Troubleshooting / EPS moulding machine

EPS Moulding Machine Troubleshooting

The most common EPS moulding machine 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:

Poor bead fusionPart density off targetParts shrinking or warpingLong cycle timesParts sticking in the mouldPentane gas build-upSteam supply problemsBead conveying problems

Poor bead fusion

Hits OEE: Quality

Symptoms: Moulded parts break between the beads or crumble at the surface.

Steam pressure or time too low
Check the steam pressure at the mould and the steaming time against the recipe.
Beads aged too long or too short after pre-expansion
Check the bead ageing time in the silos.
Condensate in the steam
Check the steam traps and drain on the steam line to the machine.
Mould steam vents blocked
Clean the vents in the mould.

Prevention: Fusion checked by breaking sample parts each shift.

Part density off target

Hits OEE: Quality

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

Pre-expansion density varying
Check the pre-expander steam and time settings and the bead density after pre-expansion.
Mould not filling completely
Check the fill injectors and the fill air pressure.
Mould cavity worn or damaged
Inspect the mould and its vents.
Raw bead grade changed
Check the bead grade against the specification for the part.

Prevention: Part weight checked on samples each hour.

Parts shrinking or warping

Hits OEE: Quality

Symptoms: Parts shrink, bow or swell after demoulding.

Cooling time too short
Check the cooling and vacuum time in the cycle.
Vacuum during cooling weak
Check the vacuum level reached during cooling.
Moisture left in the parts
Check the cooling step and the drying of parts after moulding.
Steaming too long
Compare the steam settings with the recipe.

Prevention: Dimensions checked on samples each shift.

Long cycle times

Hits OEE: Performance

Symptoms: Cycle times grow, and output per shift falls.

Vacuum system weak
Check the vacuum pump, tank and valves, since cooling depends on vacuum.
Cooling water too warm
Check the cooling water temperature and flow to the mould.
Steam supply slow to reach pressure
Check the steam supply and accumulator.
Parts sticking at ejection
Check the ejection air and the mould surface.

Prevention: Cycle time trended per mould.

Parts sticking in the mould

Hits OEE: Availability

Symptoms: Parts stick to the mould or break during ejection.

Mould surface dirty or coated
Clean the mould surface and its vents.
Ejection air pressure low
Check the ejector air supply.
Parts still soft at ejection
Check the cooling time and vacuum.
Mould damaged
Repair damaged mould areas that hold the part.

Prevention: Sticking and broken parts recorded per mould.

Pentane gas build-up

Hits OEE: Availability

Symptoms: Gas detectors alarm, or pentane from the beads builds up in silos or enclosed areas.

Ventilation in the moulding or storage area weak
Check the ventilation rates in the areas where beads are stored and processed.
Bead silos not vented
Check the silo vents and their outlets.
Ignition sources near the beads
Control hot work and electrical equipment in classified areas; pentane is flammable.
Gas detectors not working
Test and calibrate the gas detectors on schedule.

Prevention: Gas detectors tested on the schedule the site sets.

Steam supply problems

Hits OEE: Availability

Symptoms: Steam pressure at the machine drops during the cycle, and fusion suffers.

Boiler output too low for the demand
Check the boiler capacity against the peak demand of all machines.
Steam traps failed
Test the traps on the supply line.
Steam accumulator not recharging
Check the accumulator pressure between cycles.
Control valves sticking
Service the steam control valves on the machine.

Prevention: Steam pressure at the machine logged.

Bead conveying problems

Hits OEE: Availability

Symptoms: Beads block in the conveying lines or the mould does not receive enough material.

Static charge holding beads in the lines
Check that conveying lines are earthed.
Conveying air too weak
Check the blower and its filter.
Beads bridging in the silo
Check the silo outlet and its agitation.
Damaged or kinked lines
Repair damaged conveying lines.

Prevention: Conveying stops recorded.

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

Related equipment guides: steam boiler · vacuum pump · silo / hopper · injection moulding · compressed air system

Stop the same fault coming back

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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