In the aluminum extrusion industry, the moment a profile exits the die at temperatures reaching 500–550°C marks a critical point in the production process . At this stage, the hot, semi-solid aluminum is highly susceptible to surface damage, deformation, and scratching—defects that can render the final product unusable for high-value applications like anodized architectural components or automotive parts .
A felt conveyor belt for aluminum extrusion is more than just a transport mechanism; it is a critical component that safeguards product integrity, reduces downtime, and optimizes throughput. Unlike traditional metal slats or fabric belts, endless needled felt belts offer a unique combination of heat resistance, surface protection, and dimensional stability .
For plant managers, maintenance engineers, and procurement specialists, selecting the appropriate felt conveyor belt—whether PBO, Kevlar, Nomex, or Polyester—directly impacts scrap rates, die life, and overall equipment effectiveness (OEE) . This guide provides an in-depth analysis of felt belts used in aluminum extrusion, detailing material science, application zones, and technical specifications to help you make an informed purchasing decision.
Understanding the Extrusion Process: Temperature Zones and Requirements
The run-out table, where profiles are transported and cooled, is divided into distinct temperature zones. Each stage requires a specific type of felt belt to handle varying thermal loads and mechanical stresses .
| Process Stage |
Temperature Range |
Primary Function |
Recommended Belt Material |
| Die Exit / Runout Table |
500°C – 600°C |
Immediate support, scratch prevention, initial cooling |
PBO, PBO/Kevlar blend |
| Primary Cooling Table |
200°C – 500°C |
Continuous transport, further cooling, shape stabilization |
Kevlar (Para-Aramid) |
| Stretcher / Saw Table |
Up to 280°C |
Transport for cutting and stretching processes |
Nomex (Meta-Aramid) |
| Storage / Stacking |
Up to 180°C |
Final transport, stacking, surface protection |
Polyester |
Material Selection: PBO, Kevlar, Nomex, and Polyester
The choice of fiber material defines the belt’s performance, lifespan, and cost-effectiveness. Here is a breakdown of the four primary materials used in aluminum extrusion felt belts :
1. PBO (Polybenzoxazole) – Ultra-High Temperature Zone
PBO (often branded as Zylon) represents the pinnacle of heat resistance for felt belts. It is specifically engineered for the harsh environment immediately following the extrusion press.
- Temperature Resistance: Up to 600°C continuously. This is the only material capable of withstanding the initial blast of heat without degrading or burning the aluminum surface .
- Application: High-capacity presses (>2000T), large and complex profiles, and the “front end” of the runout table .
- Advantages: Exceptional thermal shock resistance, low elongation, and no surface marking. PBO belts often have a characteristic orange or brown color .
- Key Specs: Thickness ranges from 4mm to 12mm; typical widths are up to 2,200mm .
2. Kevlar (Para-Aramid) – High-Temperature Zone
Kevlar is a workhorse in the extrusion line, offering a balance of high heat resistance, durability, and cost-effectiveness.
- Temperature Resistance: Up to 480–500°C (peak/short-term) and ~200°C continuous .
- Application: Primary and secondary cooling tables, handling/transfer tables.
- Advantages: Excellent abrasion resistance and tensile strength. Prevents elongation under heavy loads. Standard Kevlar belts are usually yellow .
- Key Specs: Commonly available in thicknesses of 5mm to 14mm and widths up to 3,000mm .
3. Nomex (Meta-Aramid) – Medium-Temperature Zone
Nomex is used where temperatures are still significant but not extreme, such as downstream operations.
- Temperature Resistance: Up to 280°C .
- Application: Areas post-stretcher, saw tables, and pre-cutting transfer.
- Advantages: Good thermal stability with a lower cost structure. Often white in color. Suitable for most standard extrusion profiles .
- Key Specs: Density typically ranges from 0.15 to 0.45 g/cm³ .
4. Polyester – Low-Temperature Zone
Polyester belts are the economical choice for the final stages of the extrusion line.
- Temperature Resistance: Up to 150–180°C .
- Application: Saw tables, stacking areas, storage, and anodizing preparation lines.
- Advantages: Lower cost, easy to replace, and provides a non-marking surface. Usually beige or white .
- Key Specs: Commonly available in thicknesses like 3mm, 5mm, 6mm, and 8mm .
Top 5 Critical Advantages of Seamless Endless Felt Belts
To protect high-value aluminum profiles from defects, the belt itself must be flawless. Here’s why endless needled felt construction outperforms laced or spliced alternatives :
- Zero Surface Defects (Scratch-Free): The key benefit is the smooth, non-marking surface that prevents scratches and dents on delicate, high-finish extrusions (e.g., polished or anodized surfaces). This ensures high-quality output and reduces scrap rates .
- Elimination of Weak Points: Laced or spliced belts create a “weak point” that is prone to failure under high temperatures and tension. Seamless belts distribute stress evenly, significantly increasing the belt’s operational lifespan .
- High Tensile & Low Elongation: Needled felt belts, particularly those reinforced with aramid fibers (Kevlar), exhibit minimal stretch. This maintains consistent belt tracking and tension, ensuring stable production speeds and reducing maintenance needs .
- Superior Wear & Abrasion Resistance: The high-density fiber structure of needle-punched felt provides excellent resistance to friction from sharp edges and heavy loads, ensuring long service life even under continuous operation .
- Thermal Stability & Conductivity: Felt acts as a natural insulator, allowing for a controlled cooling process. It prevents surface oxidation and “hot spots” on the profile .
Technical Specifications to Consider
When procuring a felt conveyor belt for your extrusion line, ensure you verify the following technical parameters with your supplier:
- Width: Typically ranges from 20mm to 3,000mm depending on the press size and profile dimensions .
- Length (Circumference): Varies widely, from 1,780mm to 25,000mm for standard lines, with some systems requiring up to 40,000mm .
- Thickness: Standard range is 3mm to 14mm. For heavy-duty applications, customized productions up to 80mm are possible .
- Density: Ranges from 0.15 to 0.45 g/cm³; higher density generally indicates better wear resistance and compression set behavior .
- Surface Treatment: Options include PU (polyurethane) finishing for enhanced surface smoothness, anti-static finishes to prevent dust attraction, and edge sealing to prevent fraying