Section 6 of 8
Rollstock Specifications
Web width, repeat, diameters, core, splices, eye mark, COF, sealing and unwind direction: what your packaging machine needs.
| Parameter | What it is | Usual value |
|---|---|---|
| Web width | Total width of the roll, edge to edge. | Defined by the pouch layout on your machine: perimeter plus longitudinal seal on vertical or horizontal form-fill-seal. Tolerance is confirmed per project (typically ±1 mm). |
| Repeat length | Length of each print (one pouch) in the unwind direction; matches the distance between eye marks. | Equal to the pouch length. Limited by the circumference of the printing cylinder, which is why it is fixed before engraving. |
| Maximum outside diameter | Largest roll diameter your machine's unwind accepts. | Common values from 300 to 500 mm (12 to 20 in); a larger diameter means fewer roll changes. Tell us your equipment's limit. |
| Core diameter | Inside diameter of the cardboard core the film is wound on. | 76 mm (3 in) is standard; 152 mm (6 in) on some machines. It must match your unwind shaft. |
| Weight and length per roll | Net film weight and approximate length per roll. | Calculated from web width, gauge and outside diameter. State the maximum weight your operator or lift can handle. |
| Splices | Film joints inside a roll, resulting from roll changes during printing or lamination. | A maximum per roll is agreed (for example up to 2) and each splice is flagged with a visible colored tab on the roll edge so the operator can remove it. Splices are made without losing registration. |
| Unwind direction | Which side of the film faces out (print outside or inside) and the orientation of the design as it leaves the roll. | Indicated with the standard eight-position diagram or a photo of your machine; it depends on how the tube is formed (see below). |
| Eye mark (registration mark) | Printed mark that the machine's sensor reads to cut and seal in the right place. | Dark, high-contrast rectangle (typically black on a light or white background) at the film edge, on the order of 10 × 5 mm, one per repeat, at the position your machine requires. |
| Coefficient of friction (COF) | How easily the film slides over itself and over the metal of the forming collar (static and dynamic). | For machine forming, a controlled and relatively low COF is targeted (on the order of 0.2 to 0.4 dynamic film-to-film); it is adjusted with slip additive in the sealant layer. A high COF stalls the film on the forming collar. |
| Sealability and treatment | Temperature, pressure and dwell time at which the inner layer forms a hermetic seal; corona treatment for printing and laminating. | PE seals over a wide window at moderate temperature; CPP and RCPP require higher temperatures. The seal window and seal strength (N/15 mm) are specified. Cold seal is available for heat-sensitive products. |
| Packaging and delivery | How the roll arrives at your plant. | Rolls bagged or stretch-wrapped, on pallets, standing or lying down depending on weight, protected from dust and moisture; each roll carries an identification label (product, lot, length, weight and unwind direction). |
Unwind direction.
Unwind direction states which side of the roll carries the print (facing out or facing in) and how the design comes off the roll: foot or head of the pouch first, to the right or to the left. A roll wound the wrong way prints upside down on the machine or cannot be formed at all, and there is no way to correct it once it has been manufactured.
To specify it, use the standard eight-position diagram that comes with the technical data sheet, or send us a photo or a section of the roll you run today marked with the direction the film comes off. If you change machines or forming collars, check it again before repeating an order. When in doubt, we define it together on the first sample.
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