A method has been developed to evaluate the quality of the board used in the manufacture of corrugated boxes. This method can be used by the board manufacturer to monitor and minimise damage occurring during the board and box manufacturing processes. The MD shear stiffness of corrugated board has been shown to be a good measure of damage to the fluted medium in corrugated board. It has also been used as an indicator of the general performance of the corrugated box. This new method of measuring shear stiffness is based on torsional stiffness and is quick, reliable and repeatable. The torsional parameter is termed "Dynamic Stiffness" and the instrument called a "Dynamic Stiffness Tester" (DST). The board torsional stiffness has been shown to be directly proportional to MD shear stiffness. The method does not use any electronic equipment that requires calibrating and is therefore very reliable in the field. The corrugated board test sample is 25mm wide with testing span of 100mm. This sample size allows selective testing of areas of a corrugated box that, for example, may have been damaged by excessive pressure during printing. The torsional measure is not significantly affected by the sample squareness and off-axis mis-alignment can be up to 20° without any appreciable change in results. The dynamic stiffness is proportional to the width of the sample and a sample cutting template has been designed to keep this variation to a minimum. The tester has been used to measure the shear stiffness variability over the width of a corrugator and the damage caused by excessive pressure during printing. This paper outlines the theory behind the tester, gives typical results for a range of corrugated board grades and demonstrates the effect of various degrees of board damage.
展开▼
