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Polymer & Plastics · Solve a Problem

Extrusion Troubleshooting & Process Diagnostics Matrix

Pick the defect you can see on the line. The matrix gives the usual root cause, the checks that confirm it and the engineering remedy — process first, material second — so a line stoppage is diagnosed before anything is reordered.

Root Cause · Why it happens

Critical shear stress exceeded at the die exit orifice due to high molecular weight resin entanglement or excessive loading of rigid fillers without sufficient rheological slip.

Diagnostic Checklist · What to check
  • Check current Die Shear Rate (γ̇) using our matrix calculator.
  • Monitor real-time melt temperature in the final barrel zones.
  • Inspect die land for build-up or scoring marks.
Engineering Remedies · The Solution
  • Increase die zone temperature by 5 °C – 10 °C to lower melt viscosity.
  • Introduce a Polyfluoropolymer Processing Aid (PPA) masterbatch at 1.0% – 2.0% LDR to coat the die land.
  • Reduce screw RPM slightly to lower volumetric output (Q).

Use this when

  • The line is running but the product is being rejected.
  • A defect returned after a resin, masterbatch or screw change.
  • You need a structured check list before calling a machine supplier.

How the number is produced

  • Each defect is mapped to its dominant root cause on blown film, pipe or compounding lines.
  • Diagnostic checks are ordered cheapest and fastest first.
  • Remedies separate a process fix from a material or additive fix.

Materials for this job

Engineering aid only. Validate against your own instrumented trial, the polymer datasheet and the applicable ASTM / ISO method before locking a process window or a specification.

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