Direct answer
Choose a checkweigher from the smallest weight difference that must be classified reliably at normal line speed, not from capacity alone. Prove dynamic repeatability with real packs, specify product spacing and stabilisation, match the reject to the pack, and define challenge tests, reject confirmation and data records.
Define the inspection task
State what the checkweigher must detect: underfill, overfill, a missing component, a count error or a process trend. Record nominal pack weight, tare variation and the smallest unacceptable difference.
The required task determines performance. Detecting a missing leaflet in a heavy carton can be more difficult than rejecting a clearly underfilled lightweight pouch.
Measure the dynamic production conditions
Record pack length, width, height, centre of gravity, belt contact, liquid movement, product settling, required spacing and sustained line speed. Vibration, drafts, unstable transfers and touching packs can reduce weighing performance.
Provide normal and worst-case packs for trials, including tare extremes and product distributions.
Specify classification and reject performance
Agree the decision limits, repeatability evidence and the expected false-reject risk. Match air blast, pusher, drop, diverter or stop-and-alarm action to pack mass, fragility and speed.
A complete system should confirm that the reject device operated and that the non-conforming pack entered a secure reject area. Define full-bin, low-air and failed-reject responses.
Plan records and process feedback
Decide whether the checkweigher is only a final inspection or also provides feedback to the filler. If feedback is used, limit correction speed and magnitude so individual outliers do not destabilise the process.
Record recipes, user changes, tests, alarms, rejects and batch summaries according to the site’s quality and legal requirements.
Information to prepare
- Nominal product and gross-pack weights
- Tare distribution and smallest defect to detect
- Pack dimensions, stability and spacing
- Minimum, normal and maximum line speed
- Required repeatability and classification evidence
- Reject method, confirmation and secure collection
- Recipe, audit and production-data requirements
Packaging Automation UK
Inspection, conveying and line-control integration around packaging machinery.
Official references
Check the current source before relying on dates, thresholds or legal duties.