Packaging machinery question guide
Direct answer: Pouch or film seals leak when the material surfaces do not form a continuous bond across the intended seal. Common causes include product contamination, incompatible or variable film, insufficient or excessive heat, uneven pressure, inadequate dwell, wrinkles, poor tracking, damaged tooling or movement before the seal has stabilised.
Do not respond to every leak by increasing temperature. A contaminated or wrinkled seal can remain defective at a higher setting, while excess heat can distort or weaken the material.
| Factor or method | What it means | Why it matters |
|---|---|---|
| Material | Film or pouch structure, sealant layer, thickness, coating and batch. | Must be compatible with the process and proposed temperature window. |
| Cleanliness | Powder, liquid, oil, fibres, product tails and condensation. | Creates channels or prevents surface contact. |
| Process settings | Temperature, pressure, dwell, speed and cooling. | Work together; one setting cannot be assessed in isolation. |
| Tooling and tracking | Jaw flatness, contamination, wear, parallelism, film position and wrinkles. | Determines whether the whole seal receives the same action. |
| Testing | Visual check, leak test, peel or burst method, conditioning and sample selection. | Must match the actual finished-pack requirement. |
Temperature activates the seal layer, pressure brings the surfaces into contact and dwell provides time for the bond to form. The useful combination depends on material, thickness, jaw design, speed and product condition.
Change one variable at a time within the material supplier’s guidance and record actual rather than display conditions where verified measurement is available. Check both seal strength and film damage.
Product may enter the seal only on particular doses, speeds or pack positions, so the defect is not present on every cycle. The inclusion interrupts the bond or forms a channel through it.
Review dose cut-off, product drop, settling time, dust extraction, fill height and pouch handling. Retain failed packs so the product position can be compared with machine timing.
Changes in film thickness, curl, coating, registration or web tension can move wrinkles or unsupported areas into the seal. Poor tracking can also place printed or non-seal layers where the process expects the sealant surface.
Compare material batches and roll position. Confirm unwind direction, registration marks, web guides and the condition of rollers and forming parts before changing the sealing recipe.
Record material batch, machine and jaw, product condition, settings, line speed, time, stop/restart events, failure location and test result. Photograph the seal and mark orientation so repeated patterns can be identified.
Use good and failed samples from the same period. A structured record makes it possible to separate material, contamination and machine causes instead of changing several settings at once.
The final machine configuration and any compliance or performance claim must be confirmed against the actual application, samples, site conditions and agreed test method.
Send failed and acceptable packs, material information, settings and a description of the leak-test method so Lancing can help structure the next investigation.
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