Shrink Wrap Tunnel

Overview

A shrink-wrap tunnel is a post-packaging system that envelops wrapped products in a protective, heat-shrunk plastic film. The process involves forming a tube of film around the product and sealing the overlap, then passing the wrapped item through a heated chamber where radiant heaters and circulated hot air cause the film to shrink tightly around the product.

Shrink tunnels are used for bundling (e.g., six-pack beverage cans), tamper-sealing (e.g., cosmetic boxes), and product stabilisation (e.g., stacks of books). They operate continuously or intermittently and are commonly integrated with upstream wrapping stations and downstream code-and-label equipment.

How it works

The Film Unwind Station supplies film from a large roll, maintained at constant tension by the Film Tension Brake. The film is guided by the Film Guides and drawn into the Wrapper Sealer Unit.

Products arrive on the Infeed Conveyor at a controlled speed set by the Infeed Motor and confirmed by the Spacing Sensor. They pass through the Film Forming Tube, a tapered tube that wraps the film around the product. The Tube Mandrel shapes the film into a tube, and Tube Guides hold it centred.

Once the product exits the mandrel, the Seal Jaw clamps down, and the Seal Heating Element heats the overlapped film edges, fusing them together. Immediately after, the Cutter Wire cuts the film to length for the next product. The Wrapper Servo and Cutter Servo time these operations to the infeed conveyor speed.

The wrapped product continues onto the Discharge Conveyor, entering the shrink tunnel. The tunnel is divided into three heating zones:

• Top zone: The Top Heating Zone contains radiant heaters (halogen or electric elements) mounted above the conveyor. The Heater Bank (Top) emits infrared energy, focused by the Heater Reflector.
• Bottom zone: The Bottom Heating Zone mirrors the top, with Heater Bank (Bottom) suspended below. A Heater Shield protects the discharge motor from excessive heat.
• Side zone: The Side Blower Zone houses Side Blower Motors on the left and right, with Blower Nozzles directing hot air at the product sides.

The central Blower System pulls air through the heating chambers via the Main Blower Motor and Main Blower Fan, drawing through the Intake Filter for cleanliness. The Flow Damper Valve adjusts air circulation rate. Air is heated as it passes across the radiant elements and returned to the tunnel.

The Temperature Control System system monitors three Temperature Sensor (Top), Temperature Sensor (Bottom), and Zone Temperature Sensor sensors via the Temperature Control Board PLC. Proportional heater contactors (Heater Contactor) regulate power to maintain set-point temperatures. The Temperature Display shows real-time zone temps and allows operators to adjust shrink profiles for different film types.

As the wrapped product travels through the tunnel (dwell time 8–30 seconds depending on film thickness and product mass), the film gradually shrinks around the product, conforming to its shape and providing a neat, tamper-evident seal.

Film selection and applications

Typical shrink-film choices include PVC (lowest cost, good strength), LDPE (softer, better for delicate products), and POF (polyolefin film, strong and clear). Thinner films (12–20 µm) shrink faster and are suitable for lightweight products, while thicker films (40–75 µm) provide structural stability for heavier bundles.

Tunnels are commonly paired with pre-wrapping equipment (VFFS machines or dedicated bundling stations) for full automation in beverage, cosmetics, pharmaceutical, and fresh-food packaging lines.