Coding sachets and stick packs
Sachets and stick packs are normally coded while the packaging material is flat and controlled inside the packing machine. Printer choice depends on film structure, intermittent or continuous movement, available print window and the position of seals and artwork.
Code the flat web inside a controlled print window
The printhead must complete the message while the film is in the correct position. On an intermittent machine the web may stop for the print; on a continuous machine the printer must synchronise with moving film.
Film and artwork
Identify the laminate, outer printable surface, colour, coating, treated side, repeat length and any supplier variation. The approved print area should be clear of seals, folds, tear notches and critical artwork.
Machine movement
Record web direction, intermittent dwell or continuous speed, acceleration, registration mark, tension, tracking and the available distance between printhead and downstream contact.
Message and verification
Provide the full date, batch, lot, text, barcode or 2D content at its final size. Define whether approval is visual, scanner-based, verified or inspected inline.
Technology routes for sachet and stick-pack lines
| Route | Where it can fit | Critical checks |
|---|---|---|
| Thermal transfer overprinter | High-quality dates, batches, logos, barcodes, QR or DataMatrix on compatible flexible films; intermittent and continuous variants are available in the verified T30/T50 range. | Printhead width, print length, film movement, ribbon, host-machine mounting, encoder or trigger, cassette access and final symbol quality. |
| Hot foil coder | Simple repeated date or batch text on suitable intermittent packing machines where the small print area and type-based process are acceptable. | Dwell, heat, pressure, ribbon, type change, film support, legibility and position relative to sealing. |
| Thermal inkjet or other inkjet | May be considered where the film or finished pack can be presented with a controlled print gap and suitable ink. | Ink adhesion and drying, print distance, web or pack movement, downstream contact and line integration. |
Protect the code through forming and sealing
A print that looks good on flat film can be distorted, scuffed or hidden when the pack is formed.
- Map the finished sachet or stick pack back onto the flat web and mark the seal, fold, cut and registration areas.
- Check whether the code crosses a curve, gusset or high-tension area after forming.
- Allow ribbon or ink to cool or dry before contact with rollers, forming shoulders, belts or product.
- Run the printed film through the complete machine cycle and inspect the finished pack.
- Test representative product fill and sealing conditions where they can affect the surface or code.
Use the full worst-case job
The longest batch, date or variable-data message can change the print time and printed area. A small demonstration date may pass even when the production barcode, QR code or multi-line text does not fit the available window.
Review the verified T30 and T50 TTO data against the host-machine cycle before selecting the printhead width and mode.
Sachet coding trial sequence
1. Identify film
Record supplier, material structure, surface, colour, artwork version and reel orientation.
2. Print full jobs
Run the largest human-readable and machine-readable messages using the proposed ribbon or ink.
3. Make finished packs
Pass the coded web through forming, filling, sealing and cutting at the agreed production movement.
4. Inspect after handling
Check position, legibility, adhesion, rub, scanning and any effect from heat, pressure, product or pack flexing.
Information for a sachet or stick-pack quotation
Send a reel or sufficient cut film for a representative trial, plus finished empty and filled packs if available. Mark the intended code position on both the flat web and finished pack.
Provide the packing-machine make, model, web width, film direction, registration repeat, cycle or film speed, intermittent dwell, available mounting space and controller signals.
Supply the complete message and every important variant. State how dates and batches are calculated, whether barcodes or 2D codes use GS1 data and whether the printer receives data from an operator, PLC or business system.
Describe changeover frequency, ribbon or consumable access, cleaning limits, guarding and the expected response to printer not ready, missed print or failed inspection.
Sachet and stick-pack coding FAQs
Which coding machine is used for sachets and stick packs?
Thermal transfer overprinting is often assessed for high-quality variable data on flexible film, while hot foil can suit simpler intermittent duties. The packing-machine motion, film and message determine the final choice.
Should the code be printed before or after the sachet is sealed?
Printing on the controlled flat web before final forming or sealing is often the most stable route. The exact mounting point must avoid seal areas and provide safe access without affecting the packaging process.
What film sample is needed for a coding trial?
Provide production film from the final supplier and print batch where possible, including all colour and coating variants. Mark the intended code position and supply the complete worst-case message.
Can a barcode or QR code be printed on a sachet?
It may be possible using a suitable printer and symbol size, but film movement, contrast, distortion, quiet zones and final-pack handling must be tested. The finished pack should be scanned or verified as required.
What packing-machine information is needed?
Provide the make and model, intermittent or continuous motion, film speed or cycle, web width, registration method, available mounting space, print window, controls signals and photographs or drawings of the web path.
Test the real film on the real packing cycle
Send production film, the full code artwork and the packing-machine details so Lancing can assess the print window and trial route.