Thickness Distribution
Cross-machine thickness variation describes the geometric thickness distribution measured across the width of a continuous web. Quality control systems track caliper profile across paper and paperboard webs to maintain uniform bulk and convertibility. The term governs mechanical thickness measurements made across the full cross-machine width of single-ply and multi-ply paperboards.
The measurement boundary excludes local surface roughness peaks measured over microscopic distances.
Cross Machine Control
Induction heating coils and localized air jets control calender roll thermal expansion to correct thickness variations online. Thickness gauges sweep back and forth across the moving web, feeding high-resolution spatial data to automated control software. The control system adjusts sectional calender roll temperatures to expand or contract specific zones across the machine width.
Localized roll expansion reduces the gap between calender rolls, which decreases web thickness at specific cross-machine locations. Maintaining a uniform caliper profile prevents localized high spots that distort finished roll structure during high-speed winding.
Winding Integrity
Roll build quality directly determines web runnability through offset printing presses and converting machinery. Uneven thickness across the web causes soft spots and web breaks during high-speed web feeding. Printing presses suffer from uneven ink transfer when web thickness varies across the printing nip.
