Pulp Moulding Machine Troubleshooting: Causes & Fixes

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Problems on this page:

Parts with thin spots or holes Part weight varying Parts warping after drying Parts sticking in the mould Dryer energy use too high Vacuum pump faults Tool changeover slow Pulp preparation problems

Parts with thin spots or holes

Hits OEE: Quality

Symptoms: Moulded trays or packs have thin areas or holes and fail strength checks.

Forming mesh blocked or damaged

Clean the forming screens and repair torn mesh.

Slurry consistency too low

Check the consistency of the pulp slurry against the recipe.

Vacuum during forming too weak

Check the vacuum level at each forming tool.

Forming time too short

Check the dip or forming time setting.

Prevention: Part weight and strength checked on samples each hour.

Part weight varying

Hits OEE: Quality

Symptoms: Moulded parts weigh more or less than the specification.

Slurry consistency unstable

Check the consistency control and the mixing in the stock tank.

Vacuum varying between tools

Check the vacuum at each tool and the vacuum lines.

Forming time changed

Compare the forming time with the recipe.

Fibre furnish changed

Check the raw material against the specification.

Prevention: Part weight recorded on samples each hour.

Parts warping after drying

Hits OEE: Quality

Symptoms: Parts warp or shrink unevenly after the dryer or hot press.

Drying uneven across the oven

Check the oven temperature profile and airflow.

Hot press temperature or pressure wrong

Check the press settings against the recipe.

Moisture left in the wet part too high

Check the transfer vacuum and the wet part moisture.

Tool surfaces worn

Check the press tools for wear.

Prevention: Flatness and dimensions checked on samples.

Parts sticking in the mould

Hits OEE: Availability

Symptoms: Wet or pressed parts stick to the tool and tear on transfer.

Transfer blow-off air weak

Check the blow-off air pressure and timing.

Mesh or tool surface dirty

Clean the tool surfaces.

Release agent missing where it is used

Check the release agent dosing.

Transfer timing wrong

Check the timing between forming and transfer tools.

Prevention: Torn parts counted per tool.

Dryer energy use too high

Hits OEE: Performance

Symptoms: The dryer uses more gas or electricity per part than it used to.

Wet parts carrying too much water into the dryer

Improve dewatering at forming and transfer, and check the vacuum there.

Dryer insulation or doors leaking heat

Check the insulation and door seals for gaps.

Exhaust damper open too far

Check the exhaust setting so humid air leaves without dumping heat.

Burner tuning drifted

Have the burner combustion tuned.

Prevention: Energy per part recorded weekly.

Vacuum pump faults

Hits OEE: Availability

Symptoms: The vacuum pumps trip or lose capacity, and forming gets weak.

Seal water supply low

Check the seal water flow and temperature to each pump.

Fibre carried over into the pump

Check the separators and their drains ahead of the pumps.

Pump worn

Measure the pump output against its curve.

Leaks in the vacuum lines

Find and repair leaks at joints and valves.

Prevention: Vacuum level trended per forming tool.

Tool changeover slow

Hits OEE: Performance

Symptoms: Changing forming and press tools takes long, and the first parts after the change are scrap.

Next tools not cleaned and staged

Clean, inspect and stage the next tools before the run ends.

Tools moved without a lifting aid

Use a lifting aid or tool cart; tools are heavy and the press tools are hot.

Settings not stored per product

Store the forming time, vacuum and press settings per product.

Tool alignment found by trial

Use locating pins or marks so tools seat in the same place every time.

Prevention: Changeover time recorded per tool change.

Pulp preparation problems

Hits OEE: Quality

Symptoms: Lumps, fibre bundles or contaminants in the slurry show up as defects in the parts.

Pulping time too short for the raw material

Check the pulping time and the rotor condition in the pulper.

Screens worn or bypassed

Inspect the screens and replace worn baskets or plates.

Raw material dirtier than usual

Check incoming bales and agree the quality with the supplier.

Agitator in the stock chest stopped or weak

Check the agitator so the slurry stays mixed.

Prevention: Slurry checked for lumps and contaminants each shift.

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

Related equipment guides: pulper · vacuum pump · industrial oven · hydraulic press · thermoforming machine

Stop the same fault coming back

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