Recognise the symptom before changing settings
Describe what changes, where it first appears and whether it follows a product batch, packaging batch, filling head, lane, speed, temperature or time in the run. Typical observations include:
- known-good packs reject intermittently
- weights change with line speed
- adjacent packs affect each other
- results differ from a static scale
Likely causes to separate
A symptom can have several unrelated causes. Treat the following as hypotheses to test rather than a list of settings to change at once.
- insufficient spacing or pack transfer disturbance
- conveyor vibration and poor support
- airflow, hoses or guards touching the weigh section
- liquid slosh or product movement
- incorrect belt speed, filter, tare or reject timing
Check in this order
Check 1
Verify the checkweigher with approved test packs.
Check 2
Observe infeed spacing and transfer onto the weigh belt.
Check 3
Check for physical contact and vibration.
Check 4
Compare stable and disturbed products at different speeds.
Check 5
Confirm recipe, tare, filter and reject delay.
Corrective actions to evaluate
After the cause is demonstrated, select the least disruptive correction that returns the process to a safe, repeatable and approved state.
- stabilise pack spacing and transfer
- isolate the weigh section from vibration and contact
- allow product to settle or reduce speed where necessary
- restore the validated recipe and calibration
- correct reject timing after measurement is stable
Prevent the problem returning
- use routine test-pack checks
- retain recipes by pack and speed
- inspect belts and supports
- trend reject reason and head-of-line fill data together
Record evidence, not only the final setting
Capture the product and packaging batches, machine recipe, head or lane, speed, temperature, vessel level, symptom frequency, intervention and post-correction results. This creates a usable centreline and allows recurring loss to be prioritised through OEE or downtime analysis.
Common questions
What is the first check for checkweigher false rejects and unstable weights?
Verify the checkweigher with approved test packs.
What commonly causes checkweigher false rejects and unstable weights?
Common causes include insufficient spacing or pack transfer disturbance, conveyor vibration and poor support, airflow, hoses or guards touching the weigh section.
Should the machine be adjusted immediately?
Change one controlled variable at a time after the measurement method, product condition, packaging and safety state are confirmed.
When should production be stopped?
Stop and follow the site safe-isolation and escalation procedure when there is risk of injury, contamination, fire or explosion, uncontrolled product release, damaged guards, unsafe pressure or an unverified quality result.
What information should be recorded?
Record product and pack batch, recipe, machine settings, filling head or lane, time, temperature, speed, symptom, corrective action and the evidence that performance returned to the approved condition.