This blog has touched on many occasions on what cardboard boxes are and what corrugated fiberboard is – their basic building material. Almost always a cardboard box has two liners and corrugated wavy flutes in the middle for extra strength. Now is the time to shed some light on basics of the manufacturing process itself.
It all typically starts with a large roll of containerboard – a special, thick, heavy paper. Most of the time this is paper with high or one hundred percent recycled content. The paper is fed onto a belted corrugator machine. There heavy rollers with grooves together with hot steam press into the paper medium in a controlled manner to form the flute waves. Next immediate step is to apply glue onto the sides of the newly produced corrugated medium. An insulating air cushion is formed in the process between the flutes and the liner – the size of the flutes (and thus the insulating amount of air in-between) can be used as barrier protection and can be customized up to product requirements. The adhesive used here is in its simplest form – starch plus water combination. Often glue is made of urea, ammonium and hard water – such a mixture might have unforeseeable consequences on food shipped in cardboard boxes so the starch-water mixture is a lot safer. Another liner is applied to the other side of the flutes and the combination can be repeated if extra heavy items are to be shipped.
Further down the production line, corrugated fiberboard runs through the trimmer where sheets are nicely trimmed by a circular saw and stacked into uniform equal pieces. Special machine “fingers” separate the boards from each other into sheets which will later be folded into boxes. Next, perforators drive holes into the cardboard for folds or handles. Excess and trimmed leftovers are fed back into the recycling process for further reuse up to several times over.
Folding machine is the next station – this is where the corrugated fiberboard is gradually starting to resemble cardboard boxes as we know them from the packaging supplier shelves. Before a box is all set to be stacked into production pallets and shipped off to warehouses, the paperboard will go through the ink kitchen. This is where dyes and colors are electronically mixed into desired shades and tones. Almost always the paint used here is water-based to ensure fast drying and prevent chemical bonding with oil-based colors. The printing presses of these corrugated paper mills are of two varieties:
- Flexographic – used for drawings and text
- Lithographic – for photographs and more complex imaging
Bleach can be added in advance in the paper manufacturing process to improve printing qualities of boxes as needed.
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