How Heavy Duty Packing Boxes Are Made

Here at Big Brown Box, we are incredibly proud of the quality of our heavy duty packing boxes. In fact, we’re so proud we want to share the secret of how these brown bundles of joy and protection are made. Seeing as they are at the core of our business, we felt this could only be done properly through its own special article.

Heavy Duty Packing Boxes: From Truck to Tree

It’s easy to forget that these humble, unassuming cardboard boxes used to be soaring leviathans that held top soil together, provided habitats for fauna, and acted as the lungs of our world (Editor’s Note: Big Brown Box source all of our raw materials from sustainable sources. We’re not tearing anyone’s lungs out here folks). We often get asked how they process works, so we went searching for the people who know such things – as in not our content creation team – and asked them a few questions. The answers may surprise you. They probably won’t, but they might.

First, the basics: cardboard packing boxes are essentially made up of a flute (made of recycled paper, go recycling) sandwiched between two liners (made up of cardboard). These days, it is common for these liners to also consist of a considerable portion of recycled content, sourced either from old cardboard or various sources of second hand paper.

In The Beginning, There Were Trees

Cardboard packing boxes don’t grow on trees; they grew as trees. When talking about large cardboard boxes, we talk about two different types of liners. A liner is the material that lies on top and beneath the fluting (the bit in between). Typically, a cardboard box will have a Kraft paper outer and a test paper inner liner. This is because Kraft is a higher quality than test and has a smoother finish, allowing it to be printed on easier. Kraft also has the added benefit of being more difficult for water to penetrate, which is a beneficial trait for the outer liner.

To get this smooth finish, Kraft paper has to be made from softwood trees that have long fibres; think Pine, Spruce, or Fir trees. As mentioned earlier, the majority of European paper is made from sustainable forests owned by companies such as SCA (Svenska Cellulosa Aktiebolaget) who plant two trees for every one cut down. Long fibres are also stronger in tension strengths, which is why Kraft paper is often described as having a high tear and burst resistance.

Test papers are often made from hardwood trees that have short fibres, or recycled paper, which is why it is cheaper and has a more abrasive quality. Hardwood material comes from Oak, Sycamore, Birch, and Chestnut, and again is sourced predominately from sustainable sources.

Pulping The Wood

Creating the paper involves a long process to ensure the wood chips that are pulped are as clean and suitable for the purpose as possible. To begin with, the trees are cut and lumbered to create tons of logs that are passed through a machine to be debarked and chipped.

These chips are then passed through one of two pulping processes – mechanical pulping or chemical pulping. Mechanical pulping involves grinding of the wood to reduce wood to individual cellulose fibres by forcing the debarked logs against a revolving stone to make a pulp. The stone is sprayed with water to remove fibres from the pulp stone. This does, however, result in little removal of lignin, a non-fibrous constituent of wood) that binds fibres together and reduces paper quality. The plus side is that mechanical pulping is low cost and generates a higher throughput.

Chemical pulping involves ‘cooking’ wood chips to reduce the raw material into individual cellulose fibres. There are two types of chemical cooking, sulphite and sulphate, and both result in better separation and reduction of lignin, allowing for a higher quality of paper to be produced. Sulphate is the more popular of the two. It uses alkaline solutions to digest wood and then adding sodium sulphate to increase the strength of the pulp - this is where the term “Kraft” comes from, as it is Swedish for “strength”.

Heavy Duty Packing Box Fluting

Fluted cardboard is the wavy piece of cardboard sandwiched between the liner of the heavy duty packing box and is what give a box it’s strength (Kraft) and protection from knocks and impact damage. A corrugated roller machine is used to create the ruffled shape of the fluting.

Fluted cardboard is the same as normal cardboard, simply undergoing the fluting process to make the cardboard into fluting.

The Production of a Heavy Duty Packing Box

Now that the origin of the key components of the heavy duty packing boxes have been established, all that needs to be done in to combine them into the end product: the heavy duty packing box itself. A passing the flute through a corrugator in which hot steam is sprayed onto the cardboard to allow it to be pressed, another rolled glues one side of the flute. The two liners ae then adhered to the board by the machine, followed by a trim to the sides by a circular saw to ensure they are straight.

The machine then cuts the board as many as nine times; this is determined by the FEFCO (European Federation of Corrugated Board Manufacturers) guidelines. The FEFCO guidelines outline essentially any box style you could imagine; all that are bespoke to the individual productions are the measurements and any additional flaps required.

After the boards have been cut, the corrugator separates the boards into layers and stacks them into packs ready to be fed to the trimmer. The job of the trimmer is to precisely cut the more delicate aspects of the box, such and handles and flaps; it has sharp and rubber blades to allow for the lines that need to be cut out. A bending machine then folds the boxes along the scored lines, and glue or stitches are applied to the places which will come together to form the box. Glue is the most common adhesive to use for boxes, and is much more hygienic which is important for industries such as food, stitching can also be used as can staples but these are costlier options and mostly only used for heavy duty boxes that need a tougher adhesive.  Once the adhesion has been applied another machine then folds the sections to secure them together and the flat boxes are piled up to be sent out to customers.