Introduction
In the production of rubber seal strips and foam sealing strips, extrusion defects directly affect sealing performance and product lifespan. Knowing common defects, their causes, and practical remedies helps B2B buyers assess quality and guides suppliers to optimize processes.
1. Inaccurate Dimension
| Identification | Causes | Remedies |
| Uneven or inconsistent thickness | Improper draw ratio or puller speed | Fine‑tune puller and screw speeds within ±5% of target |
| Abnormal shrinkage after cooling | Unstable barrel temperature | Maintain barrel temperature fluctuations within ±2 °C |
2. Blow Holes & Cavities
| Identification | Causes | Remedies |
Visible holes or cavities on edges or surface | Moisture or contaminants in resin vaporize under heat | Pre‑dry resin at 120 °C for 4 hours |
| Inadequate resin drying or filtering | Clean hopper, screw, and die to remove residues |
3. Sharkskin Melt Fracture
| Identification | Causes | Remedies |
| Fine or coarse “sharkskin” cracks on the surface | Excessive shear rate in the polymer melt | Reduce screw speed by 10–15% |
| Increase die temperature by 5–10 °C |
4. Clogging & Chatter Marks
| Identification | Causes | Remedies |
| Streaks, chatter marks, or asymmetric profiles | Jammed nozzle or die | Clean die and nozzle of foreign particles |
| Misalignment of extrusion line | Align equipment within ±0.1 mm tolerance |
5. Warpage & Sink Marks
| Identification | Causes | Remedies |
| Twisted, warped strips or surface indentations opposite ribs | Internal stress from uneven cooling and shrinkage | Balance puller speed and cooling airflow |
| Redesign die for uniform wall thickness |
6. Bubbles & Pits
| Identification | Causes | Remedies |
| Surface bubbles, pits, or dashed lines | Incorrect mix ratio or moisture uptake | Control mix ratio within ±1% accuracy |
| Trapped air in the melt | Add vent ports and pre‑dry raw materials |
7. Weld Lines
| Identification | Causes | Remedies |
| Visible lines where separate melt flows meet | Split‑and‑rejoin polymer flow in the die | Increase barrel temperature by 5 °C |
| Clean die and raise back‑pressure |
Conclusion
By optimizing extrusion parameters and mold design, you can significantly reduce defects in rubber seal strips and improve both performance and durability. OKIN’s factory, equipped with 21 extrusion lines (including 6 co‑extrusion and 3 foam lines), delivers high‑quality, custom seal strips worldwide.
Contact us today to optimize your sealing solutions!