In fiberglass pultrusion, the mould (or die) is the heart of the whole process — it directly shapes surface quality, dimensional accuracy, and production efficiency. Long-term operation still tends to surface a familiar set of problems. Here’s a rundown of the most common issues and how to fix them.
1. Design and Structural Issues
1.1 Uneven Heating
Symptoms: uneven color, partial curing, or soft spots on the finished profile.
Causes: poorly laid-out heating elements or unbalanced temperature control.
Fix: switch to a multi-zone temperature control system and improve insulation around the mould.
1.2 Improper Die Taper or Transition Design
Symptoms: dimensional deviation, difficulty pulling.
Causes: incorrect die taper or a rough transition zone.
Fix: recalculate taper based on resin shrinkage and profile geometry, and polish transition zones smooth.
1.3 Resin Flow Channel Problems
Symptoms: air bubbles, dry spots, uneven impregnation.
Causes: a poorly designed or blocked resin flow path.
Fix: redesign the flow channels for even resin distribution across the fibers.
2. Material and Manufacturing Problems
2.1 Surface Roughness or Chrome Layer Peeling
Symptoms: scratches or a dull surface on the finished product.
Causes: poor polishing or a low-quality chrome coating.
Fix: use high-hardness tool steel, polish carefully, and inspect the chrome layer regularly.
2.2 Insufficient Hardness or Excessive Wear
Symptoms: the mould wears fast, and profile dimensions drift.
Causes: weak mould material or poor lubrication.
Fix: switch to premium mould steel such as H13 and keep up regular lubrication and cleaning.
3. Operation and Maintenance Issues
3.1 Fiber Breakage or Mould Blockage
Symptoms: high pulling resistance, broken fibers.
Causes: cured resin build-up or the wrong temperature setting.
Fix: keep the mould cavity clean, control curing temperature precisely, and maintain smooth inlet chamfers.
3.2 Difficult Demoulding
Symptoms: the product sticks to the mould, or its surface gets damaged coming out.
Causes: poor surface finish or the wrong release agent.
Fix: pick a suitable release agent and apply it evenly before every run.
3.3 Improper Temperature Control
Symptoms: incomplete curing or a brittle finished product.
Causes: a faulty thermocouple or uneven heating.
Fix: calibrate temperature sensors regularly and use multi-point control systems.
4. Maintenance Recommendations
- Clean the mould cavity after every production run to clear resin residue.
- Polish the cavity regularly to keep the surface smooth.
- Inspect heating systems and thermocouples on a schedule.
- Apply anti-rust oil and seal the mould during extended downtime.
5. Common Mould Problems and Their Effects
| Problem Type | Typical Symptoms | Impact on Product |
|---|---|---|
| Uneven Temperature | Partial curing, color difference | Reduced strength and appearance quality |
| Blocked Resin Flow | Dry spots, bubbles | Poor surface finish |
| Incorrect Taper | Difficult demoulding | Low production efficiency |
| Chrome Peeling | Rough surface | Dimensional inaccuracy |
Conclusion
Sound design, precise manufacturing, and regular maintenance are what keep a mould lasting and producing high-quality fiberglass profiles. As a professional pultrusion mold manufacturer, we provide custom FRP moulds, pultrusion equipment, and technical support tailored to different production needs.
Contact us:
Website: frphk.co
Email: [email protected]
WhatsApp: +86 189 5198 8522