Why Does Your Forming Fabric Lose Shape Too Soon? Mastering Dimensional Stability

Forming fabrics are the backbone of the papermaking process, but when they lose shape due to lengthwise elongation or widthwise shrinkage, the consequences are significant: sheet defects, increased downtime, and higher costs. Dimensional stability is a critical quality parameter that impacts both paper makers and forming fabric manufacturers. In this blog, we explore how paper makers can optimize their operations and how manufacturers can design stable fabrics, fostering collaboration to enhance fabric life and paper quality. Let’s dive into actionable strategies for both audiences.

For Paper Makers:

To take Control of Dimensional Stability Paper makers play a vital role in managing forming fabric performance by understanding its characteristics and collaborating with suppliers. Here are six key strategies to address dimensional stability challenges:

1. Verify Stretch Margin to Manage Elongation Modern: High-speed paper machines typically accommodate 2–3% stretch, often equipped with automatic stretch rolls, while older machines have less than 1% stretch margin, making them more susceptible to elongation issues. Ensure your machine has at least 1% stretch margin to handle the typical 1% elongation of forming fabrics over their lifetime. If your machine lacks sufficient margin, consider two options: install mechanisms to accommodate elongation or use shorter fabrics with tighter mounting. There are no shortcuts here—verify your machine’s capacity with your supplier to prevent issues.

2. Optimize Tension and Drag Load: Maintain fabric tension within the recommended range of 4–7 kg/cm, noting that most faster machines operate at 7 kg/cm. Keep tension slightly below the machine’s drag load to avoid excessive elongation or width shrinkage. Over-tensioning, especially on machines without auto stretch rolls, can exacerbate shrinkage. Work closely with your supplier to fine-tune tension settings and control drag load, ensuring better stability and consistent performance.

3. Understand Synthetic Fabrics and Modulus: Unlike rigid metal wires, which offered no elongation but only one-fourth the lifespan, modern synthetic fabrics are flexible and prone to elongation. To choose the right fabric, ask your supplier for the fabric’s Modulus value—a higher Modulus indicates greater resistance to elongation. Compare Modulus values across suppliers, alongside other parameters like weave structure and material, to select the best fabric for your machine’s conditions.

4.Collaborate on correct fabric Length: The correct fabric length is critical for fabric performance. Provide your supplier with accurate minimum and maximum machine length and stretch margin. This data, combined with the fabric’s Modulus, allows suppliers to determine the actual supply length, ensuring a stable fit on your paper machine.

5.Allow a Stabilization Period: After installing a new forming fabric, allow a 3–7 day stabilization period to let the synthetic material settle. Avoid over-tightening during this phase, especially if no slippage occurs, as excessive tension can cause further stretching and compromise dimensional stability. Consult your supplier for guidance on proper tensioning during this critical period.

6. Prioritize Maintenance for Longevity: Regular cleaning and inspections are essential to minimize wear that worsens dimensional instability. A well-maintained fabric ensures consistent performance, reduces the risk of elongation or shrinkage, and extends lifespan. Schedule routine maintenance checks to keep your fabric in top condition.

7. Ensure Proper Machine Alignment: Misalignment in the wire table can cause seam leading at one edge, resulting in width shrinkage. Cross-check your machine’s alignment to ensure a true table, working with your maintenance team or supplier to verify and correct any issues. Proper alignment is a simple yet effective way to maintain fabric stability.

Impact for Paper Makers: By implementing these strategies, you can achieve stable fabrics that improve sheet quality, reduce waste, and extend fabric lifespan, ultimately lowering costs. Collaboration with suppliers is key to tailoring solutions to your machine’s specific needs.

For Manufacturers:

Designing Fabrics That Stay Stable Forming fabric manufacturers are at the forefront of tackling dimensional stability issues, designing products that resist lengthwise elongation and widthwise shrinkage. Here are five critical design considerations to deliver high-performing fabrics:

1. Optimize Weaving Tension: Proper tension or crimp percentage during weaving is the foundation of dimensional stability, particularly for SSB (sheet support binder) fabrics. The top plain weave structure typically requires double the crimp of the bottom twill structure to ensure stability. Precise tension settings during weaving create a balanced structure that resists elongation under machine tension (4–7 kg/cm).

2. Perfect the Heat Setting Recipe: Effective heat setting relies on the 3T principle: Temperature, Tension, and Time. Maintain a temperature of 190°C, optimal machine direction (MD) and cross direction (CD) tension, and controlled cooking time (number of rounds with gradual temperature increases). This process stabilizes the fabric structure, minimizing elongation and shrinkage under operational stresses.

3. Achieve Optimum Modulus: With proper weaving and heat-setting settings, the fabric’s Modulus (500 / elongation % at 5 kg/cm) is optimized, indicating how much the fabric will elongate during operation. A higher Modulus reduces elongation percentage, but an excessively high Modulus can flatten warp crimp, weakening seam strength. Balance Modulus to ensure durability without compromising other fabric properties.

4. Determine Optimal Supply Length: Designing the correct supply length is a critical challenge. Obtain precise minimum and maximum paper machine length and stretch margin from the customer. Use these data alongside the fabric’s Modulus and growth (elongation in the first 3–7 days) to calculate the actual supply length, which may vary from the order length, ensuring the fabric runs stably and meets machine requirements.

5. Account for Width Contraction: Forming fabrics experience width shrinkage under MD tension, so manufacturers must study and standardize the shrinkage percentage for each design. Adjust this as an allowance during fabrication to ensure the final width meets customer requirements under operational tension, preventing shrinkage-related issues on the paper machine.

6. Deliver Customized Solutions: Forming fabrics are tailor-made products, designed to meet the specific requirements of each paper machine. Avoid generalized designs by collaborating with paper makers to understand their machine’s tension, stretch margin, and operating conditions, ensuring a fabric that delivers optimal stability and performance.

Your Role as Manufacturers: By focusing on these design principles, you can create fabrics that withstand tension and mechanical stresses, providing paper makers with consistent sheet quality and extended fabric life.

Collaborate for Success: Dimensional stability is a shared challenge that requires close collaboration between paper makers and manufacturers. Paper makers can optimize machine settings, maintenance, and fabric selection, while manufacturers can refine weaving, heat setting, and design customization. Together, these efforts ensure stable fabrics that enhance papermaking efficiency and quality.

Ready to Take Action? PMC Centre is your trusted partner for guidance. With our team’s extensive expertise, we provide tailored solutions to improve your bottom line, especially for selection of right forming fabric for your need. Visit www.pmccentre.com for more resources, and share your dimensional stability insights in the comments below!

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