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Corrugated Boxes Background

We have included this section to help you select the proper style and type of box to meet your packaging and shipping needs.
Measurements

box a Box sizes are measured by using inner dimensions unless otherwise specified. The size of your contents actually determine the inner box dimensions. Domestically (within the United States), those dimensions are listed in the following sequence: Length (L) x Width (W) x Depth (D)*. Internationally, the dimensions are stated as Length (L) x Breadth (B) x Height (H).

Dimensions are based on the opening of an assembled box. Looking at the opening, the longer of the two sides is considered the "length." The shorter of the two sides is the "width." The side perpendicular to the length and width is the "depth" of the box.

*Exceptions are bookfolds, bin boxes & divider bins where "width" precedes "length" & "depth" of the measurement sequence.

How To Measure A Box - The Quick Way

box b Looking at the opening of the box, measure the longest or length panel first. Using a tape measure, place it in the bottom of the box approximately one inch from the back wall and measure from left to right. Repeat the process for the shorter width panel. Then, folding a side flap inward until it is perpendicular to its vertical side wall, place the tape measure at the end of the flap and extend it downward until it rests on the inner flap at the bottom of the box (see illustration). This exercise will give you the depth dimension of the box.

One-piece, die-cut boxes, such as the "mailer-style" with a tuck-in top, do not have flaps when assembled, but the measuring procedure is basically the same. For the box depth, use the inside back panel as it has a visible score line (crease separating back panel from lid). For the width of a die cut box, measure between the score lines found on the inside of the top or lid. And, of course, for the length of the box, place your measuring rule on the bottom of the box approximately one-inch from the back panel. Measure from left to right.

 
Box Construction - What you need to know

box c The "Manufacturer's Joint" is where the two ends of the side panels meet to form the box. At that point, the panels are fastened together with tape, staples or glue. This description applies to regular slotted shipping cartons (RSCs). The side panel thickness and content weight determine the type of seal used for the manufacturer's joint. For example, glue is used for most single wall boxes, but staples are found in some double wall and in most triple wall boxes. In contrast, die-cut boxes are one-piece panels scored and folded together. They do not have a manufacturer's joint.

 
Box Strength

box d The strength of a corrugated box starts with its material. A corrugated sheet consists of two major components - linerboard and medium. Linerboard is the flat paper that covers both sides of the sheet and the medium is the "fluted" or arched paper found between both liners. The flute, when anchored to the linerboards with a starched-based adhesive, resists bending and pressure from all directions. When placed vertically on its ends, the flutes form vertical columns, capable of supporting considerable amounts of weight.

Flutes come in five basic heights and shapes - the most common are "B-Flute"(used for die-cut boxes) and "C-Flute (used for RSCs). B-flute is compressed and appears thinner, but don't be fooled. It is made with more paper to provide stronger side wall protection from blows and punctures. C-flute is taller, with more air space, but offers enhanced stacking strength. For excellent graphic reproduction, consider E-flute.

The amount of virgin pulp fibers and the length of those fibers in a corrugated sheet substantially contribute to box strength. For example, the difference between a 200# test box and a 275# test box is that the latter has more pulp fibers in its corrugated linerboard. The 200# test box is rated to hold up to 65 lbs. of box and contents while the 275# box can hold up to 95 lbs. A 350# test box is rated to hold up to 120 lbs. of box and contents. The following chart shows Bursting Test and Edge Crush Test performance standards of corrugated box liners based on the combined weight of a box and its contents.

 
Linerboard Performance Standards
Max Wt. Box/Contents
(lbs.)
Min. Burst Test Single/Double Wall
(lbs. per sq. in.)*
Min. Edge Crush Test (ECT)
(lbs. per in. width)
Single Wall Corrugated Boxes
20 125 23
35 150 26
50 175 29
65 200 32
80 250 40
95 275 44
120 350 55
Double Wall Corrugated Boxes
80 200 42
100 275 48
120 350 51
140 400 61
160 500 71
180 600 82
Triple Wall Corrugated Boxes
240 700 67
260 900 80
280 1100 90
300 1300 112
* Minimum puncture test, Triple Wall board (in. oz. per in. of tear)
 
Look for the Manufacturer's Stamp

seal A way to be sure that the material of the box that you're purchasing meets industry standards is to look for the Manufacturer's Certification Stamp, usually printed on one of the bottom flaps of the box. The stamp identifies the material as "singlewall," "doublewall" or "triplewall." It also certifies the Mullen Bursting Test ( most common is 200 lbs. per square inch) or the Edge Crush Test (ECT 32 lbs. per inch). The Mullen Test measures the bursting strength of the corrugated linerboard while the Edge Crush Test measures linerboard stacking strength. The 200 lbs. Mullen box and the 32 ECT box are comparable in stacking strength. But that is where the similarity ends. The Mullen Test box is better suited for the protection of heavier contents while the Edge Crush Test box provides lighter weight cartons with good stacking characteristics. When in doubt as to which box to use, always select the Mullen Test box because the construction of the linerboard cannot be altered. For example, 200# Mullen Test linerboard must be made of 42# per square inch basis weight paper and the medium or flute paper cannot be less than 23# per square inch basis weight.

single wall
Single Wall
double wall
Double Wall
triple wall
Triple Wall
 
When & What Box to Use

When to use a single wall 200# test box - when the box and contents weigh less than 65 lbs. This weight limit works fine for multiple light-weight items in a box or for a masterpack box where individual boxes are packed tightly in organized rows and stacks. If a single heavy item is to be shipped in a single wall, 200# test box, we recommend a weight limit of 45 lbs. or an upgrade to a 275# test single wall box. Simply apply common sense and always err on the conservative side.



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