Allot Tech
Filling Nozzle Dripping and Stringing: Diagnose the Product Cutoff
A drip on the neck can become a capping, labeling or hygiene problem. Identify whether liquid continues after valve closure, hangs below a closed valve or forms a thread when the nozzle lifts. These observations lead to different checks; a drip tray only collects the symptom.
Classify the cutoff failure
| Pattern | Possible route to investigate | What to record |
|---|---|---|
| Continuous liquid after closure | Valve seating, worn seal, closing command or residual pressure | Time between command and stop; affected head |
| A delayed drop from the tip | Product trapped below the shutoff, tip wetting or nozzle geometry | Delay and location of the retained drop |
| A thread during nozzle lift | Viscosity, temperature and product break-off mechanism | Length and break point with actual product |
| Different next dose after strong suck-back | Air entry or changed product inventory in the nozzle | Bubbles and consecutive dose weights |
Inspect safely before replacing parts
Stop and isolate electrical, pneumatic and product pressure according to the machine procedure before opening the product path. Check valve seat cleanliness, seals, reassembly orientation and the recent cleaning or maintenance record. Use the specified compatible replacement parts. Never observe a moving nozzle by reaching through a guard or defeating an interlock.
Test the entire supply path
Compare the same recipe at normal and low tank levels. Record pump operation, pressure changes, hose routing and whether flexible hoses retain product under pressure. One dripping head suggests its branch or valve; all heads changing after a refill suggests a shared supply condition. A positive shutoff near the outlet may reduce retained liquid, but the product passage, particles and cleanability must still be verified.
Use suck-back as a measured adjustment
- Preserve the baseline setting and compare product cutoff without changing several parameters together.
- Adjust only within the supplier-approved range. Measure neck contamination and the following doses, not just whether the visible drop disappears.
- If air is drawn into the path, the next dose varies or the nozzle becomes contaminated, stop treating increased suck-back as an improvement.
- For stringing product, compare controlled temperature and nozzle lift timing with an appropriate break-off mechanism. Do not heat beyond the approved product process.
Specify an observable clean-cutoff requirement
Agree which surfaces must remain clean, how dripping events are counted and which products, fill ranges and container necks are included. Observe repeated starts, stable operation, stops and format changes. Record actual good output, rejects, cleanup time and every head tested. A short video with water or a fitted collection tray cannot establish clean cutoff with your sauce, oil or lotion.