How Cardboard Packaging Is Made Strong
While cardboard packaging may look simple enough, there is in fact quite a lot of engineering that has gone into making it strong enough to hold items during transport and storage.
Flute Grade and Crush Resistance
The wavy layer inside the corrugated board is known as the flute. The flute grade will affect the crush resistance of the box. A-flute being the thickest flute is ideal for very heavy or fragile items. B-flute is thinner than A-flute and is more suited to slotted boxes that will be stacked under great compression. C-flute is the most common flute grade used for general purpose packaging and is the strongest of the three in its class. E-flute is the thinnest of all the flute grades and is ideal for when a fine print finish is required. However the E-flute does not have the same bulk as the other three flute grades and therefore is not as strong for load bearing.
Liner Weight and Load Capacity
The flat outer layer of corrugated cardboard are the liners, which are measured in grams per square meter (gsm). In general a lightweight liner of around 125gsm is adequate for parcel packaging for retail purposes. More heavy duty items may require a heavier weight liner of 200gsm or above. Increasing the weight of the liners on a box is one of the simplest ways to increase the load bearing capacity of that box without having to alter the outer dimensions of the box.
Fibre Direction and Stacking Strength
Paper fibres have a natural ‘grain’ or direction induced during manufacture of the paper. In the case of the liner this is important and in packaging we typically specify whether the machine direction (MD) or cross direction (CD) is uppermost in the box. This is particularly important for items that are to be stacked in a warehouse or on vehicles and can be subjected to above average levels of compression. In such cases specifying the liner with the machine direction of the paper fibres (MD) orientation up the sides of the box provides better resistance to compression.
Score Lines and Corner Rigidity
The Score Lines: A simple fold is created by scoring the cardboard, i.e. pressing it rather than cutting it. It is very important to ensure that the score lines are correctly positioned to maintain the box’s corner rigidity to prevent it from racking or splaying.
Moisture-Resistant Treatments
Water or moisture in packaging can bring down the strength of cardboard packaging very quickly. In order to combat this and keep packaging strong in cold and humid conditions, many cardboard packaging materials are treated with wax or water resistant clay coatings on the liners of packaging boxes. WRAP’s guidance on packaging material performance provides further details on how packaging materials perform in a variety of situations including the effect of moisture on packaging materials. For Cardboard Packaging see https://capscases.co.uk/services-2/sustainable-cardboard-packaging.
By knowing how to specify the right combinations of these factors you can ensure that any supplier can design and make the right packaging for you before they even start to make any!
