If you take a blank of corrugated board and fold it without using a score line, you will notice that the fold is unpredictable, the outer liner crumples, and the edge of the panel might not be where you anticipated it. However, if you place a proper score line in the correct spot, the blank will behave in a different way. The fold will take on a specific trajectory, adjacent panels will fold together in a more controlled manner, and the resulting container will be much easier to maintain in a true shape.
The purpose of the score line is not to sever the material. Instead, it creates a space for the material to bend in a controlled manner. On paperboard, this usually takes the form of a narrow crease. In corrugated board, the score line compresses a portion of the board so that the board is able to fold with less force. You need to apply a specific amount of pressure during the scoring operation. Insufficient pressure will result in a stiff and inaccurate fold, whereas excessive pressure will result in the compression of the flutes, the destruction of the board, and the deformation of the edge of the material.
The positioning of the score line is just as important as the amount of pressure that you use during the scoring process. When a score line is located a couple of millimeters off its desired location, it can significantly alter the relationship between the various panels. Panels can fold over each other improperly, seams can become misaligned, and the entire container can become distorted. These errors are particularly difficult to spot while the blank is still unformed, because the issues do not become apparent until multiple folds interact with each other.
To get a better sense of what happens under varying scoring conditions, take a number of scraps of corrugated board and make several folds. Create one shallow score line, one more controlled, and one deliberately too heavy. Fold each of these pieces by the same angle and observe the differences. Notice how easily each piece folds, whether the surface of the liner exhibits any damage, the degree to which the flute is compressed, and whether the fold follows a linear path. By completing this experiment, you will learn far more than by merely reading about the appropriate amount of pressure to apply during scoring.
Once you have gained an understanding of the scoring process, you can move on to making a simple blank with two or three attached panels. Draw your desired panel widths accurately, mark the position of the score lines, and fold your blank. Use a square to verify whether your panels are meeting at uniform angles. If the panels appear to deviate from their desired angles, or if the panels do not close uniformly, attempt to identify the source of the error. Was your score line placed incorrectly? Was your blank cut unevenly? Or did the fold diverge from the desired crease line?
Your score lines also impact the overall dimensions of your folded product. The thickness of the board does not vanish upon folding, so the crease line dictates where each panel terminates within the assembled package. This is why the design of your blank, the scoring operation, the folding operation, and the measurement of your blank should be considered as a unified process.
A quality fold will rarely command much attention. It should allow the board to fold smoothly, enable the panels to come together predictably, and cause minimal distortion to the board’s flutes or liner. Next time you examine your folded samples, examine the corners of the container first. The condition of the folds will often indicate whether the scoring operations were performed correctly.
