By Josh Gibson, gauging industry technology manager, Quad Plus

In roll-to-roll manufacturing, consistency, accuracy and safety are critical. Yet, many converters still rely on outdated gauging systems that typically are radiation-based, require routine calibration, involve regulatory burdens and fail to meet today’s quality control expectations. How can maintenance and safety risks be reduced while improving real-time control and product consistency across different substrates? For a growing number of operations, the answer is ultrasonic measurement.

Ultrasonic systems (see Figure 1) operate using the ultrasonic absorption measurement method, where a transmitter emits low-frequency oscillations that pass through the material, and a receiver detects the transmitted and reflected signals (see Figure 2). The energy loss and oscillation amplitude are inversely proportional to the material’s basis weight and thickness, ensuring high-precision, real-time measurement.

Advantages of ultrasonic systems

Ultrasonic measurement addresses several persistent issues found in traditional gauging systems. These are the most significant advantages that matter to converters.

1. No Recalibration Between Product Changes. Other sensor technologies often require recalibration when switching materials. Ultrasonic technology, by contrast, largely is material-independent. Once set up, it can handle changes in thickness, density and material type without operator intervention.
2. Radiation-Free Operation. Radiation-based systems (such as beta gauges) involve strict handling procedures, regulatory compliance, shielding requirements and end-of-life disposal plans. Ultrasonic systems are safe, require no special certifications and eliminate all ionizing exposure risks.
3. Lower Service and Support Burdens. Legacy systems are prone to service interruptions, part shortages and limited technical support. Ultrasonic gauges are simpler to maintain, with fewer moving parts and no radioactive sources to replace. This makes them more future-ready and reduces downtime.

Enhanced profile accuracy and process control

Modern converters demand better control over cross-directional (CD) and machine-directional (MD) profiles. Even small thickness variations can cause major issues in converting, such as coating defects, roll rejections or misaligned laminations. Ultrasonic systems help prevent these problems by delivering continuous, high-resolution data that integrates directly with feedback control systems.

Operators can view real-time profile maps that reveal thickness trends or defects as they occur (see Figures 3 and 4). Unlike older systems that lag or offer lower resolution, ultrasonic gauges support immediate adjustments, either manually or through automated feedback.

When integrated with process controls, this data enables fine-tuned changes to die bolts, coatweights or nip settings, improving product consistency and reducing material waste. This especially is valuable when working with expensive substrates or tight tolerances.

Application versatility across substrates

One of the key strengths of ultrasonic measurement is its broad applicability across a wide range of materials commonly used in roll-to-roll converting. Unlike radiation-based systems that may require calibration for each new material, ultrasonic systems work effectively with materials that transmit sound waves, making them more flexible in mixed-production environments. Ultrasonic systems are well-suited for a wide range of materials, including the following:

• Polyethylene, polypropylene, PET and other plastic films
• Aluminum and metal foils
• Paper and coated paper products
• Multilayer composites and laminates
• Battery electrode coating

Ultrasonic systems are particularly valuable for converters that run different product types on the same line. Instead of adjusting the measurement system for each substrate, the same ultrasonic sensor often can handle multiple materials with minimal set-up. This reduces downtime and changeover time while maintaining accuracy. Operators can rely on a single measurement approach for diverse jobs.

This includes advanced applications, such as battery electrode coating for electric vehicles and energy storage systems, where precision and consistency are critical to product performance and safety. The technology also is well-suited for specialty materials where consistent thickness is critical, but traditional sensors struggle. For example, clear or highly reflective films that may scatter light do not present an issue for ultrasonic waves.

Easier compliance and safety management

One of the most immediate benefits of switching to ultrasonic measurement is reduced regulatory burden. Radiation-based gauging systems require strict oversight due to their use of ionizing sources, which are regulated at both the state and federal levels.

Without radioactive sources, there is no need for the following:

• Radiation safety officers
• Licensing or regulatory paperwork
• Disposal plans or sealed source replacements

For manufacturers expanding to new sites or scaling up production, avoiding the regulatory red tape associated with nuclear systems can accelerate set-up timelines and reduce permitting delays. It also ensures smoother compliance during inspections, whether from OSHA, the Nuclear Regulatory Commission (NRC) or industry-specific auditors.

