What is FSI and Why Is It Important?
FAQ
FSI (Fiber Support Index) quantifies the number of support points per unit area on the paper-side surface of forming fabrics.
Each MD/CD yarn intersection creates a fiber anchoring point. Higher FSI = more uniform fiber mat = better retention + fewer sheet defects.
Typical FSI Ranges by Structure:
- Single Layer: 50-80
- Double Layer: 80-120
- Triple Layer: 130-170
- SSB: 150-200+
Recommendation: Culture paper and tissue grades should target FSI >150 for minimal sheet marking and best formation quality.
Technical Background
This answer is based on PAPTEX's expertise in Forming Fabric. PAPTEX provides engineered fabric solutions to 200+ paper mills worldwide.
Related Resources
- 📖 View our Product Knowledge for more information
- 📋 Browse Forming Fabric related articles
- 📞 Contact PAPTEX Engineers for personalized recommendations for your paper machine
Last updated: July 2026
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