Verifying Board Caliper before Cutting Brass Embossing Tooling
Verifying true substrate caliper under standard foot pressure before cutting brass embossing tooling prevents fiber shearing, smashed matrixes, and costly die remakes.
Low-Angle Grazing Light Inspection
Illumination Angle
Directing illumination at angles below fifteen degrees across a flat paperboard surface accentuates micro-topographical defects through high-contrast shadow projection. In quality control operations, low-angle grazing light inspection reveals surface irregularities such as cockle, washboarding, and localized crushing. Light rays cast long shadows behind bumps or depressions, making defects visible to optical sensors.
The inspection technique applies to sheet-fed print verification and web inspection systems.
Shadow Contrast
Low incident angles amplify micro-relief features by maximizing shadow length relative to surface height. Light source positioning parallel to the sheet surface accentuates paperboard defects that remain invisible under overhead diffuse illumination. High-contrast line-scan camera arrays record reflected intensity variations across moving paper webs at high production speeds.
Defect detection algorithms process shadow geometry to identify debris particles, coating streaks, and die marks before printing. Optimizing light frequency prevents false readings caused by background color variations on printed sheets.
Defect Visibility
Shadow amplification allows immediate identification of surface flaws prior to high-value print and coating passes. Early detection prevents waste by identifying defective paperboard rolls before processing on press lines. Automated optical systems flag defect locations and signal marking equipment to reject sub-standard sheets.
Quality assurance teams use grazing light tables for manual spot audits of finished folding cartons.