Core diameter (reel core)

The core diameter is the inside diameter of the cardboard or plastic tube on which rollstock is wound. The reel slides onto a shaft or mandrel on the packaging machine, so the core must match exactly.

Common sizes

• 3 inch (about 76 mm): common on small and medium VFFS and HFFS machines.
• 6 inch (about 152 mm): used for heavy, large-diameter reels, fast lines and intermediate converting steps.

Always confirm with your machine documentation.

Why it matters

The wrong core will not fit, or will wobble, causing uneven web tension, print-to-cut misregistration and seal faults. Rewinding a delivery onto new cores costs time and waste.

Specify together with

• Web width.
• Maximum outside diameter and reel weight or length.
• Unwind direction (print in or out, head or foot first), usually shown on a numbered winding chart.
• Maximum number of splices per reel and how they are marked.
• Core material: cardboard is standard; plastic may suit humid or high-hygiene areas.

Tip

Ask for reel labels showing core size, length, winding direction and design name, and store reels so cores are not crushed.