Znanstveno stručni simpozij grafičara Blaž Baromić, Senj, Hrvatska ,19. – 21. lipnja 2003; Zbornik radova


Darko Babić; V. Vančina-Kropar; B. Lajić
Faculty of Graphic Arts in Zagreb
Getaldićeva 2
10000 Zagreb


Modern food, chemical, and pharmaceutical industry pack their products in big transport corrugated board boxes, but they also use small board boxes for individual commercial packaging. It is a common practice to make the grain direction of those small folding board boxes parallel to the box height, which creates large amounts of useless waste material in their production process in the graphic industry. This adds to box prices, but it also has negative consequences for the environment protection because it increases board consumption per box. The grain direction of big transport boxes is not the issue, but if this research proves that the folding board box strength is only slightly different when different height and grain dispositions are taken into account, and if the machines used in the production process react in the same way to those box types, we might be able to recommend to the graphic industry a new way of producing such boxes. The new production system would make a better use of board sheets by changing the grain direction, which, in turn, would make the production cheaper and would be ecologically better.

Key words: BCT-test, box blanks, tensile breaking strength, grain direction


The bearing capacity of small board boxes, which are closed by sticking, is very important, especially in aesthetic way. Although all the board boxes producers know that the grain direction in these boxes is parallel with the height of the box, we have started to investigate the bearing capacity of the box with the grain direction perpendicular its height. In this investigation, the attention has not been paid to the appearance of the grooves, which could look somewhat different because of the change of grain direction, but one wanted to find out the bearing capacity of such small boxes produced from boards. The boards of 250 g/m2 of different qualities were varied. Somewhat lighter board than usually used was chosen, with the intention that the strength of the material itself participates as little as possible in the obtained result.


2.1 Materials

We have examined 4 commercial boards of nominal grammage 250 g/m2.. The boards were produced as two- and three-layer boards, composed of woodfree (virgin cellulose fibres), CTMP and recycled fibres. Only the board No 2 was coated. The structure and description of investigated boards are presented in Table 1.

Number of Board Composition Description
1 2 3
1 two-layer
upper: woodfree, coated
lower: recycled fibre, uncoated
2 three-layer
upper, lower: woodfree, coated
middle: CTMP fibre
Voluminous chromo-board
for special
3 two-layer
upper: woodfree, coated
lower: recycled fibre, uncoated
Graphic and
packaging board
4 two-layer, uncoated
recycled fibre, bleached (white)
Graphic and
packaging board

Table 1.
Structure and description of commercial board grades
(250 g/m2)

2.2 Methods

Samples of all investigated boards were conditioned at 23 oC
and 50 % RH before the measuring of basic and mechanical properties, done by using standard methods.
The following properties of boards were measured:
basic: thickness/caliper (ISO 534), grammage (ISO 536) and mechanical: tensile breaking strength and tensile elongation/tensile strain (ISO 1924/2).

Relatively small boxes were made/produced from investigated boards;
30 boxes of each board (all together 120 boxes),
15 with grain direction parallel with the height of the box, and
15 with grain direction perpendicular to the height of the box.
The grain direction (MD) was marked by the letter A and
the cross grain direction (CD) was marked by the letter B.

The boxes were produced according to the following blank design:
a) the height of 150 mm and the ground plan of 50 x 50 mm,
b) the height of 200 mm and the ground plan of 50 x 50 mm,
c) the height of 200 mm and the ground plan of 70 x 70 mm.

The box blanks were done on plotter – cutter Premium line CM 1320,
Congsberg System (Norway) and cutting of box blanks is presented in Figure 1.

Figure 1. Cutting of box blanks on plotter – cutter
Premium line CM 1320

Figure 2.
Investigated box blanks

In figure 2 some of investigated box blanks are presented.
The box blanks were glued together by hot-melt polyurethane adhesive in order to avoid, eventual, weakening of the glued connections and at the same time false results of box strengths were avoided too.

The testing of box strength was performed by the BCT method and the compression tester Acquati (Milan, Italy) was used (Figure 3).

We tested 5 boxes with grain direction (A) parallel with the height of the box and 5 boxes with grain (B) direction perpendicular to the height of the box for each board and each blank design (a, b and c).

Figure 3.
Testing of box strength by tester Acquati (Milan)

Figure 4.
The look of the box after BCT testing

During the squeezing, the boxes were deformed up to the stopping of the computer-aided tester at the moment when the first plastic deformation of box was achieved. The look of box after BCT/compression is shown in Figure 4.


