Sachet machinery buyer guide

Sachet Film and Seal Guide for Reliable Filling Production

A sachet machine can only make a reliable pack when the film structure, forming geometry, product and sealing process are compatible. Film should therefore be treated as an engineered component of the line, not as a generic consumable.

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Sachet Film and Seal Guide for Reliable Filling Production

1. Start with the finished-pack requirement

Define the product’s moisture, oxygen, aroma, light and chemical sensitivities; the intended shelf life; distribution conditions; opening method; print quality; recycling or material-policy constraints; and any food-contact or sector-specific documentation required by the project.

The packaging converter can then propose a structure. The machine supplier must verify that the proposed structure forms, tracks, seals and cuts on the selected equipment.

2. Understand the functions within a laminate

A flexible laminate may combine an outer printable layer, one or more barrier or strength layers, adhesive or tie layers and an inner heat-seal layer. The exact construction controls stiffness, friction, puncture resistance, barrier, sealing temperature and compatibility with the product.

Do not approve film from a shorthand description alone. Obtain the complete structure, total thickness, tolerances, sealant identity, coefficient-of-friction data where relevant and a technical data sheet.

3. Match film to the forming and web path

Film stiffness and slip affect how the web passes over rollers and around the forming shoulder. A material that is too soft, too stiff or inconsistent can wrinkle, wander or resist forming. Reel width, core size, winding direction, maximum diameter and splice method must fit the unwind system.

For printed film, specify the eye-mark size, contrast, pitch and position. The registration sensor needs a consistent target outside distracting artwork.

4. Establish a seal operating window

A usable seal window combines temperature, dwell time and pressure. The line must create an adequate seal at production speed without distortion, burn-through, sticking or damage to the product. Jaw surface, pattern, alignment and cooling can materially affect the result.

Record settings during trials, but do not treat one temperature value as universal. Actual interface temperature, ambient conditions, machine speed, jaw mass and film batch can change performance.

5. Protect the seal area from product contamination

Powder dust, liquid tails, sauce strings and granules trapped across the jaw can create leak paths. Control methods include extraction, anti-drip nozzles, product cut-off, settling delay, sachet length, fill height and correctly timed jaw closure.

The filler, forming set and seal jaws should be evaluated together. Increasing jaw temperature rarely solves a seal contaminated by product and can damage the laminate.

6. Define seal and pack tests

Agree practical acceptance tests such as visual inspection, peel or burst testing, vacuum or pressure leak testing, dye penetration where appropriate, drop testing and storage trials. The chosen method should reflect the failure mode and the pack’s end use.

Sampling frequency, acceptance limits and measurement equipment belong in the production quality plan. Retain traceable film and pack samples from acceptance trials.

7. Control converter specifications and incoming material

Approved artwork does not replace a technical film specification. Set tolerances for reel width, print repeat, registration position, gauge, winding, joins, telescoping, blocking and core condition. Identify how non-conforming reels will be quarantined and reported.

Any change in resin, adhesive, layer thickness or manufacturing site may affect machine behaviour and should pass the agreed change-control process.

8. Build a film-to-machine handover pack

Keep the approved structure, safety and compliance documents, reel drawing, artwork, registration details, sealing trial report, machine recipe, jaw drawings and quality checks together. This reduces troubleshooting time and protects repeatability when film is reordered.

Good practice: reserve enough production-grade film for factory acceptance testing, commissioning and operator training. Laboratory samples or hand-made reels may behave differently on the machine.

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Common questions

Frequently asked questions

Can any heat-sealable film run on a sachet machine?

No. Reel dimensions, stiffness, friction, forming behaviour, sealant, print registration and product compatibility must all suit the machine and application.

Why do sachet seals leak intermittently?

Common causes include product contamination, unstable temperature, insufficient dwell or pressure, jaw misalignment, wrinkles, inconsistent film and unsuitable sealant.

Who should approve the film?

The product owner, packaging converter and machine supplier should jointly confirm product protection, compliance, machinability and seal performance.

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Get my machine recommendation for your application

Send the product, target dose, sachet dimensions, film and required output. Lancing Ltd will review your application and recommend a practical machinery route before a detailed quotation.

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Troubleshooting framework

Connect each seal failure to product, film, machine and test conditions

A leaking sachet is not automatically a temperature problem. Wrinkles, contamination, registration, pressure, dwell, cooling, jaw alignment and laminate variation can produce similar symptoms. Record the conditions before changing several settings at once.

Observed issue	Checks to make before adjustment
Intermittent channel leak	Look for powder, particles, liquid smear, film fold, print or coating variation, jaw damage and whether the fault occurs after stop-start or refill.
Weak seal across the full width	Confirm the correct heat-seal layer, jaw temperature measurement, pressure, dwell, speed, cooling and film orientation.
Wrinkled cross seal	Check film tracking, forming alignment, web tension, product bulge, static, jaw parallelism and whether the film is pulling during closure.
Print or cut out of position	Check eye-mark contrast and location, print repeat, photocell setup, web slip, film stretch and the correction limit.
Tear notch damages the seal	Confirm notch position, cutting tool, laminate response, seal width and distance from product and printed code.
Seal passes warm but fails later	Define cooling and conditioning before test, product migration, internal pressure, transport simulation and the selected integrity method.

