Overview #
Flat pouches and sachets sit at the intersection of barrier engineering, print precision, and high-speed converting — and the margin for error at each stage is narrow. A laminate structure that looks correct on paper can fail at the seal jaw if the heat-seal layer is mismatched to the sealant film, or delaminate in transit if the adhesive coat weight was under-specified. This guide walks through our production process from substrate selection through final QC, with the machine parameters and inspection thresholds we actually run on our converting lines. It is most relevant to brand partners in food, nutraceuticals, personal care, and single-serve consumer goods who are specifying flat pouches or sachets for the first time or moving production to a new OEM supplier.
Laminate Structure Selection and Substrate Specification #
The laminate stack is the first decision we lock down with every brand partner, because it drives every downstream process parameter. For a standard dry-food flat pouch, our default structure is PET 12µm / adhesive / AL foil 9µm / adhesive / CPP 70µm — total caliper approximately 105–115µm. For sachets requiring moisture barrier only (no light block), we substitute the foil layer with VMPET 12µm, which reduces total caliper to 85–95µm and cuts material cost by 15–20% without sacrificing WVTR performance for most ambient-shelf applications.
The critical barrier parameters we verify against before confirming a structure:
| Structure | OTR (cc/m²/day) | WVTR (g/m²/day) | Typical Application |
|---|---|---|---|
| PET / AL / CPP | < 0.01 | < 0.01 | Coffee, pharma, high-fat snacks |
| PET / VMPET / CPP | 0.5–1.5 | 0.3–0.8 | Dry snacks, powder sachets |
| PET / PE | 80–120 | 8–15 | Non-barrier sachets, wipes |
| BOPP / CPP | 150–200 | 3–6 | Confectionery, ambient dry goods |
| Kraft / PE | N/A | 10–20 | Eco-positioned sachets, tea |
OTR and WVTR values are tested per ASTM F1927 and ASTM F1249 respectively. For food-contact structures, all sealant films we specify comply with FDA 21 CFR §177.1520 (polyolefin resins) and EU Regulation 10/2011 on plastic materials in food contact. We do not accept laminate rolls from our film suppliers without a migration test certificate for food-grade jobs.
Adhesive coat weight for dry lamination runs at 3.0–4.5 g/m² (dry weight) on our Nordmeccanica laminators. Below 2.8 g/m² we see bond strength drop below 1.5 N/15mm — the minimum we accept for pouches that will go through form-fill-seal at the brand’s packing line. Above 5.0 g/m² the adhesive can bleed at the web edge and contaminate the seal zone.
Printing Process Parameters and Register Control #
We print flexible pouch substrates on 8-colour rotogravure presses at web speeds of 150–200 m/min for standard jobs, stepping down to 120 m/min for fine-detail work or metallic ink layers. Gravure is our default for flexible packaging runs above 50,000 linear metres — the ink laydown consistency at speed is simply not replicable on flexo for high-coverage designs with tight colour tolerances.
Colour management follows the G7 Master Qualification methodology. Our press operators target a ΔE of ≤ 2.0 against approved Pantone-referenced colour standards on every production run. For brand colours where the Pantone reference falls outside the CMYK gamut — which happens frequently with saturated oranges and certain blues — we specify a spot ink mix and run it as a fifth or sixth colour station rather than attempting a process-colour approximation that will drift run-to-run.
Register tolerance on our gravure lines is ±0.15mm in the machine direction and ±0.20mm cross-web. For sachets with a tear notch or euro-slot that must align to a printed panel, we tighten the cross-web spec to ±0.10mm and add a 100% vision system check at the press delivery. Misregister above 0.3mm is visible to end consumers on fine-line designs and is a rejection trigger in our inline QC protocol.
Ink adhesion is tested per ASTM D3359 (cross-cut tape test) at the start of each press run and after any ink or substrate roll change. We require a minimum rating of 4B — any result below 4B stops the press for corona treatment verification. Our standard corona treatment target on PET film is 42–44 dynes/cm, measured with dyne test pens at roll receipt and again at the press unwind.
Heat Sealing, Slitting, and Converting QC #
Heat sealing is where most flat pouch failures originate — not in the laminate structure, but in the seal jaw parameters. On our pouch-making machines (Totani and CMD equipment), we run seal jaw temperatures between 160°C and 200°C depending on the sealant film. CPP seals at 160–175°C; LLDPE requires 175–190°C; for retort-grade CPP the jaw temperature goes up to 195–205°C. Dwell time is 0.8–1.2 seconds at production speed.
