Quantifying Surface Elevation Variance along Score Lines Using Optical Profilometry
Optical profilometry quantifies score elevation variance down to sub-micron resolution, identifying die wear and coating micro-fractures before carton assembly.
Surface Slope Sdq
Slope Metric
Topographic variance across a paper or board surface derives from root parameters such as surface slope sdq, quantifying the root mean square gradient of height deviations sampled along a designated profile. Mechanical finishing units and calender rolls establish this gradient during web consolidation, setting the micro-geometric steepness that dictates subsequent ink transfer efficiency and adhesive wetting behavior. Higher gradient values denote abrupt height transitions that disrupt uniform liquid spread during gravure printing or high-speed lamination runs.
Production tolerances for premium coated substrates restrict gradient variation tightly to prevent skipping in microscopic void networks.
Gradient Profile
Spatial sampling intervals dictate how optical and mechanical stylus instruments resolve micro-irregularities across cellulose webs. Short cutoff filters isolate high-frequency asperities from broader waviness features, ensuring the computed gradient reflects true fiber-level topography rather than large-scale sheet curl. Mathematical differentiation of height coordinates yields local slope values, squaring each incremental measurement before averaging over the evaluation length to generate the final root mean square output.
Transfer Mechanics
Fluid distribution across a rough substrate depends entirely on local inclination angles constraining capillary flow within micro-valleys. Elevated gradient readings increase fluid resistance by forcing coatings along tortuous microscopic pathways, altering penetration depths during size press application. Excessively steep micro-features trap air pockets beneath laminating adhesives, compromising bond strength and creating visual blemishes across finished packaging surfaces.