Flexible Packaging Printer Cut Ink Rejection from 8% to 0.5%

Background & Challenge

A flexible packaging printer in East China, focused on BOPP film printing, suffered an 8% ink-rejection rate without surface treatment — frequent customer complaints and rising rework costs.

Diagnosis

On-site testing showed film surface tension of only 31 mN/m, far below the 40 mN/m required for water-based ink. The film had been stored too long and the line had no in-line treatment step.

Solution

We installed a 1.6 m in-line corona system at a power density of 15 W/(m²/min), with PLC auto-tracking of line speed (100–200 m/min) and dyne-level monitoring.

Results

• Film dyne level held steady at 40+ mN/m
• Ink rejection dropped from 8% to 0.5%
• Overall throughput rose about 20%