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Uneven PET Bottle Wall Distribution: Qualification Trial Review
Review PET bottle wall distribution by agreed measurement positions, cavity and preform lot, then verify the applicable bottle functions.
What to establish first
Use the agreed bottle-assessment method to map the variation, then compare preform, mold and process records. Visual appearance alone cannot qualify wall distribution or establish the cause of a local weak area.
Three checks before a change
- Identify the preform specification, material lot, mold cavity and approved bottle drawing. Compare current samples with the qualified reference.
- Record the actual approved heating and blowing sequence with the machine specialist. Relate the observed pattern to cavity, time and material changes.
- Evaluate the defined bottle functions and distribution criteria with the packaging team. Verify a supported correction using controlled, traceable samples.
Interpret the observed pattern
| Observed pattern | Next review |
|---|---|
| Local thickness varies but mass is unchanged | Keep the agreed location map and individual measurements. Total bottle mass cannot establish how material is distributed at the required functional regions. |
| Pattern follows one cavity or preform lot | Link samples to cavity, material and approved operating records. Ask packaging and equipment owners to define a controlled comparison before copying another format’s settings. |
| Thickness improves but bottle function fails | Retain the functional result and revise the trial assessment. Approval must cover the applicable package requirements, not thickness alone. |
Evidence to record
Use these fields as a worksheet. Keep individual results and comparison samples; an overall average alone may hide the affected condition.
| Record item | Required evidence |
|---|---|
| Preform and material lot | Identify the exact format, lot and document revision; attach a representative sample or record. |
| Mold cavity and drawing | State the location, method, instrument and operating condition so a comparison can be repeated. |
| Process record and sampling time | Link the observation to an individual sample and a common timestamp; retain both normal and affected cases. |
| Agreed bottle-assessment results | Record the approved assessment, action, verification result and responsible person; keep unresolved items visible. |
Controlled trial and acceptance
Agree the observation, affected boundary and acceptance method before starting a trial. Identify the product-package combination, approved settings and responsible equipment or quality owner. A test must have a clear question and a controlled disposition for trial material.
Compare the existing and proposed condition with identified samples using the same measurement basis. Change only what the responsible owner has authorised. Include the relevant steady-running, stop or restart case; one passing sample does not establish repeatable operation.
Keep results, samples and configuration revisions together. Record what passed, what remains open and the exact approved scope. If a correction moves the defect to another process step or compromises another acceptance requirement, retain that result and continue the assessment.
Common question
Can changing the preform weight alone solve every weak-wall pattern?
Material, geometry and the qualified process must be reviewed together. A weight change needs its own trial and does not identify the original cause.
Technical reading
The linked manufacturer material provides engineering context. This worksheet is an independently written diagnostic framework; the installed equipment’s approved instructions and the site’s product acceptance determine the actual procedure and limits.
China Beverage Machinery is operated by Allot Tech (Suzhou) Co., Ltd. for machinery sourcing, configuration planning and export project coordination.