(1) The adhesive in the composite film has not been fully hardened.
(2) Improper heat sealing conditions.
(3) The distance between the heat sealing knife and the cooling knife is too long.
(4) There is a problem with the inner sealing film.
(5) The heat resistant sealing of ink is poor, resulting in the composite strength of the film in the heat sealing part.
(6) Dust, spray powder and other substances are attached to the hot cover.
(7) The composite strength is low or the composite strength at the heat seal drops too much.