We validate every new job with a seal strength test per ASTM F88 — our minimum acceptance threshold is 25 N/25mm for food pouches and 35 N/25mm for retort applications. Seal width is specified at 8–12mm for standard flat pouches; below 6mm we see seal integrity failures under drop-test conditions (ISTA 2A protocol, 1.0m drop height).
Our inline QC checkpoints on the converting line:
- Seal integrity: 100% hot-tack pull test on first 500 pouches of each run, then AQL 2.5 sampling per ISO 2859-1 for the remainder
- Dimensional check: Length ±1.0mm, width ±0.8mm, measured every 250 pouches
- Tear notch position: ±0.5mm from print register mark, 100% vision check
- Pinhole detection: Offline dye-penetration test on 5 pouches per 10,000 units for foil-laminate structures
Slitting is done on automatic tension-controlled slitters at 200–250 m/min. Slit edge quality is inspected under 10× magnification — any feathering or delamination at the slit edge triggers a blade change and a 100% re-inspection of the affected reel.
Specification Notes for Brand Partners #
When you brief us on a flat pouch or sachet project, the first things we need are: product type and fill weight, required shelf life and storage conditions, and whether the pouch will run on your own FFS line or be pre-made and hand-filled. These three inputs determine the laminate structure, sealant film selection, and whether we need to build in a specific seal-jaw compatibility profile.
The most common brief mistake we see is brands specifying a “foil pouch” without defining the barrier requirement. Aluminium foil adds cost and weight — if your product only needs WVTR < 1.0 g/m²/day, a VMPET structure will meet the spec at lower cost and is easier to recycle. We will always challenge the brief on this point and provide a barrier comparison before confirming the structure.
Our typical process: digital colour proof in 3–5 working days, physical laminate and seal sample in 10–15 working days, production lead time 20–28 working days after sample approval and purchase order. Gravure cylinder engraving adds 8–12 working days to the first-order timeline and is amortised across the run — we provide cylinder cost transparency upfront.
Frequently Asked Questions #
Q1: What is the minimum laminate bond strength you accept before a pouch job goes to converting?
A: Our minimum bond strength threshold is 1.5 N/15mm, tested after dry lamination curing. Any laminate reel measuring below this value is quarantined and re-laminated — we do not convert sub-spec material because weak bonds will propagate to seal failures on the brand’s FFS line.
Q2: What is your MOQ and lead time for flat pouches with custom gravure printing?
A: Our standard MOQ for gravure-printed flat pouches is 50,000 units per SKU. Production lead time after sample approval is 20–28 working days. First-order timelines include 8–12 working days for gravure cylinder engraving, which we quote separately and transparently.
Q3: How do you ensure food-contact compliance for your laminate structures?
A: All sealant films used in food-contact pouches comply with FDA 21 CFR §177.1520 and EU Regulation 10/2011. We require migration test certificates from our film suppliers for every food-grade material lot and retain these on file for customer audit. For products sold in both the US and EU, we specify materials that satisfy both frameworks simultaneously.
Q4: Can you produce sachets with both a tear notch and a resealable zipper on the same pouch?
A: Yes — we run zipper insertion inline on our Totani pouch machines. The zipper profile adds 3–5mm to the top seal zone, so we adjust the overall pouch height accordingly. Tear notch position is held to ±0.5mm from the zipper track via vision-system registration, ensuring the consumer tear opens cleanly above the zipper without cutting into it.
Q5: What causes delamination in transit and how do you prevent it?
A: The most common cause is under-cured adhesive — dry lamination adhesive requires 40–48 hours at 45–50°C in our curing oven before the bond reaches full strength. If a reel is slit and converted before full cure, the bond strength reads acceptable at ambient temperature but fails under the flex stress of FFS machine handling. We enforce a mandatory 48-hour cure hold on all laminate reels before they are released to the converting line, with cure time logged per reel ID.
Planning a packaging project? Contact our team to request a complimentary specification review and sample quote.
On the VMPET substitution — we’ve had issues with the metallisation layer surviving the lamination nip on structures below 90µm total caliper, particularly when running water-based adhesive at elevated cure temperatures. What coat weight are you specifying on the adhesive layer between the VMPET and CPP?
The 9µm foil spec is spot on — we went down to 7µm once to hit a cost target and had pinhole failures show up in OTR testing within the first production batch.
Watch the CPP thickness spec closely — we’ve seen converters swap 70µm for 60µm CPP to hit cost targets, and the seal strength on a standard 3-side sachet dropped enough to fail our 1.2 bar burst test.
The VMPET swap is real but that 15–20% material saving can quietly disappear if your laminator isn’t dialed in — we saw adhesive coat weight creep up to 3.8 g/m² on the VMPET runs versus our 3.2 g/m² spec on foil structures, which ate about half the savings at volume.