Seal trial protocol

Establish an operating window rather than one successful setting

Fix the inputs

Use identified product and laminate batches, the approved sachet drawing, declared fill temperature, dose, speed, registration and coding setup. Record ambient conditions where they could affect the film or product.

Challenge normal variation

Include start-up, stable running, stop-restart, product refill and the upper intended output. For multi-lane machinery, sample each lane rather than mixing results.

Apply the agreed test

Condition packs as required, apply the pack owner’s visual, dimensional, strength or leak-test method and retain labelled samples with machine settings and results.

The test method and pass criteria must be appropriate to the product, laminate, seal design and distribution risk. This guide does not prescribe one universal leak test.

Build the full trial plan Add the film data to the RFQ

Additional buyer questions

Film, sealing and leak-test questions

What film data should the converter provide?

Request laminate structure, thickness, reel width and core, winding direction, print repeat, eye mark, sealant layer, normal tolerances and any storage or conditioning requirements.

Why should a seal window be tested at more than one setting?

A single point can fail when speed, product temperature, film batch or ambient conditions change. A practical operating window gives production room to remain stable.

Should leak tests be performed immediately after sealing?

That depends on the chosen method and pack system. Some tests need a defined cooling or conditioning period. The timing should be written into the acceptance procedure.

Can a good empty-pack seal prove filled-pack performance?

No. Product contamination, internal pressure, fill temperature and sachet shape can alter the seal. Filled packs should be tested under representative conditions.

Define the project around your product and pack

Send the laminate, sachet drawing and pack-integrity requirement

Provide the film specification, reel and artwork data, product and fill temperature, seal pattern, tear feature, coding, output and intended test method. Lancing Ltd can include these inputs in machine and trial planning.

Get my machine recommendation Call 01494 623015

Protect the proven film and seal process

Put every film substitution through a controlled change review

A replacement reel described only as the same size or thickness is not necessarily equivalent on the machine. Changes to the laminate, sealant, surface, print, reel geometry or converter tolerance can alter tracking, registration, heat transfer, jaw release and pack integrity. Record the approved material and define what evidence is required before a substitute enters production.

Proposed film change	Questions for the change review	Evidence before approval
Laminate construction	Are the layers, barrier function, adhesive system and product-contact sealant unchanged, and is the new construction suitable for the product and intended pack life?	Converter specification, material identification and filled-pack trials using the agreed integrity method.
Sealant layer or sealing response	Does the material seal, release and cool within a usable window at the proposed production condition, including normal stops and restarts?	Recorded machine settings, labelled samples across the agreed window and documented seal or leak-test results.
Thickness and stiffness	Does the web form, track, fold and cut consistently without creating wrinkles, curl, registration drift or a changed finished-pack shape?	Dimensional checks, run video, web-tracking observations and samples from start-up and stable operation.
Surface friction, coating or treatment	Could the change affect unwind, forming, jaw release, static, coding adhesion or movement through downstream guides and counters?	A representative line run that includes coding and the actual discharge or secondary handling route.
Reel, core and winding	Are reel width, maximum diameter, core, splice, winding direction and print orientation compatible with the installed unwind and web path?	Incoming-material check against the approved reel specification and confirmation on the machine.
Artwork, ink and registration mark	Are repeat length, eye-mark contrast, code zone, seal clearance, tear feature and cut position unchanged across converter tolerances?	Approved artwork and web drawing plus registration, code and cut samples from the production-intent reel.

Keep a controlled approved-film record

Link supplier, construction, reel data, artwork revision, trial reference, machine recipe and retained samples under one material identity. A purchasing substitution can then be checked against the film that was actually proven.

Separate machine evidence from pack-owner approval

The machine trial can show forming, sealing, registration and filled-pack behaviour under recorded conditions. The pack owner remains responsible for selecting the integrity method and confirming product compatibility, barrier and shelf-life requirements. Use the trial and acceptance guide to keep those decisions traceable.

Do not release a substitute film solely because one empty sachet seals successfully. Confirm the production-intent product, film, machine condition and the agreed pack test.

Record a film-change trial Review VFFS film interfaces

Film change control

Treat a new laminate, converter or print repeat as a controlled process change

Two reels that look similar can behave differently in forming, tracking, sealing, coding and integrity testing. Preserve the material identity and trial evidence behind the approved machine settings.

Material comparison	Record structure, thickness, sealant layer, surface, friction/handling information, barrier declaration, reel/core, winding and supplier data.
Artwork comparison	Check web width, print repeat, eye mark, lane pitch, code area, seal/cut relationship and revision—not only the visible design.
Machine trial	Run forming, tracking, registration, coding and sealing over the intended speed/stop conditions using the actual product.
Seal-window review	Establish an approved operating range through the agreed method; do not copy a single temperature from another laminate without testing.
Pack evidence	Retain identified accepted and failed packs, integrity results, settings, reel references and observations from start, refill, pause and restart.
Release and revision	Authorise the material and recipe together, then control later substitutions and artwork changes through the site quality system.

For food applications, the film supplier and food business should confirm material suitability and current food-contact requirements for the intended use. See the Food Standards Agency food-contact-material guidance. A machinery trial confirms runnability and the sealing process; it does not replace migration, shelf-life or regulatory assessment.

Prepare the pack and web specification Plan print registration Define seal and integrity checks