Nozzle selection
Balance bore, position and cut-off.
Read the guide →Finished-pack cleanliness
How do you avoid container-neck contamination during paste filling?
Avoid neck, rim and thread contamination by controlling nozzle alignment, fill position, cut-off, product pressure, container movement and target headspace. Diagnose when the contamination appears before changing the capper or adding a stronger nozzle.
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Diagnosis
Find the first point at which product reaches the closure area.
Inspect incoming empty packs, the fill itself, nozzle withdrawal, conveyor transfer and cap application. A clean pack at the nozzle that becomes smeared later needs a different correction from a tail deposited during filling.
| When contamination appears | Likely factors | Evidence to capture |
|---|---|---|
| During discharge | Nozzle centring, splash, trapped air, excessive speed or poor fill position. | Close side and top video of the real pack. |
| At nozzle withdrawal | Stringing, delayed drip, excessive gap or withdrawal timing. | Stop-motion or slow video through closure and movement. |
| During transfer | Overfill, low headspace, unstable container or abrupt guides. | Pack level and conveyor behaviour through the next station. |
| At capping | Product already on threads, cap contact, tilted pack or closure presentation. | Pack inspection immediately before and after cap application. |
Buyer question
Why does product reach the neck, rim or threads?
Common causes are off-centre filling, excessive drop height, splashing, overfill, a product tail, delayed drip, trapped air, container movement or insufficient headspace. The root cause should be identified at the first contaminated point.
Do not rely only on the final capped pack. Inspect the empty container and each transfer stage so a filling fault is not confused with a capping or handling fault.
Buyer question
How does nozzle position affect contamination?
A nozzle too high can increase free fall and tail movement, while one too low can contact the pack, restrict displaced air or become coated in the rising product. Lateral misalignment can put product directly onto the rim.
Set height and centring with production containers and tolerances. Where the nozzle dives, verify the motion and safe clearance over repeated cycles.
Buyer question
Can suck-back or shut-off solve every neck-contamination problem?
No. Shut-off and suck-back can improve a tail or delayed drip, but they do not correct overfill, poor alignment, container instability, feed pressure or air escaping through a narrow opening. Excessive suck-back can also affect dose or pull air into the tip.
Treat nozzle closure as one part of the complete fill profile and prove it after a normal production stop.
Buyer question
How does container motion contribute to smearing?
A container can tilt, bounce or move before the product tail has broken, causing the strand or filled surface to contact the rim. Abrupt conveyor acceleration and close spacing can also move an overfilled product into the closure area.
Record nozzle closure and container release in the same video. Adjust timing, guides, acceleration and headspace as a system.
Buyer question
How should cleanliness acceptance be defined?
Define which surfaces must remain free of product, how many sequential packs will be inspected, the conditions of the run and what happens after a stop and restart. Use photographs or a reference pack where visual judgement could differ.
The acceptance method should include both fill quantity and presentation, because a correctly dosed pack can still be unsuitable for sealing, capping or labelling.
Related questions and guides
Continue the specification with the next practical decision.
Use the related pages to connect this answer to product trials, machine selection and a quotation-ready application.
Anti-drip behaviour
Diagnose pressure, shut-off and delayed drips.
Read the guide →Line integration
Control transfer and capping after filling.
Read the guide →Need to solve neck or rim contamination?
Send production packs and a continuous video from nozzle discharge through capping, together with fill level, product temperature and current line settings.