introduction to corrugated boxes

I n t r o d u c t i o n t o C o r r u g a t e d B o x e s

L A S Z L O H O R V A T H , P H . D . , C P L PA P R I L 2 3 , 2 0 2 0

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Design Steps for Stacking Strength…

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3

! 1871 Albert Jones patented the first idea of a fluted paper

! 1874 Oliver Long suggested the creation of the single face board

! Late 1870, Machinery wasdeveloped to make corrugatedboard

! 1890 Another liner was added which resulted the first single wall corrugated board

History of CorrugatedBoards

4

Components:

! Linerboard! Corrugating Medium! Adhesive

! Linerboard and medium are characterized using Basis Weight Grades

! Basis Weight: Weight of the board in lbs per 1000 sq. ft.

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! Most common medium is the 26 lbs / 1000 sq./ft.

! Basis weight grade specified board is characterized by weight and Mullen burst strength.

Corrugated Board Basics

Linerboard Grades (lbs. /1000ft2)

Basis Weight Grades

Burst Strength (Psi)

26 70

33 85

38 92

42 100

69 135

90 160

Corrugating Medium Grades(lbs. /1000ft2)

23

26 (most common)

30

33

36

40

>

! Corrugated Board Types

Corrugated Board Basics! Corrugated Flute Types

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!?B +,A

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Corrugated Board BasicsCharacteristics A-flute C-flute B-flute E-flute

Stack Strength Best Good Fair Poor

Printing Poor Fair Good Best

Die Cutting Poor Fair Good Best

Puncture Good Best Fair Poor

Storage Space Most Fair Good Least

Score/Bend Poor Fair Good Best

Cushioning Best Good Fair Poor

Flat Crush Poor Fair Good Good

C

Corrugated Board Basics! Double wall corrugated

! Provides extra strength to the box

! Allows the utilization of the

advantages of multiple board types

! BC or AB-flute board:

! B-flute side prints better

! A or C-flute side strengthens

B

! The Corrugated Board Grade identifies the liner and medium combination.

! Outside liner - Medium(Flute type)- Inside liner! Example

! 42-26C-42! 56-33C-56! 33-26B-33-26C-33

! Board grade identifies specific performance attributes of combined board

Corrugated Board Basics

D

! Burst Strength test (TAPPI 810)

! Measure the resistance of the corrugated board against rupture

! Measures the strength of the liners

! Edge crush test (TAPPI T811)

! Measures the strength in the flute direction

! Used to determine box stackingstrength

Corrugated Board Mechanical Properties

!E


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Box Basics

Minor Flap

Depth

Length

Manufacturer’s Joint

Width

Major Flap

Crease or Score Manufacturer’s Joint

!3

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Corrugated Box -Sizes

!4

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Corrugated Shipper - Styles

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Corrugated Shipper - Styles

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How Corrugated Folds:

!@

! Truck: National Motor Freight Classification (NMFC)

! Rail: Uniform Freight Classification (UFC)

! Requires all box to comply with the requirements and have the Box Certificate.

Carrier RulesMaximum Weight of Box andContents

(lbs.)

Maximum Outside

Dimensions, (Length + Width + Depth)

(in.)

MinimumBursting Test

(lbs. per sq in.)

Minimum Edge Crush Test

(lbs. per sq in.)

Single Wall

20 40 125 2335 50 150 2650 60 175 2965 75 200 3280 85 250 4095 95 275 44120 105 350 55

Double Wall80 85 200 42100 95 275 48120 105 350 51140 110 400 61160 115 500 71180 120 600 82

!C

Basics of Mechanics of Corrugated Box

!B

Compression

! Definition: compression load resulting from static (warehouse stacking) or dynamic (clamping) load on a container or other package

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Compression

3E

Definition: Resistance of the box against compression forces applied perpendicularly to one or more of its faces.

What is box compression strength?

3!

