Whatever you call them, you see corrugated boxes everywhere, it is made by a special corrugated box-making machine.  From front porches and distribution centers to moving trucks and manufacturing facilities, corrugated boxes are a part of our daily lives.  Just because we all use them, doesn’t mean we all understand them.

1. The steps of corrugated box manufacturing

The humble cardboard box is one of the most used packaging materials. It is a core product in packaging manufacturing. It not only fills the shelves, but it can be seen all throughout the supply chain too. When looking at a cardboard box, typically printed and branded with inviting colors and wording, it is hard to imagine it started life as a tree. We discuss the box manufacturing process step by step.

As consumers, we often forget to consider how items came to be, but we think the packaging should be celebrated. So, how does a tree finally become a box?

Corrugated Box

1) The tree

While we ideally look for recycled cardboard for box production, at one point, a cardboard box started life as a tree. Typically, the trees used for box manufacturing are softwood trees such as pine and fir trees. The reason they are chosen is that they have long fibers which can help to create a smooth finish for the cardboard as well as create tension which increases the strength.

Many manufacturers will choose wood from sustainable and managed woodland; this means that any trees that are felled are replaced to help maintain the ecosystem of the forest. The paper and cardboard created will have different coloring depending on the tree used. For example, silver birch trees will produce a dark color, while spruce will create a light brown color.

2) The pulp

From felling the tree, wood chips are made. These wood chips are then broken down into pulp. This can be done by grinding the wood against a stone or chemically cooking the wood chips. With this, you can add chemicals such as sodium sulfate to increase the strength of the pulp. For most cardboard, the pulp is left as the same color. However, it can also be bleached to create a white appearance.

3) Corrugation

Once the pulp has been dried, you can then start to create cardboard. For corrugated cardboard, it requires two pieces of paper or card called liners and a portion of fluted cardboard, which sits in between the liners. Fluting helps to give the cardboard further strength and a higher level of protection against damage.

Rolls of the paper made from the dried pulp are fed through a corrugated roller, which flutes or ruffles the paper. Depending on the quality of the box being made will depend on the level of fluting required. As increasing the fluting leads to higher use of material and therefore increased strength, this is used for high-quality boxes. For cheaper boxes, less fluting can be used which can help to create space-saving, a reduced amount of material used, and can lower the carbon emissions.

The corrugation machine uses hot steam to create the flutes. At the same time glue is rolled down each side of the flute, so that it sticks to the liners. Once corrugated cardboard is formed, it is then trimmed to provide straight edges.

Corrugated Box

4) Cutting

Now that you have complete corrugated cardboard, it is time to cut the card to size, depending on the box requirements. There is a comprehensive guide, and many of the machines are programmed to cut the cardboard to scale automatically depending on production demand. Once the basic outline has been cut, the card is then sent to a trimmer.

The trimmer is designed to deal with intricate aspects that the cutting machine cannot handle. A trimmer can add handles to boxes and cut flaps that are needed to construct the box. The trimmer also scores the cardboard, making it easier to fold when the box is ready for assembly.

5) Assembly

Assembly will depend on the requirements of the box. The use of flaps and slots may be best for businesses that want to construct their boxes on demand. As well as these, boxes built with tape are often efficient to be constructed as and when they are required. Usually, for more robust boxes, glue and stitching are used to fold sections together and keep the box secure.

Specific innovative machinery can construct boxes for you on demand. For example, the Aopackmachine is an on-demand box-making machine. It creates the perfect size box depending on your needs to reduce waste and ensure the best fit. The box is constructed for you which can significantly reduce packing production time.

After assembly, offcuts can be recycled to continue in the chain of box making. After the boxes have been branded, printed, and utilized, they can be recycled and create a continuous cycle of recycled box manufacturing.

2. Corrugated box types

Half-Slotted Boxes: Consists of one piece with a glued, stitched, or taped manufacturer’s joint and top and bottom flaps. They are shipped flat, ready to use, and require closing using the flaps provided.

Slotted Boxes: Consists of one piece with a glued, stitched, or taped manufacturer’s joint and top and bottom flaps. They are shipped flat, ready to use, and require closing using the flaps provided.

Telescope Box: Consists of more than one piece and is characterized by a lid and/or bottom telescoping over the body of the box.

Folder Boxes & Trays: Usually consist of only one piece of board. The bottom of the box is hinged to form the side walls and the cover. Locking tabs, handles, display panels, etc., can be incorporated into some designs.

Slide Boxes: Consists of several pieces of liners and sleeves sliding in different directions into each other. This group also includes outside sleeves for other cases.

Rigid Boxes: Consists of two separate end pieces and a body and require stitching or gluing of fiberboard or wood.

Partitions: Interior fitments such as inside liners, pads, separators, dividers, etc., whether tied to case design or as singular items. Any shown number of panels is arbitrary and may be increased or decreased, as required.

Fold-Up Pads: Interior fitments such as inside liners, pads, separators, dividers, etc., whether tied to case design or as singular items. Any shown number of panels is arbitrary and may be increased or decreased, as required.

Corrugated Box

This refers to the wave shapes, or ridges, that are pressed into a sheet of material that has been softened by steam. This material is then sandwiched between flat sheets of material to form a corrugated fiberboard. Flutes serve as protective cushioning and help strengthen a carton. Different widths and configurations offer distinctive performance advantages. Corrugated cartons feature either of the types below.

