Quality characteristics and defect evaluation for corrugated


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Quality Catalogue
Quality characteristics and defect evaluation for corrugated board packaging

QUALITY CATALOGUE FOR CORRUGATED BOARD PACKAGING
QUALITY CHARACTERISTICS AND DEFECT EVALUATION FOR CORRUGATED BOARD PACKAGING
Verband der Wellpappen-Industrie e.V. (VDW) / German Corrugated Board Association Hilpertstraße 22 D-64295 Darmstadt Germany
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QUALITY CATALOGUE FOR CORRUGATED BOARD PACKAGING
1. Introduction
This catalogue is intended to be used for customer´s quality assurance of the packaging deliveries (e.g. folding boxes, blanks) made from corrugated board. This catalogue helps to define best practice and can be considered as 'state of the art'.
Special conditions apply for all other types of packaging, these conditions are to be agreed separately. The requirements for the transportation of the packaging in respect of bundling, palletisation and strapping are also outside of the scope of this document and to be agreed separately as hygiene-related matters.
This scope of this catalogue covers converting quality issues of both corrugated board and the subsequent packaging made from corrugated board. The catalogue could be used as a supplement to the German standards DIN 55468-1 and RALGZ 492.
2. Explanatory notes
This catalogue distinguishes between the following types of defects:
Critical defects (CD)
Defects whose existence/occurrence can bring about critical consequences e.g. here they may: • endanger human life or health, • violate statutory provisions, • lead to the destruction or transformation of the packed goods, • significantly impair either the reliability of the storage or the efficiency of the
production tools and/or the filling equipment and/or the packing equipment.
Major defects (MJD)
Defects whose existence/occurrence can bring about impairments, e.g. they may: • lead to performance inefficiencies and thus to the failure of the
packaging/package, • lead to complaints by the customer, • cause loss of efficiency in the production, impair the efficiency of production
tools and/or of the filling and packing equipment.
Minor defects (MND)
Defects whose existence/occurrence do not have any significant consequences, e.g. they may represent / lead to a general reduction in quality.

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The different types of defect are assigned to defect classes that are defined as follows:

Defect class 1: Defect class 2A: Defect class 2B: Defect class 3:

Packaging unusable Usability of the packaging seriously impaired Usability of the packaging impaired to a lesser extent Usability of the packaging impaired but does not significantly affect the properties of the packaging

Sample specifications based on ISO 2859, Part 11 have been laid down for the respective defect classes. A statistically secured test procedure requires that the test pieces are drawn randomly from the production run. Folding boxes that have become unusable due to their transportation and other external influences have to be excluded from the evaluation. The envisaged goods defect limit (AQL) corresponds to a significance probability level of 95%.

A delivery with this high probability level will be anticipated as long as the following defect limits in the shipment (batch) are not exceeded:

Table 1: Setting the AQL values

Type of defect Critical defect (CD): Major defect (MJD):
Minor defect (MND):

Defect class 1 2A 2B
3

AQL value

0.65 1.0
1.5 4.0
6.5

Defect class 1 does not contain any defect level, as such defects may well lead to a delivery rejection.
The batch size “N” The batch size (delivery quantity) is the quantity of packaging run that is presented for testing at one time as defined in the following guidelines.
The sample size “n” is the quantity of the packaging that is taken from the batch for the evaluation.
The acceptance number “c” is the highest permitted number of defective items of packaging found in the sample.

1) DIN ISO 2859, August 2014: Sampling procedures for inspection by attributes – Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection

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In the case of a single defective item of packaging (folding box, blank) with multiple defects, only the most serious defect is evaluated. Defects to multiple items of packaging from different ranges of key characteristics will be added up within their defect class.
Table 2: Samples - basic table

Batch size N (no. of items)

up to -

500

Sample size n

AQL

0.65 1.0

1.5

2.5

4.0

6.5

Number of defective items permissible in the sample (acceptance number “c”)

N or 10

0

0

0

1

1

2

501 1,201 3,201 10,001 35,001 -

1,200 3,200 10,000 35,000 150,000

20

0

1

1

1

2

3

32

1

1

1

2

3

4

50

1

1

2

3

4

6

80

1

2

3

4

6

8

125

2

3

4

6

8

12

In the case of very large orders, it is recommended that the total delivery will be subdivided to acceptable batch sizes, e.g. one loading unit.
Arbitration tests should be based on the valid standard climate. As this quality catalogue was being completed, the standard climate is 23 °C and 50 % relative humidity according to DIN EN 20187.
Note the following when using this quality catalogue:
The thickness (height) of the corrugated board is an approximate value in millimetres. The heights of the various flutes are shown in Table 3. The thickness of multiwall corrugated board is to be calculated by addition.

