Protective film can be loaded on the wrong side, folded into the clamp, wrinkled, stretched, or left on a surface that the film supplier does not approve for forming. Trapped air and uneven film tension create marks that can resemble sheet or mold defects.
The film grade, orientation, age, adhesion, and forming approval should be verified. Marks should be compared with wrinkles or overlaps visible before heating. A defect that follows the film when it is changed or removed is not a mold-surface problem.
Loading procedures should identify which side remains protected and where film must be removed for sealing, bonding, or tool contact. Storage temperature and age matter because adhesive behavior changes over time. Additional heat should not be used to make an unsuitable film conform.