March 2007

Colines Air Knife vs. Vacuum box

The ColinesĀ® Research & Development department, in cooperation with the partner companies belonging to B-Pack Holding, developed some key components for a good extrusion of cast film by considering not only the quality, but also the functionality, the practicality, the easiness, improving the systems. This deepening for example illustrates why normally we propose our Colines Air Knife instead than the vacuum box. The default technical choice is this but the customer can install the vacuum, if he wishes. Reasons for the choice of the air knife in order to remark the following advantages in comparison to the vacuum box Air Knife Dynamic vacuum with high air exchange ratio that helps: - Complete suction of smokes and waxes - Better refrigeration and thus better haze and gloss - Better cleaning of the chill-roll - Variable position of the chill-roll with respect to the die and consequent great production flexibility - Possibility to create the ideal working conditions for every product - Reduction of the melt instability - Better control of the edges - Precise management of the shear stress - Which allow to achieve: better optical/mechanical characteristics of the film and higher production capacity of the line Vacuum box -Non-dynamic vacuum - Low suction of smokes and waxes - Deposit of smokes and waxes on the chill-roll -Many stops of the line for the cleaning of the chill-roll - Increase of scraps at the start-up - Lower film quality as far as haze and gloss are concerned - Relative position of die and chill-roll bound by mechanical constraints - Inability to achieve the ideal working conditions for several products - Limited flexibility of the line - Inability to vary the shear stress value, without acting on the die lip, with consequent extension of the time required to set the line