Problem overview
Motor ampere (load) is a direct indication of how hard the screw is working to move the melt. High or rising load means the melt viscosity is higher than normal, the screw is over-fed, or there is extra resistance downstream.
Running at high load increases shear heat, which can lead to yellowing and degradation, and puts mechanical stress on the gearbox and screw.
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Use PVC Problem SolverCommon symptoms
- Ampere higher than normal at the same output
- Ampere rising slowly during the run
- Fluctuating ampere
- High load together with high melt pressure
- High load with yellowing or burnt specks
Possible causes
| What you see | Possible causes |
|---|---|
| Constant high load | High melt viscosity — low lubrication, low barrel temperature in zones 1–2, high filler loading |
| High load and high back pressure | Resistance at adapter / die — low adapter or die temperature, blocked screen |
| Load rising over time | Plate-out or build-up, screen pack clogging, rising feed rate |
| Fluctuating load | Unsteady heating; inconsistent batch weighing or mixing; irregular feeding |
| High load after formulation change | Change in lubricant balance, filler, or processing aid level |
What to check
- Feeder (dosing) speed in relation to main screw speed
- Zone 1–2 barrel temperatures and adapter / die temperatures
- Melt pressure reading
- Internal and external lubricant quantities in the formulation
- Filler loading and raw-material changes
- Heater and thermocouple condition
Processing and formulation factors
Melt viscosity
Low temperatures in the feed zones, low lubrication or high filler all increase viscosity and load.
Lubrication balance
The ratio of internal to external lubricant controls both fusion and flow. Adjusting it changes ampere — but it also affects fusion, so it should be done carefully.
Feeding
Over-feeding the screw raises load. Feeder and screw speed should be balanced.
Downstream resistance
Cold adapter or die, or a clogged screen, increase back pressure and load.
Practical troubleshooting checklist
- Compare current ampere, RPM and output with a good earlier run
- Check feeder speed vs screw speed
- Verify zone 1–2, adapter and die temperatures
- Check melt pressure and screen pack
- Review lubricant quantities batch-wise
- Change one variable at a time
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Use Grade FinderWhen to contact a technical team
- Load stays high after temperature and feeding are corrected
- You need to increase output without raising load
- High load is accompanied by yellowing or poor fusion
This guide gives general starting points. Results depend on your formulation, raw materials and machine; changes should be confirmed with controlled trials.
Frequently asked questions
Why is PVC extrusion ampere suddenly high?
Common reasons are low barrel temperature, low lubrication, over-feeding, a clogged screen, or a change in filler or raw material.
Does lubricant affect extruder load?
Yes. Lubrication balance has a strong effect on melt viscosity and therefore on motor load.
Is high ampere harmful?
Running continuously at high load increases shear heat and mechanical wear, and can lead to discolouration.
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