Stretch Film – Methods of Application
This technique is used where volumes are low or where wrapping activities are dispersed around a site. The stretch film applied is controlled by the operator dispensing the film from a lightweight hand roll.
Core Brake Machines
Here the rotating loads pulls the film off a braked roll of film so that the stretch occurs between the load and the roll. As the film is not supported during the stretching process, necking-in occurs at high levels of stretch and lay-on forces can become great enough to cause crushing of all but the most robust products. To avoid both these risks stretch levels have to be kept low and are rarely higher than 20-30%.
Simple Pre-Stretch Machines
On these machines the rotating load pulls the film through a pair of free-running rollers geared together so that the roller nearer the load rotates at a faster rate than that nearer the unwinding roll of film. The stretch therefore takes places between these two rollers and little necking-in occurs. However, high lay-on forces can still build and so on of the rollers is equipped with a clutch device that allows slippage to take place. In practice this allows the film to retract somewhat to avoid load crushing. Stretch levels of up to 50-60% can be achieved on these machines.
Powered Pre-Stretch Machines
On these systems the two pre-stretch rollers are driven by external power and not by the rotating load. The film is this pulled from the roll and fed to the load. Lay-on forces can thus be carefully controlled by the speed with which the film is fed to the load. Load stability is further enhanced by the film’s high re-stretch resistance achieved from high levels of stretch – up to 300%.
View our range of Stretch film here or speak to one of our team today about your stretch film needs.