Direct answer
First determine whether the problem is quantity, visible presentation or both
Bottles can show different liquid heights even when the dispensed quantity is similar because internal volume and shape vary. Conversely, equal-looking levels can contain different quantities. A structured diagnosis records the measurement method, bottle identity, product condition, nozzle channel, machine state and time after filling before any adjustment is made.
| Observed symptom | Possible area to check | Evidence |
|---|---|---|
| Level varies but mass is stable | Bottle internal geometry, wall shape, meniscus or reading position | Matched bottles, mass result and timed visual check |
| One head differs | Calibration, air, valve, tubing, seal, nozzle or channel setting | Head-coded samples and swap/inspection record |
| All heads drift together | Product temperature, supply level, pressure, density or machine setting | Time series with product and supply conditions |
| Restart bottles differ | Priming, settling, pressure recovery or product in the nozzle path | Separate start, stop and restart samples |
Why can bottles look uneven when the dispensed quantity is correct?
Internal bottle volume, shoulder shape, wall thickness, base shape and mould variation can change liquid height. The meniscus and viewing angle also influence a visual check. If presentation matters, specify a separate level tolerance or use a fill-to-level principle where suitable rather than assuming quantity control will create an identical appearance.
What can make one filling head behave differently from the others?
A single head can differ because of calibration, trapped air, hose length, restriction, valve wear, seal condition, nozzle geometry, channel setting or product distribution. Identify samples by head before adjusting the whole machine. If the symptom follows a component after an approved swap, that evidence helps isolate the cause.
All inspection and maintenance must follow the manufacturer’s safe isolation and service procedure.
Can trapped air or bubbles distort a fill check?
Yes. Air can change apparent volume, disrupt pump priming, create foam or continue releasing after the bottle leaves the filler. An immediate visual or volumetric check may therefore differ from a result taken after a defined settling period. Record when the sample is measured and whether bubbles are part of the accepted product condition.
How can product-feed conditions cause fill variation?
Changing product level, pressure, temperature, viscosity, pump speed, return flow or tank agitation can alter the supply presented to the dosing system. Some filling principles are more sensitive to particular changes than others, but none should be evaluated without a defined production supply condition.
Compare trial and production arrangements. A machine calibrated from a small gravity-fed vessel may behave differently when connected to a long pipe run or production pump.
Why should restart bottles be assessed separately?
Restart bottles can expose loss of prime, pressure recovery, nozzle drips, product settling or recipe sequencing that is not visible during continuous running. Record the first agreed number of bottles after a normal start and after representative planned or fault stops. Decide in advance whether they are accepted, checked or rejected.
What evidence should be recorded before adjusting the filler?
- Product, temperature and supply condition
- Bottle batch and individual sample identity
- Nozzle or channel number
- Machine recipe and relevant settings
- Start, steady-run, stop or restart state
- Quantity or mass result, visible level and measurement time
- Foam, bubbles, drips and neck condition
Change one controlled factor at a time where practical and keep the previous accepted setting available. Continue with the maintenance and troubleshooting guide when the evidence indicates wear, restriction or a recurring mechanical fault.