  • A-Flute: Flute thickness of 4.7 mm
  • B-Flute: Flute thickness of 2.5 mm
  • C-Flute: Flute thickness of 3.6 mm

Depending upon the stacking strength, puncture resistance, and crush strength required for the carton; one of the above three common corrugations is used in single-wall, general-purpose cartons. A-Flute has excellent stacking strength, B-Flute has good puncture resistance, and C-Flute has the optimum combination of both.

  • E-Flute: Flute thickness of 1.5 mm and is generally used for light applications such as pizza boxes, mailers, shoe boxes, etc.
  • BC Flute: This flute is a double-wall combination made from one B-flute, single-wall sheet, and one C-flute, single-wall sheet. The result is a strong corrugation used when extra thickness or stacking strength is needed.
  • AC Flute: This flute is a double-wall combination made from one A-flute, single-wall sheet, and one C-flute, single-wall sheet. The result is a very strong corrugation used when extra strength is needed.

Basis Weight Testing: A measurement of mass per unit of area that is expressed in pounds per thousand square feet. Basis weight is used to describe linerboard, corrugating medium, and boxes.

The Mullen Burst Test- Measures the bursting strength of the corrugated board.  The Mullen test presses a rubber diaphragm bubble against the board in a defined area to measure the pounds of pressure per square inch (psi) it takes to burst the board. Many customers like Mullen tested boxes for the protection of heavier contents because they are concerned about the linerboard bursting outward.

ECT (Edge Crush Test)- Measures the box board’s top-to-bottom compression strength (also known as stacking strength).  This test looks at two areas of strength: box compression strength (BCT) and stacking strength.  If a customer is concerned about the maximum weight a box can withstand, then ECT is your test.  Today, this is the most common type of test used.

ISTA Testing:  Performance testing specified by the International Safe Transit Association.  Generally includes testing of shock and vibration effects on the packaging.

HAZMAT/UN Testing: Shipments of dangerous goods or hazardous materials are highly regulated. Based on the UN Recommendations on the Transport of Dangerous Goods model regulations, each country has coordinated design and performance requirements for shipment.

Corrugated Box

3. General corrugated definitions

Broke: Paper trimmings, paper damaged due to breaks on a paper machine, or paper not manufactured to the required quality specification. Broke is usually fed back into the paper manufacturing process.

Carton Dimensions: Dimensions refer to the interior of a carton – length x width x height – and measured in millimeters. Length (L) is the longer side of the opening and width (W) is the shorter. Height (H) is the length between the openings on either end.

Cellulose: The main fibrous material in paper.

Corrugated Fiberboard: This material refers to the composite structure formed by gluing one or more sheets of fluted, corrugated material to one or more flat facings of linerboard.

  • Single-wall carton: This is a corrugated fiberboard carton made by gluing a sheet of fluted corrugated material between two flat sheets of linerboard.
  • Double-wall carton: This is a corrugated fiberboard carton made of three sheets of linerboard interleaved with two sheets of fluted corrugated material.

Die Cutting: The process of cutting a corrugated sheet into a shape that will convert to the required box size when assembled. A rotary die cutter uses a cylindrical die and is generally capable of higher speed than a flatbed die cutter, as the sheet flow basically continues. A flatbed die cutter uses a flat die. The corrugated sheet momentarily stops to enable the required cutting. This method provides both high accuracy and intricate shapes not available from the rotary process.

Double-facer: A double-facer, or double backer, is the part of a corrugator that bonds a single-face board to another liner. This produces a double-faced corrugated sheet.

Folding Cartons:  Multi-layer paperboard cartons that are printed or coated and cut into carton blanks. The carton blanks also incorporate creases, which enable the carton to be formed for packaging the customer’s product.

Functional Coatings: The lamination of polyethylene and/or plastic or foil films to paper substrates, providing a water or grease-proof barrier. Typically used in high-humidity applications in both tropical and cold temperatures. Also for use with meat, seafood, pet food, fruit, and produce.

Kraft: This term describes the natural, unbleached corrugated fiberboard used in making cartons.

Linerboards: Linerboards form the inner and outer facings of corrugated fiber boxes and are chosen for their structural and/or decorative properties. They can be made from white or brown, kraft or recycled fibers, or a blend of both.

Pasting: Two, three, or four plies of paper and paperboard are glued together. They form a solid fiberboard with a thickness ranging between 0.8mm to 3mm. The boards are used for a variety of applications. Shoe boxes, screen printing, display boxes, board games, book covers, and ring binders.

Pulp: Primary raw material from which paper is made. A fibrous product produced by mechanical or chemical processes, or a combination of both.

RSC: This is the abbreviation for regular slotted carton. This is the most commonly used style of carton. One side is glued, taped, or stapled during manufacturing. This type of carton is well suited for easy set-up, filling, and closure.

Sheet Feeder: A corrugating plant that has no converting equipment and produces only corrugated sheets. Its customers are typically independent sheet plants. The term ‘sheet feeder’ can also mean the device at the front of die cutters/flexo folder gluers.

Sheet Plant: Comprises converting equipment and does not produce its own corrugated board. Typically, sheet plants are smaller operations offering their customers personalized service.