Uneven film thickness is a common quality issue in flexible packaging production. For food factories using coextruded packaging film, thickness variation can affect sealing strength, forming stability, transparency, barrier performance, and machine running efficiency. When film is too thin in some areas, it may tear or leak. When it is too thick, it may cause waste, poor forming, or unstable sealing.
During coextrusion, each material layer must be fed at a stable rate. If screw speed, melt pressure, or resin feeding is unstable, the film thickness may change across the roll. This is especially important for multi-layer film because each layer may serve a different function, such as sealing, puncture resistance, or oxygen barrier.
The die gap controls how molten material flows into film form. If the die gap is not adjusted evenly, or if temperature varies across the die, the film may become thick on one side and thin on the other. Regular die cleaning and calibration help reduce uneven packaging film thickness.
Cooling speed affects film shape and thickness distribution. Poor air ring control, uneven water cooling, or unstable chill roll temperature can create film waves, thickness marks, and flatness problems.
Different materials have different melt flow properties. If PE, PA, EVOH, or other resin layers are not matched well, thickness stability may be affected during production.
Uneven film thickness may cause poor vacuum retention, sealing failure, weak puncture resistance, and unstable roll performance on automatic packing machines. For bulk food packaging orders, even small thickness variation can create high defect rates.
A reliable coextruded film supplier should check thickness tolerance during production, monitor extrusion pressure, inspect roll width, and test sealing strength before shipment. Buyers should confirm thickness range, tolerance standard, roll width, film structure, and application before placing repeat orders.
