What should be paid attention to when mounting paper? When mounting face paper onto grey board, the grain direction of the grey board and face paper should be as consistent as possible: intersecting grains can easily cause warping and deformation; this is especially noticeable in large-area mounting. Check the flatness of the mounting paper after a few days to see if the grain is even.
How should fold lines be arranged? Fold lines should follow the grain direction: folding with the grain results in smooth folding and is less prone to cracking, while folding against the grain easily leads to bursting and cracking. The V-grooves and die-cutting lines after mounting grey board should also take the grain into account. Incorrect fold line direction is a common cause of mass cracking.
What is the relationship between stiffness and grain? The stiffness of cardboard has a clear directionality: stiffness is better with the grain, and more flexible against the grain. The load-bearing direction of the box should match the grain to prevent the lid from collapsing. Matching stiffness involves arranging the grain according to “where the stress is applied.”
How to avoid cracking? Folding against the grain carries a high risk: widening the pressure grooves, adjusting the die-cutting lines, and using more flexible face paper are all remedial measures; however, the fundamental solution is to correctly determine the grain direction during cutting. Check for cracking by folding ten times and observing each time.
How to calculate cutting? The grain direction (groove direction) must be marked during cutting and layout: this must be specified on the die-cutting diagram, quotation, and production order; different grains require different amounts of paper, directly affecting cost and waste. Confirm the grain marking with the packaging factory before placing the order.
The same piece of cardboard folded horizontally and vertically yields completely different results: cracking, warping, and collapse—many problems stem from the grain. This article clearly explains the grain of cardboard for packaging boxes, making it easy for customers making gift boxes and color boxes to learn.
What is grain? Cardboard is composed of fibers, which are arranged along the machine direction during papermaking: the direction along the fibers is called the “grain direction,” and horizontal is called “reverse grain.” The grain direction determines the bending characteristics and crease appearance of the cardboard.
