Blown Film Machines —
From Single Layer to 9-Layer Co-Extrusion

A blown film machine converts plastic resin pellets into continuous tubular film in five stages: resin is fed into a heated barrel where a rotating screw melts and pressurises it; the melt is forced upward through an annular die and inflated with compressed air to form a bubble; the bubble is cooled by an air ring, collapsed by a nip board and wound into rolls. In multi-layer co-extrusion machines, two to nine extruders feed separate material streams into a single die simultaneously, producing a film with distinct functional layers fused in the melt state.

A 3-layer ABA configuration is the standard for courier bag production. The two outer A layers — typically LLDPE or mLLDPE — provide tensile strength, puncture resistance and a printable surface. The inner B layer can carry PCR content or lower-cost resin blends without affecting outer surface quality. A 2-layer AB machine is a lower-cost entry point if PCR content is not a requirement.

In an ABA structure, the two outer layers use the same material and the inner layer uses a different one — the most common configuration for courier bags where outer layers need identical properties. In an ABC structure, all three layers use different materials independently, giving more flexibility where inner and outer surfaces need different properties. ABA machines use two extruders; ABC machines require three independent extruders.

Screw diameter determines the volume of resin that can be melted per revolution, setting the output ceiling of the machine. A larger diameter screw processes more material per unit time but requires more motor power, a larger footprint and a taller factory ceiling. Actual output also depends on film thickness, material formula, line speed and cooling efficiency. As a general reference, LayerQuestar's ABA range covers from approximately 85 kg/h at Φ45×2mm to 280–300 kg/h at Φ80×2mm under standard polyethylene conditions.

LayerQuestar blown film machines are configured to process LDPE, HDPE, LLDPE and mLLDPE for standard bag and film applications; PP for food and industrial film; EVOH and PA as barrier layers in 5-, 7- and 9-layer structures; PLA/PBAT blends for biodegradable film; and PCR content in co-extrusion core layers. Different materials require different screw geometries and temperature profiles — biodegradable compounds require centre-wind winding, and hygroscopic materials such as PA and EVOH require pre-drying before processing.

Blown film is formed by inflating extruded melt into a bubble and cooling it with air — producing a biaxially oriented film with balanced strength and lower optical clarity. Cast film is formed by extruding melt through a flat die directly onto a chill roll — producing higher clarity and gloss but primarily machine-direction orientation. Blown film is appropriate for bags, pouches, agricultural and industrial film. Cast film is preferred for cling wrap, CPP film and applications where maximum optical clarity is the primary requirement.

On-site installation and commissioning of a standard LayerQuestar blown film machine typically takes 5–7 days, covering mechanical assembly, electrical connection, calibration and operator training. Most operators reach independent operation within 1–2 weeks. The total timeline from contract signing to first production run — including manufacturing (30–45 days), the 72-hour factory acceptance test and sea freight — is typically 60–90 days depending on destination and machine complexity.

Available optional upgrades include: IBC (Internal Bubble Cooling) for increased output on the same footprint; Automatic Thickness Control (ATC) for real-time die gap adjustment; an online thickness gauge for continuous measurement and quality data logging; a rotating die head for improved film roll flatness; a dual-lip air ring for finer cooling control on high-speed or thin-gauge lines; and a quick screen changer that reduces screen replacement to within seconds, minimising downtime when processing PCR or contaminated materials.