Define the result before requesting a figure
“Fill accuracy” must refer to a stated measurement and operating condition
A useful accuracy requirement identifies what is being checked, the product state, the bottle format, the fill setting, the sampling point and the acceptance rule. Delivered volume, net mass and visible fill level are related, but they are not interchangeable. A bottle can show a different visible level because of internal geometry or manufacturing variation even when the delivered quantity is unchanged. A mass check can also require an agreed density basis before it is converted into volume.
Separate quantity, mass and visible level
| Requirement | What it describes | Evidence needed |
|---|---|---|
| Delivered volume | The volume placed into the bottle under the agreed product and machine conditions | Measurement method, equipment, product temperature, sample sequence and treatment of bubbles or foam |
| Net mass | The product mass after allowing for the container or tare | Tare method, scale suitability, product loss, evaporation or residue, and whether density conversion is required |
| Visible fill level | The apparent height of product in the finished bottle | Bottle internal geometry, transparency, normal bottle variation, settling time and viewing method |
| Headspace or brimful relationship | The space remaining above the product or its position relative to a pack feature | Reference point, bottle variation, closure displacement and the time at which the observation is made |
Define the dose range as a set of production conditions
Record the minimum, normal and maximum fills that will actually be manufactured. For each setting, identify the product, bottle and planned rate. A wide nominal range does not by itself confirm that one dosing component or one calibration method will be practical across every format. The minimum dose may expose priming, retained-volume or resolution effects, while the largest fill may be limited by product flow, foam, available cycle time or bottle headspace.
Control product condition during verification
Temperature can alter viscosity, flow and density. Mixing, recirculation or product replenishment can introduce air. Settling or separation can change the material presented to the filler during a batch. Record the condition expected in production and use it during the trial. Where a substitute medium is proposed, state which parts of the final performance cannot be confirmed until the production product is available.
Use a representative sampling sequence
- Samples after the machine is primed and the accepted production state is reached
- Samples at the minimum, normal and maximum fills
- Samples from the first accepted bottles after a planned stop or restart
- Samples after product replenishment or a normal supply interruption
- Samples before and after a recipe, bottle or dosing-part change
- Separate recording of rejected, reworked or non-representative bottles
Include the bottle in the measurement review
The usable neck opening can change nozzle choice and product entry. Flexible walls can affect tare or handling. A transparent bottle can make level variation commercially important even where quantity is acceptable. Supply several samples of each materially different format so bottle variation is not mistaken for dosing variation. Identify the least stable bottle and the format with the smallest opening or most restrictive shoulder.
Write a result that can be repeated
The acceptance record should identify the machine setup, product batch or condition, bottle and closure, fill setting, measurement equipment, sampling sequence, calculation method and treatment of outliers or non-production events. It should also state whether start-up and restart bottles are part of the accepted sequence. This allows the same test to be understood during a supplier trial, factory acceptance and site acceptance.