Where can the code be applied?
A coder can mark a controlled web before it is formed into a pack, or mark the finished pouch, bag or flow-wrapped product after sealing. Web coding can offer a stable surface and consistent print position, but the system must follow intermittent or continuous machine motion. Finished-pack coding depends more heavily on product presentation, pack shape and conveyor control.
Common applications include VFFS pillow packs, stand-up pouches, sachets, flow-wrap, HFFS packs, lidding films and printed labels. Each material family can contain different coatings, pigments, adhesives and barrier layers, so the commercial film specification—not a generic description such as “polypropylene”—should drive testing.
Laser versus TTO for flexible film
| Decision | Laser coding | TTO coding |
|---|---|---|
| How the code is made | Changes or removes part of a compatible surface layer. | Transfers ink from a ribbon onto the film. |
| Routine coding consumable | No ink ribbon; extraction filters and planned service items can remain. | Ribbon and printhead-related maintenance form part of the process. |
| Film flexibility | Every construction and colour must create a safe, readable response. | Broad film choice when the ribbon is matched to the substrate. |
| Message capability | Strong for dates, batches, serial data and proven 1D or 2D codes. | Well suited to larger, high-resolution variable text, graphics and codes. |
| Main qualification risk | Unacceptable heat effect, distortion, perforation or low contrast. | Ribbon adhesion, smudging, printhead wear or ribbon-management issues. |
| Integration | Needs beam access, guarding, extraction, focus and correct synchronisation. | Needs a suitable bracket and platen/roller arrangement for machine motion. |
Which laser source should be tested?
CO₂ can interact effectively with many coated, printed and organic packaging surfaces, but thin films may need careful wavelength and energy control. UV sources are frequently assessed for heat-sensitive or recyclable mono-material films because the interaction can be confined close to the surface. Selected fibre sources may work with particular pigments, foils or engineered layers.
Choose the source after the mark mechanism is proven. A system that makes an attractive stationary sample may not have enough marking time at peak web speed, and a fast sample is not acceptable if it weakens a barrier or seal area.
What should the qualification trial check?
- Every film variant: include supplier, colour, print and recycled-content changes.
- Real code content: test the densest date, batch, barcode or 2D message.
- Normal and peak speed: reproduce the available marking time and machine motion.
- Pack integrity: define acceptable appearance, seal, strength and barrier checks.
- Registration: confirm the code stays within the reserved artwork area.
- Extraction: assess fumes and particles from all marked layers.
- Changeovers: prove recipes, focal adjustment and operator message selection.
Oxford Traceability can use the film, code artwork and line information to structure a representative sample marking trial.