Dual Beam Telecentric Triangulation for Web Thickness Measurement
Dual beam telecentric triangulation delivers non-contact web caliper measurement by cancelling flutter and eliminating lens magnification errors across moving webs.
Continuous Web Flutter
Dynamic Resonance
Transverse oscillation in a moving substrate running through high speed printing presses and coating lines introduces register errors across the printed image. Continuous web flutter describes this uncontrolled lateral and vertical displacement between span guides during paper conversion. Tension profiles across the unsupported length govern the frequency and amplitude of the harmonic waves generated by aerodynamic drag and roller eccentricity.
Converters monitor high speed camera feeds and laser displacement sensors to quantify the deviation before wrinkles or web breaks occur on the production floor.
Tension Distribution
Unbalanced draw settings between successive print units create the instability that feeds lateral wave formation in lightweight publication grades. Air entrainment at the nip of driven chill rolls lifts the passing substrate and forces the edges to oscillate against the running plane. Operators adjust brake torque on the unwinding stand and increase vacuum pull on drying cylinders to dampen the periodic vibration.
High tensile stiffness mitigates the deflection under aerodynamic loading, whereas extensible packaging films require lower acceleration rates to maintain stability through the drying tunnel.
Image Distortion
Periodic displacement alters the dot gain pattern across the cylinder contact zone and blurs fine screen rulings in offset lithography. Stroboscopic inspection lamps reveal the standing wave nodes where ink transfer fails due to localized loss of contact between the blanket and the moving web. Web tension fluctuations exceeding five percent of the nominal setpoint invariably trigger register faults that ruin entire rolls of laminated folding boxboard.
Mechanical dampers placed midspan absorb the kinetic energy of the oscillation and preserve dimensional accuracy throughout the print run.