Choose Right Corrugated Board for Your Packaging Box

                                                                                                                      ---------- 2018.07.20

Corrugated fiberboard
is a material consisting of a fluted corrugated sheet and one or two flat linerboards. It is made on "flute lamination machines" or "corrugators" and is used in the manufacture of shipping containers and corrugated boxes.
The corrugated medium and linerboard board both are made of kraft containerboard, a paperboard material usually over 0.01 inches (0.25 mm) thick. Corrugated fiberboard is sometimes called cardboard, although cardboard might be any heavy paper-pulp based board.
Several properties and characteristics can be measured for corrugated board. Some of these include:
  • Edge crush test
  • Burst strength
  • Flat crush test
  • Bending resistance
  • Impact resistance
  • Cushioning, shock absorption
  • Tear resistance
  • Grammage (mass per unit of area) for components and for combined board
Corrugated fiberboard is anisotropic; many of its properties are highly directional. For example, edge crush, bending stiffness, tensile, and surface characteristics are different, depending on the orientation to the flutes and the machine direction of manufacture.
Corrugated board is manufactured on large high-precision machinery lines called corrugators, usually running at about 500 feet per minute (150 m/min) or more. These machines, over time, have become very complex with the objective of avoiding some common problems in corrugated board production, such as warp and washboarding.
The key raw material in corrugating is paper, different grades for each layer making up the corrugated box. Due to supply chain and scale considerations, paper is produced in separate plants called paper mills. Most corrugating plants keep an inventory of paper reels.
Common flute sizes are "A", "B", "C", "E" and "F" or microflute. The letter designation relates to the order that the flutes were invented, not the relative sizes. Flute size refers to the number of flutes per linear foot, although the actual flute dimensions for different corrugator manufacturers may vary slightly. Measuring the number of flutes per linear foot is a more reliable method of identifying flute size than measuring board thickness, which can vary due to manufacturing conditions. The most common flute size in corrugated boxes is "C" flute.
Standard US Corrugated Flutes
Flute Designation Flutes per linear foot Flute thickness (in) Flutes per linear meter Flute thickness (mm)
A flute 33 +/- 3 3/16 108 +/- 10 4.8
B flute 47 +/- 3 1/8 154 +/- 10 3.2
C flute 39 +/- 3 5/32 128 +/- 10 4.0
E flute 90 +/- 4 1/16 295 +/- 13 1.6
F flute 125 +/- 4 1/32 420 +/- 13 0.8

To choose the right corrugated material and box for your products seems much straight forward task. Although there is nothing incredibly difficult about choosing the right box there are a surprising amount of details that do need to be considered before you can decide on the best option.  One of those details is whether or not your product will need a single, double, or triple wall box.  If you look at the picture to the left you will see a nice diagram showing the difference between these materials.   
Corrugated gets its strength from two things:  the flutes and the liner paper weight. Notice from the diagram that the flutes are manufactured as arches.  Arches, which have been used over and over throughout history in many building projects, are the strongest way to span a given space.  The flutes are formed as arches and glued between the liners.  The liners can be made of varying paper weights which also will affect the strength of the box.  The heavier the paper the stronger the box. In Unico, we usually use corrugated kraftliner paper weight 70gsm, 90gsm, 110gsm, 140gsm, 200gsm, 250gsm, etc. You can choose which is suitable to your boxes. 
Now let's compare the different materials.  Single wall is by far the most used corrugated material.  It is strong and durable enough for most packaging needs whether that be as a shipping container or a retail packaging box. Doublewall corrugated with two sets of fluted material is stronger than singlewall, but not necessarily twice as strong as you might think.  It is used generally when heavier items or glass items are shipped and need extra protection and strength that the doublewall box can offer.  Triplewall boxes are much less common than singlewall or doublewall and are used in large bulk type boxes that are sometimes filled with granular products.  Triplewall is very sturdy and strong, but also much more expensive than the other options and therefore is uncommon.  There is one more material type that I have not mentioned yet and that is singleface corrugated.  Look back at the diagram once more and see that there is the fluted medium, but only one liner.  This material is only used as inner packaging to wrap glass and provide cushioning for shipment.
Fast Speed Corrugated Board Laminating Machine- Unico Packing  

There is a specific set of rules for all boxes that are to be used as shipping containers but to keep things simple, most products will be well protected in a single wall box.  That is the place you should start when searching for a new box.  Use doublewall when you have a product that is quite heavy or large or if you are shipping items that need extra cushioning qualities from the box walls. 
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