Mastering Spiral Dryer Fabric Manufacturing: Essential Practices and Technical Insights

In the world of Paper Machine Clothing (PMC), spiral dryer fabrics play a critical role in ensuring efficient drying processes, fabric stability, and overall paper production quality. At PMC Centre, we delve into the intricacies of spiral fabric manufacturing to help fabric manufacturers optimize their operations. Drawing from real-world queries and expert responses, this blog post explores key aspects of spiral formation, assembly, and performance influencing factors. Whether you're troubleshooting coil variations or selecting mandrel sizes, these insights provide actionable guidance grounded in industry best practices.

Understanding Spiral Fabric Basics:

Spiral dryer fabrics are constructed by winding monofilament yarns into coils, which are then intermeshed and joined using pintle yarns. This design offers superior dimensional stability, high air permeability, and resistance to heat and moisture—making them ideal for high-speed paper machines. However, achieving consistent performance requires precise control over manufacturing parameters, from mandrel selection to environmental conditions.

The diameter of the spiral yarn typically ranges from 0.55 mm to 1.00 mm, tailored to the fabric's end-use in dryer sections. Factors like coil dimensions, winding methods, and heat-setting protocols directly impact the final fabric's runnability, lifespan, and ability to prevent issues like edge cracking or rippling.

Recommended Mandrel Sizes and Coil Specifications:

When producing spiral fabrics, mandrel size is crucial for maintaining coil uniformity. While mandrel manufacturers (such as Leo at www.hr-leo.de/en/) customize based on spiral diameter, general guidelines ensure compatibility across horizontal and vertical winding machines. Mandrel sizes remain relatively consistent regardless of machine orientation, focusing instead on spiral diameter and coil specs.

Here's a breakdown of typical coil dimensions for common spiral diameters:

| Spiral Diameter (mm) | Coil Width (mm) | Coil Height (mm) |

|----------------------|-----------------|------------------|

| 0.55 | 5.5 – 6.0 | 3.2 – 3.6 |

| 0.70 | 6.5 – 7.0 | 3.8 – 4.1 |

| 0.90 | 7.5 – 8.5 | 4.5 – 4.9 |

| 1.00 | 8.5 – 9.5 | 5.0 – 5.5 |

These ranges support optimal intermeshing during assembly, minimising defects like loop distortion.

Horizontal vs. Vertical Spiral Winding: Performance Differences:

The choice between horizontal and vertical winding machines affects production efficiency and fabric quality. Horizontal winding offers superior coil alignment due to even tension distribution, enabling higher speeds (>2000 RPM) and better control over coil width. This results in enhanced uniformity and easier joining, though the machines are more expensive.

Vertical winding, while cost-effective, may introduce slight pitch variations, complicating pintle insertion unless pre-heated. Speeds are typically lower (<1500 RPM), potentially leading to minor inconsistencies. However, post-heat-setting, these differences largely equalize, yielding comparable dryer fabric performance in terms of stability and air permeability.

Environmental Controls in Spiral Formation:

Maintaining optimal conditions during spiral manufacturing is non-negotiable. Recommended parameters include a temperature of 22–25°C and relative humidity of 50–60%. Deviations can cause inconsistent coil dimensions, increased static (especially below 30% humidity), and yarn breakage.

Impacts include:

- Assembly Issues: Reduced spiral stability and difficult pintle insertion.

- Fabric Performance: Variations in caliper and CFM (cubic feet per minute), non-uniform shrinkage during heat-setting, and on-machine problems like tracking issues or edge cracks.

Controlled environments ensure repeatable quality and extend fabric life.

Influence of Coil Formation Speed:

Coil speed—whether medium (~700 RPM) or high (~1500 RPM)—affects pitch consistency. Mixing coils from different speeds in the same fabric can create micro-variations, leading to joining difficulties, localized tight/loose zones during heat-setting, and potential rippling on the paper machine.

Best practice: Avoid mixing speeds; segregate coils to maintain assembly stability and uniform heat-setting, ultimately preserving fabric integrity.

Pintle Diameter Selection: Matching vs. Oversized:

Pintle choice influences fabric modulus and permeability. Using a larger pintle (e.g., 0.90 mm with a 0.70 mm spiral) fills more loop space, boosting MD tensile strength and stability—ideal for high-speed, long dryer sections.

Matching diameters (e.g., 0.70 mm for both) prioritize CD flexibility and uniform sheet support, suiting marking-sensitive grades and medium-speed machines. Neither approach is inherently superior; selection depends on operational priorities.

Managing Coil Height and Width Variations:

Tolerances are : ±0.15 mm for both height and width. Exceeding this causes uneven intermeshing, variable insertion forces, and non-uniform shrinkage. End-use risks include fabric waviness, rippling, and reduced lifespan.

If variations occur due to mandrel inconsistencies or uncontrolled environments, segregate coils by size to mitigate issues.

Best Practices for Turns Per Inch (TPI) in Coil Formation:

For 0.55–1.00 mm monofilaments, aim for 8–12 TPI to balance strength and flexibility. Thinner yarns (0.55 mm) favor 10–12 TPI for compact loops; thicker ones (1.00 mm) use 8–10 TPI to prevent rigidity.

Emphasize controlled tension, temperature, and humidity during winding. Stabilize coils immediately post-formation to ensure dimensional repeatability.

Pintle Preheating: Benefits and Considerations:

Preheating pintles to 80–100°C enhances pliability, reducing stresses and easing insertion—especially with less uniform vertical-wound spirals. It's optional for horizontal machines but helps overall conformity.

Regardless, monitor pintle shrinkage during heat setting to avoid edge cracking of Spiral Fabric during running on hot and humid condition of paper machine.

Manual vs. Automatic Joining Systems:

Automatic systems excel in consistency and productivity, minimizing skill-dependent defects. Manual methods are cheaper but slower and prone to errors, though heat-setting often mitigates quality gaps. For high-volume production, automation is preferred.

Conclusion: Optimizing Spiral Fabric Performance:

Spiral dryer fabric success hinges on subtle interactions like geometry, pintle choice, and process controls—not always evident in specs but critical on the paper machine. By adhering to these practices, fabric manufacturers can achieve superior runnability, longevity, and efficiency.

At PMC Centre, we offer unbiased consultancy to resolve PMC challenges through data-driven expertise. For deeper dives or custom solutions, explore our resources at www.pmccentre.com

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