Uneven film thickness / transverse thickness variation

Calendered film thickness variation along the width direction exceeds allowable tolerance; transverse thickness variation manifests in multiple distribution patterns such as one end thicker and the other thinner, or middle thicker and both ends thinner. Uneven thickness directly affects the uniformity of mechanical properties and consistency of optical properties of the film — thick areas have higher strength but reduced light transmittance, thin areas are easily stretched and broken. In subsequent stretching and winding processes, uneven thickness also causes deviation and wrinkles.

1. Mold/tooling factors: Improper crown adjustment or wear of calender rolls causes uneven roll gap. 2. Mold/tooling factors: Roll temperature unevenly distributed along the axial direction. 3. Operational factors: Insufficient feed width or uneven material bank shape. 4. Mold/tooling factors: Bearing clearance causes one end of the roll to float.

1. Process parameter optimization and adjustment: Precisely adjust roll gap crown and cross angle. 2. Mold/tooling improvement and maintenance: Check whether roll heating medium (oil, water) channels are locally blocked. 3. Equipment inspection and system maintenance: Adjust feed uniformity so the bank width covers the roll surface working area. 4. Material/formulation optimization: Check and adjust bearing clearance. 6. Preventive management: Establish standardized process parameter cards and quality control limits for each mold/product, and regularly conduct process capability index (CPK) evaluations. For recurring problems, use fishbone diagrams or 5Why analysis to trace the root cause, and solidify countermeasures as PFMEA control points. Establish a regular equipment maintenance system and implement life management for key tooling such as dies/spinnerets/calender rolls/coating heads.

The essence of transverse thickness unevenness of calendered film is uneven distribution of roll gap along the axial direction. The core of the solution is "precise compensation": compensate roll deflection through precise adjustment of crown and cross angle, combined with real-time feedback fine-tuning from the online thickness gauge, to ensure the roll gap is uniform and consistent under working load.