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Table 3: Flute types
Flute
G F E D B C A K

Flute height h mm < 0,6
≥ 0.6 to < 1.0 ≥ 1.0 to < 1.9 ≥ 1.9 to < 2.2 ≥ 2.2 to < 3.1 ≥ 3.1 to < 4.0 ≥ 4.0 to < 5.0
≥ 5.0

Flute pitch t mm ≤1.8
1.8 to < 2.6 > 2.6 to ≤ 3.5 > 3.5 to ≤ 4.8 > 4.8 to ≤ 6.5 > 6.5 to ≤ 7.9 > 7.9 to ≤ 10.0
>10.0

In addition, different papers for corrugated are in use. Depending on the corrugated board layer, linerboard or papers for medium will be used.
Linerboard are papers used for flat facing. Papers for medium are papers used for flute(s).
Linerboards and medium papers are characterised by different basis weight and technical values and are subdivided as follows:

Linerboards:

- kraftliner (e.g. brown, white) - testliner (e.g. brown, white) - schrenz - other

Medium:

- wellenstoff - semichemical pulp - other

An example of sampling

A shipment of N = 20,000 folding boxes is to be evaluated. According to Table 2, n = 80 folding boxes which should be taken completely randomly.

The sample should be distributed over the entire shipment (beginning, middle and end).

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In the sample, the following numbers of defects may be present for each defect class:

Defect class 1: Defect class 2A: Defect class 2B: Defect class 3:

no defects one defect at AQL 0.65 or two defects at AQL 1.0 three defects eight defects

Only the most serious defect in each of the folding boxes sampled is evaluated.

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3. Quality catalogue 3.1 Characteristics of the packaging material

No. Property 1 Linerboard grade

Drawing Test method

Evaluation

Visual inspection to see whether the linerboards used match the order by colour and grade (see also following page)

correct/wrong

Score

Defect class
2 A

AQL value 0.65

2 Condition of the facings
3 Flute type and flute direction in the packaging
4 Flute structure

Visual inspection for creases, blisters and other damage.

good to acceptable / 2 B

4.0

unacceptable

Visual inspection to see whether the flute type and

correct/wrong

1

-

flute direction correspond to the customer's order

(see DIN 55468-1 and following page).

Test by cutting the flute, preferably in the

correct/wrong

2 B

1.5

cover/flaps area.Exception: Effect of the ejection

rubber in the area of the creases and cutting lines.

5 Bonding of the corrugated board
6 Alignment of flute and liner

Test by tearing to see whether the adhesion is adequate (visible tear).
Visual inspection

good to acceptable 2B

-

unacceptable

1

yes/no

3

6.5

7 Flatness of the board

Flatness according to specification

yes/no

2 B

1.5

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Explanatory notes on the table
No. 1 The choice of linerboards and papers for medium is left to the manufacturer, provided that no special arrangements have been made. With regard to the colour of the linerboards used, these should be checked whether for example a required white or coloured paper has been used.
Typical variations in paper colour are caused by the manufacturing process and accordingly should not be taken into account in the visual inspection.
The surface of the linerboards used are usually machine finished (see DIN 6730). If the paper has a finished side then this will normally be placed on the outside.
No. 3 It should be tested whether the flute was delivered according to the order. For test purposes, a cut will be made on an unprinted surface cross to the flute direction, away from the edge.
There is a difference between single-wall and multiwall grades. Multi-wall grades are combinations of various flute types. Due to various processing factors, thickness of the finished board is not an indicator for the flute type, this can be referred to the flute pitch (see Table 3 and DIN 55468, part 1).
With regard to the fluting direction in the finished folding box, it should be tested to determine if the flutes direction is in line with the order. Unless agreed otherwise, flutes direction runs parallel to the slots of the box.
No. 5 Good to acceptable applies as long as the packaging's functionality is ensured.
No. 7 Warp is measured as a warp in percentage. The corrugated board sheet is laid on a flat surface with the bend facing upwards. The maximum elevation divided by the distance between the two supporting edges expressed as a percentage gives you the degree of warp.

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3.2 Converting issues Note: All data relates to the standard climate of 23 °C and 50% relative humidity.

No. Property

Drawing Test method

Evaluation

1 Structural design of the box 2 Dimensions

In line with the specification/drawing
Determination of the distance between two creasing centrelines or between a creasing centerline and the associated outer edge.
Tolerances up to 300 mm: ± 3 mm over 300 mm to 700 mm: ±4 mm over 700 mm to 1,200 mm: ± 0.6 % over 1,200 mm: as agreed
Special tolerances may be required for machine converting.

yes/no OK/not OK

3 Dimensional tolerances for die-cuts and embossments
Manufacturer's process: 3.1 rotational
Manufacturer's 3.2 process: flatbed
die-cutting

Test for deviations from specified dimensions. Tolerance ± 0.5 %, min. of ± 1 mm. The measurements are either made from creasing centerline to centreline or to the outer edge of the flat die-cut.

yes/no

Score

Defect class 1

AQL value −

2 A

0.65

2 B

4.0

2 B

1.5

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Quality characteristics and defect evaluation for corrugated