The batch average must meet the nominal quantity.
A target set above nominal may help protect the average, but excessive mean bias creates avoidable product giveaway. The required setting depends on process variation and the control method.
UK measurement guide
UK packaged-goods considerations for weigh filling.
General engineering guidance on target setting, checks, records and checkweigher integration when goods are packed by weight in the UK.
Scope and responsibility
Use the machine as part of a documented quantity-control system.
A weigh filler measures or controls the dose placed into a pack, but the complete packaged-goods process also includes tare, product variation, transfer loss, sealing, inspection, sampling, records and corrective action. Machine settings alone do not demonstrate legal conformity.
For UK packaged goods made up to a predetermined constant quantity, the government guidance describes the average-system rules commonly summarised as the three packers' rules. The applicable method and tolerable negative error depend on the product, nominal quantity and regulatory context. The packer should confirm the current requirements and obtain competent legal-metrology advice where necessary.
Three-rule framework
Control the population, not only the mean display on the filler.
The UK Government guidance explains three conditions for packages produced under the average system. The wording and applicable tolerable negative error should be checked against the current official source for the nominal quantity concerned.
Only a limited proportion may fall below the defined threshold.
The threshold is linked to nominal quantity. Use the current official table and a documented sampling or checking method rather than a generic percentage.
No package may fall below the lower limit defined by the rules.
Individual-pack control and reject handling therefore remain important even where the overall average is satisfactory.
Measurement system
Define tare, reference equipment and the point of legal quantity.
- Identify whether the declared value is net weight and how tare is established and maintained.
- Use suitable checking equipment and a controlled verification or calibration process.
- Decide whether checks are made at the filler, after closing, or on the final finished pack.
- Account for product lost between the weighing hopper and the sealed package.
- Record sampling frequency, results, rejects, adjustments and corrective action.
- Protect recipe, target and feedback permissions from unauthorised changes.
- Review rules for variable-weight or catch-weight products separately from fixed nominal packs.
Legal metrology boundary.
This page provides general machinery and process guidance, not a legal determination for a particular product or packing operation. Requirements can depend on pack type, nominal quantity, marking, sales method and the equipment used for control.
The packer should use the current legislation and official guidance, involve the relevant quality and legal-metrology competence and consult Trading Standards or a specialist adviser where interpretation is uncertain.
Machine and checkweigher settings
Reduce giveaway by controlling bias and variation separately.
The filler target influences the process mean. Product flow, feeder resolution, in-flight material, hopper level and mechanical stability influence variation. Raising the target can protect against low packs but does not correct the root cause of an unstable distribution.
A finished-pack checkweigher can identify individual packs and monitor the running process after transfer and closing. Where feedback is used, it should be associated with the correct pack, delayed for the physical distance through the line and bounded so that isolated variation does not cause an unstable target response.
Before changing the target, review consecutive net weights, mean, sample standard deviation, minimum, maximum, out-of-band packs, reject operation and the tare method. Record the reason and authority for each adjustment.
Specification questions for a new line.
- Nominal quantity and all required pack sizes.
- Product, pack and tare variation.
- Applicable quantity-control system and checking frequency.
- Reference/check scale and checkweigher requirements.
- Required reject method and reject confirmation.
- Batch, recipe, audit and data-retention requirements.
- Who may change targets and feedback limits.
- Product transfer loss, spill and seal-area contamination.
- FAT and site-acceptance evidence.
Build the quantity-control method into the line specification.
Lancing can review the target, product, pack, filler, checkweigher and controls interfaces while your quality and legal-metrology advisers confirm the applicable compliance method.
Packaged-goods questions
Questions for engineering and quality teams.
Does setting the filler above nominal guarantee compliance?
No. The complete distribution, individual low packs, tare, checking system, records and applicable rules must be controlled. A high target can also create unnecessary giveaway.
Is filler calibration the same as checking finished packs?
No. Filler checks assess the dosing system. Finished-pack checks include tare, transfer, closure and any product loss or contamination after discharge.
Can an automatic checkweigher replace all sampling decisions?
It can provide valuable individual-pack and trend data, but its suitability, verification, reject controls, records and place in the legal control system must be defined for the operation.
What is the e-mark?
The official UK guidance explains when the e-mark may be used and the responsibilities associated with it. Confirm the current requirements from the government source rather than assuming that a machine feature grants eligibility.
Who is responsible for legal conformity?
The business packing or importing the goods holds the relevant legal responsibility. Machine supply and process guidance do not transfer that responsibility.