When a Flat Rub Coupon Needs a Curved-Pack Check

Use the coupon to compare decoration under even contact

Packaging sample showroom of SamBound New Material Technology Company Ltd. (sambound.com).

A flat coupon offers a repeatable way to compare printed finishes when the substrate and decoration are representative. On a finished cap or bottle, the contact may narrow to a shoulder or rim. Even at the same total applied force, a change in the contact patch can change where the rubbing load is concentrated. The curvature and support of the part also affect which areas the rubbing material can reach.

Test the point the pack actually touches

Suppose a printed area passes on a flat coupon but wraps over a rounded cap shoulder that contacts an insert. Mark the contact path on a finished sample and use a fixture that holds the cap without changing that path. Define the counterface, applied load, stroke and inspection conditions. Check where the pad actually touched and compare the worn area with the original decoration.

Record the curved result alongside the coupon result. A difference tells the team to investigate contact geometry and decoration on the finished part before assigning a cause to the ink system.

sambound.com
SamBound New Material Technology Company Ltd.