! Box Compression Strength can be determined in two ways:

! Calculated using simplified McKee equation

! Measured using a short term box compression test

Box Compression Strength

33

! Box Compression Test (BCT):

! Where:ECT – edge crush test (lbf/in)P – box perimeter (2L + 2W) (in)Z – caliper of combined corrugated board (in)

! Calculation is not applicable for all size and construction

! Mainly applies to RSC, HSC, or Telescopic Boxes

Calculation of Box Compression Strength

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34

Short-Term Compression! ASTM D642 – Compression Test for Shipping

Containers (https://www.astm.org/Standards/D642.htm)

! Procedure! Apply preload

! 50lb for single wall box! 100lb or 500lb for double or triple

wall box

! Recommended: 5 samples! Record load and deflection (500lb @ 0.5”

or 1000psi)! Test until visual failure! Failure of the box does not mean that the

package failed

Measurement of Box Compression Strength

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https://www.astm.org/Standards/D642.htm

Load-Deflection Curve

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Failure Modes Based on Aspect Ratio

! Always run the tests until visible failure occurs!

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3C

Determining Stacking Strength

! Stacking Strength– the amount of load that the box can safely hold.

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3B


! Influencing factors:

! Product and package interaction! Humidity! Time! Stacking misalignment! Pallet overhang! Transportation

! Fix safety factors or Retention Analysis are used to account for these influencing factors

3D


! Fixed safety factor: often used when the exact conditions that the package will be subjected to are not known. conditions that the package will be subjected to

! Range of safety factors can be found in ASTM D4169

! Depends on:! Assurance level! Package type! Transportation mode

! Warehouse (static)! Vehicle (dynamic)

4E


! Assurance Levels:! The levels are determined based on

! the product value, ! the desired level of anticipated damage that can be

tolerated, ! the number of units shipped, ! the knowledge of the shipping environment, or ! other criteria

! ASTM Assurance Levels:! Level 1 – Low probability, High intensity events (more severe than Level 2)! Level 2 – (Commonly used)! Level 3 – High probability, low intensity events (less severe than level 2)

4!

Safe Stacking Strength using Fixed Safety Factor method:

! Suppose you compression test a package in the lab under standard conditions and get a compression strength of 800 lbs. The package is made out of corrugated box without any rigid internal supports. The client want to use Assurance Level II.

! How much is the safe stacking strength of the package in a warehouse?

Example 1

43

Safe Stacking Height using Fixed Safety Factor Method:

! BCT= 800 lbs.

! Safe Stacking Strength=?

Example 1

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Determining Stacking StrengthRetention Analysis:! Aimed at evaluating the compression

strength retained by the package in the presence of the debilitating influences

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Determining Stacking StrengthRetention Analysis:

! Humidity Factor (H)! Humidity weakens the box

because of absorption! 85% Relative Humidity (RH) is

common in warehouse acrossthe U.S.

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! Storage Time Factor (T)! Box weakened due to fatigue! Common to store loads up to

90 days.

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Storage Time in Days

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! Pallet Pattern Factor (PP):

! Column stacked and aligned: 8% loss! Column stacked and misaligned: 10-15% loss! Interlocked: 40-60% loss! Overhang: 20-40%! Deck board gap: 10-25% loss! Excessive handling: 10-40% loss

4C

Example 2

H (85%)= 0.60T (90 days)= 0.55PP (Column stacking, misaligned) = 0.85PP (Deckboard gap)= 0.75

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/2;/ < /233 < /2.3 < /263-.//126;

- 5;. 9:

Corrugated box strength: 800 lb

4B

Example 3

H (85%)= 0.60T (90 days)= 0.55PP (interlock stacking) = 0.40PP (Deckboard gap)= 0.75PP (Overhang)= 0.80

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- ;>21 9:

Corrugated box strength: 800 lb

62% Reduction

4D

Box Analysis in PDS 6.1

=E

T H A N K Y O U F O R Y O U R A T T E N T I O N

L A S Z L O H O R V A T HA S S O C I A T E P R O F E S S O RD I R E C T O R , C E N T E R F O R P A C K A G I N G A N D U N I T L O A D D E S I G N

A P R I L 2 3 , 2 0 2 0

41

introduction to corrugated boxes

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