paper used to make the liner of the board may be virgin kraft paper or a recycled “Testliner” paper and the liner may be natural “Brown” or bleached “White” to produce a white corrugated board which may prove more suitable for printing.

Corrugated board is then converted into a packaging design to make it useful. Over the years many styles have been developed with particularly efficient designs – such as the “Fefco 0201 Amercian Box” becoming extremely common. 

The Fefco coding system was created to identify common designs and some of the more common examples are shown above. All are made from one or more sheets of Corrugated board cut to size and shape. In some cases, such as the “0427”, the box with fold and slot together without needing to be joined. Others such as the ubiquitous “0201” have a seam which is commonly glued and with it’s flaps taped across when it is folded out to be errected.

A standard Fefco design is specified by stating Fefco style number, the flute/board grade, inner dimensions of the complete box and the join type where necessary. Further detail might need to be included such as join flap sizes and other dimensions.

In practice, bespoke packaging will often be a variant from a standard design (which may be a simple as the addition of handholes for example).


Corrugated Board Production

Corrugated board is made on a “Corrugator” fed from paper reels at the start of the machine, travelling with heat and steam applied though rollers to corrugate the fluting(s) and glue the paper layers together. The width of the paper determines the total width of the corrugated board coming out of the machine with slit knives cutting that down to the width (“deckle”) required for each order whilst a high speed “chop” knife cuts the board to length thus outputing Corrugated board sheets at the end of the machinery’s production line.

Corrugator efficiency is achieved by planning work order mix to maximise the utilisation of the full width of the paper reels going in. They run at high speed where production capacities often exceed 200 million m2 per annum (that is the board content of around 8 million medium sized “48 x crisp” boxes per week).

A Corrugator producing Corrugated board may be located in the same building as the manchines required to print and manufacture boxes from that board. That operating model is known as an “Integrated Plant” and is generally most suited to large volume case work such as high volume outer boxes for the high turnover and predictable demand from major corporate food companies. The high run volumes and forward demand forecasts aids planning to maximise production efficiency to drive costs down.

However for Corrugated Packaging where the requirement is for a wide variety of packaging styles with lower typical order volumes (below the tens of thousands that are generally more suited to an Integrated Box plant) it is more common for the Corrugated board to be supplied into the packaging manufacturer by dedicated Corrugated Board producers from plants equiped with large and efficient Corrugators. Corrugated Board factories that are focused mainly upon the production of Corrugated Board are known as a “Sheet Feeders” and supply numerous separate box manufacturing sites (known in the industry as “Sheet Plants”) with the Corrugated Board they require to manufacture a more diverse range of packaging styles and requirements on a short order lead time basis.

In this operating model the Corrugator efficencies are achieved by computerised scheduling of the large number of individual orders received from multiple packaging manufacturers, in order to maximise the paper utilisation across the width of the Corrugator. Multiple orders are then distributed, typically in full lorry loads, as the raw material into the “Sheet Plant” packaging manufacturers on an immediate delivery basis.


Corrugated Packaging Manufacture

The manufacture of packaging from Corrugated board is known as “Conversion”. Smithpack is therefore a Corrugated Packaging Convertor or “Sheet Plant” manufacturer.

Due to the variety of packaging requirements, in order to offer a decent range of styles, sizes and types of corrugated packaging requires a wide range of production equipment capable of handling a variety of size board and boxes. The principal processes are: Printing, Slotting, Creasing, Die-cutting, Jointing (Glue, “Stitch” or Tape) and production machinery may be able to handle some or all of these operations subject to various limitiations of the machine’s size and type.

Smithpack Manufacturing

Smithpack have a wide range of production machinery including a recently added computerised quick-set 3M Flexo-Printer-Slotter-Folder-Gluer, semi-automatic die-cutter, a 3.6M Printer Slotter, small format printer, and folder-gluers and stitchers in a modern factory with automatic bundling, strapping and pallet press facilities.