A wall thickness inspection record is the written trail of every bottle you measure. For each bottle it should name the bottle type and mould cavity, the marked points you measured, the reading at each point, whether the gauge passed its daily check, who ran the test, and whether the bottle passed or failed.
Why does a wall thickness inspection record matter?
Blow-moulded bottles do not have a uniform wall. The neck, shoulder, body, heel and base stretch differently, so a single average reading hides the thin spots that cause drop or top-load failures.
Industry voluntary methods for plastic containers treat wall thickness as a profile across distinct regions, not as one number for the whole bottle. The record is how you prove which bottle, which point and which reading led to a pass or a fail.
Without those fields, two labs can measure the same bottle type and still cannot compare results.
Which fields belong on every bottle row?
Keep one row per bottle, or one row per marked point if your plan requires it. The fields below are the ones a later review still needs.
| Field | What to log |
|---|---|
| Date and time | When the bottle was measured |
| Bottle type / SKU | The design or drawing the bottle belongs to |
| Mould and cavity | Which mould and which cavity made the bottle |
| Lot or run | The production lot or shift run |
| Measurement points | Each marked location, described by zone, not by a size |
| Reading at each point | The value shown on the gauge at that point |
| Minimum on that bottle | The thinnest reading found on the scan |
| Gauge and ball in use | Instrument identity and which target ball was selected |
| Calibration status | Daily check pass, or that a multi-point calibration was run |
| Operator | Who measured and who reviewed |
| Disposition | Pass, fail, or hold, against your predetermined limits |
Acceptance criteria come from the interested parties for that bottle, not from a universal wall-thickness number. Write the limit you used next to the disposition so the row stays readable later.
How should you describe measurement points?
Mark the bottle before you measure. Voluntary methods for plastic containers ask you to mark the desired test locations from the container design and the parties' specifications, then measure at those marks.
On a typical bottle, log points by zone rather than by a length from the base.
- Neck or finish, where threads and sealing surfaces sit
- Shoulder, where the neck opens into the body
- Body or panel, at more than one height and around the circumference
- Heel, where the body meets the base
- Base or push-up, including any known thin corners
Our guide to how to measure bottle wall thickness walks through placing the target ball inside and scanning the wall on the probe tip. For where HDPE walls usually run thick or thin, see HDPE bottle wall thickness.
Want a wall-thickness check on bottles like yours? Tell us your test requirements. We source similar samples, run the test and send you the video. No need to ship samples.
What calibration and setup details belong in the record?
A reading means little if the gauge was not checked that day. Before the first bottle, verify calibration of the equipment, then note the result on the record or on a linked daily-check sheet.
For a Hall-effect gauge, also log which target ball the instrument was set to. The probe reads the magnetic effect of that ball, so a mismatched ball identity makes every later reading unreliable.
If the daily check against a known shim is outside tolerance, run a multi-point calibration and write that on the record before you continue. Our calibration chapter covers ball identification, the daily check and multi-point calibration for the MTG-100.
Keep bottles at a consistent age and condition within one comparison set. Mixing freshly blown bottles with aged stock on the same sheet makes the disposition hard to defend.
How does a Hall-effect gauge support the inspection record?
A Hall-effect thickness gauge measures wall thickness without cutting the bottle. A steel target ball sits inside; a magnetic probe touches the outside; the gauge reports the gap between them as wall thickness.
Because the bottle stays intact, the same unit can go back to the line or into a retain sample after you finish the row. Live maximum, minimum and average functions help you capture the thinnest point of a scan for the record.
Our MTG-100 Hall-effect thickness gauge is built for non-destructive wall and base checks on non-magnetic bottles and containers. Use the hold function when you need a steady value to write down.
Frequently asked questions
Is one thickness reading enough for a bottle?
No. Voluntary methods for plastic containers measure distinct regions, and optional destructive checks even split the bottle into shoulder, panel and base. One body reading can miss a thin heel or shoulder.
Can I leave calibration off the bottle sheet if it is in a separate log?
You can point to a daily-check log, but the bottle row still needs a clear link: which gauge, which ball, and that the check passed before this lot. Otherwise a later audit cannot tie the reading to a verified instrument.
Get a test video for your bottles
Tell us your test requirements, such as the material, the size and the test you need. We source similar samples here, run the test on the instrument you are looking at and send you the video. No need to ship samples.
Questions about a model or a test? Email Amy Zhao, Export Manager, at [email protected].