Corrugated 101
Corrugated fiberboard cartons (commonly referred to as corrugated boxes) are extremely cheap boxes used widely in retail packaging, product displays, and many other applications that require lightweight, resistant packaging.
They have two main components: The Linerboard and the Medium.
Linerboard is the flat material found on the outer and inner surfaces that adheres to the medium. The Medium is the wavy paper that’s glued between the liners. Both are made of a special kind of heavy paper called containerboard.
Corrugated Composition
The strength of a corrugated box will depend on the linerboard and medium combination the box has.
- Single Face: A corrugated medium is glued to one linerboard sheet. The flutes are exposed.
- Single Wall: Also known as doubleface. The corrugated medium is glued between two sheets of linerboard.
- Double Wall: Three sheets of linerboard are glued with two mediums in between.
- Triple Wall: Four sheets of linerboard are glued with three mediums in between
Flutes
Are the arches the corrugated medium has. They are anchored to the linerboard with an adhesive to avoid the linerboard to bend. When pressure is applied to the board, the space in between the flutes acts as a cushion to protect the content of the box. It also serves as an insulator, protecting the package from sudden temperature changes. Additionally, the linerboard protects the flutes themselves from damage.
Types of Flutes
Corrugated boards are made with different flute profiles. Larger profiles are used to provide greater vertical compression, cushioning, and strength. Smaller profiles are mostly used in retail packaging due to their enhanced graphic capabilities.
Flutes of the same type may have similar sizes, but vary in their thickness and use. The five most common flute profiles are:
A-Flute: The original corrugated flute design. It has approximately 33 flutes per foot.
B-Flute: Often used for canned goods. It has approximately 47 flutes per foot and measures 1/8″ thick.
C-Flute: Commonly used when shipping cartons. It has approximately 39 flutes per foot and measures 5/32″ thick.
E-Flute: It has approximately 90 flutes per foot and measures 1/16″ thick.
F-Flute: Used mostly in small retail packaging. It has approximately 125 flutes per foot and measures 1/32″ thick.
Likewise, different flute profiles can be combined in one single piece of combined board. Mixing these profiles allows designers to adjust the compression strength, cushioning, and thickness of the board.
How to Measure a Box
The dimensions of a box are always stated in this sequence: Length, Width, and Depth. Some exceptions include bookfolds, bin boxes, and dividers, where the order changes to Width, Length, and Depth.
The length and the width are the longest and the shortest dimensions of a box, respectively. The depth is the distance between the opening of a box and the opposite panel.
The dimensions of a box are measured from inside when the box is assembled. Inside dimensions are used because the thickness of the corrugated boards may vary. For example, a B Flute box will have different outer dimensions than an E Flute Box.
When you measure the inside of a box, make sure to measure from the crushed fold line at the center of the score. If you need to measure outer dimensions as well, make sure to communicate when including “OD” along with the size (e.g. 15” x 24” x 12” OD).
Box Styles
Most boxes are in one of these categories : Telescope Boxes, Folders, Rigid Boxes, Slotted Boxes, Interior Forms, and Self-erecting Boxes. Corrugated boxes can also be custom-designed to fit the specific needs of a client.
Telescope Boxes
“Telescope Style” describes a box where the cover extends over at least two-thirds of the depth of the bottom piece, where a Box with Cover indicates a box where the cover extends less than two-thirds of the depth. Additionally, the top and bottom pieces fit over each other perfectly.
Common types of this box include:
Full Telescope Design Style Container (FTD) and Design Style Container with Cover (DSC): The boxes are two pieces made from two scored and slotted trays.
Full Telescope Half Slotted Container (FTHS): The body of the box is made from two half-slotted containers.
Folders
These boxes are made from one or several pieces of combined board. Their bottom surface is unbroken and made to fold around the product. Some common types are:
One Piece Folder (OPF): A piece of board is cut in a way that provides a flat bottom. It also has flaps that form the sides and ends of the box. Finally, the extensions of the side flaps meet to form the top.
Trays : They are frequently used as containers for more delicate products and parts. These boxes are made from a single piece of combined board with an unbroken bottom. Additionally, they have several layers of corrugated material in the end panels.
Five Panel Folder (FPF): It has a fifth panel that is used as a closing flap and completely covers the side panel. They are scored and have a single cut.
Rigid Boxes
They consist of two identical end panels and a body that folds to form the two side panels, an unbroken bottom and the top. Then, flaps are used to form the joints that seal the box.
