Online Acoustic Wave Sensing for Paperboard Score Quality Control
Inline acoustic wave sensing detects sub-surface paperboard delamination during scoring, stopping un-creased board defects before downstream cartoning line jams.
Laser Ultrasonics
Material Testing
Non-destructive evaluation methods use light to generate sound waves inside a moving web of paper or board. Through laser ultrasonics, a mill can measure the elastic properties of the substrate while the machine is running at full speed. This technology eliminates the need for manual sampling and laboratory testing of reels.
Wave Generation
Pulse lasers hit the surface of the paper to create a tiny thermal expansion that sends an ultrasonic wave through the material. A second device, known as an interferometer, detects the vibrations on the other side and calculates the speed of the sound. The speed of these waves in laser ultrasonics relates directly to the stiffness and thickness of the fibre network.
By measuring the velocity in both the machine direction and the cross direction, the system provides a real-time map of the structural strength. This allows the operator to adjust the jet-to-wire ratio or the press load immediately if the values drift. The process works without physical contact, meaning the web is never at risk of tearing due to a sensor drag.
Online Monitoring
Continuous data streams from the sensor allow for the optimization of chemical additives and refining energy. Because laser ultrasonics provides instant feedback, it reduces the amount of out-of-specification material produced during a grade change. The accuracy of the system remains high even in the vibrating environment of a paper machine.