What are Die Plate, Bleed, Creasing, and Die Cutting? Packaging Design Terminology Explained

What Is a Die-Cutting Plate

A die-cutting plate, also known as a die board, is a steel-rule die used in the die-cutting process. The designer unfolds the box structure into a flat layout, and the technician inlays steel blades into a wooden or resin board according to the layout. The steel blades are arranged along the box's contour and crease lines, forming a complete die-cutting plate.

A die-cutting plate typically contains two types of lines: cutting lines (which cut through the paper) and creasing lines (which create folds without cutting through). These two types of lines must be clearly distinguished on the plate; otherwise, batch defects will occur where "the parts that should fold get cut, and the parts that should cut only get creased."

In the era of digital die-cutting, there is also a laser die-cutting plate, where steel blades are cut directly into the resin board by a laser engraving machine. It offers higher mounting precision and is suitable for small-batch, multi-variety custom packaging box applications.

What is Bleed

Bleed is the safety margin that extends the design artwork beyond its edge, typically 3mm. The reason is that die-cutting has a tolerance of ±1-2mm; if the background color of the design only reaches the trim line, any die-cutting offset will result in white edges.

The standard practice is: all color blocks, text on solid backgrounds, and background images that need to extend to the full page must extend at least 3mm beyond the trim line. This 3mm extension area is the bleed area. When designers deliver files, they must ensure that the content within the bleed area is complete.

Bleed and "safe margin" are two different concepts: bleed extends outward to prevent content from being cut off; the safe area is inset 3-5mm inward to prevent critical content (such as brand logos, text) from being too close to the edge where it could be cut off or worn away by finger contact.

What Is Scoring

Scoring is the process of pressing a fold line into paper so that the paperboard can be folded neatly along a predetermined position. On the die-cutting plate, a score line is made with a blunt-tipped scoring rule (a rounded steel wire), not a cutting blade.

The width and depth of score lines have strict parameters: if too shallow, the board cannot be folded and the paper will crack at the fold; if too deep, the paperboard will break at the score line and the box will open during transportation. Common empirical values are a score depth of about 0.4mm for 250g coated paper, about 1.0mm for E-flute corrugated paper, and about 1.5mm for grey board paper.

The score line should typically be ≥3mm from the edge of any printed content; otherwise, the breaking of paper fibers at the score line will cause the printed layer to crack, resulting in white cracks on the finished product.

What is Die-Cutting

Die-cutting is a process that uses a die to cut desired shapes on printed materials. The die-cutting machine presses the die onto the substrate, where the steel rule cuts through the material under pressure, while the creasing rule creates fold lines, forming the shape in a single operation.

Key die-cutting parameters include: die-cutting speed (1500-4500 sheets per hour), die-cutting pressure (adjusted according to paper grammage), and die-cutting accuracy (qualified within ±0.3mm). Offset coated paper, E-flute corrugated paper, grey board paper, self-adhesive labels, etc. can all be die-cut.

Die-cutting is typically followed by a "waste stripping" process, where excess paper edges cut during die-cutting (called "waste edges" or "matrices") are removed manually or by an automatic waste stripping machine, leaving the formed box blanks. Box blanks for irregular-shaped boxes, handle boxes, and drawer boxes are all formed through die-cutting and waste stripping.

The Relationship Between the Four Terms

To summarize the relationship in one sentence: bleed is reserved on the design draft → the process engineer creates a die based on the flat layout → the cutting blades on the die cut out the box shape, and the creasing blades press the fold lines → the die-cutting machine completes cutting and creasing in a single pass → after waste removal, the box blank is obtained.

When procuring, if you only receive a flat layout drawing, you cannot determine the die parameters. The most reliable approach is to ask the supplier to provide die-cut samples or actual box blanks, and verify each cutting line and creasing line against the flat layout.

Common Misconceptions

Myth 1: The more bleed margin, the better. Excessive bleed actually wastes paper and increases die-cutting difficulty; a standard of 3mm is sufficient.

Myth 2: Crease lines can be deepened arbitrarily. Creases that are too deep will cause the board to crack, while those that are too shallow will not fold properly; precise adjustment should be made according to the paper's grammage.

Myth 3: The higher the die-cutting precision, the better. Precision is affected by paper material, equipment, and operation, with ±0.3mm being the common industry standard; excessive pursuit of precision will drive up costs.