Slotted Boxes
In this type of box, the blank is scored and slotted for folding purposes. They are usually made from only one piece of corrugated fiberboard and shipped and stored flat to save storage space. Then they are assembled when required.
Some common types are:
Regular Slotted Container (RSC): The two outer flaps are one-half the container’s width, meeting at the center of the box when folded. All flaps have the same length. The most common style is the RSC.
Full overlap Slotted Container (FOL): This style of box is extremely resistant to rough handling and gives the product extra cushioning to avoid damages. When the outer flaps are closed, they come within one inch of complete overlap. All flaps have the same length.
Overlap Slotted Container (OSC): Used when the length of the box is greater than the width. This results in a long gap between the inner flaps. Additionally, the box is closed with staples that go all through the overlap area to keep the outer flaps from pulling apart.
Half Slotted Container (HSC): This box is the same as a Regular Slotted Container (RSC). The only difference being it doesn’t have one set of flaps.
Center Special Overlap Slotted Container (CSO): The length of the box is no more than twice its width. Because the inner flaps meet at the center of the box, they provide a level base that protects the top of the product.
Center Special Slotted Container (CSSC): The inner flaps have no gap, which gives products inside a level base. They are especially strong because both the top and bottom of the box double the thickness of a corrugated board. The Inner and outer flaps are cut to different lengths and meet at the center of the box.
Center Special Full Overlap Slotted Container (SFF): This style of box gives extra cushioning and stacking strength with its three full layers of combined board over the entire top and bottom. The inner flaps of the box meet at the center and outer flaps fully overlap. The inner and outer flaps are cut to different lengths.
Interior Forms
They are usually used to fill voids inside a box, separate and cushion products, or strengthen the structure of the box. They have a wide variety of dividers, build-ups, partitions, and other inner packaging pieces. They can have different shapes such as a simple rectangle, slotted, die-cut, or scored.
Some common types of interior forms are:
Partitions (or Dividers) are mostly used for packaging fragile items. They have a separate cell for each item inside a box.
Tubes are scored rectangles that are folded to form a structure with several sides.
Pads are used to fill spaces or separate layers or sections of products. They consist of plain shapes of corrugated or solid fiberboard.
Inner Packing Pieces are used to provide cushioning and separation to products as well as to fill voids inside a box. They are scored and/or folded pieces of fiberboard.
Inner Pack Forms are designed to position the products inside a box away from its walls to add extra protection. They are usually die cut fiberboard pieces.
Self-erecting Boxes
They are usually a regular slotted container with a style similar to a telescope box.
The Mullen and ECT Tests
The corrugated packaging industry has two standards to describe and measure the construction of boxes. These are the Mullen and the Edge Crush Test (ECT).
To certify the box meets the stated specifics, a Box Maker’s Certificate (BMC) is placed on the bottom of an outside flap.
The Mullen Test measures how much pressure (lbs. per sq. in.) is needed to rupture the walls of a corrugated material. This test certifies that the box can withstand a certain pressure applied by a Mullen tester.
The Edge Crush Test (ECT) measures how much top to bottom pressure (lbs. per in.) a box can withstand before crushing. The result allows us to determine the stacking strength of a completed box.
FIBERBOARD PERFORMANCE STANDARDS
| SINGLE WALL | ||
| Max Wt. Box/Contents(lbs.) | Min. Burst Test(lbs. per sq. in) | Min. Edge Crush Test(lbs. per in. width) |
| 20 | 125 | 23 |
| 35 | 150 | 26 |
| 50 | 175 | 29 |
| 65 | 200 | 32 |
| 80 | 250 | 40 |
| 95 | 275 | 44 |
| 120 | 350 | 55 |
| DOUBLE WALL | ||
| Max Wt. Box/Contents(lbs.) | Min. Burst Test(lbs. per sq. in) | Min. Edge Crush Test(lbs. per in. width) |
| 80 | 200 | 42 |
| 100 | 275 | 48 |
| 120 | 350 | 51 |
| 140 | 400 | 61 |
| 160 | 500 | 71 |
| 180 | 600 | 82 |
| TRIPLE WALL | ||
| Max Wt. Box/Contents(lbs.) | Min. Burst Test(lbs. per sq. in) | Min. Edge Crush Test(lbs. per in. width) |
| 240 | 700 | 67 |
| 260 | 900 | 80 |
| 280 | 1100 | 90 |
| 300 | 1300 | 112 |
