Shrink tunnel
Encyclopedia
A Shrink tunnel or Heat tunnel is a heated tunnel mounted over or around a conveyor system
. Items such as packaging, have shrink film loosely applied; with heat, the film shrinks to fit snugly around the wrapped object.
(electrical resistance), Infrared heater
, steam, or gas flame. Often forced air is used to improve convection
, sometimes focusing the heat on one component of the item.
Tunnels are available with or without a conveyor system. Some are built into a production line or are integral with machinery that also applies the shrink film. Others are movable by hand or by castors. A shrink tunnel, referred to as an oven, may be equipped with an integrated conveyor of two different kinds. The roller conveyor
or the belt conveyor
. Roller conveyors can be used with polyolefin
, PVC
, and shrink polyethylene
films. The space in between the rollers is filled with hot air from the bottom of the tunnel to shrink the film layer around the object, creating a sealed package. When used with polyolefin and PVC based films the rollers are called "live" or spinning. When used with polyethylene films the rollers are called "dead" or not spinning. The tunnels with Teflon
mesh belts and polymer
mesh belts are used for smaller packages, or when the package may have an instability and need a stable platform.
Some heat shrink tunnels have two or more zones for heating and controlled cooling.
Conveyor system
A conveyor system is a common piece of mechanical handling equipment that moves materials from one location to another. Conveyors are especially useful in applications involving the transportation of heavy or bulky materials...
. Items such as packaging, have shrink film loosely applied; with heat, the film shrinks to fit snugly around the wrapped object.
Uses
- Shrink labelLabelA label is a piece of paper, polymer, cloth, metal, or other material affixed to a container or article, on which is printed a legend, information concerning the product, addresses, etc. A label may also be printed directly on the container or article....
s - Combining small items for sale and display (example: bottled water)
- Tamper resistant or Tamper-evidentTamper-evidentTamper-evident describes a device or process that makes unauthorized access to the protected object easily detected. Seals, markings or other techniques may be tamper indicating.-Tampering:...
bands or seals - Form large unit loadUnit loadA unit load combines individual items or items in shipping containers into a single "unit" that can be moved easily with pallet jack or forklift truck...
s for transport - Form primary barrier on foods such as cheese, meats and fish
- Skin packSkin packSkin pack, or skin packaging, is a type of carded packaging where a product is placed on a piece of paperboard, and a thin sheet of transparent plastic is placed over the product and paperboard....
s
Types
The heat source can be based on Heating elementHeating element
A heating element converts electricity into heat through the process of Joule heating. Electric current through the element encounters resistance, resulting in heating of the element....
(electrical resistance), Infrared heater
Infrared heater
An infrared heater is a body with a higher temperature which transfers energy to a body with a lower temperature through electromagnetic radiation. Depending on the temperature of the emitting body, the wavelength of the infrared radiation ranges from 780 nm to 1 mm. The relationship...
, steam, or gas flame. Often forced air is used to improve convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
, sometimes focusing the heat on one component of the item.
Tunnels are available with or without a conveyor system. Some are built into a production line or are integral with machinery that also applies the shrink film. Others are movable by hand or by castors. A shrink tunnel, referred to as an oven, may be equipped with an integrated conveyor of two different kinds. The roller conveyor
Lineshaft roller conveyor
Lineshaft roller conveyors are, as their title suggests, powered via a shaft beneath the rollers. These conveyors are suitable for light applications up to 20 kg such as cardboard boxes and tote boxes....
or the belt conveyor
Conveyor belt
A conveyor belt consists of two or more pulleys, with a continuous loop of material - the conveyor belt - that rotates about them. One or both of the pulleys are powered, moving the belt and the material on the belt forward. The powered pulley is called the drive pulley while the unpowered pulley...
. Roller conveyors can be used with polyolefin
Polyolefin
A polyolefin is a polymer produced from a simple olefin as a monomer. For example, polyethylene is the polyolefin produced by polymerizing the olefin ethylene. An equivalent term is polyalkene; this is a more modern term, although polyolefin is still used in the petrochemical industry...
, PVC
PVC
Polyvinyl chloride is a plastic.PVC may also refer to:*Param Vir Chakra, India's highest military honor*Peripheral venous catheter, a small, flexible tube placed into a peripheral vein in order to administer medication or fluids...
, and shrink polyethylene
Polyethylene
Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...
films. The space in between the rollers is filled with hot air from the bottom of the tunnel to shrink the film layer around the object, creating a sealed package. When used with polyolefin and PVC based films the rollers are called "live" or spinning. When used with polyethylene films the rollers are called "dead" or not spinning. The tunnels with Teflon
Polytetrafluoroethylene
Polytetrafluoroethylene is a synthetic fluoropolymer of tetrafluoroethylene that finds numerous applications. PTFE is most well known by the DuPont brand name Teflon....
mesh belts and polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
mesh belts are used for smaller packages, or when the package may have an instability and need a stable platform.
Some heat shrink tunnels have two or more zones for heating and controlled cooling.