BEARING CAPACITY OF BOARD BOX AND GRAIN DIRECTION

Autori

Darko Babić, Vesna Kropar –Vančina, Denis Jurečić

Grački fakultet, Getaldićeva 2, 10000 Zagreb

Abstract:

In this work 6 boards of small (250 g/m 2 ), medium (350 g/m 2 ) and higher (450 g/m 2 ) grammage and different qualities were investigated by Taber method (ISO 2493). Small and medium boxes were made from all investigated boards with grain direction parallel and perpendicular with the hight of the box. Bearing capacity of all boxes was performed by BCT method. From the obtained results of BCT tests it can be concluded that the box strengths are, almost, the same in both directions A (MD) and B (CD).

Key words: BCT test, bending stiffness, box, grain direct-ion ..

1. Introduction

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 ( Hanlon et al., 1998) . It is a common practice to make the grain direction of those small folding board boxes perpendicular to the box height, which creates large amounts of useless waste material in their production process in the graphic industry ( Brody & Marsh, 1997) . 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. This research was conducted because in avaluable literature it was immposible to find any research already done by other authors. 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.

2. Experimental

We have investigated 6 commercial boards of different qualities; 4 of the same, relatively, small grammage (250 g/m 2 ) 1 of the medium grammage (350 g/m 2 ) and 1 of higher grammage (450 g/m 2 ). The boards were produced as two- and three-layer boards, coated and uncoated composed of woodfree, CTMP and recycled fibres. Samples of all investigated boards were conditioned at 23 o C and 50 % RH before the measurement of bending stiffness (Taber 15 o , ISO 2493). Investigated boxes were made from all boards with grain direction parallel with he height of the box e.i. in grain direction (MD) marked by the letter A and with grain direction perpendicular to the height of the box e.i. in cross grain direction (CD) marked by the letter B 20 boxes of each board (10 in A and 10 in B direction) all togather 140 boxes. The boxes were produced according to the following blank design: with the height of 100 mm and the ground plan of 50 x 50 mm, with the height of 200 mm and the ground plan of 50 x 50 mm, with the height of 200 mm and the ground plan of 70 x 70 mm, with the height of 193 mm and the ground plan of 60 x 108 mm and. with the height of 160 mm and the ground plan of 60 x 227 mm. compression tester G. Acquati (Italy) was used (ISO 12048).

3. Results and discussion

Experimental results include results of bending stiffness of all investigated boards, determined by Taber method (ISO 2493) as well as, results of bearing capacity of investigated boxes performed by BCT method. During testing, the boxes were deformed up to stoping of the computer aided tester at the moment when the first plastic deformation of box was achived.

Table 1. Experimental results of flexurall stiffness of investi-gated boards in grain direction (MD) A and in cross direction (CD) B (determined by Taber method 15 o in mNm according to ISO 2493)

Table 2. Experimental results of the BCT tests

4. Conclusions

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