Technical Felt production

Needle Punching Production Process

Raw Material Preparation & Blending: Synthetic fibers such as polyester, polypropylene, or aramid, or blends with natural fibers like wool, are proportionally mixed according to product requirements. For brittle fibers (e.g., refractory fibers), lubricants are added to reduce needle-induced damage.

Opening & Cleaning: An opener is used to separate and loosen the fiber clusters and remove impurities, resulting in a fluffy, loose state.

Carding into Web: The loosened fibers are fed through a carding machine, which further separates and aligns them into a parallel, single-layer thin web.

Web Laying: The single-layer thin web is cross-lapped or layered using a web-laying machine to build up the required thickness and weight (e.g., some patents mention building up to 30–35 cm thickness).

Pre-Needling: The layered web first enters a pre-needling loom, where a relatively lower needling frequency (e.g., 500 punches/min) and penetration depth are applied to give the web its initial form and integrity.

Main Needling: This is followed by main needling, typically using multiple needle looms (e.g., bottom needling and top main needling) with higher frequencies (e.g., 650 punches/min) and densities. For specialty products, double-sided needling may be employed to achieve uniform consolidation.

Core Principle: The barbs on the needle edges hook surface fibers and carry them into the web's interior during penetration; upon retraction, the fibers are released and remain trapped inside, creating vertical entanglements that lock the structure.

Key Parameters: Needling density and needling depth are the two most critical factors affecting product strength. Increasing these parameters within a certain range improves mechanical properties, but beyond the optimal point, excessive fiber breakage occurs, leading to a decline in strength.

Heat Setting (Thermal Bonding/Stabilization): Heat is applied to relieve internal stresses within the fibers, stabilizing the felt's dimensions. For example, refractory fiber blankets may be heat-treated at 500°C to remove lubricants, while common synthetic fiber felts are set at temperatures around 100–150°C.

Surface Finishing: Includes singeing (burning off surface fuzz) and calendering (pressing for a smooth, dense surface) to improve appearance, surface finish, and performance — particularly important for filtration applications.

Inspection & Cutting: Finally, the finished felt is inspected for quality and then cut into sheets, rolls, or punched into specific shapes according to the final application.