Control Color Throughout the Production Line in Paper Mills with Inline Color Measurement

Maintaining precise color consistency and brightness across batches is crucial. However, controlling these parameters can be challenging due to variables in raw materials, production processes, and environmental conditions.?

An effective solution is an inline color measurement and control system, which monitors and adjusts color directly on the paper machine so that color remains within narrow tolerances throughout the production line. This technology not only improves product quality but also operational efficiency while reducing waste.

Challenges in Color and Brightness Consistency

Paper mills often face issues with color consistency, as various factors can cause color shifts during production. Traditional methods for color measurement often involve manual sampling, where color quality is checked periodically. This approach, however, can result in delays between detection and correction of color discrepancies, leading to wasted materials and increased costs.

As the last parameters to be brought into specification during machine startup, color, and brightness require careful monitoring to ensure they meet product standards. Achieving this consistency manually can be resource-intensive and inefficient. Inline color measurement systems address this challenge by allowing for real-time monitoring and adjustments, liberating operators from the tedious task of constant monitoring.

How Inline Color Measurement Works

An inline color measurement system includes a non-contact spectrophotometer mounted on a custom frame to position it at the correct distance over the production line. This device, coupled with quality control software, continually measures color and brightness. It provides real-time data on color deviations, allowing immediate corrective actions through an automated, closed-loop control system.

In a closed-loop control system, the output (color measurement) is constantly monitored and compared to the desired input (target color), and any deviation is corrected automatically, ensuring the system operates within the desired tolerances.

Some of the key features included in an inline color measurement system include:

• Non-Contact Spectrophotometer: The device measures color without touching the paper, ensuring that ambient light, vibrations, and web speed do not affect accuracy.
• Automatic Adjustments: The system automatically adjusts colorants, saving time and reducing the need for operator intervention.
• Error-Free Swivel Mechanism: If a paper break occurs, the frame swivels away, allowing the machine to be re-threaded without damaging the instrument.

This setup allows operators to control color consistency with minimal manual adjustments, allowing them to focus on other critical aspects of production. The system’s automated corrections maintain color quality with precision, even when actual colors deviate from target values, ensuring a high-quality product.

Measuring Color at Key Stages in the Production Line

Inline color measurement systems can monitor color at various stages of production, each offering distinct advantages:

1. Liquid Paper Stock Stage: Measuring color in the pulp stage provides an early warning of color changes before the pulp reaches the machine. Although this measurement does not correspond directly to the finished product color, it enables proactive adjustments, helping operators control color from the very start of production.
2. Press to Dryer Section: For laminated décor paper, measuring color between the press and dryer helps account for the refractive index of resin or varnish, ensuring that the color appearance meets expectations before final drying. This approach minimizes waste by allowing strips to be redyed as and when needed, reducing the need for additional lamination.
3. Before Reel Up: Measuring color just before winding (reel up) offers excellent correlation to lab results and ensures consistency in the final product. This method is particularly useful for products like colored tissue, test liner, security paper, and fine papers, where color precision is critical.

Benefits of Inline Color Measurement in Paper Mills

Implementing inline color measurement and control offers significant benefits to paper mills, including:

• Faster Startup and Transition Times: Automated color adjustments speed up the startup process and streamline transitions between color shades, enhancing overall production efficiency.
• Reduced Dye and Waste Costs: The system detects color deviations early, allowing for quick corrections that minimize dye costs and reduce material waste.
• Better Product Quality: Consistent color and brightness improve the quality of the finished product, leading to higher market acceptance and customer satisfaction.
• Improved Operator Efficiency: By automating the color control process, operators can focus on other production areas, optimizing resource allocation.

Fast Return on Investment

An inline color measurement system enables paper mills to achieve consistent color quality across production runs with minimal variation, providing a fast return on investment. By reducing rework and minimizing waste, mills can achieve cost savings while meeting the stringent color standards demanded by their clients.

Maintaining color integrity across production lines supports brand recognition so that customers receive high-quality, consistent products every time.

Conclusion

Maintaining color and brightness consistency in paper production is essential to meeting customer expectations and enhancing operational efficiency. Inline color measurement systems offer a powerful solution to this challenge, enabling real-time monitoring and automatic adjustments throughout the production line. By adopting this technology, paper mills can achieve a higher level of precision, reduce waste, and streamline production, ultimately leading to improved profitability and customer satisfaction.

For paper mills looking to improve their color management processes, inline color measurement provides a reliable, efficient, and cost-effective approach to maintaining color quality throughout the production line.