From a workforce perspective, ultrasonic systems are safer and easier to manage. There’s no risk of radiation exposure, which can be a concern for older systems if shielding is damaged or procedures are not followed precisely. This improves the overall safety profile of the production floor and makes it easier to train new operators.

For companies operating internationally, avoiding radiation-based systems also simplifies compliance with varying global standards.

Supporting sustainability and material efficiency

For converters focused on reducing waste and improving material efficiency, ultrasonic measurement offers a practical advantage. By delivering high-resolution, real-time data, these systems help operators maintain tighter control over basis weight and thickness targets. This reduces the over-application of materials, minimizes edge trim and cuts down on rejected rolls due to out-of-spec products.

The ultrasonic basis weight sensor is installed on a polypropylene woven bag tape extrusion line, where it continuously monitors and controls the basis weight (gsm²) in real time. The system ensures precise thickness consistency across the web, optimizing product quality and minimizing material waste. Providing instant feedback to the extrusion process enables rapid correction of deviations, enhancing production efficiency and ensuring compliance with tight customer specifications. The sensor’s non-contact, maintenance-free design makes it ideal for continuous operation, even in high-speed, high-temperature extrusion environments.

Traditional systems often require wider safety margins to compensate for lagging data or lower accuracy. That extra buffer may seem minor per roll, but it adds up across millions of linear feet. Ultrasonic systems make it possible to produce closer to spec, directly supporting material savings and reduced scrap rates.

For converters pursuing ISO 14001 or serving customers with strict environmental requirements, improving measurement precision is a simple but high-impact step. It supports leaner production, reduces landfill waste and helps quantify sustainability improvements in measurable terms.

Moving beyond contact measurement

While radiation-based systems often are replaced due to safety and compliance concerns, contact measurement systems present a different set of challenges. These older systems rely on physical contact with the web to assess thickness, which introduces a number of process limitations and long-term reliability issues. These include the following:

1. Physical Wear and Drift. Contact gauges depend on mechanical components, such as rollers and probes, that wear down over time. This wear can result in calibration drift or surface damage, leading to inaccurate readings that aren’t always obvious until defects appear in the final product.
2. Risk of Material Damage. Soft or delicate materials can be marred or distorted by the pressure of contact measurement devices. This especially is problematic in the production of optical films, barrier layers or specialty coatings, where even slight surface disruptions can result in scrap.
3. Slower Response and Limited Resolution. Mechanical systems often struggle to keep up with fast line speeds or rapidly changing web dynamics. Because they rely on physical engagement, they may fail to capture fine variations across the web or respond slowly to sudden changes in thickness.
4. No Integration with Closed-Loop Control. Many contact systems operate as standalone units with limited connectivity. This makes it difficult to integrate them into modern feedback loops or digital control platforms. In contrast, the ultrasonic systems from the author’s company are designed with an architecture that integrates easily into customer control systems.
5. Maintenance Interruptions and Downtime. Because contact gauges involve moving parts, they require more frequent cleaning, recalibration and mechanical service. Even small buildups of dust or coating material can interfere with accurate readings.

For converters currently relying on contact gauges, ultrasonic measurement represents a safety and compliance upgrade, along with a substantial leap forward in reliability, precision and operational efficiency.

A better fit for industry 4.0

Ultrasonic gauging also provides a low-risk, high-impact upgrade for converters adopting smart systems. It integrates with modern automation platforms, enables real-time analytics and supports smarter decision-making. As plants adopt predictive maintenance and cloud-based control, ultrasonic measurement helps maintain quality and efficiency without the complexity of older, less adaptable systems. 

Josh Gibson brings more than 24 years of industrial manufacturing experience to his role as gauging industry technology manager at Quad Plus, where he has spent the past 14 years specializing in process control and gauging technologies. He played a key role in launching the Quad Plus gauging division and continues to lead advancements in web handling and feedback control systems for extrusion and converting operations. Gibson holds an AAS Electronics Engineering Technology and a BAS Automated Manufacturing Technology from ITT Technical Institute. His expertise includes electrical design, system programming and closed-loop process control for sheet extrusion lines. He can be reached at email: jgibson@quadplus.com, www.quadplus.com.