At a glance
- Check material condition and process history before changing multiple machine settings at once.
- PA6 moisture control is a frequent troubleshooting starting point because the polymer is hygroscopic.
- Defects such as splay, flash, short shots and warpage can have several different causes.
- Supplier processing guidance and the actual grade TDS should define the acceptable operating window.
Move from visible defect to a controlled processing check
- 01Describe the defect
Record location, frequency and start time
- 02Verify material condition
Grade, lot, moisture, drying and contamination
- 03Review machine settings
Melt, mold, pressure, speed and residence time
- 04Inspect mold and geometry
Gate, venting, cooling and wall transitions
- 05Change one variable
Document the result and validate repeatability
Start with material condition
Before adjusting the machine, confirm that the correct grade is being used, packaging was intact, drying followed the grade recommendation and dried material was protected from moisture reabsorption. PA6 is hygroscopic, so material history can materially affect melt processing.
Also review whether regrind level, color masterbatch or other additions changed at the same time as the defect appeared.
Common defects and first checks
The table below is best treated as a diagnostic starting point rather than a universal recipe. Any setting change should stay within the machine, mold and material supplier's validated limits.
- Splay or silver streaks: check moisture, contamination, trapped gas and thermal history
- Short shots: check fill resistance, melt/mold temperature, injection profile, venting and gate restriction
- Flash: check clamp condition, parting line, pressure, viscosity and melt temperature
- Burn marks: check trapped air, venting, injection speed and excessive local shear
- Warpage: check uneven cooling, fiber orientation, packing, mold temperature and geometry
- Weld-line weakness: check flow-front temperature, venting, gate location and material/fiber orientation
- Dimensional variation: check moisture conditioning, packing consistency, cooling and lot/process stability
What helps a technical review
- Grade and lot reference
- Drying record
- Melt / mold temperatures
- Injection pressure, speed and cycle notes
- Photos and description of the defect
Special considerations for glass-filled PA6
Glass-filled PA6 adds fiber orientation to the troubleshooting picture. Flow direction, gate position and weld lines can strongly affect mechanical properties and dimensional behavior. Increasing glass content can improve stiffness while making anisotropy more significant.
When a defect appears after changing from GF15 to GF30 or between suppliers, compare not only machine settings but also the complete compound formulation and shrinkage behavior.
A disciplined troubleshooting sequence
Record the defect, cavity location and process data; confirm material identity and drying; compare against the last known-good production condition; then change one major variable at a time. This makes the root cause easier to identify than changing temperature, pressure and speed simultaneously.
If the problem follows a resin or grade change, retain samples from both lots and provide the supplier with machine data, drying conditions, defect photos, part geometry and the previous material reference.
Applied support
How STRANTOP supports troubleshooting
STRANTOP can coordinate a material-side review with affiliated engineering-plastics resources when a customer provides the grade, lot and process history. We do not treat every molding defect as a resin complaint; the aim is to separate material, handling, machine and tool effects quickly enough to support production decisions.
Discuss your material requirement →Questions we hear from buyers and processors
What should I check first when PA6 shows splay?
Material moisture is an important first check, along with contamination, trapped gas and thermal history.
Can higher mold temperature fix every surface problem?
No. Surface defects can come from multiple causes, and settings should remain within the grade and mold's validated process window.
Why does glass-filled PA6 warp differently?
Fiber orientation creates directional shrinkage and stiffness, so gate location, flow pattern and cooling can strongly affect warpage.
Technical review
This resource is maintained by STRANTOP's technical and commercial team with input from affiliated PA6 polymerization and engineering-plastics resources. It is intended to help customers frame a material discussion; grade-specific specifications, processing conditions, compliance claims and final suitability remain subject to the applicable supplier documentation and customer validation.