From the results of thickness (20 test pieces were measured for each board) and grammage (also 20 test pieces were measured for each board) specific volume (v) was calculated for all investigated boards. The results are given in Table 2.
In the same table the results of tensile breaking strength and tensile elongation (tensile strain) of investigated boards are presented. Obtained results are mean values of 10 tests done in grain direction (A) and 10 tests in direction perpendicular to grain direction (B), as well as, standard deviations.

No of testing Board Specific
[cm3 g-1]
Grain direction Tens.
Difference of the A and B direction tensile breaking strength (%) Tens.
1 2 3 4 5 6 7 8 9
1 1 1,17 A 254,90 40,92 33,084 1,14 0,347
2 B 101,90 2,331 3,24 0,389
3 2 1,51 A 290,70 62,84 10,667 1,81 0,630
4 B 182,70 5,437 2,79 0,268
5 3 1,13 A 285,80 57,20 12,653 1,97 0,357
6 B 163,50 5,563 3,53 0,377
7 4 1,17 A 163,77 57,21 12,736 1,17 0,190
8 B 93,70 3,466 2,06 0,133

Table 2. Tensile breaking strength and tensile elongation (tensile strain) of investigated boards

The results of box strength performed by the BCT method are presented in Table 3.

1 2 3 4 5
1 1 A 50x50x150 116
2 B 94
3 A 50x50x200 120


4 B 102
5 A 70x70x200 120

96,66 (3,34)

6 B 116
7 2 A 50x50x150 220


8 B 188
9 A 50x50x200 198


10 B 168
11 A 70x70x200 222


12 B 192
13 3 B 50x50x150 108


14 A 96
15 B 50x50x200 104


16 A 84
17 B 70x70x200 102


18 A 90
19 4 A 50x50x150 98

65,53 (34,47)

20 B 64
21 A 50x50x200 84


22 B 64
23 A 70x70x200 102 68,72
24 B 70

Table 3. Results of the box strength


From the results of the measuring, shown in table 2, it can be concluded that our hypothesis proved correct and that the tested board tensile elongation is almost twice as high in the grain direction than it is transversely to them. This can be read from table 1, columns 6 and 8. It is evident from column 8, which shows the tensile elongation of board, that the elongation is always greater in the direction transverse to the grain direction. Table 2 also shows that the board tested does not differ at all from the accepted standards of the material used for the production of board folding boxes. Table 3 gives the BCT test results, according to the grain direction and the box height. We tried to establish weather the results for a bigger plan view surface and a higher box with the same plan view surface differ greatly. The analysis of table 3, column 6 shows that the smallest ratio (3.34%) was detected in the first box (dimensions 70x70x200) and the biggest (34.47%) in box 4 (dimensions 50x50x150). Other indicators and comparisons are not consistent in their results regarding the relation of the box height and strength. The results of the research focusing on the relation of the plan view of a box and its strength are equally inconsistent, so the only conclusion to be drawn from it is that the strength of a box cannot be determined by cardboard quality. This is shown by table 2, where the results for the tensile strength of different board types are the same as those given in table 4, column 2, whereas the compression strength results, given in column 3, are completely different. The general conclusion to be drawn from the research is that the compression strength of the boxes does not differ greatly in relation to the change of grain direction (34.47% at the most), which confirms our initial hypothesis. The conclusion is supported by figure 5, showing the correlations of grain directions, box

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Figure 5:
Simultaneous representation of board types and compression strength of finished boxes, according to their grain direction

dimensions, and board types. The logical continuation of the research would be the testing of the boxes in an automatic packaging machine. If the obtained results turn out to be similar to those of our research, we could advise the graphic industry to reconsider the traditional way of making cardboard boxes with fibres parallel to the box height. This would enable us to save much material, because box blanks in a cardboard sheet would be placed in such a way as to make maximum use of material and the waste quantity would be reduced, which would help protect the environment by reducing paper consumption.


Cardboard Tearing strength scale Compression strength scale
1 2 3
1 4 2
2 1 1
3 2 3
4 3 4

Table 5: Cardboard quality scales comparison

We want to thank Holding Bilokalnik Factory IPA, especially its CEO, engineer Mr. Španiček, and the head of its Central Laboratory, Mrs Franjka Stojević, engineer, who helped us greatly with the box blanks making and measuring of the results.


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