Crease line: The "invisible skeleton" of paper product forming

In the production workshop of a cardboard box factory, the metal wheels of the creasing machine roll at a constant speed, leaving a uniform depth creasing line on the surface of the cardboard. This seemingly simple mark is actually the key to the formation of the paper product. The crease line is not a randomly drawn mark. It is a "guide line" precisely calculated based on the packaging design dimensions. Its depth and width form a strict matching relationship with the material and thickness of the cardboard. The crease depth of corrugated boxes is usually controlled at 1.2 to 1.5 millimeters, which not only ensures the smoothness during folding but also prevents the cardboard from breaking. The crease lines on the cover of hardcover books need to be shallower and thinner to ensure flexibility when flipping through.

In industrial production, the precision of the creasing line directly determines the pass rate of packaging. When the cardboard is folded along the crease line, the force on the fibers is concentrated on the preset trajectory, effectively reducing wrinkles and damage at the folded corners. In the field of express packaging, standardized creasing lines can enable cartons to be formed quickly and improve packaging efficiency. In food packaging, it ensures the airtightness of the packaging box and prevents food from deteriorating due to irregular folding. This "invisible skeleton" may seem insignificant, but it builds a bridge from flat cardboard to three-dimensional containers in the chain of modern packaging industry.

With the popularization of environmental protection concepts, creasing line technology is also adapting to new materials. In view of the loose fiber structure of recycled cardboard, engineers adjusted the texture and pressure of the creasing wheel to reduce the creasing depth while ensuring the folding performance. This not only reduced material loss but also maintained the practicality of the packaging. The existence of the indentation line is essentially a manifestation of "precise control" in industrial production. It achieves a balance between function and efficiency with a tiny trace.