Fold Line

/ˈfoʊld laɪn/

General Definition

The Fold Line consists of graphic lines defined within the packaging structural map (Dieline) that pinpoint the exact location where the packaging material (such as paperboard or corrugated board) must be bent or folded in a controlled manner during final assembly. The primary purpose of the Fold Line is to transition the flat two-dimensional structure into the final three-dimensional packaging shape. Unlike cut lines, these lines do not separate the material but merely indicate the precise folding location for the operator or assembly machinery.

Real-World Usage

In the production process, the Fold Line is physically created through the Creasing operation, where controlled pressure is applied to the material to produce a clean, non-cracking crease on the printed surface. These lines are crucial, especially in collapsible packaging or lock-up boxes. If the Fold Line is not correctly defined in the Dieline file or is inaccurate during production, the final packaging will not close properly, its locks will fail to engage, or it will exhibit an irregular appearance, resulting in an inferior product.

The importance of the Fold Line during design is evident in maintaining the Safe Area; the designer must ensure that no critical text is positioned near these lines, as it would lose legibility upon folding. Furthermore, the folding sequence and direction, as indicated by these lines, directly impact the speed of final product assembly at the factory, and any geometric error in these lines will disrupt the assembly process.

Consultant's Note

Our expert consultation focuses on the precise distinction between the terms Fold Line and Creasing. The Fold Line is simply the name the designer uses in the graphic file to indicate the folding point, while Creasing is the industrial process that enables that folding through physical pressure application. In essence, every Creasing operation facilitates a Fold Line in the final product. While the designer typically defines the fold lines in the Dieline file with a 0.5-point graphic stroke, the actual blade thickness (Creasing Rule) is determined by the paper or board thickness and can range from 2 to 6 points (approx. 0.7 to 2.1 mm). This choice is made by the die-maker based on necessity and approval. It is these changes in thickness and the various errors in printing and die-cutting that make the Safe Area so critical in design.

Designers must ensure the Fold Line in the Dieline file is defined with a unique Spot Color and is distinct from the cut lines. This color separation serves as a visual rule for the lithography operator and die-maker, allowing them to easily distinguish the function of each line and prevent the accidental substitution of creasing lines with cutting blades. Additionally, for packaging involving multiple material types or thicknesses (e.g., window patches), separate folding instructions for each material must be provided.

Aligned with: ESKO ArtiosCAD / Packaging Structural Standards / Die-Cutting Process