Troubleshooting / Depositor

Depositor Troubleshooting

The most common depositor problems on the plant floor, with the likely causes and the fix for each. Part of the OEE Lab troubleshooting directory.

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Problems on this page:

Deposit weight variesTailing or stringingDripping between depositsDeposits in the wrong placeProduct not feeding from the hopperInclusions jamming the valvesLeaking sealsFaults after cleaning and reassemblyProduct skinning or drying in the hopper

Deposit weight varies

Hits OEE: Quality

Symptoms: Deposits are heavier or lighter than the target and vary from nozzle to nozzle.

Air trapped in the hopper or product
Keep the hopper level steady and deaerate the product where needed.
Valves or piston seals worn
Replace worn seals and valves.
Product viscosity changing with temperature
Hold the product temperature steady.
Nozzles not balanced
Check each nozzle and clean partial blockages.

Prevention: Deposit weights checked per nozzle at start-up and every hour.

Tailing or stringing

Hits OEE: Quality

Symptoms: Product strings between the nozzle and the deposit and lands on the tray or the edge.

Cut-off not clean
Adjust the cut-off or the nozzle valve timing.
Suck-back setting too low
Increase the suck-back.
Product too cool or too thick
Check the product temperature and recipe.

Prevention: Deposit shape checked on the first trays of each run.

Dripping between deposits

Hits OEE: Quality

Symptoms: Drops fall from the nozzles between cycles.

Nozzle valve worn
Replace the valve or the nozzle seal.
Suck-back not working
Check the suck-back setting and mechanism.
Hopper pressure too high
Check the hopper level and any pressurisation.

Prevention: Nozzle seals replaced on a fixed schedule.

Deposits in the wrong place

Hits OEE: Quality

Symptoms: Product lands off centre in the tray, cup or on the belt.

Timing to the conveyor wrong
Reset the timing for the line speed.
Nozzles misaligned
Align the nozzle bar.
Trays or cups not located
Check the tray guides and indexing.

Prevention: Deposit position checked at each changeover.

Product not feeding from the hopper

Hits OEE: Availability

Symptoms: The hopper has product but deposits are short or missing.

Product bridging in the hopper
Use an agitator or adjust the product consistency.
Hopper level too low
Keep the level within the working range.
Inlet valve blocked
Clear and check the inlet valve.

Prevention: Hopper level control checked at start-up.

Inclusions jamming the valves

Hits OEE: Availability

Symptoms: Fruit pieces, nuts or chips jam the valves or are cut up.

Valve type not suited to particles
Use a valve designed for particulates, such as a rotary valve.
Particles larger than the nozzle allows
Check the particle size against the nozzle.
Particles not evenly mixed
Keep the product mixed in the hopper.

Prevention: Particle size checked on each raw material lot.

Leaking seals

Hits OEE: Quality

Symptoms: Product leaks from the pistons, valve bodies or hopper joints.

Seals worn or damaged
Replace the seals on a schedule.
Seals fitted wrongly after cleaning
Follow the reassembly sheet and check the seals.
Cleaning chemicals attacking seals
Check seal material against the cleaning chemicals.

Prevention: Seal inspection at each reassembly.

Faults after cleaning and reassembly

Hits OEE: Availability

Symptoms: The depositor does not run correctly after cleaning.

Parts swapped between heads
Mark parts so each goes back to its own position.
Missing O-rings or seals
Count the seals at strip-down and reassembly.
Valves not timed after reassembly
Run the timing check before production.

Prevention: A reassembly checklist signed off before production.

Product skinning or drying in the hopper

Hits OEE: Quality

Symptoms: A skin or dry lumps form on the product in the hopper and end up in the deposits.

Hopper left uncovered on long runs
Fit and use the hopper lid between refills.
Product held in the hopper too long
Make smaller batches so product is used within its hold time.
Hopper jacket too hot for the product
Check the jacket temperature setting for sugar or chocolate based products.

Prevention: Hopper hold times written into the work instruction for each product.

Guidance only. Always follow lockout/tagout and your site's safe-work procedures, and verify against OEM manuals before acting.

Related equipment guides: mixer / agitator · industrial oven · spiral conveyor · progressive cavity pump · filling machine · proofer · enrober · cooling tunnel · dough divider · chocolate tempering machine

Stop the same fault coming back

Recurring depositor stops usually trace to a cause you cannot see by hand. The partner we recommend is Fabrico: it tracks OEE and downtime live from PLCs, IoT sensors or AI cameras; where cameras are fitted, the video of a stop sits next to its machine data so the cause can be reviewed; and a technician opens the work order from the stop in the same system. Data is hosted in the AWS EU region, and Fabrico and the company behind it hold ISO/IEC 27001, ISO/IEC 20000-1 and ISO 9001.

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Related tools: full troubleshooting directory · OEE calculator · downtime cost · MTBF / MTTR · glossary

Methods that cut recurring stops: the six big losses · root cause analysis · preventive vs predictive maintenance · TPM · SMED & changeover