WEBFREX NV

A frame is a driving unit that has sensors mounted on it for scanning films and sheets. To get full performance from the sensors, the frame must be very rigid and have a high performance driving mechanism.

The frame is either built with rigid steel I-beams or has a monocoque design. The resulting structure is very strong, allowing the mounted sensors to measure film and sheet thickness with high accuracy even in harsh environments.

For these frames, Yokogawa has developed a dedicated CPU with high performance and reliability.

WEBFREX NV has a variety of easy to use operation and monitoring screens. Operation screens display an easy to comprehend profile showing the frame / sensor status and the thickness measurement data. Operation management screens facilitate the management of various film and sheet grades as well as reporting. With a single mouse click, online guidance screens can be displayed from each of these screens.

Highly accurate Beta-ray, X-ray, and Infrared sensors are available for a variety of measurement applications. These are non-contact sensors that can measure objects without damaging them.

Measuring range:

• Beta-ray sensor (0 to 5,000 g/m² with aluminum)
• X-ray sensor (0 to 1,200 g/m² with aluminum)
• Infrared sensor (0 to 2,000 μm with PP)

Beta-ray sensors irradiate objects to measure their thickness (basis weight), calculating this based on the attenuation of the radiation as it passes through the object. Beta-ray sensors can measure any object provided the thickness is within the specified measuring range.

¹⁴⁷Pm (promethium), ⁸⁵Kr (krypton), and ⁹⁰Sr (strontium) sources are available and are selected depending on the object that is to be measured.

Beta-ray sensors measure both the object and the surrounding air layer. The sensor compensates for this by using an air purge mechanism to keep the air layer at a constant temperature and density, thereby minimizing its impact on measurement accuracy. It also contains an automatic compensation function for the decay of the radiation source and a calculation function to reduce radiation noise. These and other functions ensure stable and highly accurate measurement.

X-ray sensors irradiate objects to measure their thickness (basis weight), calculating this based on the attenuation of the X-ray as it passes through the object. The sensitivity of the X-ray sensor varies according to the atomic weight of the object that is measured. Being particularly sensitive to metallic elements, the X-ray sensor is often used to measure IT-related materials such as ceramic sheets (like MLCC) and battery electrodes.

The X-ray sensor uses a unique tube with a reflective triode structure that achieves outstanding stability and high output.

As with the Beta-ray sensor, the X-ray sensor has a compensation function that maintains the air layer at a constant temperature to minimize its impact on measurement accuracy.

Infrared sensors irradiate objects to measure their thickness (basis weight), calculating this based on the attenuation of the infrared light as it passes through the object. They are sensitive to CH groups and can be used with many different types of films and sheets.

Machine direction (MD) thickness and cross-machine direction (CD) thickness are controlled by the control unit. Based on the type of film making machine (such as cast and bi-axially oriented) and response time, the appropriate control method can be selected from the following options:

• Virtual zone sampled data PI control
• Expert fuzzy control
• Finite settling model predictive control

Other control methods are available: CD adaptive control continually monitors the process status during CD control to automatically recognize and adjust mappings between actuators and measurement points on profiles. By formulating rules based on the customers' control know-how, peaks can be aligned to achieve a flat roll shape ( roll shape control).

This method utilizes MD to control the thickness of films and sheets. Either sampled data PI control or finite time settling response control can be selected. Up to four loops can be implemented for each measurement operator station.

Virtual zone profile control has already achieved satisfactory results in many processes. It generates profiles at the midpoint between real bolts as well as on these bolts to perform control calculation. This prevents the occurrence of profile peaks and troughs between the bolts, which often become a problem in conventional profile controls only intended for profiles on the bolts. (Yokogawa patents)

Virtual Zone Profile Control

Expert fuzzy control based on fuzzy logic incorporates the manual bolt operation expertise of experienced machinery operators. This control method is effective with machines (mainly bi-axially oriented machines) where there is low repeatability of profile response to bolt manipulations, realizing more stable control than conventional control methods. Expert fuzzy control employs the concept of the virtual zone.

Expert Fuzzy Rule

Finite settling model predictive control applies the finite time settling response method to profile control. This predictive control employs a dead time internal model and a first-order lag system so that even machines with long lag times can settle down to target values within the shortest possible time. The control has a dramatic effect on machines with long lag times.

Finite Time Settling Response

Mapping is the most important parameter of CD control; however, it varies depending on operational conditions such as stretch ratio and machine speed. For this reason, setting parameters for each grade and re-tuning have been required to maintain optimum control.

Always monitoring the process status during CD control, CD adaptive control automatically recognizes and adjusts mappings between actuators (such as heat bolts) and measurement points on profiles using a proprietary Yokogawa algorithm that combines the steepest descent method with a neural network.

Automatic Mapping Control

Roll shape control incorporates rules that have been formulated based on the customers' know-how and applies it to CD control. By means of CD control, it improves roll shape by eliminating outstanding peaks.

Roll Shape Control

Optional software packages are available that provide profile stack server and a real time 3D profile view and analysis function. These packages can store, display, and analyze profile data for extended periods, and can be used to judge film production quality at a single glance.

The profile stack server runs on a user PC or measurement operator station.

• Stores profile data of manufactured film and sheet automatically in real time
• Stores up to several lines of profiles on a roll-by-roll basis
• Saves long-term profile data
• Open database structure allows users to easily access data via a PC
• The integration of this package with a quality rating cutting system helps ensure the efficient and stable production of high quality products

• Invokes and displays profile data collected by the profile stack server in three dimensions on a roll-by-roll basis
• Displays profiles and machine directional trends at the position indicated by a cursor
• Specifies and zooms in on a range for analysis