Flow Wrapping Machine

Overview

A flow wrapper is the fastest, most versatile secondary-wrapping machine in use today. It continuously wraps individual products (confectionery, bakery, frozen items, pharmaceuticals) in plastic film, seals both the length and the ends, and ejects them at 30–300 packs per minute. The core mechanism is elegant: film is threaded vertically through a tapered forming tube; as the product pushes through, the film wraps around it like a sleeve. Two heated rotating wheels (fin seal wheels) running just past the former seal the film overlap lengthwise; then heated jaws clamp and crimp the pack ends, trapping the product inside a hermetic envelope. The machine is fast, reliable and tolerates a wide range of product sizes with minimal changeover.

Film supply and registration

Film (typically 200–400 mm wide) arrives on a large roll mounted on the Film Reel. An Film Motor with encoder feedback unwinds the film at precisely controlled speed. A Film Tension arm (a dancer or brake) maintains constant tension so the film is taut but not strained. The film descends through a Film Guide (a slot or roller guide) and enters the top of the Film Former.

Product arrives from the Infeed System: a Infeed Conveyor carries the item to a Product Stop, which positions it consistently at the forming tube entrance. A Product Sensor confirms product presence before the next cycle.

Forming and longitudinal seal

The product enters the Film Former, a precision tapered stainless-steel tube. As the item advances, the film naturally wraps around it in a spiral; the tapering mandrel ensures smooth, wrinkle-free wrapping. By the time the product exits the tube, the film has formed a loose sleeve around it with an overlap edge where the leading film meets the trailing film.

The Fin Seal Wheels, two rotating, heated wheels positioned just past the former, clamp the film overlap and run it through the nip at 180–250 °C. The heat fuses the two film surfaces together into a strong, clean seam running the length of the pack. The wheels are precision-machined with a slight crown to distribute pressure evenly. Each Seal Wheel contains embedded Wheel Cartridge heater elements controlled by a PID Wheel Heater. The wheels must be maintained hot continuously; a thermistor measures temperature and the Wheel Heater adjusts power to keep temps within a tight band (e.g., 225 ± 5 °C).

End sealing and crimping

The wrapped, longitudinally sealed pack advances into the End Crimp Jaws. The jaws clamp from above and below, trapping the film ends. A Jaw Actuator (pneumatic or servo) applies clamping force, and the heated Upper Jaw and Lower Jaw (each at 250–280 °C, with Jaw Heater Element cartridges inside) melt and seal the film edges. The jaw faces are precision-machined and teflon-coated to prevent sticking. Dwell time is typically 0.5–2 seconds depending on film thickness.

Optionally, a Cutter Actuator can fire during the seal dwell, using a Cutter Blade and Cutter Anvil to cut away excess film (the "fin") sticking beyond the crimp, creating a cleaner finished pack. More commonly, the excess is left on and trim later.

Synchronisation and speed

All operations, product feed, film advance, longitudinal seal, end seal, must be perfectly timed. The Main Drive (a variable-frequency Main Motor driving via Timing Belt and Pulley distribution) coordinates everything. The Control System (a Control PLC running a motion profile) orchestrates actuators and monitors sensor feedback. Modern machines use registration marks (printed on the film) and an inline Product Sensor to detect pack position in real-time, allowing the PLC to trigger jaw clamps at the exact moment the pack exits the former, eliminating timing drift.

Materials and flexibility

Flow wrappers run an astonishing variety of films: LDPE and LLDPE (the standard, low-cost choice), oriented PET/PE laminates (better barrier and stiffness), cast polypropylene CPP (high gloss, moisture-proof), and cellophane (traditional, biodegradable). The key is that film must be thermoplastic and seal at predictable temperatures. Product size changes require adjusting the forming tube (not always quick) and reprogramming jaw spacing, film tension and seal timing in the PLC, typically 15–30 minutes. Some machines use quick-change forming tubes or modular mandrels to speed changeover for small-size variants.

Why flow wrappers dominate

Flow wrapping is fastest because there is no dead time between packs: the product is continuously advancing through the forming tube, and the jaws work on a new pack every 2–4 seconds at high speeds. Unlike L-sealers (which require product to sit still during sealing), flow wrappers move the product through in one shot. Throughput can reach 200–300 packs per minute for small, light items. The film consumption per pack is tightly controlled by measuring web tension and calculating advance per cycle. Scrap is minimal if the cutter is not used.

Limitations and alternatives

Flow wrappers struggle with very irregular product shapes (the former tube expects somewhat cylindrical symmetry), soft items that deform (requiring very low jaw pressure), and products larger than about 120 mm across. For such cases, alternative machines like envelope sealers (wrapping sides first, then ends) or shrink-sleeve applicators (slipping a large tube over the product) are used.