InKraftSens

When manufacturing and processing flexible plastic or fiber webs, homogeneous web tension distribution is crucial to quality. Thin, low-complexity, natural fiber-based or recycled materials, which are not only required by law for packaging, have more fluctuating properties and narrower process windows than established composites. Flatness deviations, wrinkles, inclusions, and process induced stresses have a far more critical effect. The earlier such deviations are detected and readjusted or rejected, the fewer faults and rejects there will be.

Testing methods such as Schmidt hammer, strip tests or similar methods only provide offline and random results. Inline methods are based on the dynamic pressure principle or measuring films/rolls and can lead to web damage, wear, and falsification of results. Optical methods are limited in terms of imprinted materials and are expensive.

A new inline measuring method uses the aspect that the contact between the web and the measuring unit changes with varying web force. This affects the heat flow from the tempered measuring unit into the web. Thin-film thermocouples can measure the transferred heat in real time and with high resolution, as it was successfully demonstrated in IGF 20340 BG “RobInPro”. Applied to a web guiding element and provided with a suitable protective coating, they result in a space-saving measuring system gentle to the web for the future inline control of web force distribution. Therefore, the proof of concept, i.e., a sensor is to be developed and the measuring method validated. A demonstrator and a test setup for parameter studies will be created. Development steps on the way to a measurement system and a measurement method meeting industrial requirements will be:

1. Development of a sensor setup and of friction-reducing protective coatings on test substrates
2. Development of a measurement system consisting of a sensor array, temperature control, electrostatic discharge, data transmission and data processing and construction of a test environment
3. Validation of the measurement system in laboratory environment using a polymer film and a paper composite
4. Further development and scaling of the sensor array to industrial scale
5. Validation of the measurement system on a pilot plant or production machine of the web processing or web production
6. Development and validation of the measurement method; deduction of R&D requirements

Fields of application for the measurement system and method include the manufacturing of technical products, the packaging of consumer goods, the finishing of flexible materials and much more. The innovative solution addresses the efforts to adaptive machines, safe products, and minimal resource consumption, and supports SMEs to manage the strong sustainability trend.